CCA PERFORMANCE OBJECTIVES

These sample questions represent the general nature of the CCA examination.  No representation is made as to whether or not these questions will actually appear on the examination.  No representation is made as to whether the study of this material will ensure successful completion of the CCA examination.  These questions and sample study answers are current at the time of publication.

NUTRIENT MANAGEMENT

BASIC CONCEPTS OF PLANT NUTRITION

1. List the 18 elements (including Ni) essential for plant nutrition

Carbon (C), Iron (Fe), Hydrogen (H), Manganese (Mn), Oxygen (O), Boron (B), Nitrogen (N), Molybdenum (Mo), Phosphorus (P), Copper (Cu), Potassium (K), Zinc (Zn), Calcium (Ca), Chlorine (Cl), Magnesium (Mg), Sulfur (S), Nickel (Ni), and Sodium (Na)

Internet Link: http://agguide.agronomy.psu.edu/sect2/tab2-4.htm More Information on the 16 essential elements

Internet Link: http://ces.ncsu.edu/cumberland/fertpage/plantnutri.html More Information on the 16 essential elements

Internet Link: http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_MG091 More Information on the 16 essential elements

2. Classify the essential elements as macronutrient or micronutrient

Structural:   C, H, O

Macronutrient: N, P, K, Ca, Mg, S

Micronutrient:  Fe, Mn, B, Mo, Cu, Zn, Cl, Ni

Internet Link: http://www.soils.wisc.edu/~barak/soilscience326/primary.htm Information on primary and secondary nutrients

3. Describe the function of N, P, and K in plants

Nitrogen (N) makes up 1-5% of the plant by weight and is the most frequently deficient. Nitrogen is used to build proteins which then make up the framework of many plant structures such as chloroplasts, mitochondria, and other structures important in biochemical reactions.  Nitrogen is also an integral part of nucleic acids. Nitrogen is a constituent of all living cells and is a necessary part of all proteins, enzymes, and metabolic processes involved in the synthesis and transfer of energy. Ref: Havlin et al., Soil Fertility and Fertilizers, 6th ed., 1999, Prentice Hall, p89-91.

Phosphorus (P) makes up 0.1-0.4% of the plant and is involved in energy transfer and storage.  Adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are formed in the presence of sufficient P. P is responsible for such characteristics of plant growth as utilization of starch and sugar, cell nucleus formation, cell division and multiplication, fat and albumin formation, cell organization, and transfer of heredity.

Potassium (K) makes up 1-4% by weight of the vegetative tissue. The most important function of K<+>+</+> is the activation of enzymes. It is also important on osmotic regulation and can affect the rate of transpiration by controlling the stomatal opening. Potassium is needed to produce ATP for photosynthesis, nitrogen uptake, protein synthesis, transpiration and translocation of sugars formed in leaves to other parts of the plant.

Internet Link: http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_MG091 Further study material from the University of Florida

Internet Link: http://uog.edu/soil Further study material from the University of Guam

4. Classify each macronutrient as mobile or immobile in the plant

Mobile: N, P, K, C, H, O, Mg, Mo

Immobile: Ca, S, Fe, Cl, Zn, B, Mn, Cu

Nickel (Ni) - variable mobility in the plant.  Under some conditions, nickel may be highly mobile in the phloem and under others it may be immobile.  This reaction is highly variable among plant species, as well as genotypes within species.  Their mobility is dependent upon environmental conditions prevalent during plant growth and on stage of plant development. Nickel is closely associated with seed germination.  [Ref. Rengel, Z.  1999.  Mineral Nutrition of Crops, p. 206-208, 215-217, 218.  Food Products Press, Haworth Press, Inc. New York.]

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/macronut.html#mobile Further study material from Cornell University

Internet Link: http://www.uark.edu/depts/agronomy/purcell/nutrients2.html Further study material from the University of Arkansas

5. List chemical uptake forms of each macronutrient

From air and water

C (CO<->2</->)

H (H<->2</->O)

O (O<->2</-> & H<->2</->O)

Soil medium

N (NO<->3<+>-</+> & NH<->4<+>+</+>)

P (H<->2</->PO<->4<+>-</+> & HPO<->4<+> 2-</+>)

K (K<+>+</+>)

Ca (Ca<+>2+</+>)

Mg (Mg<+>2+</+>)

Sulfur (SO<->4<+> 2-</+>)

Soil medium

Fe (Fe<+>2+</+>)

Mn (Mn<+>2+</+>)

B (HBO<->3</->)

Zn (Zn<+>2+</+>)

Cu (Cu<+>2+</+>)

Cl (Cl<+>-</+>)

Mo (MoO<->4<+>2-</+>)

Ni (Ni<+>2+</+>).

These are the chemical forms most commonly taken in by plants

Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999. Prentice Hall Inc.

6. Describe how nutrient needs change as plant growth progresses from germination to maturity

When a plant is young nutrient needs are small, but as it grows nutrient uptake increases rapidly.  At the time a plant is exhibiting its maximum growth rate is also the time at which maximum nutrient uptake occurs.  After reaching the maximum growth rate (nutrient uptake), uptake declines just as does the growth rate.  In fact, the rate of nutrient uptake mirrors exactly the growth rate of plants, and nutrients are thus needed in the greatest quantities during the periods of maximum growth.  As a plant approaches maturity, its need for essential nutrients decreases to zero, thus uptake ceases.  Ref. Havlin, et al., Soil Fertility and Fertilizers, 6th ed., 1999, Prentice Hall, p358-59.

7. Explain why it is important to use chelated forms of micronutrients

Chelated forms have the ability to perform very efficaciously under conditions where other micronutrient forms fail. These conditions have to do with the 1) pH (acidity –low pH , alkalinity – high pH) in the soil, water or in a substrate 2) the ability of a soil or substrate to adsorb nutrients like clay soils and (coco-)peat can do and 3) the level of elements like phosphates. A high pH, a high sorption capacity of a soil and the presence of phosphates would make a standard micronutrient inactive Fe3+ (in solution) + 3OH- (in solution) Fe(OH)3 (solid) A Chelate protects the micronutrient from any precipitation reactions that can otherwise happen with the unprotected micronutrient. Therefore chelated micronutrients offer you a secure way of applying micronutrients that you can rely on. The chelating agents most frequently used in agriculture and horticulture are called EDTA (Ethylene Diamine Tetraacetic Acid), DTPA (Di-ethylene Triamine Pentaacetic Acid) and EDDHA (Ethylenediamine-N,N'-bis(2-hydroxy-phenyl acetic acid)). EDTA forms a good stable bond with iron, manganese, zinc, copper and even with the secondary elements calcium and magnesium. DTPA and EDDHA are used for iron only to give extra stability and increase the performance of the iron chelate.

Internet Link: http://www.plantprodsolutions.com/index.php?id=163

BASIC CONCEPTS OF SOIL FERTILITY

8. Describe the role of the following in supplying nutrients from the soil

a. soil solution: The soil solution contains hundreds of dissolved organic and inorganic substances thus deriving the name solution. Its purpose is to serve as a constantly replenished, dilute nutrient solution bringing dissolved nutrient elements to plant roots. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999. Prentice Hall Inc.

b. cation exchange sites: With increased number of cation exchange sites in the soil, the number of possible nutrient sources in the soil also increases. The nutrients may not be available for immediate use by plants because they may be locked onto the exchange site until another ion can replace them.

c. organic matter: Organic matter, including plant and animal residues, is the main source that supplies carbon and energy to soil organisms. It is a major soil source of P and S and the primary source of N for most plants. As soil organic matter decays these nutrient elements are released as soluble ions that can be taken up by plant roots. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999. Prentice Hall Inc.

d. soil minerals: The inorganic mineral fraction of the soil that comes from rocks can provide nutrients to plants in the same way as organic matter, either by way of the soil solution or by contact exchange where the root is directly touching the soil.

e. plant residue:  Acts as a store house for nutrients and provide hydrogen, oxygen, carbon and other essential micronutrients.

9. Describe nutrient mineralization, immobilization, and uptake antagonism

a. mineralization: The conversion of an element from an organic form to an inorganic state as a result of microbial decomposition. Most of the inorganic ions released by mineralization are readily available to higher plants and to microorganisms. Mineralization and the decay of organic tissues is also an important source of N, S, P, and other essential elements for plants. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p847, 453.

b. immobilization: The conversion of an element from the inorganic to the organic form in microbial tissues or in plant tissues, thus rendering the element not readily available to other organisms or to plants. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p843.

c. uptake antagonism:  The uptake of nutrients, even if there is an adequate supply in soluble form, may be impeded by many factors.  Some of these are: soil compaction, cool temperatures, low soil moisture, excessive soil moisture, nutrient competition, excessively acid or alkaline conditions, the soil type that the plant is growing in, the health of various microorganisms in the root zone that may affect uptake, the plant's genetically determined abilities for uptake, and other conditions that compromise the regular health and metabolic functioning of the plant. Ref.  Brady, N.C. and R. R. Weil, 1999.  Elements of the Nature and Properties of Soils, 13th ed., p. 25.   Prentice Hall.

Internet Link: http://muextension.missouri.edu/xplor/waterq/wq0206.htm Further study material from the University of Missouri

10. Describe mass flow, diffusion, and root interception of nutrients

Mass Flow: When dissolved nutrients are carried along with the flow of soil water toward a root that is actively drawing water from the soil. In this type of movement, the nutrient ions are analogous to leaves floating down a stream, but allows for nutrient uptake even at night when water is only slowly absorbed into the roots. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p25.

Diffusion: Movement of nutrient ions from areas of greater concentration toward the nutrient-depleted areas of lower concentration around the root surface. The random movement of ions in all directions causes a net movement from areas of high concentration to areas of low concentration, independent of any mass flow of the water in which the ions are dissolved. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p25-6.

Root interception: Nutrients that are taken up in plants as roots continually grow into new, undepleted soil. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p25.

11. Describe how cation exchange capacity (CEC) influences nutrient mobility of the following

Cation exchange capacity (CEC) is the sum total of the exchangeable cations that a soil can adsorb. Through cation exchange, hydrogen ions from the root hairs and microorganisms replace nutrient cations from the exchange complex. The nutrient cations are then forced into the soil solution where they can be assimilated by the adsorptive surfaces of roots and soil organisms thus increasing plant nutrient availability, or they may be removed by drainage water. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p329-30, 335.

12. Classify the following as mobile or immobile in the soil

a. Ammonium:  A monovalent cation (NH4 +) so it is relatively immobile in the soil, as long as the soil has a sufficiently high CEC to retain it.

b. Nitrate:  An anion (NO3- ) thus soil CEC has no effect on it, and it is very soluble in water, making it very mobile in the soil. 

c. Phosphate:  The phosphate ion is a polyatomic ion with the empirical formula PO43?; it consists of one central phosphorus atom surrounded by four identical oxygen atoms in a tetrahedral arrangement. Phosphate becomes mobile where the natural retardation potential is insufficient, or has been depleted due to long-term loading. In many intensive agroecosystems continued inputs of phosphorus (P) over many years can significantly increase soil P concentrations and the risk of P loss to surface waters.

d. Sulfate: The sulfate ion is a polyatomic anion with the empirical formula SO42?.  The anion sulfate is negatively charged; therefore it is not attracted to soil clay or organic matter edges or surfaces, with rare exceptions.  Since it is not held by clay or organic matter it is mobile within the soil solution. 

Mobile nutrients move with soil water (mass flow) so are easily leached. 

Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 121-123.  Prentice Hall Inc.

Internet Link: http://www.uark.edu/depts/agronomy/purcell/nutrients2.html Further study material from the University of Arkansas 

13. Describe how the following soil characteristics affect nutrient uptake

a. texture: There are three broad groups of textural classes: sandy soils, clayey soils, and loamy soils. The general rule that applies with texture and nutrient availability is that the greater the surface area, the greater the soil's capacity to retain nutrients for plant uptake, thus clayey soils will often retain more nutrients for plant uptake. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p124-5.

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/texture.html#top Further study material from Cornell University

b. structure: structure affects nutrient availability depending on the soil's capacity to absorb water and the ability to allow root penetration. If a claypan is present roots will be unable to explore deeper soil in search of nutrients, whereas a soil that is loose and friable will allow exploratory root penetration.

c. drainage/aeration: low aeration or flooded soils will cause denitrification to occur. Compaction or inadequate O<->2</-> in soils restricts root growth and thus limits nutrient uptake, especially of K.

d. moisture: low soil moisture will decrease the availability of most nutrients. Many minerals are absorbed through diffusion into the root system and without adequate moisture the roots are unable to absorb sufficient nutrients. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p409-414.

e. pH:  Different nutrients are made available at different soil pH levels.  The availability of the macronutrients and others, is curtailed in acid conditions, while some of the micronutrients become so available that toxic levels in plants can be the result.  In alkaline conditions, some micronutrients will be less available.  Soil bacteria may also be strongly affected by pH, which may have adverse effects on nutrient uptake.  A medium pH range of around 5.5 to 7.0 seems to be optimal for nutrient uptake in plants.  Ref. Brady, N.C. and R. R. Weil, 1999.  Elements of the Nature and Properties of Soils, 13th ed., p.     264-265. Prentice Hall.

f. temperature: Warm temperatures greatly influence the proportion of soil organic matter, a major source of nutrients for plants.  Warm temperatures also tend to increase the processes of soil weathering, leaching, plant growth, and the rates of biochemical reactions that are the basis of plant nutrition.  But cool temperatures may be desired when fertilizing with ammonium, to retard formation of nitrate and subsequent losses of nitrogen due to leaching and denitrification.  Extreme temperatures will injure the plant, reducing uptake abilities.  A temperate climate will usually be most beneficial for nutrient uptake.  Ref. Brady, N.C. and R. R. Weil, 1999.  Elements of the Nature and Properties of Soils, 13th ed., p.  45; Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 119-128.  Prentice Hall Inc.

14. Describe how the following affect the fate of N in soil

a. fixation by clay: Certain organisms (i.e. Rhizobia, Cyanobacteria) convert the inert dinitrogen gas of the atmosphere (N<->2</->) to nitrogen-containing organic compounds that become available to all forms of life through the nitrogen cycle. The key to biological nitrogen fixation is the enzyme nitrogenase which turns N<->2</-> into ammonia which in turn is combined with organic acids to form amino acids and ultimately proteins. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p512.

Internet Link: http://www.cahe.nmsu.edu/pubs/_a/a-129.html Further study material from New Mexico State University

b. ammonification/mineralization: The biochemical process whereby ammoniacal nitrogen is released from nitrogen-containing organic compounds. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p829.

c. nitrification: The biochemical oxidation of ammonium to nitrate, predominantly by autotrophic bacteria. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p848.

d. volatilization: NH<->4</->+ + OH<+>-</+> = H<->2</->O + NH<->3</-> (gas) From this reaction we can draw three conclusions. First, volatilization will occur more frequently in high pH soils; second, ammonia-gas-producing amendments will drive the reaction to the left; and finally as a moist soil dries, the water is removed from the right-hand side of the equation, driving the equation to the right. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p498.

e. denitrification: The biochemical reduction of nitrate or nitrite to gaseous nitrogen, either as molecular nitrogen or as an oxide of nitrogen. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p835.

f. immobilization: The conversion of an element from the inorganic to the organic form in microbial tissues or in plant tissues, thus rendering the element not readily available to other organisms or to plants. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p843.

g. leaching: The removal of materials/nitrogen in solution from the soil by percolating waters. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p845.

h. symbiotic fixation: Certain clay soils (mainly those containing vermiculite and illite) can replace the cations in their lattice structure with ammonium cations.  This fixed nitrogen can then be replaced by cations that will expand the structure (Ca ,  Mg   ,Na ,H ), but not by the ones that contract it (K ).  When adding ammonium fertilizers to these soil types, this kind of fixation can compromise N availability, although some of this N will eventually be made accessible when expanding cations may replace it.  When this type of N "tie-up" is a problem in the field, fertilization with K before NH   is helpful, to fill up the sites with K  that could otherwise fix N.  Nitrogen fixation by clay may be of benefit at times, to reduce losses of N due to rapid nitrification and then leaching.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 122-123.  Prentice Hall Inc. The answer to this question is actually what was answered previously for question #14.a.

i. plant uptake:  Nitrogen is initially added to the soil by decomposing plant and animal residues and derived from the earth's atmosphere through processes of lightning and rainfall, combustion, and industry.  The organic N must be mineralized to ammonium by soil organisms in order to be absorbed by plant roots.  Some of the ammonium is fixed in soil clays and some of the ammonium undergoes nitrification due to bacterial activity, and the resulting nitrate can also taken up by plant roots.  Some of the nitrate is leached away in ground water and some of it is lost as gases after being denitrified by bacteria.  The N removed from the soil in this cycle must be replaced by natural processes or by man, or there will be a resulting deficit of N for cycling.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 87. Prentice Hall Inc.

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/nitrogen.html#top Further study material from Cornell University

Internet Link: http://www.room103.com/archive/q_nitrogencycle.htm Further study material

15. Describe how the following soil factors affect symbiotic nitrogen fixation

a. pH: Soil acidity can restrict the survival and growth of Rhizobia in soil and severely affect nodulation and N fixation processes. Rhizobia and roots of the host legume plant can be injured by Al<+>3+</+>, Mn<+>2+</+>, and H<+>+</+> toxicity, as well as low levels of available Ca<+>2+</+> and H<->2</->PO<->4<+>-</+>. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p98.

b. moisture: Moisture stress will reduce photosynthetic rates which in turn reduces N fixation. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p100.

c. nitrogen level: Maximum N fixation occurs only when available soil N is at a minimum. Excess NO<->3<+>-</+> concentration in the soil can reduce nitrogenase activity and thus Rhizobial activity and N fixation. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p98.

d. presence of correct rhizobia species: Each species of Rhizobia is very specific as to its host plant. The first time a new legume species is planted in a field, it must be inoculated with the Rhizobium pertaining to that particular species. Also, yield increases of up to 40% in alfalfa have been found by matching certain Rhizobia strains with certain cultivars. Inoculant is cheap enough and crop losses expensive enough that it is recommended to coat seed each time you plant a legume. Another reason to inoculate is that sometimes local microbe populations are not as effective at N fixation as introduced populations.

16. Recognize how crop to be grown influences the following

a. soil fertility levels: Crops either add or take-away from soil fertility.  For example corn reduces the nitrogen level in soils; whereas, nitrogen fixing crops add nitrogen to soils.  Crops affect nearly every nutrient value to some degree with some reducing nutrient levels more than others.   

b. method of applying nutrients: Various crops may require specific methods of applying nutrients and may require a combination of methods depending on the soil landscape and crop timing.  Direct placement methods, broadcast, or foliar application are the common general methods. 

Direct placement methods include Plough-Sole Placement, Deep Placement of Nitrogenous Fertilizers, Sub-Soil Placement, Localised Placement. Inserting or drilling or placing the fertilizer below the soil surface by means of any tool or implement at desired depth to supply plant nutrients to crop before sowing or in the standing crop is called placement. With placement methods, fertilizers are placed in the soil irrespective of the position of seed, seedling or growing plants before sowing or after sowing the crops.

Broadcast method refers to the uniform application of fertilizers across the entire soil surface. This may be done before the land is ploughed, immediately before planting, or while the crop is standing. Fertilizers may be broadcast on the surface then tilled or watered into soil, or banded on or beneath the soil surface. Broadcasting is efficient and often the method of choice in areas with perennial plants.

Foliar Application refers to the spraying on leaves of growing plants with suitable fertilizer solutions. These solutions may be prepared in a low concentration to supply any one plant nutrient or a combination of nutrients.

c. timing of applying nutrients: Fertilizer should be applied when plants need it, when it will be most effective, and when plants can readily take it up. Late summer and early fall fertilization may stimulate new growth that is not winter hardy, and summer drought may interfere with nutrient uptake, but spring, fall, and winter applications are acceptable. A split application may be beneficial, applying half the yearly rate in early spring and the rest in the fall as or after plants go dormant. If water is unavailable, do not fertilize at all - plants will be unable to absorb the nutrients.  Needed fertilizer can be applied in either spring or fall if soils are not sandy. Spring applications are suggested when soils are sandy. Sulfur (S) may be needed when soils are sandy, is mobile, and should not be applied in the fall. A soil test for S is suggested if soils are sandy. Split applications can be used for alfalfa and are considered to be a good management practice. This is especially true if high rates of phosphate and/or potash fertilizer are needed. If split applications are used, the fertilizer should be applied in early spring and repeated after the 1st cutting.

Internet Link: http://www.extension.umn.edu/distribution/cropsystems/DC3814.html

17. Recognize how a cropping system influences the following

a. soil fertility levels

Different crops remove differing amounts of nutrients from the soil.  Alfalfa, corn silage, and some other crops may remove as much as 250 to 300 kg N/ha, whereas wheat and other small grains or cotton remove about 100 kg N/ha.  Removal of P and K can also be significant in high-yield agriculture.  Since P levels are quite low compared to N (1/10 to 1/4) or K (1/20) in the soil, both nutrients must be replaced by use of commercial and organic fertilizers.  Both alfalfa and silage remove large amounts of K from the soils; small grains remove lesser amounts.  Potatoes are large users of P.  Leguminous crops fix significant amounts of N and thus eliminate the need for additional N on them and reduce significantly the amount of N required for the following crop. 

b. method and timing of applying nutrients

Application of N, other than as a starter fertilizer during the stand establishment year, has several deleterious effects on the forage legume stand: higher costs for fertilizer (the plant can supply it own N), more rapid thinning of the stand, and encroachment of weeds that would otherwise not be a problem.  For some crops it is important that fertilizer is applied in smaller amounts during critical times of the season or stages of development, i.e., when the plant is changing from the vegetative to the reproductive stage (seed formation) and the during the seed-filling stage.  The method of fertilizer application will vary from preplant broadcasting of all the fertilizer, to side dressing up until equipment can no longer penetrate the plant canopy without causing excessive damage, to fertigation in irrigated areas (application of fertilizer through the irrigation system).

Notes: Residue: Incorporation of crop residues, which will add organic matter to the soil, will improve a whole host of soil characteristics: structure, water infiltration, water holding capacity, and soil fertility.  Organic matter, if incorporated regularly and as deeply as possible, will develop soil tilth that will allow development of a deep root system by the crop.  The carbon:nitrogen (C:N) ratio of crops varies considerably, and therefore must be carefully considered when planning fertilizer applications.  For example, representative C:N ratios are: microorganisms, 8:1; alfalfa 13:1; rotted manure, 20:1; green rye, 36:1; corn stalks, 60:1; oat straw and timothy, 80:1; rye straw, 350:1. [Ref: Hanson, A.A.  1990. p. 75.  Practical Handbook of Agricultural Science, CRC Press, Inc.]  For individual crops, the values may vary considerably around these representative values.  However, the crop can have significant affect on N fertility of the soil, especially if large amounts of a particularly high C:N-residue crop is added.  The C:N ratios of soils in a given climatic region remain relatively constant (10:1 to 12:1) and the microflora population is relatively low.  With the addition of organic matter, the population of the decay organisms will increase dramatically, but the nitrate N in the soil essentially disappears because of the microbial demand.  This condition remains until the activity of the decay organisms subsides.  To overcome this nitrate deficit, N must be added to allow proper crop growth. [Ref.  Brady, N.C.  1990.  p. 291-295; 497-514; 535.  The Nature and Properties of Soils.  10th ed.  Macmillan.].  If the other major elements, P and K, are in good supply in the soil, additional amounts need not be added since the soil and the organic matter will release sufficient amounts to supply the crop's needs.  Addition of these elements should be based on a soil test.  Crop rotation practices: Different crops remove differing amounts of nutrients from the soil.  Alfalfa, corn silage, and some other crops may remove as much as 250 to 300 kg N/ha, whereas wheat and other small grains or cotton remove about 100 kg N/ha.  Removal of P and K can also be significant in high-yield agriculture.  Since P levels are quite low compared to N (1/10 to 1/4) or K (1/20) in the soil, both nutrients must be replaced by use of commercial and organic fertilizers.  Both alfalfa and silage remove large amounts of K from the soils; small grains remove lesser amounts.  Potatoes are large users of P.  Residues added to the soil can supplement the needs of crops grown, but under most conditions are unable to meet their entire needs.  The major value of rotations comes from increasing the tilth of the soil, via increased organic matter, greater water infiltration rates, greater water holding capacity, and reduced runoff.  Leguminous crops, nitrogen fixers, fix significant amounts of N that eliminate the need for additional N on them and reduce significantly the amount of N required for the following crop.  Long-term organic carbon trends in soil show a decline without addition of lime (where soils are acidic) and N, P, and K.  Rotations such as corn-oats-clover plus manure, lime, and NPK will reduce organic C somewhat (3.3% in 1903 to 3.15% in 1973, Morrow Plots).  Continuous corn production and the failure to rotate or add organic matter will result in large decreases in organic C and much lower crop production. [Ref.  Brady, N.C.  1990.  p. 298-300, 337; 497-514.  The Nature and Properties of Soils.  10th ed.  Macmillan.].  Sanitation practices: Sanitation practices, used to reduce disease incidence in following crops, require crop rotations as discussed in the previous section.  Therefore, the fertility considerations and strategies would be the same.  Tillage systems: The basic fertility of the soil, as it relates to crop production, is essentially the same regardless of the tillage system used: the soil must have sufficient levels of each nutrient to meet the needs of the crop being grown.  If the nutrients are not naturally present in the soil, they must be added through returning residues to the soil, addition of manures, and application of commercial fertilizers in sufficient quantities and of the proper type to meet the crop's needs.  However, there is evidence that continuous cropping, such as corn, yields better under a no-till system that under the traditional clean-till system, which includes plowing, disking, etc.   For a corn-soybean rotation this advantage also holds.  If hay is added to the rotation, there is not difference in yields between clean-till and no-till. Soil type can cause variability in this response. [Ref: Hanson, A.A.  1990. p. 223-225.  Practical Handbook of Agricultural Science, CRC Press, Inc.]   Fertilizer strategies and planning must include soil testing and meeting the needs of each crop.

SOIL TESTING AND PLANT TISSUE ANALYSIS

[Soil Sampling and Soil Test Interpretation]

18. Recognize how the following affect soil sampling methods

a. methods of previous fertilizer application: Unless fertilizer was applied uniformly over a field, the previous pattern must be considered when taking soil samples.  Broadcast application will provide relatively uniform distribution and will thus not affect soil samples.  Banding, however, may result in high amounts of the element within the row and low amounts between the row, thus sampling should include taking a cross-section from the middle of one row to the middle of the next row, being sure to include a sample from within the row itself.

b. nutrient stratification: Usually sampling from the plow layer is sufficient, but in situations where stratification has occurred, or is present, and a deep-rooted perennial crop is to be grown, the sample would better represent the field if it was taken from the layer just below the plow layer.  However, if there is sufficient fertilizer in the plow layer, this will not become an important factor.

c. within-field soil and crop variability: If a field is such that there are distinct areas that differ in soil type and they are large enough to be considered separately, then sampling should be done within each soil type.  Fertilizer should also be applied within each soil type.  If, however, separate soil type areas are not large, but there are a number of soil types across the field, as may occur in river bottoms, the sample should be taken with care so that it represents the field and not one soil type over another.  In sampling soils, the most important factor is to ensure that the sample represents the entire field.

d. nutrient tested: Different nutrients have different characteristics which must be taken into account when sampling soils.  Some nutrients are more mobile in the soil and would require deeper samples, while other nutrients will vary in amount and form due to soil temperatures and the amount of moisture in the soil, requiring timely sampling.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 322-344.   Prentice Hall Inc.,

e. predictive vs. diagnostic sampling: Predictive sampling evaluates the effectiveness of the fertilizer program for the current year, and the analytical data are used to adjust the program for the following year. Diagnostic sampling is used if a nutritional problem is suspected. Diagnostic samples detect symptomless detrimental conditions in the tree or confirms the nature of visible symptoms.

Internet Link: http://ces.soil.ncsu.edu/soilscience/publications/soilfacts/AG-439-30/ Further study material from the North Carolina Extension Service

19. Describe how to use soil analysis for

a. problem solving/diagnosis

Crop yields are determined by a variety of factors including crop variety selection, available moisture, soil fertility, crop adaptation to the area, and the presence of diseases, insects, and weeds. Soil analysis and its interpretation deal only with the fertility level (plant nutrients) of the soil. Recommended fertilizer will provide sufficient nutrients for the best possible yields. Other factors of production or management may still cause low yields, even though nutrients are adequate.

As nutrients are removed by one crop and not replaced for subsequent crop production, yields will decrease accordingly. Accurate accounting of nutrient removal and replacement, crop production statistics, and soil analysis results will help the producer manage fertilizer applications.  A soil analysis is used to determine the level of nutrients found in a soil sample. As such, it can only be as accurate as the sample taken in a particular field. The results of a soil analysis provide the agricultural producer with an estimate of the amount of fertilizer nutrients needed to supplement those in the soil. Applying the appropriate type and amount of needed fertilizer will give the agricultural a more reasonable chance to obtain the desired crop yield.  The essential question in fertilization is, "How much nutrient must be added to the soil as fertilizer for a given amount to be taken up by the growing plant?" The crop utilizes only a portion of the available nutrients in the soil. This means that more nutrients must be present than are removed by the crop. The amount added varies according to the level already present in the soil and the crop's need for the nutrient involved. The soil analysis is the starting point, since it measures the level or content presently in the soil.

Internet Link: http://www.cahe.nmsu.edu:16080/pubs/_a/a-137.html

b. nutrient program monitoring

Annual soil nutrient monitoring programs should help soil nutrient levels meet crop production requirement levels. The soil analysis reports should contain two parts: characterization and fertility status of the soil, and fertility recommendations. Soil characterization (pH, texture, percent exchangeable sodium, percent organic matter, and salinity expressed as electrical conductivity) is explained in the report. The fertility status is reported as nutrients available to the plant. The second part, fertility recommendation, contains the suggested amounts of fertilizer to apply. These amounts are based on the crop requirements, management practices affecting the crop (as shown in the information sheet), the present fertility level of the soil, and the yield goal desired by the producer. Special notification is given if the tests indicate that a salt or sodium hazard exists or if the information provided shows any other specific problems.

c. in-season nutrient management

In-season nutrient management should focus on plant testing rather than soil testing.  Late spring site-specific assessments of plant available N before the crop begins rapid uptake of N. The LSNT can help determine the N needs of corn in-season, especially on manured fields. This allows adjustment of N applications at sidedress time. Sample the top 12 inches of soil when the corn is between six and twelve inches tall. 

An example of in-season nutrient management for corn follows.  If conventional soil injection equipment can be used, the preferred N applications are either injected anhydrous ammonia or urea-ammonium nitrate (UAN). If not, dribble UAN solution between corn rows or broadcast urea fertilizer. Broadcasting a UAN solution should be avoided because it can burn corn foliage, especially on large corn. If injection or conventional broadcast application is not possible due to the height of the corn or soil moisture, then UAN could be applied using high-clearance equipment with drop nozzles. Urea can also be aerial applied.

d. pre-season nutrient planning

Pre-season nutrient planning requires that planned soil nutrient levels meet crop production requirements.  Note that yields are only partial in relation to a large amount of fertilizer applied, many of the nutrients are carried over for use by the next crop. It is this carryover, or residual effect, from one year to the next that makes heavy fertilizer applications practical in the face of other limits to yield.  A certain fertilizer application cannot be expected to produce a specific yield such as two bales of cotton or nine tons of hay. It is more realistic to assume that a balanced fertilizer program assures that nutrients are not the limiting factor in yields obtained. Research has shown that producers who use a balanced fertilizer program obtain consistently better yields than those who don't.

20. Indicate how the following may cause variability in soil test results

a. time of sampling: The ideal time to take a soil sample is just before seeding or even when the crop is growing.  There are, however, problems with taking samples at these time.  They are related to constraints on taking the sample, obtaining the soil test results, and supplying the need amendments.  Therefore, samples are generally taken any time permitted by conditions of the soil.  Under more arid conditions where NO<->3</-> content of the soil is used to assess the N status, sampling in the fall should be delayed until after the soil temperature drops below 5oC.  Ref.  Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 331.  Prentice Hall Inc.  

b. depth of sampling: Soil samples are generally taken to the depth of tillage (6 to 12 inches) for cultivated crops, since tillage generally mixes previous fertilizer and lime additions to that depth.  In pastures and lawns, a sample of the upper 2 inches is sufficient.  In no-till or minimum till operations, two samples should be taken-one from the surface 2 inches and the second from the 2- to 8-inch layer.  This is so since stratification of nutrients prevails in these types of systems.  To determine residual N, samples should be taken down to a 36-inch depth.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 329-331.  Prentice Hall Inc.

c. type of extraction method used: The extraction method used should somewhat approximate the conditions in which the plant removes the nutrient from the soil.  For example, P extractions are accomplished with NH<->4</->F/HCl (Bray-P) where soils are acidic, but where soils are basic the ammonium bicarbonate method (NH<->4</->HCO<->3</-> or Olsen-P) is used.  A method that does not approximate the environmental conditions under which the crop is grown will provide considerably different results. Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 331.  Prentice Hall Inc.

d. number of acres per sample: A soil test must be representative of the area being sampled.  Therefore, sufficient samples must be taken and averaged to provide a reasonable estimate of the field.  The size of the sampling area may vary from 10 to 40 acres, and sometimes more.  A 10-acre field from which a composite sample of about 1 pound has been taken represents, in the plow layer, approximately 20 million pounds of soil.  If the field is 40 acres, that one pound samples represents 80 million pounds of soil and so on.  This provides ample opportunity for sampling error to become very large.  Sampling error in a field is much greater than the error in laboratory analyses.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 322-324.  Prentice Hall Inc.

e. number of subsamples per sample: Since the composited 1-pound sample submitted to the soil testing laboratory represents such a large amount of soil, the more subsamples that can be combined in that sample the better it will represent the field to be fertilized.  Thus the soil cores should be taken from various representative areas of the field.  Therefore, it is recommended that the subsamples number from 15 to 40 per field for each composite sample.  Areas that differ in slope, appearance, drainage, soil type, or past treatment should be sampled separately.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 324-331.  Prentice Hall Inc.

21. Compare and contrast the following approaches for making fertilizer recommendations

a. sufficiency level: In this situation, the level of nutrients in and the pH of specific soils of a given area have been evaluated over a period of time.  These soil-test values have been correlated with crop growth and production.  Thus for a given soil type the nutrient level in the soil test can be compared with values that provided a specific response and the amount of fertilizer required for a given crop at a given production level can then be recommended. 

b. soil buildup and maintenance: A soil is evaluated for nutrient level to establish a base which is used for future evaluation.  To buildup the level of nutrients in the soil, the amount required to produce the crop plus an additional amount to increase the level in the soil is added.  Over a period of time the level in the soil will increase to a satisfactory level and thereafter maintenance fertilizer for the crop to be grown should be recommended.  Periodic soil testing, about every 3rd year, should be part of the management program.

c. base saturation: Base saturation (BS%) is defined as the percentage of the total CEC occupied by basic cations (Ca<+>2+</+>, Mg<+>2+</+>, K<+>+</+>, and Na<+>+</+>).  Generally the degree of base saturation of normal uncultivated soils is higher in arid regions than in humid regions.  In a humid region, soils formed from limestone or basic igneous rock it would have a higher BS% than soils formed acidic igneous rock or sandstone.  As BS% increases the availability of Ca<+>2+</+>, Mg<+>2+</+>, and K<+>+</+> to the crop increases.  Soils with 1:1 clays or large amounts of organic matter are able to supply nutrients to the plant at a much lower BS% than soils with high levels of 2:1 clays.  Of course BS% is correlated with soil pH-the higher the BS% the higher the pH, since the basic cations have replaced the hydrogen bonded to the soil particle.  In acidic soils, hydrogen predominates in acid soils.  In making fertilizer recommendations, the type of clay, the organic matter concentration, and the BS% should be considered.  The greater the base saturation, the smaller the amount of fertilizer required and thus recommended.  Using the BS% it is also possible to calculate the amount of limestone required by a soil. Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 22-25.  Prentice Hall Inc

22. Recognize how the following affect soil test interpretation

a. probability of crop response to added nutrients: If the soil test values are low and the probability of a significant response by the plant is thus high, the amount of fertilizer recommended for application will be high.  If, however, the soil test values are at the upper limit of the response range for a crop, or exceed it, the probability of a crop response to additional fertilizer is very low.  In this case, the recommendation would be for no fertilizer to be applied. 

b. reported nutrient sufficiency level: knowing the sufficiency level of the soil for nutrients for production of various crops allows the user to evaluate whether or not the test results show a large or a lesser nutrient requirement.  For example, a western grower receives a soil test report from the local laboratory.  The crop to be produced is potatoes.  The P level is reported as low, 6 ppm, a concentration which is considered to be low.  There is not sufficient P to produce the potato crop and at least 180 lbs/acre of P2O5 must be applied.  However, if on another field the P concentration is 18 ppm, only 60 lbs/acre of P2O5 is required.

c. results reported as ppm or lb/A: In interpreting a soil test report, one should recognize that numbers reported in ppm will be approximately 1/2 the size of numbers reported in lbs/acre if the basis for the report is the general figure of 2 million pounds of soil in the plow layer.  If the report is based on the top foot of soil, which will weight approximately 4 million pounds, then the ppm values will be about 1/4 of those for lbs/acre.

d. within-field variability: Ideally a soil test should represent as closely as possible the nutrient status of the field it represents.  Interpretation of soil tests from fields that are quite uniform can be more precise than tests from fields that have a great deal of variability.  Therefore, one should build into the interpretation the idea that some parts of the field will receive more fertilizer and some parts will receive less fertilizer than is required to meet the plant's nutrient needs.  Other parts of the field will receive the optimum amount of fertilizer.  To be more precise the field may be reduced in size or the parts that differ significantly should be evaluated with a second, or even a third, sample.

e. environmental risk: Interpreting the soil test results in terms of environmental risk will result in recommending and applying less fertilizer to a field than may otherwise be applied.  All soil test interpretations should consider environmental risk and then the recommendations should be made accordingly.

f. appropriateness of tests to region: With respect to appropriateness, at least three things should be considered when interpreting soil tests.  They are: (1) Is the region humid or subhumid?  If it is then pH and lime requirements should be considered in addition to nutrient needs.  (2) Is the region semiarid or arid?  If it is then pH and alkalinity and salinity should be considered in addition to nutrient levels.  (3) Soil phosphorus tests should be keyed to the area-Bray-P test for the humid or subhumid regions and Olson-P test for soils of the semiarid and arid regions.  To take a soil from a humid region and have it analyzed in a laboratory that routinely uses the Olson-P method will not provide the information required to make an appropriate phosphorus recommendation.  Likewise, to take a basic soil from the arid west and have it analyzed by a laboratory which routinely uses the Bray-P test will not provide appropriate information for making a phosphorus recommendation.  Ref. Havlin, J. L., et al.  1999.  Soil Fertility and Fertilizers - An Introduction to Nutrient Management, 6th ed., p. 331.  Prentice Hall Inc.

Note: Two factors should be recognized when soil testing is being used to determine the amount of fertilizer to add to a given field and crop: (1) yield responses are highly correlated with nutrient levels in the field and (2) if the nutrient level of the soil is high enough that the crop cannot realize a response (based on research), then addition of fertilizer is not an economical option.

[Plant Tissue Analysis]

23. Recognize how the following terms relate to plant nutrient level

a. critical value: the nutrient concentration in the plant below which a yield response to added nutrient occurs. Critical levels or ranges vary among plants and nutrients but occur somewhere in the transition between nutrient deficiency and sufficiency. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc. p9.

b. sufficiency range: the nutrient concentration range in which added nutrient will not increase yield but can increase nutrient concentration. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc. p9.

c. luxury consumption: nutrient absorption by the plant that does not influence yield. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc. p9.

d. toxicity level: when the concentration of essential or other elements is high enough to reduce plant growth and yield. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc. p9.

Internet Link: http://uog.edu/soil Further study material from the University of Guam

24. Recognize how the following affect plant tissue analysis results

a. crop species: nutrient concentrations differ for each crop, thus the concentration that shows a need for a specific nutrient in one crop would not necessarily indicate a need at the same concentration in another crop.  For example, K sufficiency range for cotton at the full bloom stage of development is 0.90-2.00%; for canola at the rosette to pod development stage K sufficiency range is 2.9-5.1%; potato at tuber development stage, 6-8% and when plants are 30 cm tall 4-11.5%; corn at initial silk, K sufficiency ranges from 1.7-3.0%; soybean, prior to pod set, K sufficiency is 1.7-2.5%; alfalfa, prior to flowering, K sufficiency is 2.0-3.5%. Sufficiency levels for other nutrients also show considerable variation among crops.  Subclass Dicotyledonae plants tend to contain more Ca, Mg., and B than do the Monocotyledonae.  However, the relationship is not absolute.  Ref: Mills, H. A. and J.B. Jones, Jr., Plant Analysis Handbook II, MicroMacro Publishing, Inc., p185-191, agronomic crops; p247-250, forage crops; p354-370, vegetable crops.

b. growth stage: the most critical growth stage for tissue testing is at bloom or from bloom to the early fruiting stage. There can be two peaks of nutrient demand. The first is during maximum vegetative growth and the second is during the reproductive stage. To determine the adequacy of the fertilization program, these are the optimum times for tissue testing; however, at the latest peak period, it is generally too late for corrective action. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p306.

Internet Link: http://www.agr.state.nc.us/agronomi/sampta.htm Further study material from the North Carolina Dept. of Agriculture

c. plant part sampled: the conductive tissue of the last leaf to mature is used for testing, while immature leaves at the top of the plant or more mature leaves on the lower part of the plant are avoided. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p306.

Internet Link: http://www.agr.state.nc.us/agronomi/sampta.htm Further study material from the North Carolina Dept. of Agriculture

d. crop stress level:  If plants are subjected to stress, other than nutrient stress, they tend to accumulate nutrients.  Thus if plants appear to be discolored or stunted the tissue is likely to test high in the various elements.  Only after the stress has be alleviated can meaningful tissue analyses be accomplished.

e. time of day sampled: The time of day can influence the nitrate level in plants.  Nitrate is usually higher in the morning than in the afternoon if the supply is limited.  Nitrate accumulates at night.  Therefore, tissue samples should not be taken in the early morning or late afternoon.  (Havlin et al., 1999.  Soil Fertility and Fertilizers, 6th ed. p. 306-309, Prentice Hall).

f. sample handling: for successful and reliable tissue analyses, the following procedures should be followed: Dusty or soil-covered leaves should be avoided when possible.  However, when leaves are dusty, wiping with a damp cloth may be sufficient to remove the contaminates.  It may, at times, be necessary to wash the leaves with a mild detergent and then rinse well in running water.  The washing procedure should not be prolonged.  Washing and rinsing should be done briskly.   If plant materials are to be mailed to a laboratory, or are to be stored a few days before analysis, they should be partially air dried prior to shipment or storage.  Fresh plant tissue should never be placed in polyethylene bags or tightly sealed containers.  Clean paper bags and envelopes are ideal plant tissue containers.  Ref: Jones, Jr., J.B., et al. 1971.  The proper way to take a plant sample for tissue analysis.  Crops and Soils 23(8):15-18, Amer. Soc. Agron.

g. method and timing of nutrient application: Nutrient applications to a crop should be made as close to plant uptake periods as possible. Certain exceptions may be considered appropriate as follows: 1) Use of natural organic sources of nutrients may be recommended to meet plant nitrogen needs, even if this results initially in over-application of phosphorus, provided the following fall and/or winter Application Guidelines are met. However, when the FIV is 150 or greater, management of phosphorus should be consistent with phosphorus site index requirements.  2) Rates of natural organic sources of nutrients for lengthy planting cycles, such as orchard or tree establishment may be recommended as a one time initial application, when periodic, seasonal, or surface application is not feasible. 3) Application of nutrients may vary depending on what type of crop is being grown and weather conditions; however, application timing should maximize plant utilization efficiency and minimize the potential for nutrient movement. 4) Best management practices should be used when necessary to minimize or control nutrient movement to sensitive areas or to surrounding water bodies.

Internet Link: http://muextension.missouri.edu/xplor/agguides/soils/g09131.htm Further study material from the University of Missouri

NUTRIENT SOURCES AND APPLICATION METHODS

25. Describe how the following serve as plant nutrient sources

a. organic matter: Fresh plant material contains all of the required nutrients.  As plant material is worked into the soil, or as animal manures are applied, mineralization occurs releasing CO<->2</-> and minerals.  The minerals are then available to the next crop.  Ref: Havlin, et. al., Soil Fertility and Fertilizers, 6th ed., 1999, Prentice Hall, Inc. p444.

b. irrigation water: High quality irrigation water is generally low in nutrient concentration, thus it is not a major source of nutrients for plant growth.  However, suspension liquid fertilizers may be added to the water as it is being applied to the crop.  This is an excellent means of providing fertilizer.  This method is usually most effective in sprinkler irrigation systems.  Advantages consist of reduced loss of N via denitrification, less N required for the same response and the N can be applied at the most critical time for required response.  Disadvantages include initial setup of injection pumps and metering devices and associated equipment.  Ref: Pair, C.M. (ed.)  Irrigation, Ch. XIV, The Irrigation Association, 1983.  Silver Springs, MD, p411-435.

c. commercial fertilizer: The major means whereby the fertility of a soil is enhanced.  Fertilizer may be broadcast over all the surface, applied in bands below and to the side of the crop row, or metered as a soluble solution through an irrigation system.  The nutrient applied should be in response to an evident need, usually as indicated by a soil test analysis, plant tissue analysis, or both of these analyses.  Ref: Havlin, et al., Soil Fertility and Fertilizers, 6th ed., 1999, Prentice Hall, Inc. (general reference).

d. soil minerals: Minerals contained in the parent material are significant in determining the fertility of a soil.  With the exception of N, the majority of the nutrients in a soil are inherited from its parent material.  Ref: Brady and Weil.  1996.  The Nature and Properties of Soils, 11th ed., Prentice Hall, pg. 25-42; Horrocks, R.D., and J.F. Vallentine.  1999.  Harvested Forages, Academic Press, p189-191.

e. animal manure/biosolids: Animal wastes can be a significant source of essential nutrients.  Mineralization of these nutrients make them available to subsequent crops.  Solid or liquid animal-manure handling systems may provide (lb/ton of raw waste): N 4 (beef cattle) to 44 (poultry) lb.; P<->2</->O<->5</->  4 (dairy cattle) to 64 (poultry) lb.; K<->2</->O  0.4 (swine) to 96 (poultry) lb.  Losses of N may be very high, depending on type of handling system and application method.  Ref: Havlin, et al., Soil Fertility, 6th ed., 1999, Prentice Hall, Inc., p397-402.

f. urban/industrial waste: These wastes are usually processed into materials called effluent and sludge.  Both materials may be considered as either valuable fertilizers or significant polluters of land, crops, and water.  Soils to which effluent are applied should be (1) internally well drained and of medium texture, pH of 6.5 to 8.2, and  (2) supporting a dense stand of trees, shrubs, or grasses.  Ground water must be monitored periodically for nitrate levels.  Sludge can be a significant source of N, phosphate, potash, Ca, Mg, and S.  However, metals such as Cd, Hg, Pb, etc. may be of a concentration high enough to exceed EPA standards.  Ref: Havlin, et al., Soil Fertility, 6th ed., 1999, Prentice Hall, Inc.,  p403-405.

Internet Link: http://www.fao.org/WAICENT/FAOINFO/AGRICULT/magazine/spot3.htm Further study material from the FAO

g. plant residue: These residues consist of varying amounts of the elements essential for plant growth.  The amount of each element depends on the residue-whether it is young actively growing plants, a legume or a nonlegume, mature plants, and whether or not residue represents old, weather-dried material.  As the residue is incorporated into the soil, microorganisms begin the process of utilizing the energy held in the material for their growth processes.  As they complete their life cycles, the nutrients are released and are then available for uptake by the crop being grown.

h. residual nutrients from fertilizers and manures:

Phosphorus and Potassium: Regardless of the fertilizer form, phosphorus and potassium will remain as residual forms in the soil unless plants take it up or if potassium is leached by rainfall in sandy soils. If phosphorus or potassium was applied but not used because of lower than expected yields, it usually remains in the top few inches of soil and the unused portion will be carried over as residual soil forms that are potentially available for future crops. A routine soil test is the best tool for determining the current levels of available phosphorus and potassium and to obtain fertilizer recommendations.

Nitrogen: The possibility of overwinter loss of residual nitrate makes estimation of carryover of nitrogen more difficult than for phosphorus or potassium. Except for the pre-sidedress nitrate test on corn, there is no good way to accurately estimate the amount of nitrogen available to the crop by a soil test. Therefore, accurate determination of the amount of nitrogen carryover is not possible. However, in estimating the amount of nitrogen carryover one needs to estimate the amount of residual nitrogen in the soil at the end of the growing season as well as take into account factors affecting overwinter nitrogen losses. Nitrogen carryover from the previous drought year will depend on several factors. Nitrogen carryover is likely where: 1) The crop received moderate to high amounts of nitrogen as fertilizer, or as legume or manure nitrogen credits, 2) Yields were lower than expected, 3) Soils have a silt loam or heavier-texture, 4) Overwinter precipitation amounts are near or below normal and temperatures are below normal. Nitrogen rates following a heavily fertilized but poor yielding forage crop can be reduced by 20-30% for the spring application if rainfall during the fall and winter is below normal or if the soil stays frozen during the winter. If rainfall and temperatures are normal or above, probably the best strategy will be to apply normal nitrogen rates in the spring.

i. airborne deposited material: Nitrogen polution deposition onto the water surface is the most direct pathway for airborne nutrients to affect crops. An indirect pathway involves deposition onto the land surface. Air pollution spreads across the landscape and is often overlooked as a major nonpoint source of pollution. Airborne nutrients and pesticides can be transported far from their area of origin.  The transport pathways followed by airborne nutrients and wind-blown sediment may also be affected by topographically-modified winds with subsequent implications for primary production (Danin & Ganor, 1997) and the development of aeolian landforms (Tiessen et al. 1991, Bullard & Nash, 1998).  In addition, investigations of airflow within and above valleys further our understanding of both the relationship between synoptic scale and local scale airflows (Dobosy, 1989, Whiteman & Doran, 1993) and of the sedimentological and climatological interactions between fluvial and aeolian systems. Understanding of where and why airborne nutrients and sediment are deposited is vital for determining vegetation growth areas and for distinguishing regions of sediment erosion and deposition (e.g. Tsoar, 1990).

j. shallow ground water: Nutrient concentrations in shallow (well depth of 30 meters or less) ground waters of relatively undeveloped areas were evaluated to determine background conditions relative to agricultural and urban land uses. Relative background concentration of nitrate is variable and depends in part on land use, rock type, and climate. Median nitrate concentration is significantly greater in ground water beneath rangeland than beneath forest land. Median nitrate concentration in ground water beneath rangeland in susceptible aquifers, which consist of coarse-textured deposits or fractured rock. Increased relative background concentration of nitrate in rangeland areas likely results from evaporative concentration of nominal nitrogen load associated with natural organic and inorganic sources in hydrogeologically susceptible settings.

26. Describe characteristics of slow and controlled release fertilizers

The base controlled release fertilizer charge provides a constant nutrient diet to crops even in cool, dark spring weather when fertigation is impossible. The grower can vary the controlled release fertilizer rate providing more for heavy feeders and less for salt sensitive plants and thus maintain a single water-soluble concentration for all crops. A wide range of fertilizers can be found to fit different crop types, growing systems and climactic zones. There are a number of criteria that one should consider when selecting a fertilizer program including: desired product longevity, N-P-K ratios, presence of micronutrients, economics. Some products are 100% coated and homogenous in nature, others are blends of controlled release fertilizers and other fertilizer technologies.

N still dominates controlled-release products because it is a highly-leachable nutrient, especially in sandy soils where rainfall is abundant.

The benefits of using Controlled Release Fertilizers (CRFs)include increased efficiency of applied N (equal or better production at a lower N rate), lower application frequency (fewer trips needed through the grove), a large number of resets to manage, or environmental advantages (especially on the central Florida ridge where nitrogen management BMPs are in place).

The downside of CRFs are that they traditionally cost more than water-soluble fertilizers. There also may be a lack of faith about their performance in the field. Managers used to applying dry fertilizer at least three times per year would probably ask "Can I really apply fertilizer only once a year to my sandy soil and provide all of the necessary nutrition required for maximum production?" Most growers would require proof that one annual application of CRF would actually work in their groves before using it on a large scale.

Internet Link: http://www.usgs.gov/tech-transfer/factsheets/94-066b.html

27. Describe when to use urease and nitrification inhibitors in a nitrogen fertilization program

Nitrification inhibitors are management tools available to producers that can enhance the stability of ammonium nitrogen fertilizers against loss. Benefits in terms of a yield increase from the use of a nitrogen stabilizer occur most often when the fertilizer is subject to loss conditions such as leaching or denitrification. In the absence of loss conditions, no yield benefit usually results from nitrification inhibitor use. An enhanced emphasis will be placed on the role of inhibitors in reducing leaching losses of nitrate because such products decrease the rate at which nitrates form in soil.

Urease (EC 3.5.1.5) is an enzyme that catalyzes the hydrolysis of urea into carbon dioxide and ammonia. The reaction occurs as follows: (NH2)2CO + H2O ? CO2 + 2NH3.  Urease is an enzyme that breaks the carbon-nitrogen bond of amides to form carbon dioxide, ammonia, and water. If urease is added to a mixture of urea and thiourea the activity of the enzyme is strongly diminished. Like urea thiourea is bound to the active centre of the enzyme. Thus the active site of the enzyme is temporarily blocked by the 'false substrate'. The inhibition is called competitive because urea and thiourea compete on equal terms for the binding site of urease. When surface application is the only placement option, urea-containing fertilizer (46-0-0 or 28-0-0) may be treated with a urease inhibitor prior to use in order to reduce ammonia volatilization losses. The urease inhibitor (AGROTAIN) will prevent the release of ammonia gas from the urea for a period of about two weeks (see product label for application rates and times of inhibition), giving an opportunity for the urea to be moved into the soil by rainfall over this period. Note that a soil test may underestimate amounts of plantavailable N when (1) nitrification inhibitors or urease inhibitors are applied with fertilizers, (2) more than 150 lb. N/acre are applied as anhydrous ammonia, and (3) more than 150 lb. N/acre are applied as injected manure.

Internet Link: http://www.agr.gov.sk.ca/docs/production/Nitrogenfactsheet.pdf

Internet Link: http://frec.cropsci.uiuc.edu/1991/report5/index.htm

28. Describe the physical form and analysis of each of the following nitrogen sources

Internet Link: http://www.inform.umd.edu/EdRes/Topic/AgrEnv/ndd/agronomy/NITROGEN_FERTILIZERS.html Nitrogen Fertilizers

a. anhydrous ammonia

Chemical formula: NH<->3</->

Physical state: Gaseous at atmospheric pressure; to prevent loss it is stored under pressure and/or cold temperatures (-28°F), keeping it in the liquid form for application; when released from a pressurized vessel, it expands rapidly, vaporizes, and produces a cloud of water vapor.

% of Nitrogen: 82%

Advantages/disadvantages: Cost per unit of N is often less than in other forms.  Some may be lost during application if the soil is hard, cloddy, and the slit behind the applicator does not close or fill.  Ref:  Ref: Havlin, et al., Soil Fertility, 6th ed., 1999, Prentice Hall, Inc., p140-145.

b. urea

Chemical formula: CO(NH<->2</->)<->2</->

Physical state: solid

% of Nitrogen: 45-46%

Advantages/disadvantages: Less tendency to stick and cake than NH<->4</->NO<->3</->, less sensitivity to fire and explosion, less corrosiveness to handling and application equipment. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p141,148.

c. ammonium nitrate

Chemical formula: NH<->4</->NO<->3</->

Physical state: solid

% of Nitrogen: 33-34%

Advantages/disadvantages: Widely used in cropping situations in which growing crops are topdressed.  N, NO<->3<+>-</+> and NH<->4<+>+</+> components of NH<->4</->NO<->3</-> are readily available to crops; Very hygroscopic, high risk of fire or even explosions unless precautions are taken, less effective for flooded rice than urea or NH<->4<+>+</+> fertilizers, more prone to leaching and denitrification. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., pg 147.

Internet Link: <HT{icon}{~HTTP~}{www.inform.umd.edu/EdRes/Topic/AgrEnv/ndd/agronomy/NITROGEN_FERTILIZER_AMMONIUM_NITRATE.html}>

d. urea/ammonium nitrate solution (UAN)

Chemical formula: CO(NH<->2</->)<->2</->, NH<->4</->NO<->3</->, and H<->2</->O

Physical state: liquid

% of Nitrogen: 28-32%

Advantages/disadvantages: Easy to handle and apply, applied more uniformly than solid N sources, pesticides can be applied simultaneously, safely transported in pipelines or railcars, low cost storage facilities can be used, applied through various types of irrigation systems, excellent source of N for use in formulation of fluid N, P, K, and S fertilizers, lower cost of production than most solid N sources. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p146.

e. ammonium sulfate

Chemical formula: (NH<->4</->)<->2</->SO<->4</->

Physical state: solid

% of Nitrogen: 21%

Advantages/disadvantages: Low hygroscopicity and chemical stability, good source of N and S, advantageous in high pH soils and for acid-requiring crops; undesirable to use in acidic soils already in need of liming, low N content, expensive to use as a N source. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p141,147.

Internet Link: <HT{icon}{~HTTP~}{www.inform.umd.edu/EdRes/Topic/AgrEnv/ndd/agronomy/NITROGEN_FERTILIZER_AMMONIUM_SULFATE.html}>

e. calcium nitrate

Chemical Formula: Ca(NO3)2 4H2O

Synonyms: Nitric acid, calcium (II) salt; calcium II nitrate, tetrahydrate (1:2:4); Calcium Nitrate, 4-Hydrate; Calcium Dinitrate

Physical state: White crystals

% of Nitrogen: 16%

Advantages/disadvantages: Contains all of its N in the nitrate form, which is highly susceptible to leaching and denitrification losses as soon as it is applied. It is used most extensively in the fruit and vegetable industry where a readily available source of nitrate N may be desirable. It is also used as a soluble source of calcium.

29. Describe the physical form and analysis of each of the following phosphorus sources

b. triple superphosphate: Chemical formula of main P compound: Ca(H<->2</->PO<->4</->)<->2</->.  Acronym is TSP or CSP, 44-53% P<->2</->O<->5</-> and 1-1.5% S, in the orthophosphate form, 97-100% of the P is in available form.

c. monoammonium phosphate: Chemical formula of main P compound:  NH<->4</->(H<->2</->PO<->4</->).   Acronym is MAP, 11-13% N, 48-62% P<->2</->O<->5</->, 0-2% S, in the orthophospate form, 100% of the P is in available form, .

d. diammonium phosphate: Chemical formula for the main P compound:  (NH<->4</->)<->2</->HPO<->4</->. Acronym is DAP, 18-21% N, 46-53% P<->2</->O<->5</->, 0-2% S, in the orthophosphate form, 100% of the P is in available form.

Internet Link: <HT{icon}{~HTTP~}{www.inform.umd.edu/EdRes/Topic/AgrEnv/ndd/agronomy/NITROGEN_FERTILIZER_DIAMMONIUM_PHOSPHATE.html}>

e. ammonium polyphosphate: Chemical formulas for the main P compound is (NH<->4</->)<->3</->HP<->2</->O<->7</-> + NH<->4</->H<->2</->PO<->4</-> + others.   Acronym is APP, 10-15% N, 35-62% P<->2</->O<->5</->, no S, mixed ortho- and polyphosphates, 100% of the P is in the available form.  Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p181-187.

[normal superphosphate: Chemical formula: Ca(H<->2</->O<->4</->)<->2</-> (Ca(H<->2</->O<->4</->)<->2</->).  Usually called single superphosphate (SSP), analysis is 16-22% phosphate,  11-12% S, in the orthophosphate form, 97-100% of the P is in available form.]

30. Describe the physical form and analysis of each of the following potassium sources

a. potassium chloride

Chemical formula: KCl

Physical state: solid- pink or red to brown or white

% Potassium: 50-52% (60-63% K<->2</->O)

Advantages/disadvantages: Readily dissolves in the soil water, used for direct application to the soil and for the manufacture of N-P-K fertilizers. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p214-15.

b. potassium sulfate

Chemical formula: K<->2</->SO<->4</->

Physical state: white solid material

% Potassium: 42-44% (50-53% K<->2</->O and 17% S)

Advantages/disadvantages: Greatest use on potatoes and tobacco, Same as KCl but supplies S. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p215.

c. potassium nitrate

Chemical formula: KNO<->3</->

Physical state: solid

% Potassium: 37% (44% K<->2</->O and 13% N)

Advantages/disadvantages: Excellent source of fertilizers N and K; Mainly used on fruit trees, cotton, and vegetables; higher production costs. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p215.

31. Describe the physical form and analysis of each of the following calcium and/or magnesium sources

a. calcitic lime:

Chemical formula: CaCO<->3</->

Physical state: solid

% Ca or Mg: 25% Ca, no Mg.

Advantages/disadvantages: Neutralize soil acidity, has no Mg, Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p240.

b. dolomitic lime:

Chemical formula: CaMg(CO<->3</->)<->2</->

Physical state: solid

% Ca or Mg: 17.2% Ca 20.9% Mg.

Advantages/disadvantages: Neutralizes soil acidity, contains Mg.  Dolomitic limestone has a neutralizing value of 10%% compared with 100% for pure limestone.  Not always available in a local area. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc.

c. gypsum

Chemical Formula: CaSO<->4</-> * 2H<->2</->O

Physical state: solid

% Ca or Mg:

Advantages/disadvantages: Little effect on soil pH, value for crops that demand acidic soil yet need considerable Ca, For direct application; Difficulties may be encountered in application (dustiness, clogging). Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p236, 240.

d. Potassium-magnesium sulfate

Chemical formula: K<->2</->SO<->4</->. 2MgSO<->4</->

Physical state: solid

% K is 18% (22% K<->2</->O); % Mg is 11%

Advantages/disadvantages: Supplies both K and Mg; frequently included in mixed fertilizers which are to be applied to soils requiring both K and Mg.

32. Convert fertilizer analysis of P and K from elemental to oxide form and vice versa

To convert from the oxide to the elemental form, or vice versa, the molecular weight (mw) of each element is required.

Oxide to elemental P: The amount of elemental P in phosphate (P<->2</->O<->5</->) is calculated as follows: mw of P is 30.9, O is 16; total weight of the phosphate is 30.9 x2 = 61.8 plus 16 x 5 = 80,or 141.8; %P is therefore 61.8/141.8 x 100 = 43.6%, or rounded to 44%.

Elemental P to oxide form: Situation: You want to add 50 lb P/acre.  How much 20-20-20 would be needed to add 50 lbs of P?

      -- follow the above calculations to determine that phosphate contains approximately 44% P.

      -- divide the % P in the fertilizer, in this case 20%, by 0.44 to obtain %P in the fertilizer, e.g. 20%/0.44 = 8.8% P

      -- ask yourself the question, "How much 20-20-20 (NPK) must be applied to add 50 lb P/acre?"  Translate this into a simple percentage problem.  "What multiplied by 0.088 will equal 50?"  Translate this into equation form: 0.088X=50, where X is the unknown amount of phosphate to be added.

      -- divide both sides of the equation by 0.088, e.g.,

            (0.088/0.088)X = 50/0.088

            (1)X=50/0.088

            One times X = X, thus

            X = 50/0.088 = 568 lb P<->2</->O<->5</->

      --  answer: 568 lb P<->2</->O<->5</-> must be applied to add 50 lb P/acre.

General Information: To convert %P<->2</->O<->5</-> to %P, multiply by 0.44 (the % P in P<->2</->O<->5</->; to convert %K<->2</->O to %K, multiply by 0.83 (the %K in K<->2</->O).  Thus 0-45-60 (NPK) would be 0-19.8-49.8 in the elemental form.  The molecular weight of K is 39.

33. Define the following commercial fertilizer terms

a. total availability:  In a commercial fertilizer, total availability is that amount that has been determined to available for uptake by the plant.  For nitrogen it refers to total Kjeldahl nitrogen (TKN); for P it is the amount that is extractable by dilute citric acid; and for K it is the amount that is water soluble. 

b. water solubility:  This refers to the amount of the element in the commercial fertilizer that is soluble in water.  It refers to the amount of potassium soluble in water.

c. guaranteed analysis:  This is the minimum amount of a given element or nutrient that is guaranteed to be in the fertilizer being sold.  For example, a label of 33-0-0 indicates that a fertilizer of this analysis is guaranteed to contain 33% elemental N.  In a 0-10-10, the minimum guaranteed P present is 10% P<->2</->O<->5</-> and K is 10% as K<->2</->O.  Other plant nutrients when mentioned in any form or manner must also be guaranteed as to the amount present.  These guarantees are made on the elemental basis.

34. Define the following terms

a. a. organic N: This is a portion of the N measured via total Kjeldahl nitrogen (TKN) that comes from the manure or biosolids.  Organic N is contained in proteins and other complex molecules in the biomass.  Much of it is present as amine group (-NH2) in amino acids and amino sugars.  The remaining organic N is tied to carbon in ring or chain structures.  The N in these cases is held by covalent bonds to carbon and hydrogen (Troeh and Thompson, 1993, Soils and Soil Fertility, p. 195-197.  Oxford University Press).  The proportion of the total N in these various sources is: bound amino acids, 20 to 40%; amino sugars, 5 to 10%; and purine and pyrimidine derivatives, 1% or less (Havlin et al., 1999.  Soil Fertility and Fertilizers, 6th ed. p. 107, Prentice Hall).

b. b. inorganic N: This is the nitrogen found in the soil in the nitrate form and to a lesser extent the ammonia form.  The latter is readily converted to the nitrate from under temperature conditions required for plant growth.

c. c. organic P: Approximately 50% of the P in the soil is in the organic form, i.e., P is conjunction with C-based compounds.  The range is typically from 15 to 80% in most soils.  Many of the organic P compounds have not been characterized.  Esters of orthophosphoric acid (H2PO4-) make up most of the organic P compounds.   The major organic P compounds identified thus far are: inositol phosphates, 10-50%; phospholipids, 1-5%; nucleic acids, 0.2-2.5% (Ref. Havlin et al., 1999.  Soil Fertility and Fertilizers, 6th ed. p. 160-166, Prentice Hall).

d. d. inorganic P:  That P not found in organic compounds in the soil.  As organic P mineralizes to inorganic P or as P is added as inorganic P as commercial fertilizers, it is absorbed to mineral surfaces of the soil or precipitated as secondary P compounds.  The most common inorganic-P compounds found in acidic soil are Al- and Fe-P minerals, while Ca-P minerals predominate in neutral or calcareous soils (Ref. Havlin et al., 1999.  Soil Fertility and Fertilizers, 6th ed. p. 166-173, Prentice Hall). 

35. Describe uses of Total Kjeldahl Nitrogen (TKN) and combustion N tests

The accuracy of combustion N analysis (CNA), compared to Kjeldahl, showed that CNA consistently converts about 1.5 %, and up to 2% more nitrogen than Kjeldahl. This translates into 0.15 - 0.25 % higher than Kjeldahl in wheat, 0.35 - 0.45% higher in canola seed (about 20% protein), and 0.50 - 0.70% higher in soybeans (about 40 % protein). This increase in protein content should be regarded as a true increase in the protein result, rather than an apparent increase. CNA analyzers do not generate nitrogen or protein - they are simply more efficient at recovery of the nitrogen than other methods.

The principle of combustion N test is to burn the sample at high temperature, and convert all of the nitrogen from the form in which it occurs in the sample to elemental nitrogen, subsequently measured by a thermal conductivity cell.

The Kjeldahl method does not detect small amount of extra nitrogen, which amounts to about 2% of the total, because despite every effort to maximize the efficiency of the Kjeldahl procedure, there are more than 20 factors which can affect the recovery of nitrogen by Kjeldahl and its conversion to ammonia, and the CNA method is more effective in converting nitrogen present in proteins, peptides and amino acids to elemental nitrogen, rather than to ammonia.

36. Use fertilizer analysis information and soil test information to calculate fertilizer application rates

As an example, given that the fertilizer is (NH<->4</->)2SO<->4</-> and it is desired to add 100 lb N/acre.  The amount to be added is calculated as follows:

Step 1   Calculation of N is in the elemental form

      -- mw of elements: N=14, H=1, S=32, and O=16.

      -- mw of (NH<->4</->)2SO<->4</-> is: (2x14) + (4x1) + 32 + (4x16) = 128

      -- %N in NH<->4</->SO<->4</-> is: 14/114 X 100 = 21.9%

Step 2 Calculation of the amount of (NH<->4</->)2SO<->4</-> must be added to apply 100 lb N/acre?

      -- divide the amount of elemental N to be applied per acre 100/0.219 = 457 lb of NH<->4</->SO<->4</-> must be added to achieve an addition of 100 lb N/ac.

37. Use manure analysis information and soil test information to calculate manure application rates

In this example P and K are in the oxide form.  Given that the manure was cattle manure without bedding and the analysis was   4-4-10 (%N-P-K), the soil analysis was 10-10-60 (lb/acre of N-P-K), and it is desired to have 250-120-270 (lb/acre of N-P-K), the calculations would be as follows. 

      -     amount of each element in a ton of manure:

            0.04 x 2000 lb/ton = 80 lb of N

            0.04 x 2000 lb/ton = 80 lb of P<->2</->O<->5</->

            0.10x 2000 lb/ton = 200 lb of K<->2</->O

                  This means that if a ton of manure was spread over an acre 80 lb of N, 80 lb of P, and 200 lb of K would be applied.

      -     the desired amount was 250-120-270, thus 190 more pounds of  N, 40 pounds of P, and 70 pounds of K per acre would be needed.

      -     using a nitrogen-based recommendation, 3.12 t/ac of manure would need be to meet the projected N demand of 250 lb/ac (250 lb/ac divided by 80 lb/ton provided by the manure equals 3.12 t/ac)

      -     this would add 250 lb/ac of P (oxide form) and 624 lb/ac of K (oxide form).  Since P and K are fixed in the soil, they will not be lost so the excess application is not a problem.

      (Ref. Havlin et. al., 1999.  Soil Fertility and Fertilizers, 6th ed., p. 397-402)

38. Describe how the following affect nutrient availability from manure

a. physical form

Some primary nutrients, such as N and P, may not be completely available for plant growth the first year manure is applied. A portion of some nutrients present in manure are in an organic form and unavailable for immediate plant uptake. Organic forms require transformation to an inorganic form to be available for plant uptake. This transformation is dependent on temperature, moisture, chemical environment, and time.

b. animal source

Manure nutrients depend on the type of animal and the plant consumed.  The following types of livestock produce the resulting manure and nutrient composition.  The data is based on lbs/day/1000-lb animal unit and should be used only as estimates.

Beef produce 59.1 Total manure,  0.31 Nitrogen, 0.11 Phosphorus

Dairy 80.0 Total manure,  0.45 Nitrogen, 0.07 Phosphorus

Hogs and pigs 63.1 Total manure,  0.42 Nitrogen, 0.16 Phosphorus

Chickens (layers) 60.5 Total manure,  0.83 Nitrogen, 0.31 Phosphorus

Chickens (broilers) 80.0 Total manure,  1.10 Nitrogen, 0.34 Phosphorus

Turkeys 43.6 Total manure,  0.74 Nitrogen, 0.28 Phosphorus

Source: USDA Natural Resources Conservation Service. Agricultural Waste Management Handbook (1992)

c. moisture content

Nutrients are stored attached to solid particle mass of the waste.  Nutrients are not attached to water therefore the less moisture content the more dense the nutrients.  The more water the less the total volume of nutrients per weight. 

In liquid and semi-solid forms, settled solids can contain over 90 percent of the phosphorus (P), so complete agitation is needed to accurately sample the entire storage if all the manure in the storage structure is going to be applied. If, however, solids will purposely be left on the bottom of the storage structure when the manure is pumped out, as is sometimes the case with lagoons, then complete agitation during sampling may generate artificially high nutrient values. In this case agitation of the solids or sludge on the bottom of a lagoon is not needed for nutrient analysis. Liquid manure is best sampled during land application, for it is potentially more difficult and dangerous to sample from liquid storage facilities than dry manure systems.

Note that usually, nutrients are expressed as N, P2O5, or K2O on a wet or “as received” basis, but some labs may instead report data on an elemental (P instead of P2O5, K instead of K2O) or dry (without water) basis; so, be sure to confirm the units.

d. state/stage of decomposition

As was mentioned before, organic forms require transformation to an inorganic form to be available for plant uptake. This transformation requires decomposition of the organic form which is dependent on temperature, moisture, chemical environment, and time. 

e. incorporation

Although manure may be sprayed, spread, or injected, incorporation into the soil is either leached, plowed, or injected.  The advantages and disadvantages of each depend on the capacity of each to expedite the transformation of the organic form to an inorganic form.  Manure that is left on the surface to leach into the soil may take a longer time to decompose than plowed or injected manures.

Internet Link: http://www.extension.iastate.edu/Publications/PM1558.pdf

39. Describe advantages and limitations of the following fertilizer placement methods

a. injection: Injection of small portions of liquid fertilizer adjacent to every individual plant.

Advantages: 1. Doesn't significantly disturb plant 2. Fertilizer is readily accessible to plant root systems 3. Minimal disturbance of surface mulch. Disadvantages: 1. Higher equipment costs

b. surface broadcast: In this method, fertilizer is spread evenly over the entire field or area to be fertilized.

Advantages: 1. Most economical from of fertilizer application 2. Raises soil fertility level over a long period of time 3. Appropriate distribution of nutrients for close-growing plants. Disadvantages: 1. Requires more fertilizer application for optimal response 2. Volatilization losses of N fertilizer 3. Fertilizer is easily washed away with runoff during heavy rains 4. Fertilizer accessible to weeds as well as crops.

Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p647-49.

c. broadcast incorporated: The fertilizer is applied uniformly over the field before planting the crop and tilling or cultivating incorporates it.  It is not always possible to incorporate the fertilizer due to the type of crop and time.

d. band: Subsurface band is when fertilizer is applied below the surface between 2 to 8 inches or below the seed 1 to 2 inches. Surface band is when the fertilizer is applied or dribbled directly over the row or several inches to the side of the row.

Advantages: 1. Higher crop recovery of nutrient 2. More efficient than broadcast 3. Enhances early seedling vigor especially when applied at planting. Disadvantages: 1. If not incorporated, dry surface soil conditions can reduce nutrient uptake. 2. Specialized application equipment is required.

Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p371-2.

e. fertigation: When liquid fertilizers are applied through irrigation water

Advantages: 1. Reduced application costs 2. Inexpensive nitrogen carriers can be used. Disadvantages: 1. Ammonia loss by evaporation 2. Certain fertilizer compounds can clog irrigation systems with precipitates

Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p649.

f. foliar: Spraying a dilute nutrient solution directly unto the plant leaves

Advantages: 1. Applied simultaneously with pesticide sprays 2. Diluted NPK fertilizers, micronutrients, and small amounts of urea can be used as foliar sprays 3. Provides adequate amount of micronutrients. Disadvantages: 1. Amount of nutrients applied in a single application is limited 2. Only a small portion of macronutrients can be provided 3. Leaf injury or burn occurs at high application rates

Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p650-1.

g. sidedress: A procedure consisting of fertilizer application, usually N, to such crops as corn, sorghum, cotton, and other crops after planting, but before the canopy closes.

h. topdress: This consists of applying fertilizer, usually N, to small grains and pastures.  Both solid and liquid sources may be used.  Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p370-374.

i. seed placed: The fertilizer is applied directly with the seed at the time of planting, making it readily available.  In some cases the emergence of seedling is delayed and yields are reduced.

Internet Link: http://www.soils.wisc.edu/~barak/soilscience326/c&smag.htm Further study material from the University of Wisconsin

SOIL pH AND SOIL LIMING

40. Define:

a. soil pH: The negative logarithm of the hydrogen ion activity (concentration) of a soil. The degree of acidity (or alkalinity) of a soil as determined by means of a glass or other suitable electrode or indicator at a specified moisture content or soil-to-water ratio, and expressed in terms of the pH scale. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p851.

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/results.html#soilph Further study material from Cornell University

b. buffer pH: buffers or buffer systems can maintain the pH of a solution within a narrow range when small  amounts of acid or base are added. Buffering is defined as the ability to resist change in pH. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p40.

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/liming.html#buffer Further study material from Cornell University

c. acidity: Active acidity- the activity of hydrogen ions in the aqueous phase of a soil. It is measured and expressed as a pH value. Soil acidity- a soil with a pH value less than 7.0. The term acidity is usually applied to surface layer or root zone, but may be used to characterize any horizon. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p827.

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/liming.html#buffer Further study material from Cornell University

d. alkalinity: (basic) a soil that has a pH greater than 7.0. The term alkaline or basic is usually applied to the surface layer or root zone but may be used to characterize any horizon or a sample thereof. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p828.

41. Describe the long term change in soil pH from applying N

Nitrogen fertilizers, because they can form nitric acid in the soil, will under the proper conditions cause the soil to become more acidic.  This may occur if large quantities of N are applied each year to grass pastures in humid areas.  (Ref.  Adams and Pearson, 1967.  Agron. Monogr. 12:161-206.  Amer. Soc. Agron, Madison, WI.; Brady, 1990 The Nature and Properties of Soils, 10th ed., p. 484-485, Macmillan.)

42. Describe how CEC, soil texture, and soil organic mater affects lime requirements

CEC, texture, and organic matter are closely related in determining the amount of lime required to change the pH of the soil from an undesirable level to a desirable level.  Finer textured soils have a greater CEC and they usually contain greater amounts of organic matter. The buffering capacity of these fine-textured soils is thus greater and each of these factors leads to a greater amount of lime required to raise the pH to the desired level.  For example, a sand may only require about 2 ton/acre of lime to raise the pH from 5.5 to 6.5, whereas a clay soil, which has a greater CEC, higher organic matter content, and thus a greater buffering capacity, will require about 9 tone/acre of lime to increase the pH of the soil from 5.5 to 6.5.  (Ref.  Brady and Weil. 2000.  Elements of the Nature of Properties of Soil, Prentice Hall, p. 269-271.)

43. Describe how soil pH affects the availability of each nutrient

Carbon: No affect since carbon comes from the atmosphere in the form carbon dioxide.

Hydrogen: No affect since hydrogen comes from the splitting of water in the photosynthesis process.

Oxygen: No affect since oxygen comes from the two components of photosynthesis; carbon dioxide and water.

Nitrogen: Soil acidity can restrict the survival and growth of Rhizobia in soil and severely affect nodulation and N fixation processes. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p98.

Phosphorus: Maximum availability is between soil pH of 5.5-6.8. A pH above or below this range causes P to form insoluble precipitates. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p62.

Potassium: In highly acid soils, toxic amount of exchangeable Al<+>+</+> and Mn<+>+</+> creates an unfavorable environment for the root uptake of K<+>+</+>.   Al<+>+</+> and aluminum hydroxide are converted to insoluble Al(OH)<->3</->.  This removes the Al<+>3+</+> from cation competition with K<+>+</+>, thus freeing the exchange sites so that K<+>+</+> can compete with Ca<+>+</+> for the sites.  Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p212.

Micronutrients: With the exception of Molybdenum (Mo), the availability of micronutrients increases with decreased pH. The addition of adequate lime reduces the solution concentration of many micronutrients, and soil pH values of 5.6-6.0 are usually sufficient to minimize toxicity while maintaining adequate availability of micronutrients. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p62-3.

Internet Link: http://www.cals.cornell.edu/dept/flori/growon/results.html#soilph Further study material from Cornell University

Internet Link: http://www.esf.edu/pubprog/brochure/soilph/soilph.htm Further study material from Cornell University

44. Describe how liming materials increase soil pH

All liming materials- whether oxide, hydroxide, or carbonate- react with carbon dioxide and water to yield the bicarbonate form when applied to an acidic soil. Liming materials react directly with acid soils replacing hydrogen and aluminum with calcium and magnesium on the colloidal complex. The hydrogen and aluminum ions are then able to be leached out of the soil. The adsorption of the calcium and magnesium ions raises the percentage base saturation of the colloidal complex, and the pH of the soil solution increases correspondingly. Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p367.

Internet Link: http://www.ipm.iastate.edu/ipm/hortnews/1994/4-6-1994/ph.html Further study material from Iowa State University

45. Describe how purity, fineness, and Calcium Carbonate Equivalent (CCE) affect neutralizing ability of liming materials

purity:  The more pure the liming material is the better the neutralizing ability is.  However there are exceptions due to the chemical composition.

fineness:  The finer the liming material, the more rapidly it will react with the soil.  For example, the oxide and hydroxide forms of lime appear in the market place as a powder, their fineness is sufficient.  However, limestone that is not finely ground reacts very slowly with the soil, thus taking longer to provide the desired crop response.  To obtain satisfactory results from the application of limestone, approximately 50% of the material should ground fine enough to pass a 60 mesh screen (smaller that 0.25 mm in diameter). (Ref.  Brady and Weil. 2000.  Elements of the Nature of Properties of Soil, Prentice Hall, p. 269-273.)

The calcium carbonate equivalent (ECCE) is a measure of the total neutralizing power of the material being applied to correct low soil pH.  It is the neutralizing power of all compounds expressed in terms of calcium carbonate.  Thus if the ECCE is provided for an amendment is higher than the conventional calcium carbonate potential for neutralizing acidity. The ECCE is technically a more accurate way stating the total neutralizing power, but if the limestones are of nearly equal purity the difference between expressing their content as elemental calcium or magnesium, or the oxides of these elements, and ECCE will be small.  (Ref. Brady, 1990.  The Nature and Property of Soils, 10th ed., p. 236-238.  Macmillan).

Note: The Calcium Carbonate Equivalent (CCE) is defined as the acid-neutralizing capacity of a liming material expressed as a weight percentage of CaCO<->3</->.

Consider the following reactions:

    CaCO<->3</-> + 2H<+>+</+> = Ca<+>2+</+> + H<->2</->O + CO<->2</->

    MgCO<->3</-> + 2H<+>+</+> = Mg<+>2+</+> +  H<->2</->O  + CO<->2</->

In each reaction 1 mole of CO<->3<+>2-</+> will neutralize 2 moles of H<+>+</+>. The molecular weight of CaCO<->3</-> is 100. Whereas that of MgCO<->3</-> is only 84. Thus, 84g of MgCO<->3</-> will neutralize the same amount of acid as 100g of CaCO<->3</->. Therefore, the neutralizing value, or CCE, of equal weights of the two materials is calculated by:

                84/100   =   100/X

Therefore, MgCO<->3</-> will neutralize 1.19 times as much acid as the same weight of CaCO<->3</->; hence its CCE is 119%. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p56-7.

Internet Link: http://hubcap.clemson.edu/~blpprt/bobweb/BOBWEB2.HTM Further study material from Clemson University

Internet Link: <HT{icon}{~HTTP~}{wtamu.edu/~crobinson/SoilFert/ECCE.html}> Further study material

46. Calculate lime application rates to meet liming requirements

Assume that you must provide a recommendation as to how much limestone should be applied for the production of a high-pH-requiring crop like asparagus to be grown in a loam soil that is currently quite acidic (pH 5.0). The cation exchange capacity (CEC) is about 10cmol<->c</->/kg, and you want to raise the pH to about 6.8. Assuming the pH-base saturation relationship is about the same as that shown in Fig. 9.8, the soil is now at 50% base saturation and will need to be brought to about 90% base saturation to reach the goal of pH= 6.8. How much of a dolomitic limestone with a CaCO<->3</-> equivalent of 90 will you need to apply to bring about the desired pH changes?

First, we need to know the cmol<->c</-> of Ca/kg soil needed to bring about the change. Since the CEC is 10 cmol<->c</->/kg and we need a 40% change in base saturation (from 50 to 90%) the Ca<+>2+</+> required is

     10 cmol<->c</->/kg x 40/100 = 4 cmol<->c</-> Ca/kg soil

Second, since each Ca++ has two charges, 4 cmol<->c</-> can be expressed in grams of Ca<+>2+</+> by multiplying by the molecular mass of Ca (40) and then divided by 2, the Ca<+>2+</+> charge, and by 100 since we are dealing with a centimol<->c</->.

 (4 cmol<->c</->/kg/2 gCa/ mol<->c</->) x (40/100 cmol<->c</->) x 1 mol<->c</-> = 0.8 gCa/kg soil

Third, we calculate the amount of CaCO<->3</-> needed to provide the 0.8 gCa<+>2+</+> by multiplying by the ratio of the molecular masses of CaCO<->3</-> and Ca.

          0.8 g/kg soil x 100(CaCO<->3</->)/40(Ca) = 2 g CaCO<->3</->/kg soil

Fourth, to express the 2 g CaCO<->3</->/kg soil in terms of the mass needed to change the pH of 1 ha 15 cm deep, we must multiply by 2 x 10<+>6</+> kg/ha.

     2 g CaCO<->3</->/kg  x  2  x  10<+>6</+> = 4 x 10<+>6</+> or 4 Mg CaCO<->3</->/ha

Fifth, since the CaCO<->3</-> equivalency of our limestone is only 90, some 100kg would be required to match 90 kg of pure CaCO<->3</->. Consequently, the amount of limestone needed would be adjusted upward by a factor of 100/90.

          4  x  100/90  =  4.4 Mg/ha or about 2 tons/acre

Ref: Brady, Nyle C & Weil, Ray R. The Nature and Properties of Soils, 1999, Prentice Hall Inc, p369.

Example 2:

Increasing pH from 5.7 to 6.5 requires adding 1.0 meq/100g soil. Thus, the quantity of pure CaCO<->3</-> needed to increase pH would be:

    (1.0 meq CaCO<->3</->/100 g soil)  x  (50 mg CaCO<->3</->/meq)  =  (50 mg CaCO<->3</->/100 g soil)

By calibrating pH changes in the buffered solution, the amount of lime required to increase pH to the desired level can be calculated. Ref: Havlin, John L., et. al. Soil Fertility and Fertilizers, Sixth Edition, 1999, Prentice Hall Inc., p51-2.

Internet Link: http://ianrwww.unl.edu/pubs/Soil/g714.htm Further study material from the University of Nebraska Cooperative Extension

47. Indicate how soil pH affects availability of heavy metals to plants

The availability of lead (Pb), copper (Cu), zinc (Zn), and cadmium (Cd) to plants increases as the soil pH increases from 3.0 to 7.0.   At the very low pH ranges absorption of these elements is less than 0.2 mmol/kg, but maintaining the soil near neutral, pH of 6.5 to 7.0, the absorption was 2 to 5 times greater.  (Ref.  Brady and Weil, 2002.  The Nature and Properties of Soils.  13th ed., p. 825-827.  Prentice Hall.)

48. Describe the effect of the following on soil pH

a.  elemental sulfur

Elemental sulfur (S) is often chosen to lower soil pH, but it must be used carefully. Elemental S has a high potential to burn plant tissue and can lower soil pH too much (pH greater than 4.0 is possible) if used improperly or at too high an application rate.  Sulfur is oxidized by soil bacteria, thereby forming sulfuric acid which is the substance that lowers soil pH. Each 10 pounds of elemental S generates enough acidity to neutralize 30 pounds of lime. Warm temperatures and good moisture and aeration are required for S oxidizing bacteria to function. Sulfur oxidation is minimal at soil temperatures less than 50 F.

Internet Link: http://virtual.clemson.edu/groups/turfornamental/Irrigation%20Water%20Quality/lowering_soilph_with_eleme.htm

b.  alum

Alum (aluminum sulfate) binds to phosphate, forming aluminum phosphate, which is less susceptible to losses in runoff.  Applied to soils (usually in poultry litter) greatly reduces phosphorus runoff from pastures.  Although alum’s short-term benefits are now well documented, its long-term effects are not. Research continues in this area.

Internet Link: http://www.ars.usda.gov/is/AR/archive/nov06/alum1106.htm

c.  ammonium sulfate (AMS)

Ammonium sulfate and sulfur-coated urea are two choices for acidifying soils. Most specialty fertilizers for "acid-loving" plants contain ammonium sulfate or sulfur-coated urea.

d.  gypsum

Gypsum does not change pH nor improve drainage in non-sodic situation.  Gypsum is used to add calcium to soils such as serpentine with very high or toxic Mg levels.  Gypsum is a fertilizer product and supplies the crop-available form of calcium (Ca2+) and sulfur (SO42-). If these forms are deficient in soil, then crop productivity will benefit if gypsum is applied. Research has not shown deficiency of Ca and normally any potential problem with low Ca levels is taken care of with application of limestone (CaCO3). Acidity problems will occur before a deficiency of Ca, so liming effectively takes care of Ca also. For calcareous soils (containing free lime) the soil system is saturated with Ca, and Ca supply and soil pH is controlled by the free lime.

Internet Link: http://www.ipm.iastate.edu/ipm/icm/node/1954/print

NUTRIENT MANAGEMENT PLANNING

49. Describe how to set a realistic yield goal by using

a.  production history:   Such a goal should include the following: soil-test history for each field; yield history for each field by crop; soil classification maps (if available) all soils on the farm; financial records for all phases of production (supplies, seed, fertilizer, weed and other pest control, equipment, labor, etc.); yield goals for each crop to be grown; matching crops best adapted to each field.  Such information will provide insights into the inherent production capacity of soils, crops that do best under the conditions of the area, a realistic basis for setting production goals (both long-term and short-term), and special challenges that may be faced.  For example, suppose one of the crops included is corn.  Records from the past 5 growing seasons in which corn was grown on the field show that grain yields ranged from 120 to 130 bushels per acre.  Soil maps indicate that the soil is a silt loam with the potential to produce 190 bushels per acre.  Soil tests indicate that the pH is 5.1 and that P and K levels are in the low to very low levels for corn production.  Past history indicates that corn rootworm is a problem, johnsongrass is a problem each year in about 1/5 of the field.  Other problem weeds can be controlled by using a preemergence herbicide.  A current soil test should be run, soil pH adjusted with application of limestone, sufficient phosphate and potash should be applied to supply a corn yield of 150 bu/ac.  Since P and K levels were so low, sufficient fertilizer should be applied to meet the crop's needs and provide a reserve that will begin increasing P and K levels in the soil.  For the first year it is not reasonable to assume that the 190-bushel potential can be reached.  Therefore, the yield goal should consist of incremental increases over a 5-growing season period.  Year 1: 135 bu/ac; Year 2: 145; Year 3: 150; Year 4: 160; Year 5: 175.  Each year assessment of performance should be made and the yield goals adjusted accordingly.  For each crop to be grown, a similar approach should be taken, assuring that special needs and challenges are met.

b. soil productivity: From the soil survey information and current and past soil tests it is evident that the productivity potential for any given crop is limited by soil type, depth, drainage, and slope.  Therefore, the yield goal should be in-line with that potential.  For example, if the soil survey indicates that the potential for grain sorghum production is 95 bu/ac, there is no reason to set a goal for 110 bu/ac.

c. management level: If a producer is not managing at a level to achieve top performance, then the yield goal should be set at an achievable level.  In a scenario as presented in 38a above, yield goals should be reduced to an achievable level 10%, 20%, 30%, etc., depending on the management level.  However, the goal should be set so that management can, over time, be improved.

d. most limiting nutrient:

Understanding the most limiting nutrient for our production crop helps build realistic yield goals.  For example, nitrogen is a very important nutrient required for plant growth and maximizing productivity in many cropping applications.  It is the most limiting nutrient for plant growth and requires application and management in many cropping systems, turf management, home gardens, lawns, and other non-legume plants.  It is important to have a proper nitrogen management plan in place to not only maximize production or to obtain a healthy lawn, but also to minimize environmental impact.  This builds realistic yield goals to help ensure a profitable and environmentally friendly nitrogen management plan.

50. Use crop nutrient requirement, crop rotation/sequence, and soil test information to determine crop nutrient needs

Given:

      -- The crop to be grown is corn.  The demand for nutrients depends on expected grain yield.  Thus if the requirement of NPK for each bushel is known we can determine the nutrient demand for any expected yield level.  In this example, only N, P, and K will be considered.  A further assumption is that no other nutrients will be deficient.

      -- The previous crop was soybeans.

      -- Expected yield is 200 bushels of corn grain per acre.

      -- N required: 1.35 lb/bu X 200 bu/ac = 270 lb/ac of elemental N

      -- P required: 0.6 lb/bu X 200 bu/ac = 120 lb/ac of elemental P

      -- K required: 1.35 lb/bu X 200 bu/ac = 270 lb/ac of elemental K

      -- The soil test resulted in the following: 75 lb/ac of N, 10 lb/ac of available P, and 100 lb/ac of available K.

With this situation, by difference, one would have to add 195 lb/ac of elemental N, 110 lb/ac of elemental P, and 20 lb/ac of K.  Since soil test information is reported in ppm, not lb/ac, one would have to convert ppm to lb/ac.

The previous crop will alter somewhat the amount of N fertilizer required.  If alfalfa has been grown for several years, for example nearly all of the N needs of a corn crop will be met in the first year.  In the second year in corn after alfalfa approximately 83% of the corn's N needs are met by residual N from the alfalfa. (Ref: Havlin, et. al., 1999.  Soil Fertility and Fertilizers, 6th ed., p. 100-105.)  The larger amount of N in the soil because of nitrogen fixation and breakdown of fine roots and nodules will be reflected in the soil test analysis.  If a soil is marginal for K, a crop like alfalfa will remove a significant amount of K over a 3 to 5 year period and the soil will become depleted during the time the alfalfa was grown in the field.  The soil test will also reflect the affect on soil K. 

51. Define P index

P Index is a runoff phosphorus loss risk assessment tool for cropland management planning. It is used to evaluate the potential for phosphorus in runoff from a specific field entering a nearby stream. The P Index currently has two types of uses 1) Nutrient management planning (for planning manure phosphorus applications according to state standards) and 2)

Water quality improvement planning (used to determing where the major sources of phosphorus (P) are on the landscape identifying possible problem areas.

52. Distinguish P-based from N-based manure application recommendations

P-based manure application recommendations refer to making recommendations based on the amount of P in the soil.  The maximum P in the soil may be 100 lb/acre (the value varies from state to state and with soil type), thus the soil is tested to determine the amount present.  Addition of manure or biosolids is then limited by the difference between the cap, the 100 lb/acre if that is the cap, and the amount in the soil.  This concept is driven by the fact that soils high is phosphorus that erodes with the soil into streams, lakes, and rivers results in pollution of those water bodies-eutrophication or a reduction of the oxygen dissolved in the water, a reduction or elimination, depending on the severity of the pollution, of fish species, and increased growth of algae and water plants.

N-based manure application recommendations refers to applying sufficient manure to meet the N requirements of the crop being grown.  Phosphorus and potassium requirements may or may not be met.

53. Describe when to use P-based recommendations for manure/biosolid application

A P-based nutrient recommendation plan should be used when danger of soil erosion is high, P levels in the soil are high, and large amounts of manure or biosolids are available to apply to the land.  The amount of P than may be applied is regulated by the state (see 47 above).

54. Given soil test recommendations and manure analysis, use manure and commercial fertilizer sources to construct a P-based and N-based nutrient application program 

Internet Link: <HT{icon}{~HTTP~}{www.extension.umn.edu/distribution/cropsystems/DC6514.html}>

Internet Link: <HT{icon}{~HTTP~}{www1.uwex.edu/ces/pubs/pdf/A2809.PDF}>

55. Define environmentally sensitive area

Some areas are subject to degradation much more rapidly than others.  These areas are said to be environmentally sensitive.  These area are subject to decline in quality or in the habitat due to activities of humans, other animals, or acts of nature-floods, landslides, fires, etc.  The habitat in some areas can absorb extensive activities, while other habitats decline dramatically in quality with very limited activity.  The existing flora and fauna enter in to causing an area to classified as environmentally sensitive.  The flora may be essential to maintaining the overall health and integrity of the area, e.g., stream riparian areas.

56. Describe the importance of the following components of an economically and environmentally sound nutrient management plan

a. maps of facilities, fields, and soils:  For a successful nutrient management plan, all facilities and fields involved in the operation should be pinpointed or located on a map of the farm or ranch.  This provides an overall view of the area being utilized.  The drainage patterns are evident and potential problems are more readily identified and serious problems can be avoided, i.e., drainage into ecologically sensitive areas, neighbor's fields, etc.  The maps, usually available from the National Resources and Conservation Service (NRCS), can aid in identifying suitable areas for land application of manures and areas that need protection or that may need special management due to environmental sensitivity. 

Internet Link: <HT{icon}{~HTTP~}{www.ces.uga.edu/pubcd/B1195.htm}>

[The NRCS Toolkit will provide excellent information and directions for completing a comprehensive nutrient management plan (CNMP).]

b. environmentally sensitive areas:  Those areas not suitable for cropping or pasturing should be identified and set aside to provide habitat for alternate species.  Plants and animals of these areas can provide diversity that indicates the health of the ecosystem.  A CNMP will environmental degradation of these areas.

c. cropping system:  A crop rotation plan is valuable because one is able to plan the optimum cropping sequence.  It makes sense to follow a high N-producing crop like alfalfa with corn, which requires large amount of N, or to follow soybeans with corn since the beans will supply a portion of the corn's N requirements.  If crops are being grown that are subject to a particular disease, planning a specific crop rotation sequence may reduce the disease incidence sufficiently to allow the crop to be economically grown.  The benefits of growing a crop like alfalfa to break up disease cycles and provide significant amounts of N to the following potato crop provide an example.  Crops on fields that have the potential put nutrients from runoff, erosion, and water movement through the soil, i.e., crops with high nutrient requirements, can be grown elsewhere on the farm because of the preparation of a map for CNMP.  Economic planning can occur in specifying a crop rotation to be followed and when put together correctly the costs of nutrients can be reduced significantly.

d. expected yields:  To determine expected yield provides the manager a goal to shoot at.  If not goal or expected yield is part of the plan it is difficult to know how much fertilizer to apply.  Expected yields compared with measured yields can, over time, provide an indication of how well the nutrient management plan is accomplishing the desired yield goals.  If one is having a difficult time in reaching expected goals, the impetus is provided to carefully evaluate all aspects of the management operation.

e. results of soil, plant, water, and manure analyses:  Nutrient management cannot be accomplished, i.e., there is no management, unless one knows the nutrient level in the soil.  This coupled with yield goals, which provide estimates of nutrient needs for the crop to be grown, is essential.  Another important part of this is application of animal manure. It manure from animals is available on the farm for application, the analysis of manure must be available.  Disposal of the manure is essential.  These manures contain significant amounts of N, P, and K that can go toward meeting the plant's nutrient requirements.  Addition of the organic matter is also important in improving the soil's structure, which in turn provides better water infiltration, less runoff and loss of soil and nutrients, and better plant growth and crop yields.  Since regulation of the amount of P to be applied to soils are in place in most areas, preparation of a map for a CNMP would be aided by information abut nutrient levels in the soil, water, and manures to be applied.

f. quantification of nutrients from all sources available to the farm:  It should be known what the quantities of nutrients, from all sources, on a fare are.  Once these quantities are known, planning can proceed to produce the crop as economically as possible. 

g. nutrient budget for each field:  Fields differ in their fertility.  Thus soil tests should be taken as a base for each field in future analysis.  Knowing how much N, P, K, etc. will be removed by each crop and how this varies depending on yield provides a basis for planning for each field.  Some fields, because of the soil type, will require much less fertilizer than others.  Crops may be grown on specific fields that do not require large amount of a given nutrient because the nutrient supplying power of the field is in line with the crop's needs. P-based nutrient management and recommendations, which by law mandates an upper limit for soil P levels, is aided by preparing nutrient budgets for each field.

h. recommendations of nutrient rate, timing, form, and method of application:  If all the other things discussed in this section have been done, then the manager can make recommendations for nutrient rate and timing.  The manager must know when and the method to use to apply the nutrients-all at one time as a broadcast application prior to planting or side dressing with part of the fertilizer after emergence of the crop.  Economic gain can be attained by purchasing an applying fertilizer during the time of year when the suppliers are not so busy-usually the fall.  The form in which the nutrients come, especially N, can differ significantly in cost.  The relative relationships in cost of these various forms can vary depending on the time of year. 

i. review and modification of plan as needed:  A manager must constantly review and modify a nutrient management plan in order to maximize its economic potential.  Over time, if good records are kept, the manager will know how a given field has changed, or he or she will understand that a given field is not responding as planned and more analysis and modification of the plan is necessary.  This must be an on-going process.  The internet sites listed in 50a above will be useful in modifying a comprehensive nutrient management plan (CNMP).  As these sites are updated, information useful in making these modifications will be made available.

57. Describe how N and P loss from the following can effect the environment

a. erosion: Each year soil erosion carries large amounts of soil, along with all the elements contained therein, into streams and other bodies of water each.  Nitrogen and P both become serious pollutants in streams, lakes, and oceans.  A major portion of the N carried into the Gulf of Mexico each year comes from soils in the Mississippi River drainage basin.  Increased amounts of both N and P in lakes can result in eutrophication, an accelerated growth of algae or water plants, thus depleting the oxygen dissolved in the water, increasing water turbidity, and general degradation of water quality.

b. runoff:  Nitrate, which is soluble in water, is carried by runoff waters.  Its influence is described in 46a.

c. volatilization:  Gaseous losses of N, volatilization, is encouraged by high nitrate levels in the soil.   Research has shown that nitrogen has two serious effects on the earth's atmosphere.  Nitric acid (HNO<->3</->), which results from burning fossil fuels and the subsequent release of nitrogenous gases (NO<->2</-> and NO), is a major component of acid rain.  Phosphorus is not volatilized.

d. leaching:  As water moves through the soil it picks up the very soluble nitrate and carries it out of the soil into the waterways.  The effect is the same as described in 46a above.  Phosphorus is fixed tightly to the soil micelle, thus it is not carried in the leachate.

e. denitrification: Denitrification is detrimental to agriculture because of the nitrogen loss.  However it is an important process that can be used to help prevent excess nitrates from building up on ground water or irrigated valleys where large amounts of nitrogen are used.

58. List the components of a comprehensive nutrient management plan

An aerial photograph or map, and a soil map of the field; A current and/or planned crop production sequence or rotation; Results of soil, plant, water, manure, or organic by-product sample analysis; Realistic yield potentials for crops in rotation; A quantification or listing of all nutrient sources; Recommended nutrient rates, timing, form and method of application including incorporation timing for the time period of the plan; Annual review and update.

Internet Link: <HT{icon}{~HTTP~}{www.ctic.purdue.edu/Core4/Nutrient/WhatsaPlan2.html}>

Internet Link: <HT{icon}{~HTTP~}{www.maeap.org/cnmp_outline.pdf}>

59. Describe how manure storage, handling, and application methods affect nutrient content and availibility

Manure storage whether solid or liquid is important and requires sample to be taken to be able to analyze the nutrient content while handling the manure samples can be taken more accurately because the manure becomes mixed and more uniform.  As you find the nutrient content you can more accurately apply the manure to your field according to the recommendations.

Internet Link: http://res2.agr.ca/initiatives/manurenet/en/man_stor_int.html Further study material

60. Describe how to obtain a representative sample of manure or effluent 

For best results manure or effluent samples taken from the tank or spreader box being used to deliver the manure or effluent is most effective.  The manure is usually mixed up better and a more accurate sample can be taken.  With solid samples, one should try to avoid large pieces or chunks or bedding or similar materials.

61. Describe how components of livestock feed affect manure nutrient content

Feed rations affect manure nutrient content by being fed for higher production levels than they can reach and the extra nutrients will not be used and just be excreted.  Each animal is different in how they use up nutrients and different feeds and feed ratios affect the levels of digested nutrients.

62. Define animal unit

A unit of feed consumption used in U.S. dairying and ranching. One animal unit is the feed or grazing requirement of a mature cow weighing 1000 pounds (453.59 kilograms). This is approximately 26 pounds (11.8 kg) of dry forage. Total feed requirements are often figured by the animal unit month (AUM), the feed required to sustain one animal unit of livestock for one month (780 pounds or 354 kg).

Internet Link: http://www.unc.edu/~rowlett/units/dictA.html

63. List how to use animal units in nutrient management planning

Regulations regarding nutrient management planning are based on size of operation which is in turn based on animal units. 

Agricultural enterprises where animals are kept and raised in confined situations are defined as animal-feeding operations (AFOs). Initial definition is based on animal units (AU) approximately equivalent to one beef cow or equivalent numbers of other kinds of animals.  When animals are fed rather than grazed, the operations congregate animals, feed, manure and urine, dead animals, and production on a small land area. Two or more AFOs under common ownership are considered to be a single operation if they adjoin or if they use a common area or system for waste disposal. There are about 450,000 AFOs in the United States of which confined animal-feeding operations (CAFOs) are a relatively small number of operations regulated by the EPA.

A CAFO is a lot or facility where animals have been, are, or will be stabled or confined and fed or maintained for a total of 45 days or more in any 12-month period; and, where crops, vegetation, forage or postharvest residues are not sustained over any portion of the lot or facility in the normal growing season.

Under the National Pollution Discharge Elimination System (NPDES) program, an AFO is a CAFO if more than 1,000 animal units are confined at the facility, or from 301 to 1,000 animal units are confined at the facility and it also meets one of the specific discharge method criteria. An AFO can be declared a CAFO on a case-by-case basis if the NPDES authority determines it to be a significant contributor of pollution to waters of the U.S. CAFOs are point pollution sources subject to NPDES permits.

Please note your state regulations regarding nutrient management planning with regard to size and definition of operation.

Internet Link: http://msucares.com/pubs/misc/m1142.htm

Nutrient Management Glossary

Acid soil: A soil that has a pH value less than 7.0.

Agronomic nutrient rate: Amount of nutrients required by a crop for an expected yield, after all the soil, water, plant, and air credits are considered. Agronomic rates consider nutrient credits from all soil tests, legumes, manure residuals, and other nutrient credits supplied from any other source.

Alkaline soil: A soil that has a pH value greater than 7.0.

Ammonium (NH4 +): A form of nitrogen that is available to plants from fertilizer and organic matter decomposition.

Ammonium Nitrate Solution: Non-pressure solution of ammonium nitrate in water usually standardized to 20% nitrogen used for direct application or for making multinutrient liquid fertilizer.  Analysis is 20-0-0.

Ammonium phosphate: A group of phosphorus fertilizer manufactured by the reaction of anhydrous ammonia with superphosphoric acid to produce either solid or liquid fertilizer.

Ammonium sulfate: Fertilizer material with an analysis of 21-0-0. It also contains 24% sulfur.

Anaerobic: A condition identified by the absence of oxygen.

Anhydrous ammonia (NH3): Fertilizer in pressurized gas form, made by compressing air and natural gas under high temperature and pressure in the presence of a catalyst. Value is 82-0-0.

Animal unit: 1000 pounds of live animal weight; a term used to determine volumes of animal manure produced.

Anion Exchange Capacity: The sum total of exchangeable anions that a soil can adsorb. Expressed as centimoles of charge per kilogram (cmolc/kg) of soil or milliequivalents per 100 g of soil (meq/100 g of soil).

Application rate: The weight or volume of a fertilizer, soil amendment, or pesticide applied per unit area.

Available nutrient: The form of a nutrient that the plant is able to use. Many nutrients in the soil are in forms the plant cannot use and must be converted to forms available to the plant.

Banded nutrients: Placing fertilizer nutrients in a band near the seed at planting, or surface or subsurface applications of solids or fluids in strips before or after planting.

Base saturation percentage: The proportion of the soil’s cation exchange capacity occupied by basic cations.

Bioremediation: The use of biological agents to reclaim soil and water polluted by substances hazardous to human health or the environment.

Biosolid: Any organic material, such as livestock manure, compost, sewage sludge, or yard wastes applied to the soil to add nutrients or for soil improvement.

Buildup and Maintenance: Nutrients applied in order to build up a target soil test level and then maintained by annual addition of the quantity of nutrients expected to be removed in the harvested portion of the crop.

Buffer pH: A soil test procedure whereby the pH of the soil is measured in buffer solution. This measurement is used in estimating the lime requirement of the soil.

Calcitic lime: Limestone consisting of CaCO3 based material with very low magnesium content.

Calcium Carbonate Equivalent (CCE): The liming potential of a material as compared to CaCO3.

Cation: An ion that has a positive electrical charge. Common soil cations are calcium, magnesium, hydrogen, sodium, and potassium.

Cation Exchange Capacity (CEC): The amount of exchangeable cations that a soil can adsorb at a specific pH, expressed as milliequivalents per 100 g of soil as meq/100 g soil, or cmol charge/kg.

Cation exchange sites: Negative charged sites on the surfaces of clays and organic matter.

Chelated molecule: A large, water soluble organic molecule that binds with a free metal ion to form a water soluble compound. This process increases the amount of metal ion or atom dissolved in the water.

Comprehensive nutrient management plan: A group of conservation practices and management activities unique to animal feeding operations, which will ensure that both productive as well as natural resource protection goals are achieved.

Critical value: The point between sufficiency and deficiency levels for a nutrient.

Crop nutrient requirement: The amount of nutrients needed to grow a specified yield of a crop plant per unit area.

Crop removal rate: The amount of nutrients that are removed from the field in the plant harvest. This would include harvested fruit, grain, forage, and crop residues that are physically removed from the field.

Crop rotation: A planned sequence of crops growing in a regularly recurring succession on the same area of land.

Crop utilization rate: The total amount of nutrients required by the crop to produce both vegetation and grain, including nutrients used to produce roots, stems, crowns, and other unharvested plant parts as well as the harvested portion that is removed from the field.

Crop sequence: The order of crops planted and harvested in a field over a period of time.

Denitrification: The transformation of nitrates or nitrites to nitrogen or nitrogen oxide gas, occurring under anaerobic conditions.

Diammonium phosphate (DAP): Fertilizer containing both nitrogen and phosphorus with an analysis of 18-46-0.

Diffusion: The movement of particles from an area of higher concentration to an area of lower concentration.

Dolomitic Lime: A naturally occurring liming material composed chiefly of carbonates of magnesium and calcium.

Environmentally sensitive area: Places on the landscape that can be readily impacted by human or natural activity so as to degrade the condition of the site.

Essential plant nutrients: Inorganic elements that are required for growth and development of plants.

Erosion: The wearing away of the land surface by running water, wind, ice, geological agents, or mechanical erosion.

Fertigation: Applying fertilizer through an irrigation system.

Fertilizer: Organic or inorganic material added to a soil to supply one or more nutrients essential to plant growth.

Fertilizer analysis: The composition of a fertilizer, expressed as a percent of total nutrients, for example total N, available phosphoric acid (P2O5), and water-soluble potash (K2O).

Fertilizer suspension: A fluid fertilizer containing dissolved and undissolved plant nutrients. The undissolved nutrients are kept in suspension, usually by swelling type clays.

Field capacity: The amount of water a soil holds after free water has drained because of gravity.

Foliar fertilization: Application of a dilute solution of fertilizer to plant foliage, usually made to supplement soil-applied nutrients.

Green manure: Plant material incorporated into the soil while green or at maturity, for soil improvement.

Guaranteed analysis: Minimal percentages of available nutrients as stated on a fertilizer label.

Gypsum: Calcium sulfate (CaSO4•2H2O) used to supply calcium and sulfur and to improve sodic soils.

Immobile nutrient: A plant nutrient that moves slowly in the soil or plant.

Immobilization: The conversion of an element from the inorganic to the organic form in microbial tissues resulting in that element not being readily available to other organisms or plants.

Impermeable layer: Soil layers, either natural or man-made, that resist penetration by fluids or roots.

Injection: The placement, by mechanical means, below the surface of soil.

Inorganic nitrogen: Mineral forms of nitrogen.

Inorganic phosphorus: A salt of phosphoric acid or any of its anions, usually orthophosphate or polyphosphate.

Leaching: The movement of material in solution along with movement of water through the soil.

Lime fineness: The particle size of limestone determined by the fineness of grinding. The finer the grind, the more reactive the material is in neutralizing acidity.

Lime material: A material capable of neutralizing soil acidity.

Lime purity: The measure of impurities in a given liming material, in order to estimate its neutralizing value.

Liming requirement: The amount of liming material required to change the soil to a specific soil pH.

Luxury consumption: The absorption by plants of an essential nutrient in excess of their need for growth. Luxury concentrations in early growth may be used in later growth.

Macronutrient: A nutrient that a plant needs in relatively large amounts. Essential macronutrients are nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulphur (S).

Mass flow: The movement of solutes associated with net movement of water.

Micronutrient: Nutrients that plants need in only small or trace amounts. Boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) are considered micronutrients.

Mineralization: The conversion of an element by soil organisms from an organic form to an inorganic form.

Mobile nutrient: A nutrient that moves readily in the soil or plant.

Monoammonium phosphate (MAP): A fertilizer composed of ammonium phosphates, resulting from the ammoniation of phosphoric acid. Typically 11% N with an analysis of 11-52-0.

N-based nutrient application: The rate of application of a nitrogen containing material so the desired amount of nitrogen is applied, regardless of the amounts of other nutrients being applied in the material.

Nitrate (NO3 -): An inorganic nitrogen form that is very soluble, easily leached from soils, and readily available to plants.

Nitrification: The process of converting ammonium to nitrate.

Nitrogen: An essential plant nutrient that is part of many compounds including chlorophyll, enzymes, amino acids, and nucleic acids.

Nutrient buildup: An increase in soil test levels of a nutrient due to application of that nutrient.

Nutrient Management Plan (NMP): A written plan that specifies the utilization of fertilizer, animal manures, and other biosolids.

Organic nitrogen: Nitrogen that is bound with organic carbon and forms organic molecules.

Organic phosphorus: Phosphorus that is bound with organic carbon and forms organic molecules.

Orthophosphate: Inorganic form of plant available phosphorus.

P-based nutrient application: The rate of application of a phosphorus containing material so that the desired amount of phosphorus is applied, based on balancing the agronomic rate or crop removal rate of the crop with the amount of phosphorus contained in a material. This amount is regardless of the amounts of other nutrients being applied in the material.

P index: An environmental risk assessment tool for assessing the potential for phosphorus movement from agricultural lands. It is usually based on an estimation of potential soil erosion, the phosphorus soil test level, and phosphorus management practices such as rate of application, source of phosphorus, and method of application.

P2O5: Phosphorus pentoxide; designation on the fertilizer label that denotes the percentage of available phosphorus expressed as P2O5.

Phosphorus: Essential nutrient for plants and animals. Component of cell walls, nucleic acids, and energy transfer molecules.

Plant available nitrogen (PAN): A calculated quantity of nitrogen made available during the growing season after application of fertilizer. PAN includes a percentage of the organic nitrogen, a percentage of the ammonium N, and all the nitrate nitrogen in the fertilizer.

Plant residues: Plant material that remains in the field after harvest.

Potassium: Often referred to as potash, it is an essential plant nutrient involved in energy metabolism, starch synthesis, and sugar degradation.

Recommended rate: Amount of nutrients recommended on a soil test report for a specific crop that meets but does not exceed the crop nutrient requirements. Recommended rates can also include nutrients used for soil test buildup.

Remote sensing: The collection and analysis of data from a distance, using sensors that respond to different heat intensities or light wavelengths.

Rhizobia: Bacteria capable of living symbiotically with higher plants by receiving food and carbon and provide a source of nitrogen to the plant.

Root interception: Method by which ions in the soil are intercepted by root growth.

Runoff: Portion of precipitation, snowmelt, or irrigation that moves by surface flow from an area.

Secondary nutrients: Those macronutrients (calcium, magnesium, and sulfur) used less often as fertilizers than the primary elements.

Sidedress: To apply a fertilizer, pesticide, or soil amendment to one side of a growing plant, either by surface application or injection.

Soil drainage: The process where water is moved either by surface channels or internal pores in the soil profile, usually by action of gravity.

Soil organic matter: The organic fraction of the soil exclusive of undecayed plant and animal residues. Often used synonymously with “humus”.

Soil pH: The degree of acidity or alkalinity of a soil, expressed on a scale from 0 to 14, with 7.0 indicating neutrality, increasing values indicate increasing alkalinity, while decreasing values indicate increasing acidity.

Soil productivity: A measure of the soil’s ability to produce a particular crop or sequence of crops under a specific management system.

Soil reaction: A quantitative term that describes the general degree of acidity or alkalinity of a soil.

Soil sampling: Process of obtaining a representation of an area of the soil or field by collecting a portion of the soil.

Soil solution: The aqueous liquid phase of the soil and its solutes contained in soil pores.

Soil structure: The combination or arrangement of primary soil particles into secondary soil particle units, or peds.

Soil test: A chemical, physical, or biological procedure that estimates the plant availability of nutrients and soil quality characteristics to support plant growth.

Soil test interpretation: Using soil test report information to manage soil fertility and monitor environmental conditions.

Soil test level: The nutrient content of the soil, as measured by an analysis of a soil sample.

Soil test recommendation: The suggested amount of nutrients to be added to the soil to achieve expected crop yields based on the supplying power of the soil, air, and water.

Soil texture: The relative proportions of sand, silt, and clay in the soil.

Starter fertilizer: A fertilizer applied in relatively small amounts with or near the seed at planting.

Sufficiency level: a) For interpretation of plant analysis: A nutrient concentration in the plant tissue above which the crop is amply supplied, and below which the crop is deficient. b) For interpretation of soil analysis: A soil test level above which economic responses to applied fertilizer are unlikely to occur.

Subsurface band: To apply nutrients, pesticides, or soil amendments in narrow bands below the surface of the soil.

Surface band: To apply nutrients, pesticides, or soil amendments in narrow bands over the surface of the soil.

Surface broadcast: To apply nutrients, pesticides, or soil amendments uniformly over the surface of the soil.

Symbiotic N fixation: Conversion of molecular nitrogen (N2) to ammonia and subsequently to organic nitrogen forms by organisms.

Topdress: To apply fertilizer, pesticides, or soil amendments on the surface.

Total Kjeldahl Nitrogen (TKN): A laboratory procedure to measure organic N and ammonium on soils and plants.

Total nitrogen: The sum of the organic and inorganic forms of nitrogen in a sample.

Toxicity level: A quantity of a material in plants, soil, or water that can harm or impair the physiological function of plants or soil.

Triple Superphosphate: A product that has a guaranteed analysis between 40 and 50% available phosphoric acid. The most common analysis is 0-46-0.

Uptake antagonism: When the excess of one nutrient interferes with the uptake of another nutrient. Usually the nutrients in question may have a similar uptake mechanism by the plant.

Urea: A nitrogen fertilizer that is a white crystalline solid, very soluble in water, which has an analysis of 46-0-0.

Urea Ammonium Nitrate solution (UAN): A non-pressure nitrogen fertilizer solution containing urea and ammonium nitrate in approximately equal proportions dissolved in water. The nitrogen content of the fertilizer solution ranges from 28% to 32%.

Volatilization: The loss of a compound in gaseous form from a solid or liquid phase.

SOIL AND WATER MANAGEMENT

SOIL MANAGEMENT

Internet Link: http://www.soils.org/sssagloss/browse.html Soil Science Society of America (SSSA) online glossary.  Excellent collection of agricultural terms.

BASIC SOIL PROPERTIES: CHEMICAL

1. Define Anion and Cation

Anion - A negatively charged ion caused by an atom gaining an electron.

Cation - A positively charged ion caused by an atom losing an electron.

(Campbell 34, 716-717)

2. Define cation exchange capacity (CEC) and anion exchange capacity (AEC)

CEC is the amount of exchangeable cations that can be absorbed by the soil. Hydrogen (H<+>+</+>) ions in the soil displace the positively charged ions (cations) that are bound to the surface of the negatively charged soil particles.  These cations are nutrients that plants need to grow. Once these nutrients are no longer bound to the soil particles, they are available for uptake by plants.  Plants release H<+>+</+> ions in respiration and they maintain an equilibrium by releasing enough H<+>+</+> to free up the nutrients that they need.  (Campbell 716-717/Brady 175)

Internet Link: http://syllabus.syr.edu/esf/rdbriggs/for345/cation.htm Further study material on CEC

Internet Link: http://bioag.byu.edu/aghort/282pres/ClayChem/sld014.htm Further study material on CEC from Brigham Young University

AEC is the sum total of exchangeable anions that the soil can absorb.

3. Describe how the following factors influence CEC

A. Percent clay: Soil with a high percentage of clay have high CEC values while those with little or no clay have low CEC values

B. Type of clay: Swelling-type clays like smectite found in vertisols have the highest CEC while soils with 2:1-type clays had the next highest overall CEC.

C. Percent organic matter: Organic matter incorporated into the soil humus has the highest CEC percentage.

D. pH: The CEC of most soils increases with increasing pH and at very low pH values the CEC is generally low. Ref: Brady 334(5).

4. Describe how mineral solubility affects availability of nutrients

When the pH of the soil drops much below pH 5, the solubility of Al and Mn can increase to such an extent as to become toxic to most plant growth.  Some plants actively excrete protons, and the resulting decrease in pH increases the solubility of iron in their environment. In addition, some plants excrete phytosiderophores that chelate the soil iron rendering it a more available form for the plants.

The solubility of nitrate means that direct agricultural runoff is a major contributor to nitrate loading on fresh waters.  Loss of phosphate by leaching from agricultural land is less than that for nitrogen.  Much of phosphate is tightly bound to the soil particles and is not immediately biologically available when it reaches fresh waters.  The solubility of hosphate is enhanced when the soil particles become incorpoated into anaerobic mud.  In waters with a heavy precipitation of carbonates, phosphates and many micronutrients form insoluble compound that precipitate to the bottom sediments.

5. Differentiate saline, sodic, calcareous, acidic, and alkaline soils

Saline : soil containing dissolved salts which are mostly left from dissolved irrigation water.  A white crust appears on surface of dry soil from the salts moving upward to the surface of the soil.  Saline soils can stunt crop growth, decrease yields, and eventually kill crop plants (Campbell 716-717/Troeh).

Sodic : soil containing Na+ as more than 15% of their available cations.  These soils have very little organic matter.  Very little, if anything can grow in these soils, and they are nearly impossible to reclaim.  A black coating appears on the surface of the soil as water evaporates from the surface (Troeh).

Calcareous : soils with a pH higher than 7.5 (Miller, G. T. 511-512).

Acidic : soils with a pH below 6.5.  The hydrogen ions in acid soils upset the CEC decreasing the availability of these minerals to the plant due to leaching and decreasing soil fertility (Miller,G. T. 511-512).

Alkaline:  Any soil having a pH greater than 7.0, which is a basic soil.

Internet Link: http://res.agr.ca/CANSIS/GLOSSARY/alkaline_soil.html Further study material from Canada

Internet Link: http://res.agr.ca/CANSIS/GLOSSARY/ Further study material from Canada

BASIC SOIL PROPERTIES: PHYSICAL

6. Define soil texture

Soil texture is the amount of clay, silt, sand, and gravel particles in a given soil.

Internet Link: http://res.agr.ca/CANSIS/GLOSSARY/texture,_soil.html Further study material from Canada

7. Use the textural triangle to identify soil textural class

(Look at Textural triangle, trace where the three soil percentages meet)

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Internet Link: http://res.agr.ca/CANSIS/GLOSSARY/texture,_soil.html Further study material from Canada

8. Describe how particle size affects surface area and reactivity of soils

Soil particle size affects the surface area in this manner:  as the size decreases the amount of surface area increases, thus providing more exchange site for holding cations.  With a greater number of exchange sites, reactivity of soil increases. Surface area within a soil increases as follows: sand (less than) silt (less than) clay.  Thus the ratio of sand, silt, and clay in a soil has a significant affect on soil reactivity. (Miller, G. T. 514-15)

9. Describe how soil texture affects the water holding capacity, available water, and wilting point of soils

Soil particle size affects the water holding capacity, available water, and wilting point of soil because different particle sizes differ in surface area.  Clay particles have a greater surface area and so they have a greater water holding capacity, decreasing the amount of available water, and a higher wilting point.  (Miller, G. T.  514-15)

10. Define soil structure

Soil structure is how the particles of soil are organized together.  (Miller, G. T. 513-14)

11. Differentiate the following types of soil structures

A. Blocky: Irregular, roughly cube-like, and range from about 5 to 50 mm across. Individual blocks are not shaped independently but are molded by the shapes of the surrounding blocks.

B. Single Grain: Has a lack of structure in which individual particles do not cohere together.  i.e. course sands

C. Granular: Consists of spheroidal peds or granules that are usually separated in a loosely packed arrangement.

D. Platy: Characterized by relatively thin horizontal peds or plates that can be found both in surface and subsurface horizons.

E. Massive: This refers essentially to soil that is structureless.  It has undergone some process, plowed or disked when too wet, that has destroyed the normal structure or aggregation of the soil.  As a result, large clods have formed as the soil has dried.  Usually a cycle of freezing and thawing, as occurs during the winter season, must be experienced to rid the soil of the massive structure. [Ref.  Brady, N.C.  1990.  p. 100-115.  The Nature and Properties of Soils.  10th ed.  Macmillan.].

Internet Link: http://www.irim.com/ssm/ssm00090.htm Further study material on Soil Structure

F. Prismatic/columnar: A soil structure type with a long vertical axis that is prism shaped and round/topped.

11. Describe how soil organisms affect soil structure

Soil organisms decompose organic matter and in the process release nutrients that are then made available to plants.  As the soil organisms decompose the organic matter, they are increasing the stability of the soil structure by releasing the slimy byproducts of decay and by the humus that is created (Brady 250).

12. Describe how soil structure affects the following

a.  permeability

Soil permeability is the property of the soil pore system that allows fluid to flow. It is generally the pore sizes and their connectivity that determines whether a soil has high or low permeability. Water will flow easily through soil with large pores with good connectivity between them. Small pores with the same degree of connectivity would have lower permeability, because water would flow through the soil more slowly. It is possible to have zero permeability (no flow) in a high porosity soil if the pores are isolated (not connected). It is also to have zero permeability if the pores are very small, such as in clay.

b.  root development

In general densly structured soils can inhibit root development whereas highly porus soils may not give the plant sufficient holding strength or sufficient nutrient holding capacity for the plant to survive.

When a seed germinates, the primary root develops at the lower end of the tiny stem of the embryo plant. Very soon, lateral roots begin to appear which, with their branches, greatly increase the absorbing area and anchoring power of the root.

Many cereals, such as wheat, oats, and corn, usually have three roots arising from the seed (seminal roots), i.e., the primary root and two almost equally large laterals. These with their branches (sometimes supplemented by other primary roots) constitute the primary root system. The remaining portion of the root system arises from the nodes or joints of the stem in the soil. Frequently, as in the brace or prop roots of corn, they grow from nodes above the soil surface. They are unbranched aboveground and are covered with a gummy substance which prevents drying out, but upon entering the soil, they branch and rebranch quite like other roots. Roots not arising from the seed or as branches of seed roots but from stems or leaves are called adventitious. In the case of the cereals and other grasses which have strong, threadlike or fibrous roots, the larger part of the root system is composed of the adventitious roots which collectively make up the secondary root system. It is worthy of note that the roots of the secondary system originate only about an inch below the soil surface, even if the grain is planted 2 to 3 inches deep.

c.  water infiltration

Water must reach the roots, but must not just pass by the roots leaching out nutrients.  Soil structure must allow for water infiltration, but must not be so porus as to leach the soil of nutrients.

d.  aeration

Oxygen plays an important role in the microbiotic action.  Dense soils may not allow sufficient oxygen to penetrate to the roots sufficating productive elements in soils and constricting the root systems and stifling growth.

13. Describe how soil organisms and soil organic matter affect soil structure

Soil organisms consisit of a wide range of sized organisms including worms and microbiological organisms.  They break up soils and increase its porus nature.  They also help to breakdown organic matter into inorganic matter that can then be utilized by the plant.

Soil organic matter builds porocity into the soil and the water retention capacity of the soil.  In addition, organic matter facilitates the growth and development of microbiological organisms in the soil which can build a symbotic relationship of microbiological organisms and health plant development or increase the wrong kind of microbioligical organisms causing plant disease.

14. Define bulk density

Bulk density is a measure of the weight of the soil per unit volume (g/cc), usually given on an oven-dry (110° C) basis.

Bulkdensity = Weitht/Volume

Variation in bulk density is attributable to the relative proportion and specific gravity of solid organic and inorganic particles and to the porosity of the soil. Most mineral soils have bulk densities between 1.0 and 2.0. Although bulk densities are seldom measured, they are important in quantitative soil studies, and measurement should be encouraged. Such data are necessary, for example, in calculating soil moisture movement within a profile and rates of clay formation and carbonate accumulation. Even when two soils are compared qualitatively on the basis of their development for purposes of stratigraphic correlation, more accurate comparisons can be made on the basis of total weight of clay formed from 100 g of parent material than on percent of clay alone.

Internet Link: http://www.geology.iupui.edu/research/SoilsLab/procedures/bulk/Index.htm

15. Describe how to determine when soil moisture conditions are favorable for field operations

Planting and field management are the major groups of field operations that rely on field moisture conditions.  Soil moisture conditions for planting are favorable if the ground is dry enough to start germination, but dry enough to prevent seed rot.  Soil conditions for field management are right if the field is dry enough to prevent compaction.  High moisture yield loss can occur in areas due to waterlogging, increased pest problems, and reduced growing seasons. Shorter-season crops, although generally less profitable, become more attractive as planting is delayed.

BASIC SOIL PROPERTIES: BIOLOGICAL

16. List sources of soil organic matter

Organic matter is made from decaying plant and animal tissue.  Higher plant tissues are the major source with animal tissues and wastes are a secondary source of organic matter. Organic matter constantly needs to be renewed due to the constant breakdown of these tissues by microorganisms (Brady 14, 254).

Internet Link: http://www.montana.edu/wwwpb/ag/baudr178.html Further study material from Montana State University

17. Describe the physical and chemical properties of soil organic matter

Physical:  plant and animal residues that exist in the soil.  The residues are usually partially decomposed and are black or brown.

Chemical: organic matter is composed of about 45% to 50% carbon with lesser amounts of oxygen and hydrogen plus small quantities of nitrogen, phosphorus, sulfur, and many other elements.

Note:  organic matter is broken down by enzymes that break the chemical bonds.  A big factor that affects the biological breakdown is the carbon:nitrogen ratio in the soil.

There are two groups of organic matter:  original tissue and humus

Original tissue - the roots and tissue part of plants

Humus - usually black or brown, the partially decomposed original tissue and the tissues that are more resistant to decomposition.  Humus has a great water and nutrient holding capacity (Brady 15-16).

Internet Link: <HT{icon}{~HTTP~}{www.agric.gov.ab.ca/agdex/500/536-1.html}>

18. Describe beneficial effects of soil organic matter

Soil OM Provides nutrients such as phosphorus, sulfur, and nitrogen to the soil.  Soil OM also aerates/loosens the soil.  OM increases the water holding capacity of the soil as well as the available water to the plants.  Organic matter is the main source of energy for all plant and animal life in the soil (Brady 15). Soil structure improves with additional organic matter (Troeh).

19. Describe how crop rotation and tillage affect the amount of carbon stored or sequestered in the soil

Carbon is very beneficial to the soil and helps the soil in many ways.  Different crop rotations have been linked to varying levels of carbon stored or sequestered in the soil.  Greater carbon levels were established with permanent crop vegetation and specific crop rotations vs. a new and different crop every year. Carbon will remain in the soil longer with conservational tillage practices. With less tillage the carbon can remain in the soil longer and improve soil quality and productivity.

Internet Link: http://www.extension.iastate.edu/Publications/PM1871.pdf   Further study material from Iowa State University

20. Explain how the following factors influence soil microbial activity

a. temperature: temperatures between 20-40°C (approx. 70-100°F) allow for the greatest amount of bacterial growth and activity.  Soil temperature extremes rarely will kill bacteria.

b. moisture: microbial action is encouraged and maximized by the same moisture levels required by plants for optimum growth.  Water levels in soil directly affect the amount of oxygen available.  The amount of available air will determine whether aerobic, anaerobic, and facultative (use both aerobic and anaerobic means) bacteria can grow well in the soil.

c. soil pH:  optimum pH values differ with various types of bacteria; however, a pH between 6 and 8 is best for most bacteria.  Bacteria will thrive when they are living within their optimum pH levels.

d. organic matter: this is the major energy source for most heterotrophic bacteria, but is not used by autotrophic bacteria.  (Brady 245)

e. salinity: most soil-borne microorganisms are readily functional in slightly acidic, neutral, and slightly basic soils.  Soils in which the salt concentration is such that they become limiting to plant growth and crop production will also result in reduced microbial activity. [Ref.  Brady, N.C.  1990.  p. 228, 265-277.  The Nature and Properties of Soils.  10th ed.  Macmillan.].

f. nitrogen application: microbial activity, of nitrogen-fixing bacteria, is affected most by the application of nitrogen.  If the amount of nitrate added to the soil is above 25 kg N/ha, nodulation decreases dramatically (1.4 nodules at 25 and 0.3 nodules per plant when 50 kg N/ha was added to seedling alfalfa). [Ref.  Horrocks, R.D, and J.F. Vallentine.  1999.  Harvested Forages.  p.  220.  Academic Press.]

g. tillage: Although tillage affects nearly all the above factors it can also create increased oxygen in the soil facilitating microbial activity.

21. Explain how the C:N ratio affects organic matter decomposition

Organisms must incorporate into their systems about eight parts of carbon for every one part of nitrogen; but because only one-third of the carbon is metabolized into their cells a C:N ratio of 24:1 is necessary for microbe survival and organic matter decomposition. Any C:N ratios that exceed 25:1 will cause the microbes to have to scavenger the area for enough nitrogen depriving higher plants of nitrogen.

SITE CHARACTERIZATION

22. Differentiate O, A, B, and C soil horizons

O:  The O group is comprised of organic horizons that form above the mineral soil.

A:  The A horizons are the topmost mineral horizons.  They contain a mixture of partially decomposed (humidified) organic matter, which is generally darker color than the lower horizons.

B:  The B horizons include layers in which illuviation of material has taken place from above and even from below.  In some cases major accumulation of materials such as iron and aluminum oxides and silicate clays occur here.

C:  The C horizon is the unconsolidated material underlying horizons A and B.  The C horizon is outside the zone of biological activity.

23. Define parent material

Parent material is the underlying geological material in which soil horizons form. Soils typically get a great deal of structure and minerals from their parent material. Parent materials are made up of consolidated or unconsolidated mineral material that has undergone some degree of physical or chemical weathering.

24. Describe how to determine the area of a field

There are various methods for determining the area of a field.  These include pace (walking the perimiter), right angle method, rectangular method, and use of GPS.  There are a number of computer programs that can be downloaded, but remembering simple rules of area for rectangules (width X height) and circles (Area = (3.1417)(d )^2/4 where d is the diamiter of the field) will give you a good approximation.

25. Describe how to determine slope of a landscape

The slope of a field is expressed as a ratio. It is the vertical distance, or difference in height, between two points in a field, divided by the horizontal distance between these two points. The formula is:

slope=rise/run or (height difference/horizontal distance)

slope % = (height difference/horizontal distance) X 100

26. Identify characteristics of well-drained and poorly-drained soils

Well drained soils can be tested by grabbing a fist full of soil, sqeezing the soil in your fist and then opening your hand.  If the soil is poorly-drained it will stay in a mud ball.  If the soil is well-drained the soil will flake away from the ball, but will retain its ball form.

27. Use a soil survey to locate soil types on a tract of land

This is to be demonstrated by the individual taking the examination, using a soil survey provided by those administering the examination.

Internet Link: http://soils.usda.gov/soil_survey/main.html Further study material

Internet Link: http://www.swcs.org/t_resources_survey_fact.htm Further study material

28. Use a soil survey to determine soil characteristics of a field

This is to be demonstrated by the individual taking the examination, using a soil survey provided by those administering the examination.

[Ref.  Brady, N.A., and R.R. Weil.  1999. p. 723-735. 12th ed.   Macmillan; Ref. Troeh, F.R., J.A. Hobbs, and R.L. Donahue.  1999.  p.  173-174.  Soil and Water Conservation: Productivity and Environmental Protection.  3rd ed.  Prentice Hall.]

Soil, slope, and erosion (Foth 318-320)

Internet Link: http://soils.usda.gov/soil_survey/main.html

Internet Link: http://www.statlab.iastate.edu/soils/soildiv/ Further study material from Iowa State University

29. Explain how the following limit land use

a. leaching potential

Highly leachable soils limites land use to crops that can survive in limited nutrient soils and soils with limited holding capacity.  On the other soils with low permability also limit land use to crops that can survive in dense soils.

b. erosion potential

High erosion limites land use to crops that survive in difficult erosion environments.  Crop and residue Cover is not only good for preventing soil erosion, but it will cut down sediment transport to water bodies and contribute to the improvement of water quality. In any case high erosion limites the nutrient value of the soil in addition to problems with land accessability for crop management and harvesting.

c. wetlands classification

Wetlands is a special area classification that is defined by each state.  Some production may be allowed depending on the state's classification of the wetland, but full scale production will be drastically limited.  Not only is production limited in the classified wetlands area, but will likely be restricted in the surounding areas as well.

d. proximity to sensitive areas

Proximity to sensitive areas such as streams (and other water sources), residentual areas, and preservation areas will limit land use to low or no management crops.  Fertilizer and pesticide use in these areas is kept to a minimun and wil likely be highly regulated.

e. runoff potential

Runoff potential is the key to each of the above limited uses.  Runoff potential is only as bad as its erosion potential or its potential to runoff into sensitive areas.  If runoff potential is high in any area it will likely prove to be poor use for agriculture due to erosion and management/production difficulties.

Internet Link: http://www.extension.umn.edu/ University of Minnesota Extension Service

Internet Link: http://www.edv.agrar.tu-muenchen.de/pbpz/leach/leachen.html Further study material on leaching potential

Internet Link: <HT{icon}{~HTTP~}{species.fxs.gov/#endangered.html}> - summary of the text of the endangered species act

SOIL EROSION

30. Describe erosion processes of detachment, transport, and deposition

Detachment: Detachment is when the soil particles are removed from the soil mass. Raindrops cause most of the detachment on smooth surfaces, the cutting-action of turbulent waters causes detachment in channels. Freezing and thawing can also contribute to detachment.

Transport: Detached particles are transported downhill by floating, rolling, dragging, and splashing.

Deposition: Eroded particles could be deposited only a few meters from their place of detachment or may travel thousands of kilometers before the are deposited. Most particles are deposited in the sea (5 to 10%), reservoirs, river beds, on flood plains, or on flat land in another section of the watershed.

31. Differentiate the following types of erosion

a. sheet: flowing surface water transports uniform layers of soil - may not be noticeable until great damage has already occurred.

b. rill: fast-flowing surface water cuts small channels or streamlets into the soil. Rills can be removed by tilling the soil.

c. gully: the small channels of fast-flowing surface water join to form deep and wide channels that intensify with each rain eventually forming gullies.  Gullies are too large to be removed by tilling the soil (Miller, G. T. 516/Troeh 67-68).

d. surface creep: soil grains between 0.5-1mm are gently moved across soil surface by saltating grains.  This is how sand dunes move and are made (Troeh 91).

e. saltation: Intermediate sized particles that move in leaps with the wind.  As the particles fall back to the surface of the earth, they break loose more soil particles of all sizes increasing the amount of wind erosion in all three areas.

f. suspension: particles that are silt size or smaller picked up by the wind and kept suspended by air currents.

g. tillage erosion: Tillage erosion is the redistribution of soil that occurs within a landscape as a direct result of tillage. Loss and accumulation are caused by variations in the amount of soil that is moved by tillage. The movement of soil by tillage is called tillage translocation. The variability in translocation is affected by the design and operation of tillage implements and by the topographic and soil properties of landscapes. Typically, tillage results in the progressive downslope movement of soil, causing severe soil loss on upperslope positions and accumulation in lowerslope positions.

Internet Link: http://www.umanitoba.ca/outreach/tillage_erosion/background/background.asp

23. Explain how the following affect the rate of erosion by water

a. duration and intensity of rainfall: breaks up soil aggregates thus freeing soil particles; transports soil particles; and compacts the soil.  Raindrops usually cause sheet erosion. Increased duration and intensity of rainfall increase the amount of erosion that occurs.

b. soil texture: finer-textured particles move more easily than sand size particles.

c. slope length: longer slopes usually have greater amounts of erosion, especially when the rainfall intensity is high.

d. slope percentage: increased slope causes an increase in the velocity of the flowing water, thus resulting in increased erosion of the soil.

e. vegetative and residue cover: plant material intercepts the raindrops and slows the movement of water and greatly reduces amount of soil carried in the water.

33. Explain how the following affect the rate of erosion by wind

a. Vegetative and residue cover: Vegetation or stubble mulch will reduce wind erosion especially in fields where the rows run perpendicular to the direction of prevailing winds. Plant roots also aid in reducing wind erosion by binding soil particles.

b. Wind velocity: Wind speeds of about 25 km/h are required to initiate soil movement. As speeds above 30 km/h are reached the amount of soil carried by the wind goes up proportionally to the cube of soil movement. Rates of erosion will be high in areas frequented by high wind speeds.

c. Unsheltered distance: The longer the distance between shelter, the higher the likelihood of high amounts of soil erosion. Shelter aids in the deflection of wind as well as the reduction of wind velocities.

d. Soil surface roughness: Wind erosion is less severe in areas where the soil surface is rough. Smoother, exposed soils are more susceptible to wind erosion.

e. Soil Texture: When soils are fine or medium textured you can increase the soil surface roughness and establish ridges in a field by tillage implements.  Ridges too low are proven to be less effective in reducing wind velocity and soil erosion.

Internet Link: http://www.ext.colostate.edu/pubs/crops/00518.html Further study material from Colorado State University

Internet Link: http://www.gov.on.ca/OMAFRA/english/engineer/facts/87-040.htm Further study material from The Government of Ontario, Canada

34. Define the concept of soil loss tolerance

Soil loss tolerance is the maximum rate of annual soil loss that will permit crop productivity to be maintained indefinitely.

35. Describe how erosion affects the following

a. crop yield potential: nutrients and organic matter are eroded away, resulting in a decrease in crop yield potential.

b. water-holding capacity: topsoil is carried away, thus leaving compacted subsoils which have lowered water-holding capacity.

c. nutrient content: nutrients are carried away with the soil, the nutrients that remain are not as available as the nutrients in the eroded soil (Brady 534).

d. organic matter content: organic material is eroded, leaving very little, if any, organic material

e. infiltration: clay and compacted subsoils limit the amount of water infiltration, thus soils experience increased erosion

f. water quality: agricultural chemical and soil runoff result in contaminated waterways

g. air quality: dust carried by the wind can cause reduced visibility, may carry diseases that cause skin disorders, and may cause potentially fatal respiratory problems (Troeh 69-95).

36. Explain how the following decrease erosion

a. strip cropping: by alternating strips of crops (like corn with soybeans) each strip catches and traps the soil and runoff is slowed and reduced.

b. contouring: planting crops in rows following the contours of the land.  Each contour acts as a dam slowing runoff and holding the soil in place.

c. terraces: a series of level terraces that follow the contour of the land may be used on steep slopes.  Terracing reduces runoff and soil loss retaining water and soil at each terrace level.

d. grassed waterway: grasses help to stabilize the soil and reduce water runoff and soil erosion.

e. surface residue: protects soil from direct impact of wind and rain and reduces runoff.  Surface residue helps in catching soil particles before they are transported in the air.

f. cover crops: allow the field to be fallow without being bare, reduce the impact of wind and rain, and reduce runoff (Miller, G. T. 521-522).

g. row spacing and direction: Soil erosion is reduced or increased by row spacing.  For example, the main affect is realized by interception of rain drops by the canopy.  These drops do not directly hit the soil and cause the splashing of water and soil into the air.  Narrower rows that allow the crop to close the canopy earlier in its growth cycle will reduce this type of erosion.  Wide rows will increase this type of erosion.  The effect is particularly exacerbated when the crop is grown on sloping land even if the rows are on the contour.

Internet Link: http://ianrwww.unl.edu/pubs/fieldcrops/g544.htm Further study material from the University of Nebraska Extension

h. conservation buffers: any tillage system that leaves at least 30% of the surface covered by plant residues for control of erosion by water and wind.

i. surface roughness: a system of establishing or creating ridges to reduce wind velocity and trapping soil runoff.

j. windbreaks: the use of tree and shrubs to decrease wind speed and soil movement, by blocking and shielding the uncovered soil.

Internet Link: http://www.seafriends.org.nz/enviro/soil/erosion.htm Further study material

Internet Link: http://www.ae.iastate.edu/ae3050.htm Further study material from Iowa State University

RESIDUE MANAGEMENT

37. Describe how the following soil characteristics differ between clean-till and high surface residue management systems

a. temperature: high surface residue maintains the soil temperature better than tilling and less evaporation occurs.

b. erosion: high surface residue decreases the amount of erosion because the crop residues protect the soil from wind and water erosion by decreasing the impact of the wind and rain and reducing runoff.

c. moisture: high surface residue allows greater moisture infiltration into the soil, more water is thus held in the soil and is thus available for plant growth.  Less soil is therefore exposed when tilled resulting is less evaporative loss (Miller, G. T. 521).

d. organic matter: In clean-till systems there is generally less organic matter incorporated into the soil than in high surface residue management systems. Clean-till systems remove the majority of organic matter without incorporating it into the soil.

Internet Link: http://pnwsteep.wsu.edu/tillagehandbook/index.html Further study material from Washington State University

38. Describe how residue cover and erosion potential differ among the following tillage systems

a. Clean-till: No residue cover, thus erosion potential is high, especially if the land is sloping.  Row crops and seeding of perennial legumes and grasses are particularly susceptible to erosion in this system.   In areas where wind erosion is a problem, this system is most susceptible to erosion since there is nothing to impede the force of the wind and the moving soil particles carried by the wind.

b. Mulch-till/Reduced-till: Contains at least 30% of residues on surface.  The 30% residue cover will intercept approximately 30% of the rain drops falling on the field and this will reduce the splattering that occurs.  On sloping fields greater erosion will occur, but there will be somewhat less than on a clean-till field.  The area covered by the debris will be more capable of allowing the water to percolate into the soil than the areas that have been struck by the unimpeded rain drops.  Wind erosion will be somewhat reduced by the surface debris, but it will not be eliminated.

e. No-till/Zero-till: Soil undisturbed prior to planting; highest amount of residue cover.  Soil erosion is greatly reduced.  The raindrops will be intercepted by the surface debris, thus eliminating the splashing caused by the raindrops.

Internet Link: <HT{icon}{~HTTP~}{pnwsteep.wsu.edu/tillagehandbook/index.html}> Further study material from Washington State University

39. Describe how to measure percent crop residue cover 

Line transect: Count the number of times a marked line intersects with a piece of residue. Use a 50- to 100-foot tape measure (or a rope with marks spaced at 1-foot intervals). Stretch the tape (or rope) between two stakes placed diagonally (at a 45 degree angle) of the crop rows. Looking directly from above the tape (vertically), count the number of times where a "foot" mark intersects with crop residue. Make consistent judgments--use only the left or right side of the foot mark on the tape (or rope) to avoid over counting residue. The resulting count converts directly into the percentage of crop residue remaining in that sample area. (Example: 38 occurrences of intersection equals 38 percent crop residue remaining). (As an alternative, a 50-foot tape measure can be used; just evaluate the marks at 6-inch intervals instead.)

Meter stick: Places for measurement can be determined randomly by throwing the meter stick (a yardstick with metric markings also can be used) into the air and taking measurements where it lands. Once the meter stick is on the soil, evaluate at each centimeter mark the crop residue occurring along one edge of the meter stick, and total these measurements. (Example: if the residue occurs at 35 centimeter marks along a meter stick, the percentage of residue remaining is 35 percent.)

Photo comparison: Compare your fields' residue cover to that in the photos herein that show a known percentage of crop residue. Remember that the perspective from an angle can be misleading. Look straight down when comparing photos.

Calculation: Calculation is a good way to get a rough estimate of remaining residue without going to the field. But remember that it is only a general guide and may not reflect what is really on the field because too many variables, including weather and differences between operations of tillage equipment, are involved. See Table 1 for information on residue cover percentage remaining on the soil surface after each operation . Multiply the factor for each operation by the existing percentage of residue left to find how much residue cover will be left after each operation.

Internet Link: http://www.ipm.iastate.edu/ipm/icm/2002/5-13-2002/cropresidue.html

RESTRICTIVE SOIL LAYERS

40. Describe characteristics of the following restrictive soil layers

a. wheel track compaction: causes reorientation of soil particles and reduces the volume of air.  This slows down water and air movement and reduces the water holding capacity of the soil.

b. tillage-induced compaction: is caused by primary tillage under less than optimum soil moisture conditions and excessive secondary tillage.  The secondary tillage destroys soil aggregation and structure allowing the soil surface to puddle and reach very high soil densities. 

c. crusting: is formed by raindrops or irrigation when surface aggregates breakdown and are compacted into the soil.  Crusting hampers seedling emergence, reduces water penetration, and causes soil runoff.

d. naturally occurring layers: can vary from clay pans to other impermeable subsoils.  Water entry is limited and the soil has a high density.

Internet Link: http://www.ag.ohio-state.edu/~ohioline/b301/301_6.html Further study material from Ohio State University

Internet Link: http://www.ext.colostate.edu/pubs/crops/00519.html Further study material from Colorado State Extension

41. Explain how restrictive soil layers hinder plant growth

Restrictive soil layers restrict plant growth in the following ways: (a) root growth may be limited, (b) access to water and nutrients may be limited because of restricted root growth, (c) water infiltration into the soil is reduced, (d) runoff of is increased with the loss of soil which in turn reduces soil fertility, tilth, and depth.

42. Explain how restrictive soil layers inhibit water, air, and nutrient movement

Restrictive layers may occure at various soil dephths.  The following outlines the restrictive layer and its impact on plant development. 

Surface seal: A surface seal or crust is a thin layer (1?10 mm) formed on the soil surface by water drop impact. It can have a porosity 90% lower than that of unsealed soil. Permeability declines during rain or irrigation when surface aggregates break down and are compacted under drop impact.  Surface sealing is largely responsible for restricted initial infiltration under rainfall or irrigation. Water that is unable to move into the soil profile will run off. Sealing and crusting may be natural, or induced when soil cover is removed. It is sometimes associated with sodicity.

Hardsetting layer: Hardsetting is an inherent feature of some soils (e.g. some texture-contrast soils and weakly structured cracking clays). Soil aggregates break down during wetting, then set to a hard, structureless mass during drying. This is

exacerbated by over-cultivation and reduction in organic matter, which reduces aggregate stability.

Surface compaction: Surface compaction is induced by tillage tool smearing, tractor wheels and farm animals when soil is sheared or compressed at the critical moisture content known as the ‘plastic limit’. It results in high soil strength and reduced porosity, preventing water from accessing the root zone. In tilled soils, a plough pan can be created directly under the tilled layer by the smearing action of tines.

Subsurface compaction: Compaction below the tilled layer is created by high axle loads under moist soil conditions. Water is unable to move freely through the soil profile. In dry conditions, subsurface compaction will prevent roots accessing deep stored moisture.

Internet Link: http://www.nrw.qld.gov.au/factsheets/pdf/land/l40.pdf

43. Describe methods for preventing and alleviating restrictive soil layers

Normal tillage can break up compaction in the plow layer; compaction below the plow layer requires deep tillage or ripping.  Minimum/no-till will have less compaction due to less machinery.  Reducing traffic in a field can reduce compaction.  Encouraging buildup of organic matter in the surface and subsurface soil, via incorporation of crop residues, will over time promote better structure and better water movement into the subsurface layers , both of which may reduce compaction (Miller, R. W. 430).

SOIL MANAGEMENT EFFECTS ON AIR QUALITY

44. Describe how soil management practices affect

a.odor from biosolids applications:  Immediate soil incorporation or direct soil injection reduce the potential for odor problems.  Weather conditions will affect odor severity when biosolids are surface applied.  Spreading the biosolids in the morning while the air is warming and rising will help dilute the odor in the immediate vicinity.

b.ammonia emissions:  Ammonia volatilization is a major nitrogen loss process for surface  applied manures and urea fertilizers.  The best soil management practices to stop ammonia emissions is incorporating or injecting the ammonia into the soil with different tillage methods.

c.particulates:  Soil management practices play a big role in the volatilization of particulates in the air.  These tiny particles can cause serious health problems over time.  The reduction of tillage and soil conservation practices  will help reduce particulates from polluting the air.

d.carbon sequestration: Terrestrial carbon sequestration is the process through which carbon dioxide (CO2) from the atmosphere is absorbed by trees, plants and crops through photosynthesis, and stored as carbon in biomass (tree trunks, branches, foliage and roots) and soils. The term "sinks" is also used to refer to forests, croplands, and grazing lands, and their ability to sequester carbon. Agriculture and forestry activities can also release CO2 to the atmosphere. Therefore, a carbon sink occurs when carbon sequestration is greater than carbon releases over some time period. Forests and soils have a large influence on atmospheric levels of carbon dioxide (CO2)—the most important global warming gas emitted by human activities. Tropical deforestation is responsible for about 20% of the world's annual CO2 emissions (IPCC Special Report on LULUCF). On a global scale, however, these emissions are more than offset by the uptake of atmospheric CO2 by forests and agriculture. Therefore, agricultural and forestry activities can both contribute to the accumulation of greenhouse gases in our atmosphere, as well as be used to help prevent climate change, by avoiding further emissions and by sequestering additional carbon. Sequestration activities can be carried out immediately, appear to present relatively cost-effective emission reduction opportunities, and may generate environmental co-benefits. At the same time, it is important to recognize that carbon sequestered in trees and soils can be released back to the atmosphere, and that there is a finite amount of carbon that can ultimately be sequestered.  There are three general means by which agricultural and forestry practices can reduce greenhouse gases:

(1) avoiding emissions by maintaining existing carbon storage in trees and soils;

(2) increasing carbon storage by, e.g., tree planting, conversion from conventional to conservation tillage practices on agricultural lands;

(3) substituting bio-based fuels and products for fossil fuels, such as coal and oil, and energy-intensive products that generate greater quantities of CO2 when used.

Internet Link: http://www.epa.gov/sequestration/faq.html#1

WATER MANAGEMENT

WATER AND SOLUTE MOVEMENT

45. Explain how the following components interact to influence the soil water cycle

[Harpstead, M.I. 1997. Soil Science Simplified. p 73. Iowa State University Press.]

The soil water cycle can be explained by the following equation:

      Total Soil Water (TSW) = WS + RF + IR - RO - ET - DP

a. Precipitation or Rainfall (RF): Water added naturally to TSW (rainfall).

b. Irrigation (IR): Water added artificially by farm manager (irrigation).

c. Runoff (RO): Water that runs off the soil before it has become infiltrated, does not become part of the TSW.

d. Soil Water Storage (WS): The amount of water that is already in the soil at any given point in time.

e. Evapotranspiration (ET): The water that is lost due to either evaporation from the soil or transpiration from the plant.

f. Deep Percolation (DP): The water that percolates deep into the soil after the soil has reached water-holding capacity and become saturated.  This water can reach below the point where it is available to plant roots.

46. Describe how soil texture, soil structure, and soil organic matter affect infiltration

The pore sizes of the soil in relation to hydrated solute molecules determine the solubility and permeability of the soil.  If the solute is larger than the pore size, the solute will act like an impermeable membrane (Miyazaki, 10-11). Naturally soils with a higher sand and gravel percentage will infiltrate water better than most clays.  Soils high in organic matter (humus) have good tilth allowing for better water infiltration in finer soils.

47. Describe how the following factors influence surface runoff

a. infiltration: The more rapid the infiltration rate, the lower the amount of surface runoff that will occur.

b. landscape position: Landscapes with the highest position would erode fastest, would have the greatest surface runoff, and the least leaching potential, and lateral flow.  Soils in these positions would be the youngest or least developed.  The soils on the hill tops, or relatively level uplands, would have the strongest development because they would remain undisturbed for the longest period of time-until they are removed by eroding slopes.  The shallow and least-developed soils would be on the lower part of the sloping landscape, called backslopes.  They would have high potential for surface runoff, but low lateral flow and leaching potential.  [Ref. Troeh, F.R., J.A. Hobbs, and R.L. Donahue.  1999.  p.  56-57.  Soil and Water Conservation: Productivity and Environmental Protection.  3rd ed.  Prentice Hall.]

c. permeability: Soil permeability has much the same influence on surface runoff, leaching potential, and lateral flow as does infiltration rate.  Infiltration rate is a function soil permeability.  Greater permeability will, therefore, result in reduced surface runoff, higher leaching potential, and a higher potential for lateral flow to occur.

Internet Link: http://physics.uwstout.edu/geo/perm_dewat.htm Further study material from UW-Stout

d. surface residue cover: Residue cover reduces surface runoff because of greater water infiltration into the soil.  [Ref. Troeh, F.R., J.A. Hobbs, and R.L. Donahue.  1999.  p.  85-87, 151, 230-231, 363-364.  Soil and Water Conservation: Productivity and Environmental Protection.  3rd ed.  Prentice Hall.]

e. surface roughness: Surface roughness is created by making ridges in the soil to help stop surface runoff by trapping or slowing down the water and soil between the soil ridges.

48. Describe how the following factors influence leaching

a. Infiltration: To leach salts from a soil, infiltration of the leachate (water) into the soil is a must.  If sodium has built up to the point it destroys the soil's structure, it is impossible for water to infiltrate it, thus leaching cannot occur.

b. Permeability: Since permeability refers to the ease with which liquids, gases, or plant roots penetrate or pass through a soil, it is tied closely to infiltration, i.e., a soil that is not permeable will not allow infiltration of water into the profile.  Without permeability leaching cannot occur.

c. Soil depth: The depth of a soil is related to leaching in that the greater the depth the more water must be applied, because of the amount the soil will hold, to successfully leach salts from the soil.

d. Water holding capacity: The leaching process is a function of the water holding capacity and depending on the type of soil some soil can leach faster that others if they have a lower water holding capacity.

e. Texture: Soil texture is related to soil composition.  The nature of the composition in its extremes is either so fine that it holds water or is so large that it allows water to pass right through. Most soils are a combination, but still leans to dense or porus in nature.  Porus soils facilitate leaching.

49. Define preferential flow

The nonuniform movement of water and its solutes through a soil along certain pathways, which are often macropores.

50. Describe how the following affect N, P, K, or S movement

a. Soil pH: The pH must be in the range in which the solute will go into solution in the solvent for solute movement to occur.  If the pH is such that the solute precipitate out, or is bound to some other substance, movement will be negligible.

b. Organic matter: Organic matter tends to absorb both the solvent and the solute, thus solute movement will be reduced by greater concentrations of organic matter in the soil.  Organic matter also has exchange sites that will hold ions, thus reducing solute movement.

c. CEC: The cation exchange capacity strongly affects the mobility of nutrients.  Cations are much less likely to be leached than anions.  The CEC attracts cations or nutrients toward the surface of the soil.

d. Soil texture: Coarse textured soils, such as sand or sandy silts or sand loams, have less surface, thus less binding of cations or other positively-charged solutes will occur and solute movement will be increased.  Such soils also will hold less water, thus resulting in more water movement, which will result of greater solute movement also.  Clays, clay loams, loamy clays, silty loams or clays will have more surface area, with more exchange sites, and positively charged cations and other solutes will be held, thus less solute movement.  The greater water-holding capacity of these soils will also result in less solute movement simply because the solvent is being held by the cohesive forces of the soil.

e. Nutrient Solubility: Movement of nutrients in the soil is based first on its solubility and then on its capacity to move.  High nutrient solubility can result in salt damage to seedlings when excess fertilizer is applied close to seeds or plants. Because nutrients in commercial fertilizers are readily available, under some circumstances more may leach to groundwater.  

Nitrogen may be fixed in a number of ways or may be leached out but is generally easily replenished.

Phosphorus solubility is determined by

  a.  soil pH

  b.  presence fof soluble Fe, Al, Mg and minerals containing these

  c.  available Ca and Ca minerals

  d.  amount and decomposition rate of organic matter

  e.  activities of microorganisms

In strongly acid mineral soils, soluble Fe, Al, and Mg can exist and react with existing phosphates rendering them insoluble.  Often the amount of soluble metal ions greatly exceeds the amount of soluble phosphates, and only minute amounts of soluble phosphate will remain [for plants and algae] at equilibrium.

Potassium (K) exists in most soils, but is almost entirely locked up in primary minerals or fixed in secondary clays. 90-98% is in relatively unavailable forms.  1-10% is in slowly available form, fixed in vermiculite and smectites in nonexchangeable positions.  1-2% is readily available for plant roots (9/10 of which is adsorbed on clay and 1/10 of which is in solution, but this applies only to terrestrial soils).  The available and fixed K are in equilibrium with each other in the same way as described for ammonium.  Brady notes that alternate wetting and drying seem to cause the fixation.

Internet Link: http://www.sare.org/publications/bsbc/chap16.htm

Internet Link: http://www.thekrib.com/Plants/Fertilizer/substrate-kelly.html#0

Parnes, R. 1990. Fertile Soil: A Grower's Guide to Organic and Inorganic Fertilizers. agAccess, Davis, CA. Soil Tests Soil tests, one of the key nutrient management tools, are discussed in detail in chapter 19.

51. Describe how the following management practices affect potential for solute movement

a. Timing of application: fertilizer applied during the fall or during wet periods, will result in greater solute movement through the soil, all other things being equal, or through surface runoff.  Nitrogen is the nutrient most likely to be an environmental problem because it moves through the soil in a solution.  Applied N can readily move to depths of 3 m.  P and K are fixed in the soil and do not move in a solution.  Surface runoff is the main source of these elements as pollutants of streams, lakes, and rivers. Ref: Havlin, et al., 1999.  Soil Fertility and Fertilizers, 6th ed., Prentice Hall.

b. Rate of application: As the rate of fertilizer application increases, the potential for solute movement increases.  Elements such as P and K do not move very far before they are fixed by the soil.  Only 10 to 15% of the P added is available to the plant in a given year.  Because these elements are fixed, they will not become a solute in the soil water.  However, nitrogen readily moves in the soil water, and higher applications of this element result in greater amounts moving in the soil water.

c. Erosion and runoff control: Control of erosion, and thus reduction of runoff, will greatly reduce movement of applied fertilizers.  All fertilizers are susceptible to movement with the soil that is carried by the runoff water.

d. Irrigation: With the soil pores filled with water, the potential for solute movement is enhanced.  Tail water also carries large amounts of solutes to the end of the field and into the drainage ditches.

e. Type of tillage operation: (a conventional tillage operation) This type of tillage has no more potential for solute movement than others, except for situations where soils are prone to erosion (sloping).  In these cases, anything applied to the soil will be carried off with the soil suspended in the runoff water.

Internet Link: http://www.soilsci.ndsu.nodak.edu/papers/1995_asa_dfr.html Further study material from North Dakota State University

52. List the processes that can transport phosphorus from a field

Eroded soil particles, runoff water, biomass removal (clear cutting, clean till tillage), leaching, and phosphorus fixation (making the nutrient unavailable for plant use).

53. List management practices that reduce phosphorus transport from a field

Saturation of phosphorus-fixing capacity, placing fertilizer so that it is readily acceptable for root systems, combining ammonium and phosphorus fertilizers, using phosphorus efficient plants, maintaining soil pH between 6.0 and 7.0, and the enhancement of mycorrhizal symbiosis.

54. Describe how lateral flow contributes to surface water contamination

Two factors determine the flow of water in soil: first is the force acting on each element of volume of the soil water, second is the resistance to flow offered by the soil pore space.

The force acting upon soil water consists of two items: gravitational force which tends to make the water fall or flow downward, and force due to differences in hydrostatic pressure at various points in the system.  Water tends to move from zones of higher to lower pressure.

Lateral flow occurs only to the extent that hydrostatic pressure differences exist.  It is always influenced by the downward pull of gravity.  In a system where drainage ditches or tiles have been installed, the difference in hydrostatic pressure half way between two ditches or tiles and the pressure at the tile or ditch will differ enough for the water to flow laterally.  In these cases, surface water could be contaminated by anything dissolved in the water-nitrate or pesticides. [Ref.  Childs, E.C.  1969.  An Introduction to the Physical Basis of Soil Water Phenomena.  p.  153-178.  Wiley and Sons.]

Other situations in which differences in hydrostatic pressure are set up will result in some movement of water, when there is excess water in the soil or the soil is saturated, that will carry contaminants into the surface water.

Internet Link: http://www.gardenwithinsight.com/help100/00000564.htm Further study material from Kurtz-Fernhout Software

PLANT-WATER RELATIONS

55. Define the following soil water terms

a. saturation: the level above field capacity when all soil pores are filled with water from rainfall or irrigation.

b. field capacity: the percentage of water remaining in a soil two or three days after it has been saturated and after free drainage has practically ceased.

c. permanent wilting point: the moisture content of the soil, on an oven-dry basis, at which plants wilt and fail to recover their turgidity when placed in a dark, humid atmosphere.

d. gravitational water: water that moves into, through, or out of the soil under the influence of gravity.

e. plant available water: the portion of water in a soil that can be readily absorbed by plant roots. The amount of water released between the field capacity and the permanent wilting point.

f. evapotranspiration: the combined loss of water from a given area and during a specific period of time. Water loss by evaporation from the soil surface and by transpiration from plants.

56. Describe how the following factors influence evapotranspiration

a. wind: wind removes moisture vapor creating a vapor pressure gradient and increasing erosion.

b. temperature: on warm and hot days there is a greater vapor pressure gradient between the leaf and the atmosphere.  This vapor pressure gradient will cause increased evapotranspiration.

c. solar radiation: regions with cloud cover will have less evapotranspiration. In arid regions with little cloud cover, there will be greater evapotranspiration.

d. relative humidity: when atmospheric vapor pressure is high, usually in regions of low humidity, there is less evapotranspiration.  In humid areas the vapor pressure is lower causing there to be a low rate of evapotranspiration. (Brady 500-501)

e. soil water status: evapotranspiration will be at its highest, at any temperature, when the soil is at or above field capacity.  As the water held in the soil's pores decreases, evapotranspiration will decline and it will approach zero as the soil approaches the permanent wilting point.

f. plant canopy: as the canopy increases, the amount of evapotranspiration will also increase.  A maximum level of evapotranspiration will be maintained for a time, and then as the crop matures, and water needs are reduced, evapotranspiration will decline.

g. crop residue surface cover: cover will reduce the amount of evapotranspiration in two ways: (1) shading the soil and keeping the temperature cooler, thus resulting in less evaporation; (2) keeping the sun from directly striking the soil surface, thus the radiant energy is reflected back into the atmosphere.  Usually the residue cover is lighter in color, which causes it to reflect a greater proportion of the radiant energy.

Internet Link: http://www.baen.tamu.edu/users/munster/agen_350_00/homeword/notes_hw26.html Further study material from Texas A&M University

Internet Link: http://www.geog.ouc.bc.ca/physgeog/contents/8j.html Further study material from Okanagan University College

57.Explain how excessive soil moisture affects plant nutrient uptake and availability

Plant nutrient availability may actually be enhanced by the formation of manganous and ferrous ions which can take part in cation exchange.  In so doing, they will increase the amounts of exchangeable Ca, Mg, and K that comes into solution.  The reduction of ferric oxides also may release phosphates into solution.  Plants must have oxygen available for use in the process of nutrient uptake.  Thus prolonged excessive soil moisture will result in less nutrient uptake.  Plants that have adapted to wet, water-logged conditions, have mechanisms whereby oxygen is transported down through the plant to the outer surface of the roots, in effect providing uptake of nutrients in aerobic conditions.

Ref: Russell, E. W.  1973.  Soil Conditions and Plant Growth, 10th ed., Longman Group Ltd., Ch. 25.

58. Explain how soil moisture deficiency affects plant nutrient uptake and availability

As the soil moisture decreases, plants will take up less nutrients because less water, which holds the nutrients in solution, is available to meet the plant's transpiration needs. Reduced root development due to soil moisture deficiency also limits above ground growth and nutrient uptake.

IRRIGATION AND DRAINAGE

59. Describe the following irrigation methods

a. furrow: Water applied to the upper end of a field and then allowed to travel by gravity to the end of the field. Furrow irrigation is the cheapest of these three types of irrigation, but only has a field water efficiency of 40-50%. It is suitable on soils that are nearly level and not too sandy or rocky.

b. sprinkler: In sprinkler irrigation, water is sprayed through the air onto a field, simulating rainfall. Various forms of sprinkler irrigation are used including center pivot, movable pipe, and solid set sprinklers. The field water efficiency is 60-70% and suitable soils for this type of irrigation are level to moderately sloping and not too clayey.

c. drip/trickle: Tiny emitters attached to plastic tubing apply water to the soil surface alongside individual plants or they may be buried 20-50 cm deep to directly wet the root zone. Water is applied at a slow rate giving drip systems the highest field water efficiency at 80-90%. Drip systems can be used on steep to level slopes with any texture, including rocky or gravelly soils.

Internet Link: http://wwwga.usgs.gov/edu/irquicklook.html Further study material from United States Geological Survey

d. flood: water is pumped or brought to the fields and is allowed to flow along the ground among the crops. This method is simple and cheap, and is widely used by societies in less developed parts of the world as well as in the U.S. The problem is, about one-half of the water used ends up not getting to the crops. Traditional flood irrigation can mean a lot of wasted water!  Some things that farmers are doing to be more efficient are 1) Leveling of fields, 2) Surge flooding, and 3) Capture and reuse of runoff.

Internet Link: http://ga.water.usgs.gov/edu/irmethods.html

e. subsurface: Though initially expensive and not suitable for many areas, the economical advantages of drip irrigation can be further enhanced by placing the irrigation tubing about 5 inches (about 12.7 centimeters) below the surface -- where the water really does get straight to where it's needed - the roots of the plant. Evaporation is greatly reduced, and there is no surface runoff.

60. Describe the following drainage methods

a. Tile: Porous clay, plastic or concrete tile is placed beneath the soil, deep enough that tillage operations will not interact with it, usually 3 to 5 feet in humid regions and 6 to 7 feet in arid regions.  Deeper placement permits greater distance between lines, whereas shallower placement makes water more available to crops.  Depending on the characteristics of the soil, the distance between parallel lines will vary, as will the distance between lateral lines.  The goal is to place the lines so that the excess water that will not otherwise drain form the soil will be moved out through the drainage tile lines.  Maintaining a suitable slope in the drain lines is very important - a minimum gradient of 0.1% for 4-inch drain lines and 0.05% for 6-inch lines.

b. Open ditch: Ditches are dug that will remove the excess water from the soil, whether it be from subsurface or surface sources.  The ditches are strategically placed so that the excess water can be removed without leaving areas that are farthest from the ditches wet.  Ditches for subsurface drainage are usually deeper and spaced farther apart than tile drains.  They may be from 6 to 10 feet deep and spaced from 300 to 650 feet apart.

c. Beds: Bedding systems and mounds are sometimes used for surface drainage where the slope is less than 1%.  The areas between drains are usually graded into a raised, convex shape.  Grassed waterways about 20 inches deep with about 8:1 side slopes are located between the beds.  Row crops may be grown on the crowns, but not in the waterways, with the rows running parallel to the waterways.  The crowned areas are usually about 65 wide

Internet Link: http://ohioline.ag.ohio-state.edu/b871/b871_2.html Further study material from Ohio State University Extension

61. Explain how to use field soil moisture measurements and the water balance equation to schedule irrigation

Field soil moisture measurement:  Water in soil is measured as a function of the volume of bulk soil.  This includes percent of water on a weight bsasis (grams/gram), percent of water on a volume basis (in/in), and inches of water per foot of soil (in/ft).  Water can also be calculated on a weight basis but should be converted to a volume measurement by multiplying water by weight by the soil bulk density. The best measurement is to take a soil sample of known volume, dry the soil and determine the water content weight and the dry soil weight.  As a general rule when 50 percent of the available water is depleated it is necessary to irrigate to prevent plant water stress.  When salts in the rootzone are excessive a lesser depletion is used to prevent excessive plant stress.

Internet Link: http://ucce.ucdavis.edu/files/filelibrary/40/975.pdf

Water balance equation: The water content in the effective root zone is estimated by using the water balance equation:

WCt = WC(t-1) + IRR + RAIN - AET - DP (1)

where:

WC(t)= Soil water content today (inches),

WC(t-1)= Soil water content yesterday (inches),

IRR= Irrigation depth since yesterday (inches),

RAIN= Rain since yesterday (inches),

AET= Actual ET (inches), and

DP= Deep percolation (inches).

Water balance calculations cannot begin until soil water content in the root zone is known. It may be established before or after crop emergence. Methods include gravimetric soil water samples or the hand-feel method (fact sheet 4.700, Estimating Soil Moisture). From this, the soil water content of successive days can be estimated using the water balance equation.

Four additional values are needed for the water balance equation. Irrigation and rain are the deposits in water balance and are measured or calculated values. Rain is measured by using rain gauges. Irrigation depth is calculated from the application rate of the irrigation system and the duration of application, or by dividing the total net amount of water applied by the irrigated area. If the depth of irrigation or rain exceeds the depth of water depleted from the root zone, the difference is considered as deep percolation (DP) or water that drained below the root zone and is not available for plants.

The last value, actual evapotranspiration (AET), is not measured easily. This is the daily withdrawal in the equation. It is estimated from weather and crop information.

The procedure used to estimate AET is as follows:

AET = ETr * KC * KS (2)

The reference ET (ETr) is the rate of water lost by a well-watered reference crop, usually alfalfa. This equation adjusts ETr by the crop coefficient (KC) and the soil dryness coefficient (KS). KC defines the stage of growth of the crop, and KS is a function of actual soil water content.

The ETr can be estimated using different ET models that relate ETr to weather conditions. To estimate ETr using ET models, daily weather information is needed. This information may include temperatures, solar radiation, humidity and wind run, depending on the particular ET model used. In several locations, daily ET rates are computed and published by Cooperative Extension agents or Natural Resources Conservation Service (NRCS) personnel as ETr values or AET values for specific Crops. If AET values are published, the crop coefficients were already considered for the particular crop.

Internet Link: http://www.ext.colostate.edu/pubs/crops/04707.html

62. Describe how soil texture affects tile drainage spacing and depth

Internal drainage depends on soil texture and is classified as excessively drained, somewhat excessively drained, well drained, moderately well drained, somewhat poorly drained, poorly drained, or very poorly drained.  The last three will usually require some form of artificial drainage for good crop yields.  [Ref. Troeh, F.R., J.A. Hobbs, and R.L. Donahue.  1999.  p.  173-174.  Soil and Water Conservation: Productivity and Environmental Protection.  3rd ed.  Prentice Hall.]

Well-drained soils show good aggregation and soil structure.  They are usually loams with good infiltration and permeability and they have sufficient slope for surface water to drain off without accumulating and causing crop damage and without causing erosion.  The pH is usually less than 8.

Poorly-drained soils may be predominantly clay or they may have a claypan, or some other physical restriction, that reduces or restricts internal drainage.  In arid areas, these soils have lost their structure or aggregation because of high levels of sodium.

63. Identify methods to reduce irrigation runoff

Three main methods are used to reduce irrigation runoff: Maximize Water Use Efficiency (WUE), Maximize infiltration, and Provide retention.  Maximize Water Use Efficiency (WUE) examines the types of plants and the delivery systems.  Maximize infiltration focuses on increased permiability of the soil. And the third, Provide retention, focuses on retarding the flow of water.

WATER QUALITY

64. Describe how nutrients, pesticides, and sediments can move to off-site areas

Nutrients: can move to off site areas through leaching, surface runoff, and erosion.

Pesticides: can move to off site areas by wind or through air currents generated by ventilation systems.  In water pesticides are move through runoff and leaching.  Animals, plants, and various objects can carry the pesticide residues offsite.

Sediments: are mainly moved to offsite areas by wind and water erosion.

65. Identify souces of information that provide water quality standards

Internet Link: <HT{icon}{~HTTP~}{www.epa.gov/waterscience/standards}>

Internet Link: <HT{icon}{~HTTP~}{www.epa.gov/ost/wqs}>

66. Distinguish between nitrogen analysis expressed as nitrate or nitrate-oxygen

Nitrate analysis is when nitrogen is expressed as nitrate as well as nitrogen associated with ammonium.  When expressed as nitrate-nitrogen, it is the amount of nitrogen in the form of nitrate only, which is considered a health-hazard.

67. Identify the health effects of drinking water containing nirate-nitrogen above the driking water standard

Some of the human health effects of nitrate contamination can include interference with the body's ability to deliver oxygen to the body causing methoglobinemia, or blue baby syndrome.  Other health effects can include cancer, disruption of the thyroid function, birth defects, and miscarriages.

68. Describe how water contamination occurs at the wellhead

Pollution moves through the soil and can contaminate aquifers.  This pollution moves through the aquifer and reaches a water well contaminating the water in the well.  The water in this polluted well may no longer be acceptable for consumption and may need to be abandoned.  In addition to pollution by way of aquifers, cracked casings and wells in drainage areas can contribute to contamination.  Fertilizer and chemical loading areas located near wellheads can also be sources of measurable contamination.

69. Explain the purpose of preventing contamination at a wellhead

About 95 percent of this country’s rural residents use ground water to supply their drinking water and homestead needs. Wells should be designed to provide clean, safe water. If improperly constructed or maintained, however, wells can allow bacteria, pesticides, fertilizer or oil products to contaminate ground water. These contaminants can put family and animal health at risk.

The condition of your well and its proximity to contamination sources determine the risk it poses to your ground water. For example, a cracked well casing may allow fertilizer, nitrates, oil or pesticides to enter the well if these materials are spilled near the well. Feedlots, animal yards, septic systems and waste storage areas also can release large amounts of bacteria, nitrates and other contaminants that could pollute well water.

Internet Link: http://waterhome.tamu.edu/texasyst/wellhead.html

69. Explain the purpose of anti-backsiphoning devices

A vacuum can form in the pipe drawing chemicals and dirty water back down the pipe and into the well.  Anti-backsiphoning devices placed between the well and the pump stop water from flowing back down the pipes, avoiding contamination of the well water.

71. Explain how high sediment levels affect surface water quality

Sediment is one of the greatest pollutants of water.  It makes the water muddy and plugs waterways, which kills fish and disrupts efficient drainage systems.  Sediment may also carry harmful pesticides and other chemicals into water supplies.

72. Describe how the following components of animal products, manures, and other biosolids affect surface water quality

As animal by-products, manures, and other biosolids are used as a nutrient for a field main focus is to meet the maximum nitrogen level.  When this happens the phosphorus level is above the recommended level.  The P can then leach down into the ground water and can also be carried away with soil particles in surface runoff.

a. nutrients

Biosolids are the nutrient-rich organic materials resulting from the treatment of sewage sludge (the name for the solid, semisolid or liquid untreated residue generated during the treatment of domestic sewage in a treatment facility). When treated and processed, sewage sludge becomes biosolids which can be safely recycled and applied as fertilizer to sustainably improve and maintain productive soils and stimulate plant growth.

b. pathogens

Once the wastewater reaches the plant, the sewage goes through physical, chemical and biological processes which clean the wastewater and remove the solids. If necessary, the solids are then treated with lime to raise the pH level to eliminate objectionable odors. The wastewater treatment processes sanitize wastewater solids to control pathogens (disease-causing organisms, such as certain bacteria, viruses and parasites) and other organisms capable of transporting disease.

Rules governing the use and disposal of biosolids contain numerical limits, for metals in biosolids, pathogen reduction standards, site restriction, crop harvesting restrictions and monitoring, record keeping and reporting requirements for land applied biosolids as well as similar requirements for biosolids that are surface disposed or incinerated.

c. heavy metals

Non-organic matter settles into sludge. For instance, small amounts (parts per million) of heavy metals and other potentially toxic materials, including flame retardants (PBDEs) and persistent organic pollutants, are commonly found in sewage sludge in parts per million levels (there has been considerable research - and there is ongoing research - on the potential impacts of these in the soil environment and significant impacts have not been found when biosolids are applied in accordance with modern regulations).

Class A biosolids that meet strict vector attraction reduction requirements and low levels metals contents, only have to apply for permits to ensure that these very tough standards have been met. Class B biosolids are treated but still contain detectible levels of pathogens. There are buffer requirements, public access, and crop harvesting restrictions for virtually all forms of Class B biosolids.

Nutrient management planning ensures that the appropriate quantity and quality of biosolids are land applied to the farmland. The biosolids application is specifically calculated to match the nutrient uptake requirements of the particular crop. Nutrient management technicians work with the farm community to assure proper land application and nutrient control.

Internet Link: http://www.epa.gov/OWM/mtb/biosolids/genqa.htm

73. Explain how nitrogen and phosphorus affect surface and ground water quality

Excessive nutrients in the water causes increased growth of aquatic plants (eutrophication) which uses much of the available oxygen from the water and choking all of the life from the waterway.

Internet Link: http://hermes.ecn.purdue.edu/http_dir/ced/ccw/crc/agen521/agen521/epadir/wetlands/eutrophication.html Further study material from Perdue University

74. Explain the purposes of filter/buffer strips and riparian areas/tree plantings on water quality

These strips and plantings help to trap sediment, which may carry other pollutants like chemicals and fertilizers.  By slowing the water flow and allowing sediment to settle out prior to entering a waterway, contamination of and runoff into water resources is avoided.

Brady, N. C. 1984. The Nature and Property of Soils.  Ninth Edition.  Macmillan, New York. 14-16, 175, 245, 250, 254, 500-501, 534, 555.

Campbell, N. A.  1996. Biology. Forth Edition.  Benjamin Cummings, Menlo Park, CA.  34, 716-17.

Foth, H. D.  1990.  Fundamentals of Soil Science.  Eighth Edition. John Wiley & Sons, New York. 46, 318-320.

Hopkins, W. G. 1995. Introduction to Plant Physiology.  John Wiley & Sons, New York. 42.

Miller, G. T.  1996.  Living in the Environment.  Ninth Edition.  Wadsworth, Belmont, CA. 511-524.

Miller, R. W., R. L. Donahue.  1990.  Soils - An Introduction to Soils and Plant Growth.  Sixth Edition.  Prentice Hall, Englewood Cliffs, NJ.  143, 430.

Miyazaki, T. 1993.  Water Flow in Soils.  Marcel Dekker, Inc., New York. 10-11

Troeh, F. R., J. A. Hobbs, & R. L. Donahue.  1991.  Soil & Water Conservation.  Second Edition.  Prentice Hall, Englewood Cliffs, NJ.  69-95, 107.

75. Define Biochemical Oxygen Demand (BOD)

Biochemical (biological) Oxygen Demand (BOD) is a test used to measure the concentration of biodegradable organic matter present in a sample of water. It can be used to infer the general quality of the water and its degree of pollution by biodegradable organic matter. It is used in general water quality management and assessment, Ecology and environmental science.

BOD measures the rate of uptake of oxygen by micro-organisms in the sample of water at a fixed temperature (20°C) and over a given period of time( usually 5 days) in the dark. To ensure that all other conditions are equal, a very small amount of micro-organism seed is added to each sample being tested. This seed is typically generated by diluting activated sludge with de-ionised water. The test generally takes place over an elapsed period of 5 days but other BOD tests are also used.

76. Describe how BOD affects water quality

The stream system both produces and consumes oxygen. It gains oxygen from the atmosphere and from plants as a result of photosynthesis. Running water, because of its churning, dissolves more oxygen than still water, such as that in a reservoir behind a dam. Respiration by aquatic animals, decomposition, and various chemical reactions consume oxygen.

Wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms, which use oxygen in the process. (The amount of oxygen consumed by these organisms in breaking down the waste is known as the biochemical oxygen demand or BOD. A discussion of BOD and how to monitor it is included at the end of this section.) Other sources of oxygen-consuming waste include stormwater runoff from farmland or urban streets, feedlots, and failing septic systems.

Oxygen is measured in its dissolved form as dissolved oxygen (DO). If more oxygen is consumed than is produced, dissolved oxygen levels decline and some sensitive animals may move away, weaken, or die.

DO levels fluctuate seasonally and over a 24-hour period. They vary with water temperature and altitude. Cold water holds more oxygen than warm water (Table 5.3) and water holds less oxygen at higher altitudes. Thermal discharges, such as water used to cool machinery in a manufacturing plant or a power plant, raise the temperature of water and lower its oxygen content. Aquatic animals are most vulnerable to lowered DO levels in the early morning on hot summer days when stream flows are low, water temperatures are high, and aquatic plants have not been producing oxygen since sunset.

Internet Link: http://www.epa.gov/volunteer/stream/vms52.html

Soil and Water Management Glossary

A horizon: Mineral soil horizon formed at or near the soil surface. It displays the greatest amount of leaching and is usually higher in organic matter and biological activity than the deeper horizons.

Acid soil: A soil that has a pH value less than 7.0.

Aggregate, soil: A mass of fine soil particles held together by clay, organic matter, or microbial gums. Aggregates are part of soil structure.

Alkaline soil: A soil that has a pH value greater than 7.0.

Alluvium: A general term for all eroded material deposited by running water including gravel, sand, silt, and clay.

Anion: An ion with a negative charge.

Anion exchange capacity (AEC): The sum total of exchangeable anions that a soil can adsorb. Expressed as centimoles of change per kilogram (cmolc/kg) of soil or milliequivalents per 100 g of soil (meq/100 g soil).

Aquifer: Layers of underground porous or fractured rock, gravel, or sand through which considerable quantities of groundwater can flow and which can supply water at a reasonable rate. May be classified as perched, confined, or unconfined.

Available nutrient: An essential nutrient in forms that a plant can absorb.

Available water: Portion of water in soil that can be readily absorbed by plant roots.

B horizon: The zone of accumulation of materials such as clay, iron, aluminum, and organic matter moving from the above horizons.

Bedrock: Solid, or consolidated, rock lying under the soil.

Biological oxygen demand (BOD): The amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water and used as a measure of the degree of water pollution.

Biosolid: Any organic material, such as livestock manure, compost, sewage sludge, or yard wastes applied to the soil to add nutrients or for soil improvement.

Blocky: Soil structure classification in which aggregates are in the shape of blocks or polyhedrons.

Buffer strip: Areas or strips of land maintained in vegetation and strategically located on the landscape to help control runoff, erosion, and entrap contaminants.

Buffering: The ability of a solution, like the soil solution or irrigation water, to resist changes in pH when acid or alkaline substances are added. Often used when speaking of soil to describe its resistance to pH changes when limed or acidified.

Bulk density: The mass of oven-dry soil per unit volume, usually expressed as grams per cubic centimeter.

C horizon: Zone of parent material; contains the material from which A and B horizons form.

Calcareous soil: A soil containing significant amounts of naturally occurring calcium carbonate, which fizzes when dilute acid is applied.

Capillary action: Movement of water in the soil through small soil pores.

Carbon-nitrogen (C:N) ratio: The ratio of the mass of carbon to the mass of nitrogen in soil, organic material, or plants.

Cation: An ion with a positive charge.

Cation Exchange Capacity: The amount of exchangeable cations that a soil can adsorb at a specific pH, expressed as centimoles of charge per kilogram (cmolc/kg) of soil or milliequivalents per 100 g of soil (meq/100 g soil).

Clay: 1) The class of smallest soil particles, smaller than 0.002 millimeter in diameter. 2) The textural class with more than 40% clay and less than 45% sand, and less than 40% silt.

Claypan: A dense, compacted layer of clay found in the subsoil that limits or slows the downward movement of water through the soil.

Clean till: May be referred to as conventional tillage. Tillage where all plant residues are covered.  Low surface residue levels provide little protection from wind and/or water erosion.

Coliform bacteria: Microorganisms, which typically inhabit the intestines of warm-blooded animals.  They are commonly tested for in drinking water analyses to indicate pollution by human or animalwaste.

Colloid: A very tiny particle capable of being suspended in water without settling out. Soil colloids have a charged surface that attracts ions.

Compaction (soil): Increasing the soil bulk density, and concomitantly decreasing the soil porosity, by the application of mechanical forces to the soil.

Composite soil sample: A soil sample resulting from mixing together many individual samples.

Conservation tillage: A general term for tillage practices that leave crop residues on the soil surface to reduce erosion.

Contaminant: Any physical, chemical, biological, or radiological substance that is above background concentration but does not necessarily cause harm.

Contour: An imaginary line perpendicular to the slope that represents the same elevation.

Contour tillage: Tillage following the contours of a slope, rather than up and down a slope. Helps prevent erosion and runoff.

Crust: A thin layer of poorly aggregated surface soil formed by wetting and drying.

Deep tillage: Tillage deeper than that needed to produce loose soil for a seedbed, usually used to loosen a compacted subsoil.

Denitrification: The transformation of nitrate to gaseous forms of nitrogen, occurring under anaerobic conditions.

Discharge: Flow of surface water in a stream or the flow of ground water from a pipe, spring, ditch, or flowing artesian well.

Drainage: Rate and amount of water removal from soil by surface or sub-surface flow.

Ecosystem: Community of animals and plants and the physical environment in which they live.

Effluent: Discharge or emission of a liquid or gas.

Erosion: The movement of soil by water, wind, or tillage.

Eutrophication: Enrichment of water by nutrients, primarily nitrogen (N) and phosphorus (P), which results in excessive plant growth. Decomposition of this plant material can result in the depletion of oxygen in water, leading to the death of aquatic animals.

Evapotranspiration (ET): Loss of water to the atmosphere from the earth's surface by evaporation and by transpiration through plants.

Fallow: Soil left idle to accumulate water and/or mineral nutrients.

Field capacity: The amount of water a soil holds after free water has drained because of gravity.

Flood plain: Land near a stream that is commonly flooded when the water levels are high. Soil is built from sediments deposited during flooding.

Fragipan: A dense and brittle subsurface layer of soil that is hard.

Friable: The ease by which a moist soil can be crumbled.

Granular: Soil structure where the units are approximately spherical or polyhedral.

Gravitational water: Water that moves through the soil under the influence of gravity.

Ground water: Water in the saturated zone below the soil surface.

Gully: A large channel in the soil, caused by erosion that is deep and wide enough that it cannot be crossed by tillage equipment.

Hardpan: A dense, hard, or compacted layer in soil that slows water percolation and movement of air and obstructs root growth. Pans may be caused by compaction, clay, or chemical cementation.

Hazardous waste: Solid, liquid, or gaseous substance which, because of its source or measurable characteristics, is classified under state or federal law as potentially dangerous and is subject to special handling, shipping, and disposal requirements.

Heavy metals: Refers to: lead, copper, zinc, mercury, arsenic, cadmium, nickel, and selenium. Some states may list additional metals.

Highly erodible land: A soil mapping unit with an erodibility index of 8 or more.

Horizon (soil): A horizontal layer of soil, created by soil-forming processes, that differs in physical or chemical properties from adjacent layers.

Humus: Highly decomposed organic matter that is dark-colored and highly colloidal.

Hydrologic cycle: Movement of water in and on the earth and atmosphere through processes such as precipitation, evaporation, runoff, and infiltration.

Hygroscopic water: Water held tightly by adhesion to soil particles. Cannot be used by plants and remains in soil after air-drying. Can be driven off by heating.

Infiltration: Entry of water from precipitation, irrigation, or runoff into the soil profile.

Irrigation: Application of water to supplement natural rainfall

Leaching: The movement of material in solution by the drainage of water through the soil.

Loading: Amount of a substance entering the environment (soil, water, or air).

Mapping unit (soil): Basis for setting boundaries in a soil map. May include one or more soil series.

Mass flow: The movement of solutes associated with net movement of water.

Massive soil: A structureless soil.

Mineral soil: A soil whose traits are determined mainly by its mineral content; mineral soils contain less than 20 or 30 percent organic matter in the US and Canada, respectively.

Mineralization: The conversion of an element by soil organisms from an organic form to an inorganic form.

Minimum tillage: Tillage methods that involve fewer tillage operations than clean tillage does.

Mottling: Spots of different colors in a soil reflecting whether iron in the soil is reduced (greenish-grey colors when poorly drained) or oxidized (reddish-brown colors when well drained). Usually indicative of cycling between poor and good aeration.

Muck: An organic soil in which the organic matter is mostly decomposed.

Mulch: Natural or artificial layer of plant residue or other material covering the land surface which conserves soil moisture, holds soil in place, aids in establishing plant cover, and minimizes temperature fluctuations.

Mulch till: A full-width tillage and planting combination that leaves some plant residues or other material on the soil surface.

Non-point Source (NPS) Contamination: Water contamination derived from diffuse sources such as construction sites, agricultural fields, and urban runoff.

No-till/Direct seeding/Zero-till: Method of growing crops that involves no seedbed preparation prior to planting.

O horizon: A surface soil horizon primarily composed of organic matter.

Organic matter: The organic fraction of the soil exclusive of undecayed plant and animal residues.

Organic soil: Soil containing more than 20 or 30 percent organic matter in the US and Canada, respectively.

Peat: Unconsolidated soil material consisting of undecayed or slightly decayed organic matter that has accumulated underwater where low oxygen conditions inhibit decay.

Ped: A natural soil aggregate, such as a granule or prism.

Percolation: Downward movement of water through soil or rock.

Permanent wilting point: The soil water content at which most plants cannot obtain sufficient water to prevent permanent tissue damage.

Permeability: Capacity of soil, sediment, or porous rock to transmit water and gases.

pH: Numerical measure of hydrogen ion concentration, with a scale of 0 to 14. Neutral is pH 7, values below 7 are acidic, and values above 7 are alkaline.

Platy: Consisting of soil aggregates that are developed predominantly along the horizons; laminated; flaky.

Point source contamination: Water contamination from specific sources such as leaking underground storage tanks, landfills, industrial waste discharge points, or chemical mixing sites.

Potable: Water that is suitable for drinking.

Preferential flow: The rapid movement of water and its constituents through the soil via large and continuous pores.

Prismatic (columnar): Soil structure where the individual units are bounded by flat or slightly rounded vertical faces. Units are distinctly longer vertically, and the faces are typically casts or molds of adjoining units. Vertices are angular or sub-rounded; the tops of the prisms are somewhat indistinct and normally flat.

Recharge: Downward movement of water through soil to ground water.

Recharge area: Land area over which surface water infiltrates into soil and percolates downward to replenish an aquifer.

Restrictive layer: A nearly continuous layer that has one or more physical, chemical, or thermal properties that significantly impede the movement of water and air through the soil or that restricts roots or otherwise provide an unfavorable root environment.

Rill: A channel in the soil caused by runoff water erosion that is small enough to be erased by tillage.

Riparian zone: Land adjacent to a body of water that is at least periodically influenced by flooding.

Runoff: Portion of precipitation, snowmelt, or irrigation, which moves by surface flow from an area.

RUSLE II: Revised Universal Soil Loss Equation: An equation for predicting, A, the average annual soil loss in mass per unit area per year, and is defined as, A = RKLSCP, where R is the rainfall factor, K is the soil erodibility factor, L is the length of slope, S is the percent slope, C is the cropping and management factor, and P is the conservation practice factor.

Saline soil: A non-sodic soil containing sufficient soluble salt to adversely affect the growth of most crops.

Saltation – Movement of individual soil particles/small aggregates by wind, in which the particles are lifted as much as 12 inches above the soil surface, then travel a short distance before dropping back to the soil surface. From 50 to 80 percent of total soil transport by wind is by saltation.

Saturated zone: Portion of the soil or rock profile in which all pores are filled with water.

Sediment: Eroded soil and rock material, and plant debris, transported and deposited by wind or water.

Single grain: A structureless soil in which each particle exists separately as in sand.

Sodic soil: Soil high in sodium and low in soluble salts.

Soil loss tolerance (T value): (i) The maximum average annual soil loss that will allow continuous cropping and maintain soil productivity without requiring additional management inputs. (ii) The maximum soil erosion loss that is offset by the theoretical maximum rate of soil development, which will maintain an equilibrium between soil losses and gains.

Soil structure: The combination or arrangement of primary soil particles into secondary soil particle

units, or peds.

Soil survey: The examination, description, and mapping of soils of an area according to the soil classification system.

Soil texture: The relative proportions of sand, silt, and clay.

Solubility: Amount of a substance that will dissolve in a given amount of another substance, typically water.

Solute: A substance that is dissolved in another substance, thus forming a solution.

Stomate: Opening in the surface of a leaf through which water vapor, carbon dioxide, and oxygen pass.

Surface creep: Movement of sand-sized particles/aggregates by wind, in which the particles roll along the soil surface. Surface creep may account for 7 to 25 percent of total transport by wind.

Suspension: Movement of fine (<0.1 mm) soil particles by wind. The particles are dislodged from the soil surface, are small enough to remain in the air mass for an extended period. From 20 percent to more than 60 percent of an eroding soil may be carried in suspension.

Tillage erosion: The downslope displacement of soil through the action of tillage operations.

Tillage pan: Also known as a plow pan. A subsurface layer of soil having a bulk density that is higher than the layer either above or below it. The compaction is caused by the forces exerted during tillage operations.

Tilth: Physical condition of the soil in terms of how easily it can be tilled, how good a seedbed can be made, and how easily seedling shoots and roots can penetrate.

Volatilization: The loss of a compound in gaseous form.

Water holding capacity: Similar to field capacity; the amount of water a soil holds after free water has drained because of gravity.

Watershed: All land and water that drains runoff to a stream or other surface water body.

Water table: Upper surface of the ground water or layer of soil saturated with water.

WEQ: An equation for predicting E, the average annual soil loss from wind erosion in mass per unit area per year, and is defined as, E = f(IKCLV), where f indicates “a function of”, I is the soil erodibility index, K is the soil surface roughness factor, C is the climate factor, L is the unsheltered distance, and V is the vegetative cover factor.

Wetlands: An area characterized by periods of inundation, hydric soils, and hydrophytic vegetation.

PEST MANAGEMENT

BASIC CONCEPTS OF PEST MANAGEMENT -- Principles of Integrated Pest Management (IPM)

1.  Describe how the following strategies are used to construct an effective IPM program

Integrated Pest Management (IPM) uses many strategies, including biological, physical, cultural, and chemical methods to control pests at a level which will ensure economic success and minimize negative impacts on the environment and human health. In order to effectively keep pest numbers below economically damaging levels, one must be familiar with the life histories of both the crops and pests involved. Goals of IPM are: 1. Optimize profits (over the long term), 2. Sustain agricultural and natural resources (over the long term), 3. More rational use of pesticides,  4. Reduce environmental contamination and costs; soil, groundwater, surface water, pollinators, wildlife, and endangered species, 5. Utilize natural biological controls; conserve and augment, use selective pesticides, proper timing of application, 6. Minimize pesticide resistance problems, 7. Minimize pest resurgence and secondary pest outbreaks, 8. Food safety; reduce residues of pesticides on food products, and 9. Worker safety; rely on pest management tactics that are safe for workers.

a. Prevention

Prevention is the act of anticipating and hindering a pest from existing.  This is done by depriving the pest of what it needs to exist by interposing an obstacle that will deprive it from occurring or advancing.  An effective IPM program will examine potential pests and establish preventative measures to minimize suspect pests populations within the above stated goals.

b. Avoidance

Avoidance is an act of emptying, vacating, or clearing away the occurrence or effectiveness of a pest.  An effective IPM program will take into account practices which will steer clear of or keep away from facilitating certain pests.  Avoidance is critical to circumventing pest populations.

c. Monitoring

Monitoring involves scouting and recording keeping.  Tracking pest populations is critical to any IPM program.  Knowing what is happening in your fields and what direction pest populations are heading are integral to the economics and health of your crop.  Monitoring allows you to find the signals from your fields and track the intensity of pest signals.

Factors to monitor in a pest management program include:

      -degree days

      -pest population size

      -control methods

      -effectiveness of treatments

      -crop damage

      -presence of insects, weeds, vertebrates, mites, diseases, nematodes

      -fertilization programs and practices

      -irrigation and drainage

      -possible side effects

d. Suppression

Suppression is the act of inhibiting or restraining the growth or development of pest populations.  It is not the elimination of or destruction of a pest, but the restraint of its population development.  This is the act of holding back, based on the above stated economic and safety goals, the advance of pest populations.

Internet Link: <HT{icon}{~HTTP~}{www.nysaes.cornell.edu/ipmnet/ne.ipm.primer.html}> Provides definitions and IPM information for those seeking basic or in-depth information on IPM.

2. Describe how to use each of the following steps on an IPM program

a. Sampling and monitoring:  Sampling procedures will vary according to the pest and crop in question.  Repeated sampling allows effective estimation and prediction of pest numbers and provides the basis for making informed, science-based decisions regarding control.

b. Identification:  Before taking any pest control action, it is necessary to correctly identify the pest (insect, mite, disease, weed, vertebrate, etc.).  Without correct identification control measures will not be effective and can cause greater harm.  Correct identification of pests makes control possible in a specific, economical, and environmentally safe manner.

c. Decision making:  Once the farmer identifies the pest and to what extent the pest population has expanded, a decision can be made concerning how to control it.  Pests should be controlled below economic damaging levels. Aids in decision making include: proper pest identification, pest monitoring methods, environmental monitoring, use of degree-day models, economic injury levels, and action thresholds.

d. Method evaluation:  The goal of IPM is to understand the life history of the pest in order to be able to chose a control method which will be the most effective, cost efficient and cause the least amount of harm to the environment, humans and other organisms.

e. Implementation:  Includes proper application of chemicals and  proper timing of treatment with regards to climatic factors as well as pest and crop development.

f. Evaluation and record-keeping:  After a pest control method is used, the area should be resampled to determine the effects of the treatment.  Was the pest control method effective?  Did it give short or long term results?  Were there any negative side effects?  It is vital to keep accurate records from year to year.  This information can be used in following years to predict pest problem areas and possible solutions to the problem.  Good record-keeping and proper evaluation will provide an increased ability to control pests in an economically profitable manner.

Internet Link: http://www.nysipm.cornell.edu/html This site outlines the six steps in pest management (some information on IPM was found in Bohmont, Bert L.  1996.  The Standard Pesticide User's Guide, p.395)

3. List the advantages of using IPM

The principles of IPM provide a more environmentally friendly and economically profitable way to manage pests.  There is a decrease in management costs, workers are exposed less to pesticides, and fish, wildlife, plants, water, air, soil and humans will be less impacted by pesticide residues.

4.  List barriers to implementing IPM

Some of the barriers to implementing IPM are as follows:

·     Lack of effective alternate control methods

·     High uncertainty of pest outbreaks

·     Lack of information about alternate control methods

·     Lower yields

·     Expense

·     Lack of “value added processor” support

·     Time commitment

·     Complexity

·     Long-term planning commitment

·     Shortage of advisors

BASIC CONCEPTS OF PEST MANAGEMENT -- Pest-Ecosystem Interactions

5. Explain how the following factors affect pest population development

a. Pathogens,  predators, and parasites:  Pathogens, predators and parasites of pests can often control population development if found in adequate numbers.  They will not totally eliminate a pest population, but they can keep the numbers in control.  An example of this interaction is lady beetles preying on aphids.  Lady beetles reduce the aphid population and the damage sustained to the crop.

b. Host plants:  Most pests have a preferred plant host, on which they have adapted to effectively feed and reproduce on the host plant.  If their host plant is found in abundance then the pest population will do well.  If the host plant has been modified, for example is genetically resistant, then the pest population will not be as successful.

c. Initial pest population: Initial pest levels can heavily influence peak population levels.  Very low levels may mean that the pest never increases to the point where it is an economic problem.  However, if the insect levels are high going into the growing season, the ultimate population may quickly reach epidemic proportions.

d. Temperature: Temperature can effect pest population development in many different ways.  Different insects have different temperature requirements.  In general, insects need warm temperatures to grow and develop.  If there is a very cold winter, summer populations may be smaller because more insects died overwintering.  Generally, the warmer the temperature the faster insects develop.

e. Moisture: The moisture levels in the environment in which the pest develops can have a significant influence on population development.  Fungal and bacterial diseases require moderate to significant amounts of moisture for development to occur to the point where the disease becomes a problem.  Some of the blights on fruit trees occur if the spring is wet and cool, but if it is not wet and cool the blight never becomes a problem.  Powdery mildew can become a significant problem if sufficient moisture is available, otherwise it may develop to some degree, but not enough to cause economic damage.  Other diseases may show similar development patterns as a function of available moisture.  Insect pests are also susceptible to the level of moisture.  If the environment is very dry, sufficient food may not be available for the larvae to survive and so the population may not develop to the degree it would with a more abundant food supply.  Humidity: Humidity is usually a function of moisture and temperature.  High moisture and low or cool temperatures result in high humidity.  Disease buildup is quite susceptible to prolonged periods of high or low humidity; under high humidity incidence of disease will increase, but under low humidity disease development will be reduced or even prevented.

f. Soil characteristics: Hardpans will sometimes prevent insects from burrowing deep enough into the soil to avoid lethally cold temperatures.  For example, Colorado potato beetles succumb to winter temperatures below -12°C.  In sandy soils they have been known to burrow to depths of 36 to 91 cm, thereby escaping the lethal temperatures. Hardpans in these soils prevent movement to the required depths and in cold winters survival will be reduced significantly.  Often overwintering sites are in the soil and when the conditions are unfavorable survival is diminished.  Ref: Pedigo, L. P.  1999.  Entomology and Pest Management, 3rd ed., Prentice Hall, Ch. 5.  (General reference on insect overwintering is: Leather, S.R. et al., 1993.  The Ecology of Insect Overwintering.  Cambridge, Great Britain: Cambridge Univ. Press.

g. Wind: Insect populations are capable of survival and develop only within certain environmental limits; desirable temperatures, humidities, and light intensities.  Bacterial and fungal populations also require optimum temperature, humidity, and light intensity for full development of the population.  Wind has the ability to alter temperature and humidity to the point that they may become less favorable to population development, thus reducing the population or causing it to develop later than it ordinarily would.  In effect, the window of opportunity for infestation of a crop may be missed. Ref: Pedigo, L.P. 1999.  Entomology and Pest Management, 3rd ed., Prentice Hall.

6. Explain how the following characteristics of insects influence their ability to survive and cause damage

a. Development time and seasonal period of activity:  Insects have fairly predictable development time and seasonal periods of activity.  Development time and seasonal activity can usually be predicted by the number of degree days that have passed.  If the insect's development time and seasonal activity period correspond with the time of plant development and harvest they can often cause significant crop damage.  Often, by slightly changing planting or harvesting dates and by rotating crops one can avoid major crop damage from insects.

b. Reproductive rate and number of generations per season:  Different insects have different reproductive strategies, but all strategies are intended to maximize survival of the species.  Some species produce multiple generations per season and others reproduce at the end of the season.

c. Overwintering and oversummering strategies:  Environmental conditions become unfavorable to most insects in the winter and sometimes in the hot summers also.  Insects who cannot handle these environmental conditions have developed overwintering (hibernation) and oversummering (aestivation) strategies to enable them to survive.  Some insects enter a state of dormancy, migrate or lay their eggs and die.

d. Feeding habits:  Insects which can use many different food sources tend to, as a rule, survive better because they are able to switch food sources in the event that one of their food sources becomes unavailable.  Insects which can only use one food source are more vulnerable, because if their food source is no longer available they will die.  However, if their preferred food source is abundant they do quite well.

e. Type of metamorphosis: There are three types of metamorphosis: no metamorphosis, incomplete metamorphosis and complete metamorphosis.  In no-metamorphosis, the organism hatches from an egg and maintains the same form.  The incomplete metamorphosis model is where the insect changes form through multiple molts.  Juveniles and adults may have different habitats and feeding habits.  Each insect species has evolved in such a way that their metamorphosis pattern enhances their survival rate.  Other sources refer to the different types of metamorphosis as gradual or complete.  A grasshopper is an example of gradual metamorphosis (larva looks like a small adult).  With complete metamorphosis, the young do not resemble the adult and go through several stages in their life cycle.  An example of complete metamorphosis is a caterpillar forming a pupa, then hatching into an adult butterfly.

Pedigo.  Entomology and pest management.  Pp. 159-162.

Internet Link: http://www.lib.ndsu.nodak.edu/subjects/ag/ent.htm Further study material from North Dakota State University

f. Dispersal and movement strategies:  Dispersal is population movement that can range from moving from one leaf to another or migrating thousands of miles.  Dispersal allows for population growth by providing more resources for a growing population of insects.  Dispersion can provide an environment where there will be more successful reproduction.  Long distance migrations are also ways for insects to avoid changing climatic conditions.

Pedigo.  Entomology and pest management.  Pp.  189-198.

Much of this information was taken from Chapter 5 of Pedigo, Larry.  Entomology and pest management.

7. Describe how environment, host plant, and pathogen interact to result in plant disease

Three things have to be present for a plant disease to develop.  The host plant must be susceptible to the disease, the pathogen (disease causing organism) must be present, and environmental conditions must be such that the pathogen can survive.  Without all three of these factors present disease will not develop.  This relationship is often referred to as a triangle in that if any one of these three factors are absent or eliminated, the disease will not be present.  For in depth information see Lucas, John A.  1998.  Plant pathology and plant pathogens.  Malden, MA: Blackwell Sciences, Inc.

8. Describe how the following plant pathogens survive and disperse

a. Fungi: Fungi do not produce their own food, nor do they have a way to digest food.  Fungi absorb nutrients directly from their environment and may produce chemicals to break down materials into an absorbable form. These nutrients are absorbed by the hyphae, or main underground cells of the fungus.  The mass of hyphae which form the underground body of the fungus is called the mycelium.  The cap we usually think of as the body of the fungus is the reproductive organ of the fungus. Most fungi reproduce by forming spores or by budding.   There are four main reproductive strategies used by fungi to reproduce.  1)  Sexual union between two spores, 2) genetic transfer of information between two cells, 3) spores which are in sacs, and  4) spores which are found in club-like structures.

Internet Link: http://www.ucmp.berkeley.edu/fungi/fungilh.html Has info on the life history of fungi

Internet Link: http://www.ucmp.berkeley.edu/fungi/fungimm.html Morphology and info on structure of fungus

b. Bacteria: Bacteria are found almost everywhere and can be both helpful and harmful.  They are single celled organisms which have a cell wall and contain DNA.  Bacteria get their nutrients in many different ways.  Some bacteria are autotrophs producing their own food (like plants) and others absorb nutrients from their environment.  Bacteria reproduce by copying their DNA and splitting in half.  Bacteria are able to reproduce at a very rapid rate, this causes populations of bacteria to grow very rapidly.

Internet Link: http://www.ucmp.berkeley.edu/bacteria/bacterialh.html Info on basic facts about bacteria

Internet Link: http://www.ucmp.berkeley.edu/bacteria/bacteriamm.html Info on morphology

c. Nematodes: Nematodes are small worm-like animals.  Most nematodes are microscopic in size and thousands of them may live in one handful of soil.  Nematodes reproduce inside of other insects and organisms.  They enter the insect and use their soft insides as a food source.  In a few days the life cycle is complete and hundreds of thousands of new nematodes exit the dead host.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/pathogens/nematodes.html Life history of nematodes included.  The site is coming from the angle of nematodes as a biological control.

Internet Link: http://ianrwww.unl.edu/ianr/plntpath/nematode/wormgen.htm Basic nematode information

d. Viruses: Viruses are microscopic in size.  They have an outer protein shell and they contain a segment of DNA or RNA.  They reproduce by inserting their DNA/RNA into a host cell.  The DNA/RNA takes control of the functions of the host cell.  The host cell begins to mass produce viral DNA/RNA and protein shells.  The cell then bursts and the new viruses emerge and look for other host cells to infect.

Internet Link: http://www.plbio.kvl.dk/~thluj3/symptoms/symplist.html Pictures of viral diseases that infect plants

Internet Link: http://www.ucmp.berkeley.edu/alllife/virus.html Basic introduction to viruses

9.  Describe how the following pathogens infect plant tissue

a. fungi

Germinating spores or hyphae penetrate the plant tissue through wounds of the epidermatic tissue, wounds of the cuticle or open stomata.  The consequent high loss of water causes finally the plant to die.

Internet Link: <HT{icon}{~HTTP~}{www.biologie.uni-hamburg.de/b-online/e33/33d.htm}> Additional information on fungi

b. bacteria

Bacteria and plants can have a mutually benign relationship where plants are dependent on bacteria for growth, and in return provide the bacteria with food. That is how alfalfa lives happily together with Rhizobium meliloti.

Indirect damage to plants can occur when bacteria promote the formation of ice crystals on soft fruit, like strawberries. After scientists discovered that secreted bacterial proteins formed the core of such crystals, they disabled the gene encoding this protein. These were among the first genetically modified bacteria used to protect crops (Source: EPA).

Bacteria can also cause diseases in plants. An example is crown gall 'tumors' that can typically grow on sunflowers, tomatoes, or roses, are caused by bacteria.  The bacteria affects the DNA altering its structure usually killing the plant.

Another  mechanism which is affected by bacteria is that they can pass bacterial genes to higher parasites: cyst nematodes (miniature worms) that are parasitic to plants.

Bacterial diseases of plants tend to cause spotting of leaves, stems or fruits; sometimes bacteria cause soft rots in which tissue becomes a slimy mess. Generally speaking bacteria cannot invade healthy plant tissue; they need a wound or an area of dead or dying tissue to start an infection.

Plant bacterial diseases can be controlled with the same kinds of antibiotics that are used to control animal diseases, such as streptomycin. However, we are generally reluctant to use these on a large scale and control is usually based on avoidance or removal of sources of innoculum.

c. nematodes

Nematodes are structurally simple organisms. Adult nematodes are comprised of approximately 1,000 somatic cells, and potentially hundreds of cells associated with the reproductive system . Nematodes have been characterized as a tube within a tube ; referring to the alimentary canal which extends from the mouth on the anterior end, to the anus located near the tail. Nematodes possess digestive, nervous, excretory, and reproductive systems, but lack a discrete circulatory or respiratory system. In size they range from 0.3 mm to over 8 meters.

After hatching, plant-parasitic nematodes move through the soil to find areas on plant roots to feed. Some nematodes stay outside the root and use long stylets to puncture cells inside the root (ring, stubby root, and sting nematodes). Nematodes which enter the root may move throughout the root (lesion nematode) and feed at many sites (causing root lesions), or stay in one feeding site (cyst and root-knot nematodes). Nematodes which stay at one feeding site swell from eel-shaped to pear-shaped and stay at the same site until they die.

Internet Link: http://www.barc.usda.gov/psi/nem/what-nem.htm Additional information on nematodes

Internet Link: http://nematode.unl.edu/wormgen.htm Additional information on nematodes

d. viruses

Symptoms depend on the type of virus and the type of plant. You may have seen pale yellow mottling or crinkling of the leaves of one of your plants. Or growth may have become inexplicably stunted. Any of these symptoms could have been caused by a virus infection. Virus symptoms might even come and go, showing up, for example, when cool temperatures slow growth.

Viruses (Virus particles or virions) are usually units consisting of nucleic acids and coat proteins called capsids. Viroids consist only of RNA, i.e. they contain no protein at all. Except for a few cases, viruses are not surrounded by a membrane. If present, the membrane around a virusparticle - as seen in electron microscopic images - stems usually from the host cell (see picture to the left). Viruses have no energy metabolism of their own. Consequently, they cannot perform syntheses and are thus unable to replicate themselves. Depending on their host species, it is distinguished between plant viruses multiplying almost exclusively within plant cells, bacterial viruses (bacteriophages) that depend on living bacteria, and animal viruses.

One way, then, to prevent virus infections in plants is to control insects or other organisms that spread viruses. Another control is to isolate cultivated plants from related wild plants and weeds, both of which might harbor viruses. Aphids, for example, can carry cucumber mosaic virus from ragweed or milkweed to cucumbers, or raspberry mosaic virus from wild raspberries to cultivated raspberries. Rip out any cultivated plant known to be infected with a virus.

10. Describe how the following weed factors affect the ability of weeds to survive and be competitive

a. Growth rate:  If weeds germinate earlier and grow faster than the crop, then they will reduce available sunlight and nutrients for crop growth.  Weeds may set seeds early and mature quickly, thus insuring the next weed crop.  If however, the crops are given their optimal growing conditions and get a head start on the weeds, they can often inhibit weed growth.

b. Seed production:  Weeds produce seeds which can be distributed by wind, birds, insects or simply drop to the ground.  Weeds produce many seeds which spread into new areas and ensure their survival.  Weeds generally produce extremely high amounts of seed that are small in size to ensure their survival.

c. Seed dormancy:  Seeds are usually dormant until the conditions are optimal for growth, usually in the spring.  Dormancy ensures that they will not start to sprout early (during winter months) and die.

d. Reproduction method:  There are different methods of reproduction.  Seeds, rhizomes and underground tubers are a few examples.  All methods of reproduction are designed to optimize the reproductive success of the weed and ensure the survival of the subsequent generations.

e. Light, temperature, moisture, and humidity: All of these factors affect weed growth as they do normal plant growth.  When these factors are outside the norm many plants have a more difficult time competing with certain weeds.  Because many weeds are more robust and more resistant to reduced photosynthetic processes, colder or hotter temperatures, problems related to reduced moisture, and diseases caused by increased moisture and humidity, these factors can benefit many weeds as they compete with other plants.

f. Life cycle:  Weed seed is very robust and usually has an enormous number of seeds which generally makes it very competitive when compared to crop seed.  The weed seed is the form of the plant that has the longest life, primarily because of its longevity in the soil seed bank.  The life cycle of the seed starts with the shift of the vegetative plant from growth to reproduction. The seed matures on the parent plant and is dispersed usually to the soil seed bank. The seed phase of the life cycle ends with seed germination and emergence.  Weed competitive advantage extends throughout the full cycle of germination, emergence, plant growth, reproductive phase and seed production.  Much of a weed’s competitive advantage is when factors (mentioned above) are outside of the norm.

Internet Link: http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_WG041 Detailed principles of weed management.  Many good weed topics linked to this, including weeds in different types of crops.

Internet Link: <HT{icon}{~HTTP~}{www.uwrf.edu./~dc01/wsglist.html}>

11. Describe competitive interactions of

a.  crops on weeds

Crops are bred to be high yielding plants and can often compete better than weeds for nutrients and sunlight if they are grown in their ideal conditions.  If crops are able to out compete weeds, then weed growth and distribution will be limited.  Dense crop canopies and narrow rows will also help limit weed growth by shading the soil.

b.  weeds on crops

Even if crops compete well for nutrients and sunlight weeds are fierce competitors and the competition will have an effect on the crop unless removed.  This competition has been long known and is even discussed in the Bible.

Internet Link: http://edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUMENT_WG041 Detailed principles of weed management (crop competition is about half way though the document).   Many good weed topics linked to this, including weeds in different types of crops.

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch3.htm#ITEM3C Cultural weed control

SAMPLING AND MONITORING

12.List advantages and limitations of the following sampling methods

a. Direct observation:  Direct observation is simple and cost effective.  However, it does not represent an overall perspective of how wide spread or contained is the problem.  For example, a farmer may observe a high number of pests in one area of a field and decide to spray all of the fields.  However, he may not know if the pest is a problem in all the fields or just in this one area.  If the pest isn't a problem in other areas, time and money would be wasted treating fields that do not have the problem.

b. Presence/absence sampling:  Presence/absence sampling is recording the presence or absence of a pest in a given area.  This is a very fast and simple way of gathering data.  However, since it doesn't give a count of how many were found in an area it is not possible to get a population estimate.  The relative presence of a pest may be determined, but it is impossible to quantify the severity of an infestation.

c. Sweep nets and drop cloths:  Sweep netting is a very common form of sampling insects in a field.  A net is drawn by a worker through the crop.  The sweeping action dislodges the insects, which fall into the net and can then be counted.  This is repeated several times in a field.  A fairly accurate estimate can be obtained using this method.  Disadvantages include required training on how to sweep a field and the necessity that the same person does the sweeping.

Internet Link: http://www.pme.iastate.edu.htm A picture of someone sweep netting an alfalfa field measuring the amount of leafhoppers.

d. Insect traps:  Insect traps, in particular pheromone traps, attract male insects by releasing female pheromones.  The males attracted to the traps are caught and die.  The advantage of pheromones traps for sampling is that they are relatively inexpensive and easy to set up.  They are an effective tool to determine whether or not a pest is in a field.  They do not provide direct population estimates, only relative estimates and are not directly related to damage levels in a field.  Pheromone traps also work 24 hours a day providing around-the-clock results.

Internet Link: http://www.roberth.u-net.com/Pheromones.htm Info on how pheromones are used in monitoring and pest control

Internet Link: http://www.uky.edu/Agriculture/Entomology/entfacts/fldcrops/ef112.htm Basic info on how to use pheromone traps and when to set traps for some moth species.

13. Describe how the following aid in monitoring pest infestations

a. weather data

Pest development and growth depend on temperature, moisture, duration, and nutrient source.  An essential aid in monitoring pest growth and population levels (infestation) is weather data.  By monitoring the temperature, moisture, and the day counts predictive models for pest infestation levels have been developed.  Weather data is the leading source for predicting pest infestation.

Degree Days:  The calculated total amount of heat required above the lower threshold for an organism to develop from one point to another in its life cycle is called a degree-day (°D).  Degree-days are the accumulated product of time and temperature between the developmental thresholds for each day. One degree-day is one day (24 hours) with the temperature above the lower developmental threshold by one degree.  For instance, if the lower developmental threshold for an organism is 51° F and the temperature remains 52° F (or 1° above the lower developmental threshold) for 24 hours, one degree-day is accumulated. Each species requires a defined number of degree-days to complete its development. The accumulated degree-days from a starting point can help predict when a developmental stage will be reached. The date to begin accumulating degree-days is known as the biofix date. Biofix dates are usually based on specific biological events such as planting dates, first trap catch, or first occurrence of a pest.  In general, monitoring begins at the biofix date and ends with the completion of the pest's developmental stage. Information on degree days and insect development is available at most universities.

b. level of infestation

Monitoring infestation levels is important for defining a given solution.  If infestation levels are monitored and found to be low a remedy can be found to keep infestation levels low.  Whereas if the level of infestation is found to be high, a stronger remedy may be required to bring infestation levels to acceptable levels.

c. time of year

Time of year plays a secondary role in monitoring pest infestations.  Most pest infestation is not dependent on time of year, but on temperature, moisture, duration, and nutrient source.  But because most of these factors happen at a given time of year it is important to note that time and be prepared to scout for specific pests.

By studying the life history of the insect in question, it is possible to determine when they will be emerging.  Monitoring can begin at or a little before the estimated emergence time or when it is hypothesized that they may become a problem.  Good record keeping from previous years can aid in predicting problem dates and periods.

d. crop growth stage

Because nutrient source is important in pest development, it is important to monitor pest infestation when plants reach certain stages of growth.  For example when the plant is in initial growth it may be important to monitor root and leaf development.  Whereas later on when fruiting it may be important to monitor fruit pests.

Because some insects are known to be a problem at certain crop stages and crops may be especially vulnerable at certain stages of development, insect levels should be closely monitored during these times to ensure that proper measures can be taken to control the populations if necessary.

Internet Link: http://ianrwww.unl.edu/pubs/insects/ Further study material from University of Nebraska-Lincoln

e. pest development stage

Pests feed differently at different stages of development.  The egg mass is not likely to do too much damage unless it affects photosynthesis or the increased moisture causes mold or fungus to occur.  The immature stages can be the most injurious to plants as insect and weed pests are ravenous for food and nutrients.  Later mature stages may also be more or less injurious depending on the pest.

14. List factors to consider when deciding how to obtain a representative sample from the following pest distribution patterns

a. Clumped:  A clumped distribution is one where the insects are found in groups with very few or no insects between groups.  When a population is very rare and very clumped a simple random sample will not give an accurate population estimation.  In such a case it may be beneficial to perform an adaptive cluster sample.  Random samples are taken.  However, when an insect is found to be present in a quadrant, measurements are taken on all sides of the quadrant.  This process is repeated until there are no insects found in adjoining sampling units.  This process allows an estimate to be made as to the size and frequency of the clumped units.  For more information on this procedure see Krebs, Charles J.  Ecological methodology.  1999.

b. Uniform:  A uniform distribution is one in which pests are found at equal distances from each other.  A simple random sample will do well at accurately sampling this type of distribution.  Depending on the distances between pests, a systematic sample could also be used.

c. Edge effect:  Edges of fields are not usually sampled unless it is believed that there will be a high number of pests in that area (Pedigo, 1999. Pg. 244).  If insects tend to prefer the edge of a field, a stratified sample may be considered.  In that case the field is divided into two sections, or strata, the edges and the middle.  A systematic or random sample is conducted in each of the two areas.  Subsequent data analysis will provide a more accurate estimate of population numbers.  On some occasions field edges may require different pest management recommendations.  One could also quite simply include the edges in the simple random sample. For very detailed information the Handbook of Sampling Methods for Arthropods in Agriculture by Pedigo and  Buntin is a good resource.

d. Random:  A random distribution is one in which the pests are found at random intervals from each other.  Perform a simple random sample as described in the (above) Uniform distribution section.

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch1.htm#item1c Info on "scouting" with some info at the end about sampling techniques

Internet Link: http://www.uky.edu/Agriculture/Entomology/entfacts/fldcrops/ef113.htm   How to set up and walk a random sample.

15. Describe how to ship samples of the following to a laboratory for evaluation

a. Weeds: Follow the directions of the company who will be identifying the weed.  In general ship a few of the weeds either fresh or dried.  If they are fresh, wrap them in towels and do not put them in plastic bags.  Include roots, shoots, flowers and fruit/seed if possible.  This will greatly aid in the identification.

b. Insects: Insects should be killed before shipment and sent in small vials of alcohol.   If sending moths carefully wrap the insect and send it in a small box. Collect several individuals in all stages of development (adult, pupae, larvae).  Often sending a sample of the host plant is helpful in identification of the insect.

c. Diseased plants:  Send the plants in sealed plastic bags.  Putting a paper towel in the bag will absorb extra moisture and help delay plant decay, especially in the warm summer months.

d. Soil for nematode analysis:  Soil may be collected for analysis because a nematode problem is suspected or to predict if there will be a problem.  If a problem is suspected, collect one-quart worth of soil samples.  These samples should be collected with a sampling rod to the depth of 8 inches.  Collect the samples along the edge of the infected area.  Be sure to include root fragments in the samples.  Also collect a separate set of samples from an uninfected area.  Clearly label all samples and send to a local analysis lab.  If samples are being analyzed to predict problems for the next season, the samples should be collected in a uniform pattern after the harvest, but before roots begin to deteriorate and the nematodes die.  If there is more than one type of soil in a field, collect samples from each soil type.  In all cases, contact the agency doing the analysis and follow their sampling instructions.  They will quite often provide bags and boxes for shipping.  Soil samples should never be exposed to excessive heat or cold prior to shipping.

Internet Link: http://www.agr.state.nc.us/agronomi/nflyer.htm Gives info on how to collect soil samples and package them for analysis.

16. List the advantages and disadvantages of the following to monitor pest infestation

a. remote sensing

Remote sensing is the science (and to some extent, art) of acquiring information about the Earth's surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information.

The main advantage of remote sensing is its ability to point users to suspect problem locations.  The main limitation is its inability to define the cause of the problem.  Additional limitations are its complexity, cost, and the timeliness of imagery.

b. forecasting models

Forecasting models for pest infestation are statistical models that predict pest development and infestation population levels.  These models consider number of days, temperature, location, and crop development to predict both stage of pest development and population levels.  The advantages of forecasting models are their ability to help in scouting and monitoring pest populations.  Their limitations are that they only help – scouting and monitoring is still necessary.

c. GPS/GIS

Global Positioning Systems (GPS) and Global Information Systems (GIS) pinpoint location.  They can help in scouting, monitoring, and mapping pest infestation.  This is very helpful in managing variable applicators and targeting infestation within the infested area without applying chemicals uniformly across the field.  This results in improved pest management and input cost savings.

Internet Link: http://www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/fundam/chapter1/chapter1_1_e.html Additional information

 IDENTIFICATION

17. Explain how to use the following information to identify a pest

a. Crop grown:  Most insects prefer a certain type of vegetation.  If the type of crop in which the pest was found is known, then it will be much easier to identify the pest.  In fact, many insect identification keys start with a question as to in which crop the pest was discovered.  Many pests prefer a certain crop and will not be found in large populations on other crops or weeds.

b. Time of year: Insects follow a regular pattern of development, death, and overwintering.  If there is a question as to what insect was found, looking at the time of year in which it was found will provide valuable clues to its identification.  For example, if you cannot distinguish between two types of grasshoppers, but you know that one species dies after the first frost and the other is more persistent, and there has been a heavy frost recently, you know that it is most likely the second species of grasshopper in the field.

c. Symptoms and patterns of damage:  Most insects cause detectable damage to the plant.  Some insects will cause one type of damage, some another.  By analyzing what type of damage is being caused it is often possible to identify what type of pest is in a given field without even seeing the pest.

d. Physical characteristics of pest:  Identifying the physical characteristics of a pest is the preferred method in insect identification.  Insects differ in many aspects, allowing accurate identification based on mouthparts, wings, legs, color and size.

e. Distribution of in field:  Closely related species may have different distributions in the field, from the edges of a field to its location on the host plant. The location where the insect is discovered can provide valuable information for identification purposes.

Internet Link: http://www.ag.ohio-state.edu/~ohioline/b545/index.html Further study material from Ohio State University Extension

18. Distinguish disease characteristics caused by fungi, bacteria, viruses, and nematodes

Identifying diseases can be quite a complicated procedure.  It takes time and experience to correctly identify diseases.  Some things to look for are: spores, dusts, or fungal growth on the plant.  These may be the signs of a fungal infection.  If the plant has oozing sores, this might be the sign of a bacterial infection.  Viruses often cause crinkling and deformation of leaves, but they can also cause other types of damage.  Nematodes are not actually a disease-causing organisms, but a carrier of bacteria, viruses and fungi. Characteristics of viral infections may be easily mistaken for other sources of damage.  When in doubt about a diagnosis, take the plant to an expert.

Internet Link: http://www.ipm.iastate.edu/ipm/hortnews/indices/plantisindex.html Further study material from Iowa State University

19. Use the following to identify mites and types of insects

a. Type and number of legs:  Insects have six legs, mites and spiders have eight (except in the first stages of mite growth when they have six legs instead of eight).

b. Type of mouthparts:  Insects have many different types of mouthparts.  Mouthparts are specific for the type of food source the pests consume.  There are chewing, sucking, rasping-sucking, piercing-sucking, and siphoning mouthparts. (Pedigo, Larry P. pg. 40)

c. Wing characteristics:  Most insects have wings that come in different shapes, colors, sizes and textures.  Insects either have one or multiple pairs of wings.  Wings also have specific veining patterns which aid in identification (Pedigo, Larry P.  pg.47-48).

d. Life cycle:  All insects and mites begin as an egg.  This egg may form as a cottony mass, slime, distinct egg, or may develop parasitic to another life form.  Further stages of development may result in intermediate stages such as larvae, pupae, and nymph.  Immature insects that resemble the adult form are nymphs and will retain similar form and attributes in their adult stage.  Larval stages generally are in the form of caterpillars and do not resemble the adult moth, butterfly, or beetle type insects.  Pupal stages represent the metamorphosis of an insect from the larval stage to the adult stage often contained within a cocoon-like structure.  Generally, insect pests are more damaging to crops in their larval stage, while the adult stage is less damaging to the crop.

Internet Link: http://info.ag.uidaho.edu/keys/main.htm A simple electronic key to identify insects

Internet Link: http://www.earthlife.net/insects/anindex.html Insect World

20. Identify the following

a. Aphids:  Small (1.0 to 6.0 mm long), soft bodied, pear-shaped, slow-moving homopterous insects.  They have fore wings that are larger than the hind wings, with very few veins in both wings.  A typical aphid has six-segmented antennae, but can vary between 3 and 6.  The most characteristic feature of an aphid is the presence of a pair of tubes (cornicles) on the dorsum between the fifth and sixth abdominal segments.  Also, the abdomen of an aphid terminates in a tail, known as a cauda.

Internet Link: http://www.chu.cam.ac.uk/aphids/aphidomorpha.html Info and picture of aphids and their life cycle

Internet Link: http://www.forages.css.orst.edu/Topics/Pests/Insects/Aphids.html Aphid information

b. Beetles:  Beetles are characterized by a hard wing, which covers the second pair of wings used for flying.  They have a hard thick exoskeleton with two thorax segments.  Beetles go through complete metamorphosis.

Internet Link: http://tolweb.org/tree?group=Coleoptera&contgroup=Endopterygota.html Good info on beetles

Internet Link: http://www.life.uiuc.edu/Entomology/insecthtmls/gifs/coleoptera.gif Drawings of different beetles and their anatomy.

c. Flies:  The distinguishing feature of true flies is that the second pair of wings has evolved to form balances called halteres. The mouthparts of flies are suctorial and have fleshy pads with drainage canals that aid in liquid uptake. Other flies have mouthparts adapted to piercing and sucking.  Fly larvae are easily distinguishable due to their lack of legs, very small head and maggot-like appearance.

Internet Link: http://www2.ncsu.edu/unity/lockers/ftp/bwiegman/fly_html/diptera.html Good info on true flies

Internet Link: <HT{icon}{~HTTP~}{www.life.uiuc.edu/Entomology/insecthtmls/gifs/diptera.gif}> Drawings of different flies and their anatomy.

d. Leafhoppers: The distinguishing characteristic of leafhoppers is that there is at least one row of spines on the hind tibiae (leg) and they have pierce-sucking mouthparts.  They also have two pair of wings.

Internet Link: http://www.inhs.uiuc.edu/~dietrich/Leafhome.html Link with pictures and a link to more leafhopper info.

Internet Link: <HT{icon}{~HTTP~}{www.life.uiuc.edu/Entomology/insecthtmls/gifs/homoptera_grey.gif}> Drawings of different hoppers and their anatomy.

e. Mites: Joint-footed animals with eight legs belonging to the Phylum Arthropoda and like spiders, ticks, and scorpions belong to the class Arachnida. They have very little body segmentation and their abdominal segmentation is inconspicuous or absent.  Mite larva have six legs after upon hatching.  After molting they have 8 legs.

Internet Link: http://tolweb.org/tree?group=Acari&contgroup=Arachnida.html Info on mites.

f. Moths: Moths take on two main forms during their life: caterpillar and moth.  Moths and butterflies are similar, but there are some distinguishing characteristics.  Moths close their wings around their body when they are not flying, while butterflies hold their wings up and erect.  Moths also have feathery antennae and butterflies have club like antennae.  Moths have siphoning mouthparts and their metamorphosis is complete.  Moth larvae usually do the most damage as the larvae (caterpillars) have chewing mouthparts.

Internet Link: http://alpha.furman.edu/~snyder/leplist/identify.htm Excellent pictures to describe the different moth families

Internet Link: <HT{icon}{~HTTP~}{www.life.uiuc.edu/Entomology/insecthtmls/gifs/lepidoptera.gif}> Drawings of different moths and butterflies and their anatomy.

g. Thrips: Minute insects (0.5 to 5.0 mm long) that have strap-like wings with long cilia (hair). They also have bladder-like tarsi (legs), asymmetrical mouthparts in that the left is developed but the right mandible is vestigial.  Thrips are very active and can cause extensive damage.

Internet Link: http://alpha.furman.edu/~snyder/leplist/identify.htm A picture of a thrips and some basic ways to identify them.

Internet Link: http://www.life.uiuc.edu/Entomology/insectgifs/thysanoptera_grey.gif Drawing of a thrip and thrip anatomy.

h. True bugs: True bugs come in many shapes and forms, but all have a triangular plate found above and between the wings called a scutellum.  They also have piercing-sucking mouthparts.  True bugs have two pairs of wings and six legs.

Internet Link: http://www.earthlife.net/insects/anindex.html Insect World

Internet Link: <HT{icon}{~HTTP~}{www.life.uiuc.edu/Entomology/insectgifs/hemiptera.gif}> Drawings of different bugs and their anatomy.

i. Whiteflies: Whiteflies are small white flying insects 2-3 mm long.  They are often found in greenhouses and look rather like tiny white moths.

Internet Link: <HT{icon}{~HTTP~}{eny3005.ifas.ufl.edu/lab1/Homoptera/Aleyrodid.htm}> Internet Link: http://www.laters.com/insects/whitefly.htm Good simple descriptions with pictures

<s12>Good general information sources<s>

Internet Link: http://ipmwww.ncsu.edu/PEST_ID/pestid.html Information on pests sorted by type of crop effected.

Internet Link: http://info.ag.uidaho.edu/keys/main.htm A key to identifying pest of the northwest.  Insects are also listed alphabetically.

Internet Link: <HT{icon}{~HTTP~}{www.insect-world.com/main/orders-key.html#key}>

<i>Pedigo, Larry P. 1999. Entomology and pest management, p83-141</i>

21. Use the following plant characteristics to differentiate weeds

It is necessary to know what the following terms mean and how they can be used to identify weeds.  Weeds differ in many ways and weed keys may ask questions about the following plant characteristics to identify the plant.  Check out these websites for more information

a. Cotyledons:  Seed leaves of a broadleaf plant that generally fall off after the first week.  Cotyledons may exhibit pubescence (hairs) and differ somewhat in shape from true leaves that emerge later.

b.  Arrangement, shape, and vein pattern of leaves:  Arrangement of leaves on the stem may alternate or opposite; shape may be long and narrow as in grasses or oval/oval elongated in dicotyledons; venation is parallel in the long, elongated leaves of grasses and is reticulate (central axis with primary and secondary branching from the base to the tip of the leaf) in dicots.

Internet Link: http://www.csdl.tamu.edu/FLORA/201Manhart/veg/leaf.shapes/leafshapes.html Leaf shapes

Internet Link: <HT{icon}{~HTTP~}{www.csdl.tamu.edu/FLORA/201Manhart/veg/leaf.margin/leafmargin.html}> Margins of leaves

Internet Link: <HT{icon}{~HTTP~}{www.csdl.tamu.edu/FLORA/201Manhart/veg/leaf.types/leaftypes.html}> Leaf types

Internet Link: <HT{icon}{~HTTP~}{www.csdl.tamu.edu/FLORA/201Manhart/veg/leaf.venation/leafven.html}> Leaf veining patterns

Internet Link: <HT{icon}{~HTTP~}{www.csdl.tamu.edu/FLORA/201Manhart/veg/leaf.arrange/leafarrange.html}> Leaf arrangement

c.. Ligules:  A structure found in some grasses.  It is positioned between the leaf axil and the stem.  In some grasses the ligule is quite large and in others it is very small.  The size and shape of the ligule is usually characteristic of a grass species.  Ligules may be membranous,  hairy or nonexistent; their shape may be tall, short, toothed, etc. [Ref.  Weed Information from Scotts Research.]

d. Auricles:  Some grasses have two ear-like projections which grow outward from the opposites sides of the collar called auricles.   Those grasses that exhibit auricles show considerable variation in their size and shape.  They are not evident on all grasses; in some grasses they are long and slender, clasping the stem to various degrees. In others they are short, non-clasping and almost non-existent.  Auricles, like ligules, are characteristic of grasses and are used for identification purposes.  [Ref.  Weed Information from Scotts Research.]

Internet Link: <HT{icon}{~HTTP~}{soilcrop.tamu.edu/publications/pubs/b6079.pdf}> Clear description and drawings of auricles

e. Hairiness of the leaves or stalk:  Pubescence is the presence of small hairs anywhere on the plant.  Pubescence can be a useful characteristic for identification.

f. Shape, color, and size of seed:  All of these are important in identifying specific weedy plants.  Sometimes one weed species will be closely related to another and the only distinguishing characteristic may be a difference in the size or shape of the seed.

g. Stem shape:  Stems shapes may be round, triangular, or square.  They may grow upright, partially upright, or decumbent.

Internet Link: http://www.csdl.tamu.edu/FLORA/201Manhart/veg/stem.habits/stemhabits.html   Pictures of stem habits

h. Life cycle:  Knowing whether a weed flowers, what the flowers look like, when it flowers, etc. can be valuable in identifying a weed.  Specific weeds must be studied to be able to use this information to identify them.  References such as the one that follows, or others published by state experiment stations, are good sources of information.  [Ref.  Watson, T. D. (ed.)  1992.  Weeds of the West (revised).  Western Society of Weed Science, P.O. Box 963, Newark, CA 94560.]

Internet Link: <HT{icon}{~HTTP~}{www.utm.edu/~rirwin/plantlifecycle.htm}> General life cycle of a plant

i. Root system:  The root system of grassy weeds is fibrous and for dicotyledonous weeds it is a taproot.  The root systems themselves may be indicative of a species simply because of the depth of penetration into the soil, the profuseness of the rooting structures, or the spreading nature.  Another characteristic of some rooting systems is horizontal or spreading roots (not to be confused with rhizomes which are underground stems, though they have the same effect in establishing new propagules) from which new plants may arise.

Internet Link: <HT{icon}{~HTTP~}{www.csdl.tamu.edu/FLORA/201Manhart/veg/roots/roots.html}> Pictures of different root types

Internet Link: <HT{icon}{~HTTP~}{ext.agn.uiuc.edu/wssa/subpages/weed/herbarium0.html}> Many pictures of weeds in different stages of development

Internet Link: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/grapes/grapesfs/weeds/index.html Links to data pages with detailed information and life history of some weeds (Adobe Acrobat required).

22. Identify plant damage caused by the following non-pest factors

There are an infinite number of causes of plant damage and it is often very difficult to discern the cause of the damage.  Damage could be pest, pathogen, genetically, or environmentally caused.  Many things can cause plant damage, so it is important to keep in mind all possible causes of plant damage and not always blame the pest.

a. Wind:  Wind can knock over, shred, or blow leaves from plants.  In prolonged instances of wind, coupled with high temperatures, and thus high evaporative demand, mild to severe leaf desiccation may occur (i.e. lodging).  Wind damaged plants may also be more susceptible to disease and insect damage.

b. Temperature extremes:  Extremely hot weather can cause water stress, wilting and yellowing.  Freezing temperatures can cause parts of the plant to freeze and die, especially blossoms which are often susceptible to late frosts and snow storms.

c. Rain, hail, and ice: Severe rain, hail and ice storms can cause physical damage to the plants such as the appearance of nitrogen deficiency caused by prolonged flooding.  Hail caused extreme physical damage and can completely destroy a crop in only a few minutes.

Internet Link: http://www.ag.ohio-state.edu/~vegnet/problem/pb625982.htm Further study material from Ohio State University Extension

d. Moisture deficiency:  Moisture deficiency can cause wilting and death, while an excess of moisture can also cause the plant to wilt.  Lack of moisture can prevent seed germination and also limit the nutrient uptake of plants due to reduced root development.

e. Sunlight:  Too much or too little sunlight can have adverse affects on crops.  Sprinkler irrigation can, on very hot days, result in scalding of plant leaves, which presents leaves that have a light green to water-soaked look.

f. Pesticide phytotoxicity:  Pesticide phytotoxicity is the death or damage of the plant due to pesticides.  Damage could appear in many different forms.  Herbicides generally due more damage to the plant itself than do insecticides.

g. Nutrient deficiency and toxicity:  Nutrient deficiency and toxicity can cause plants to be chlorotic and necrotic.  Nitrogen, Phosphorus and Potassium are the most common nutrient deficiencies.  Disease symptoms can often look like deficiencies or toxicities.

h. Standing water:  Symptoms of standing water are often the same as those resulting from a lack of water or other root injuries. They include withering of leaves, little terminal growth, yellowing of foliage, and dieback of shoots and roots.  The water deficit set up by heat, sun, and wind pulls on roots to provide water to the foliage. Even if plants are watered, the injured roots cannot take up water fast enough to meet the demands of such environmental conditions.  Roots need oxygen to grow and to absorb nutrients. In a water-saturated soil, the oxygen content is low and, without oxygen, roots cannot respire or take up water properly. Even though water is abundant, the plant cannot absorb it.

Internet Link: http://www.ag.uiuc.edu/cespubs/hyg/html/199912d.html Additional information

i. Lightning: Lightning kills or injures most crops in a circular pattern within the field. The spots are typically about 5 meters in diameter, but may be as large as 15 meters with clearly defined margins. The affected area does not expand over time. Few plants or weeds within the circle survive, but plants near the edges may show only slight injury. Plants on the edges may exhibit splitting of the epidermis, dieback of terminals, and separations in the pith. Stems may be blackened with dead leaves remaining attached.

Internet Link: <HT{icon}{~HTTP~}{cipm.ncsu.edu/ent/SSDW/nonparatlas.html}> Additional information

j. mechanical or animal:  Girdling or tearing are signs of mechanical or animal injury to plants.  The location of the injury will give you an idea of what caused the injury.  Mice and small rodents affect the lower area of plants, rabbits feed a little higher, and deer feed on the upper parts of the plant.  Also, feces near the injury will give you clearer idea of what caused the injury.  Noting the height of the injury, and the breakage or tearing, while keeping in mind any mechanical equipment that has been recently in the field will also help clarify the nature and cause of the injury.

DECISION-MAKING GUIDELINES

23.  Define economic threshold and economic injury level

The economic threshold (ET) is when the pest or weed populations result in economic losses to the crop.  At or prior to this point, action should be taken to reduce the pest and weed populations.  The economic threshold can vary for similar insects depending on the value of the crop.  The economic injury level is the level of injury to the crop caused by a pest.  The economic injury level is controlled by various chemical and mechanical practices to maintain levels below the economic threshold.

Internet Link: <HT{icon}{~HTTP~}{ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch1.htm#item1d}> Further study material from University of Nebraska, Lincoln 

24.  Describe how natural enemies impact pest population projections

Natural enemies will not totally eliminate a pest population, but they can hold a pest population in check and prevent it from increasing to economically damaging levels.  Thus, in the presence of natural enemies, the pest population will peak at a lower population size than if there were no natural enemies present.

23.  Use information about the following  make pest management decisions

Many different factors can affect pest populations and management decisions.  Keeping in mind all of the following factors will allow you to accurately assess a pest situation and be able to make correct management decisions.

a. Current crop pest data from monitoring:  One of the most important sources of pest information comes from monitoring the pest throughout the season.  This can provide information on what kind of insects are present and at what levels.

b. Pest history:  Knowing what pests have been present in past seasons and what effect they have had can influence management decisions.  Often pests will follow weather patterns so if you know, for example, the pest problems that occurred last time there was a wet spring or a mild winter you will be better able to plan ahead and use effective control measures.

c. Pesticide history:  It is important to know what pesticides have been sprayed in an area earlier in the season and also in past seasons, along with their effectiveness.  Knowing how many years you have applied a certain pesticide can help to eliminate pest resistance to certain pesticides.

d. Cropping history:  Cropping history can greatly affect the type of pests found in a field and how their populations will grow.  By knowing what crop rotation was used, what tillage system was used and past yields, farm managers can effectively plan for the future.

e. Fertility program level:  Knowledge on the fertilizers that have been used in an area can also provide important information.  Plants that are stressed because of a lack of nutrients as well as overly lush plants are more susceptible to pest attack than normal healthy plants.

f. Pest mapping:  Pest mapping from current and previous seasons will provide information on the distribution of the pest and provide insights on what kind of control measures to take.  Mapping should be done on a field-by-field basis to more accurately examine outbreaks.

g. Soil, weather, and crop conditions:  General soil, weather, and crop conditions all give insight to defining issues affecting production and crop economic value.  Soil sampling, weather monitoring, and crop supervision are essential to identification of pests and mitigating the effects of pests on crops.  These conditions need to be monitored throughout production.

26.  Use information about cost of control, potential pest damage, and crop value to decide if pest control is necessary

The goal of pest management is to control the pest so that there is not an economic loss.  When deciding if and how to control pests the cost of control should be taken into account.  If it will cost more to control the pest than will be lost in crop damage it is not economically worthwhile to control the pest.  If however, major crop damage is foreseen, it would be beneficial to take measures to control the pest.

PESTICIDE PEST MANAGEMENT -- Genetic

27.  Distinguish traditional genetic resistance from transgenic resistance to pests

Genetic resistance is the ability to not be damaged by pests and pathogens because of quality caused by a gene.  In addition, genetic tolerance is the ability of a plant to survive and experience reduced damage when attacked by an insect or pathogen.  Productivity and growth may be adversely affected, but the plant will survive.

Transgenic resistance is when the plant is resistant to attack because a gene for resistance has been artificially introduced into the plants DNA.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/info/ipmtact.html Basic genetic resistance

Internet Link: http://www-personal.umd.umich.edu/~jcthomas/JCTHOMAS/Student%20Papers%201996/J.Hines.html Basic transgenic resistance

28. Describe advantages and limitations of using GM crops in pest management

Crops can be genetically altered to improve yield, appearance, resistance to pests and many other factors.  Genes can be inserted into the plant's genome which can cause the plant to be altered for specific purposes.  Using genetically modified plants can reduce the use of pesticides which reduces costs improving profits.  Additional benefits of genetically modified crops can be increased plant nutrition for human and animal feed and resistance to frost or drought.  All these advantages result in increased crop value and increased farm profits.

Limitations or perceived limitations of using GM crops are 1) unproven crop performance, 2) market access limitations, 3) potential pollen overflow between GM and non-GM crops, and 4) potential liability issues.

Internet Link: http://www.idrc.ca/books/reports/1997/17-02e.html Genetic resistance and IPM

29.  Explain the role of susceptible refuge host populations in managing insect resistance

Susceptible refuge host populations are those which will die when they are exposed to pesticides or when they are presented with genetically resistant plants that they cannot parasitize.  Most of the pest species will be susceptible and die, but some pests will be resistant and will survive and pass along their resistant genes to the next generation.  This can cause a resistant pest population to form in response to the genetically resistant crop.  To prevent this, normal crop management procedures should still be used such as crop rotation and care not to spread pests from one field to another.

30.  List the advantages and limitations of incorporating multiple traits into crops though transgenic techniques

The advantages of incorporating multiple traits into crops though transgenic techniques are that many characteristics of the plant can be improved.  Color, texture, yield, growth rate, disease and pest resistance and other physiological characteristics can be improved which leads to a higher quality crop.  Some of the limitations of this technique are that it is extremely expensive and time consuming to identify and introduce beneficial genes into plants.  The transgenic plants can thus be more expensive than normal plants.  Sometimes the introduced genes will produce unforeseen side effects or inhibit other normal genes.  Misunderstandings about transgenic crops have also produced negative public opinion.  Pedigo, Larry P.  Entomology and pest management.  Pp. 433-466.

PESTICIDE PEST MANAGEMENT -- Cultural and Mechanical

31.  Explain how the following influence pest management decisions

a. Cropping sequence:  Crop sequencing is a very effective way to control pests.  By rotating the types of crops grown in a field it is possible to greatly reduce the damage and incidence of pest species, because most pests are adapted to one type of crop.  If pests establish themselves in a crop one year and lay their eggs there and a different crop is planted the next year, they will likely not be able to survive and the crop will be unharmed by that pest.

Internet Link: http://www.ext.nodak.edu/extpubs/plantsci/crops/eb48-1.htm#intro The effect of crop sequencing on many factors

b. Strip cropping:  Strip cropping is the practice of planting different crops in alternating strips.  There are many benefits to strip cropping.  The benefits, with regards to pest control, are that pests may be isolated on a particular strip and won't spread to other strips of the same crop, especially if there are strips of a few different crops separating them form the next strip of their preferred crop.

Internet Link: http://www.peisland.com/agrtour/xslope.html This site provides basic information on the benefits of strip cropping

c. Row spacing and plant population:  Row spacing and the plant population can affect pest control in different ways depending on the type of pest and crop involved.  Closed canopies, resulting from high plant populations and narrow rows, may encourage certain diseases that require moist or damp conditions to develop.  Air movement within the canopy may prevent such problems from developing.  Plants close together make it easier for pests to spread from plant to plant.

d. Planting date:  When the problem pest has been identified and its life history is known it is often possible to adjust the planting date in such a way that the young plant is the least effected by the pest.  Early planting may allow the plant to get well established before pest populations grow to destructive populations.

Internet Link: <HT{icon}{~HTTP~}{ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch3.htm#ITEM3C}> Cultural (planting date)

e. Harvest date and method:  Often plants can be harvested before the pest populations reach their peak and cause major damage.  Harvesting during a pest's reproductive cycle can help reduce pest populations over time.

f. Tillage:  Depending on the pest population in question, tillage may be used to disturb their life cycle by killing eggs or disrupting roots.  Tillage is also an effective weed control method.   However, do not use tillage indiscriminately.  Deep tillage may however bring weed seed to the surface where it can germinate the next spring.

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch3.htm#ITEM3D Mechanical methods of weed control

g. Crop residue:  Crop residues should be removed from the field and disposed of, or plowed under, so they do not provide food and shelter for overwintering insects.  Keep in mind that this can also negatively affect beneficial species as well as reduce available nutrients and buildup of valuable organic matter.

h. Nutrient status:  Sick plants are more likely to have disease problems and pest infestation than healthy plants.  Plant nutrition plays a key role in the health of plants.  Nutritional deficiencies or toxicities invite disease and pests.  Lesions caused from broken cell membranes resulting from nutrition problems invite bacteria, viruses, and both sucking and chewing insect pests.  In addition, a plants natural protective structures are broken down with nutritional problems creating a environment conducive to pest development.

i. Water resources:  Like nutrient problems, inadequate or over abundant water can cause plants to become diseased leading to an environment conducive to pest infestation.  Drought stresses plants and creates cracking and cell membrane breakdown leading to lesions that can become diseased and provide a great food source for insect pests.  Flooding conditions likewise cause problems through root rot, fungus, and other problems that can eventually stress the plant and cause additional disease and insect problems.

j. Variety selection:  Plant variety selection can minimize various problems.  Plants can be bread for various resistance features.  Utilizing a seed variety that contains strong resistant features can be an important method of minimizing disease and insect infestation.

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch2.htm#ITEM2H Non-chemical insect control

32.  Describe methods to minimize introducing pests into fields

You can limit introducing pests into fields by cleaning boots, clothing and all equipment before entering another field.  The following are some other prevention measures that can be taken:  use clean seed, avoid weed patches that attract insects, keep fence lines clear of weeds, clean soil sampling equipment between samples, keep property free of wild animals.

33.  Describe the concept of critical weed free period

The “critical weed free period” is the length of time weeds can compete with crops without reducing yield and the length of time crops must grow before yield is no longer affected by newly emerging weeds.

PESTICIDE PEST MANAGEMENT -- Biological

34.  Identify the following biological control agents

a. Lacewings:  Lacewings are small insects, 10 to 20 mm in length.  The adults are light green winged insects that feed on nectar.  The larvae are grayish-brown and feed on everything from spider mites to the tobacco budworm, but are mainly known for their feeding on aphids.  Larvae have been known to eat between 100 to 600 aphids.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/chrysoperla.html This site gives information on identification, life history and much more.

b. Ground beetles (Lebia grandis):  Feed primarily on Colorado potato beetles.  Ground beetle larvae find and attach themselves to potato beetle pupae and feed on them during their development.  Adult ground beetles emerge in mid-July and feed both on the ground and on plants.  They can eat up to 45 potato beetle eggs or 1 to 5 larvae each day.  It is often difficult to determine if ground beetles are present.  However, a stake wrapped in burlap and placed in a field provides a place for adults to hide during the day and provides a method of detection.  Ground beetles are not currently available commercially, but reducing the amount of broad-spectrum insecticide will increase their odds of survival.

Internet Link: <HT{icon}{~HTTP~}{www.nysaes.cornell.edu/ent/biocontrol/predators/lebiagrand.html}> A general life history with pictures

c. Lady beetles:  The lady beetle ranges from 4 to 7 mm in length and has an oval-domed body.  They are usually red or orange with black spots, but may also be black with reddish spots.  They prey mainly on aphids but switch easily to other prey bases (moth eggs, mites, beetles and other small insects) when aphids are not available.  Nectar is often necessary for lady beetle development.  Having high pollen-producing plants such as dandelions near crops many aid in the survival of lady beetles.  Both larvae and adults are very mobile and will travel to other plants when there are not enough aphids to support them on any given plant.  Lady beetles, depending on the species, can eat hundreds of aphids each day.  Adult beetles overwinter in leaf debris.  Disturbance of these areas can lead to increased lady beetle mortality.  Two species of lady beetle are especially useful.  The seven-spotted lady beetle (Coccinella septempunctata), introduced from Europe, is a very competitive predator found in the north-east/north-central states.  It eats hundreds of aphids a day, unfortunately, it is not raised commercially at this time.  The most common commercially raised lady beetle is the convergent lady beetle (Hippodamia convergens).

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/ladybintro.html Provides information on lady beetles

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/hippodamia.html Provides information on the convergent lady beetle

Internet Link: <HT{icon}{~HTTP~}{www.nysaes.cornell.edu/ent/biocontrol/predators/c7.html}> Provides information on seven spotted lady beetles

d. Minute pirate bugs:  Adults are very small (3 mm long), somewhat oval-shaped, and black with white wing patches.  Wings extend beyond the tip of the body.  Nymphs are small, wingless insects, yellow-orange to brown in color, teardrop-shaped and fast moving.  They feed by sucking juices from their prey through a sharp, needle-like beak (the rostrum).  Minute pirate bugs are predators that feed mainly on thrips.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/orius.html Information on pirate bugs

Internet Link: http://www.ipm.iastate.edu/ipm/iiin/minutep.html Info on minute pirate bugs from a human pest point of view

e. Nabids:  Also known as Damsel bugs.  Small insects (3-11mm) with a slender body and membrane of first pair of wings with small cells around the margin.  They prey on aphids and caterpillars.

f. Parasitic wasps:  Parasitic wasps are usually black or brown, but come in all different shapes and sizes.  They reproduce by laying their eggs inside other organisms where the eggs hatch and develop using the host as a nutrient source causing the host organism to die.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/parasitoids/parastoc.html This site provides links to descriptions of specific parasitic wasps.

Internet Link: http://www.ipm.iastate.edu/ipm/iiin/bparasiti.html This site provides basic information on parasitic wasps

g. Predatory mites:  Predatory mites are very small and have oval bodies.  Most have clear bodies until they feed on their prey and then they turn the color of their prey, usually reddish brown.  The female mite is larger than the male.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/galocc.html       Info on predatory mites

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/galpyri.html Info on predatory mites

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/predators/neofall.html Info on predatory mites

h. Spiders:  Spiders come in all shapes, sizes and colors, but are characterized by their rounded bodies and eight legs.  Spiders are not considered insects, but arachnids.  They typically have two body regions.  Spiders feed indiscriminately on insects and can be a great aid in reducing pest populations.

Internet Link: http://eap.mcgill.ca/PCBCR_2.htm Further study material from McGill University

Internet Link: <HT{icon}{~HTTP~}{www.ctpm.uq.edu.au/corporate/literature/news releases/1997/970505.html}>  Provides information on how spiders can provide biological control.

i. Syrphidfly larvae:  Small insects that feed on aphids.  They pierce the aphids and suck out their body fluids.  They are long and oval shaped tapering at the ends.

Internet Link: http://www.nysaes.cornell.edu/ent/biocontrol/   Links to predator and prey, with pictures

Internet Link: http://ipmwww.ncsu.edu/AG271/contents.html Insect and related pests of field crops-gives lists of pests common to different crops.  It has black and white pictures, descriptions, life histories, and control methods.

Internet Link: http://www.ento.vt.edu/Fruitfiles/syrphid.html Further study material from Virginia Tech

35. Explain uses and limitations of using biological control agents in crop production

Biological control covers two key concepts: the deliberate use of a pest’s natural enemies to suppress its population and the use of these live organisms to maintain this lower population density. A pest’s natural enemies may be arthropods (insects, mites and their relatives), bacteria or fungi. These control agents feed upon or cause disease in the pest, thereby limiting its growth, reproduction and spread.

The following are steps in biological control and demonstrate its use:

·     Identifying target pest

·     Identifying control agents and assessing level of specialization

·     Controlled release

·     Full release and identifying optimal release sites

·     Monitoring release sites

·     Redistribution

·     Maintaining control agent populations

Biological control is advantageous because of its selectivity; there is little danger of damage to non-target plant species. Biological control agents are also very effective in inaccessible areas.  Another attractive feature of biological control is its negligible environmental impact. Biological control methods generally do not bring any of the problems associated with herbicide residues, contaminated groundwater and weed resistance to herbicides.  Individual applications of biological controls are also potentially much less expensive over time. A small number of biocontrol agents can, once established, grow to very high densities and provide continuous control of a pest over a large area.  When the cost of development is considered, biocontrol is generally less expensive than chemical control. 

Biological control does have its limitations, however. It lacks the immediacy of chemical control.  Populations require time to become established, so signs of pest suppression are rarely evident in the first year.  Screening work (determining the selectivity and effectiveness of a biocontrol agent) is also very time consuming and is subject to limited funding.

PESTICIDE PEST MANAGEMENT -- Chemical

32.    Explain how the following pesticide characteristics affect pesticide selection

a. Mode of action:  The mode of action is how the pest is killed and should be appropriate for the pest, crop and season.  For example, one would not spray a juvenile hormone on a pest which has already molted into its adult form.  The environmental impact of the pesticide should also be considered.

Internet Link: http://www.agcom.purdue.edu/AgCom/Pubs/WS/WS-23.html Further study material from Perdue University Extension Service

b. Chemical and physical properties:  The chemical and physical properties of a chemical determine how the pesticide functions and how it is applied.  The chemical properties of a pesticide determine its mode of action and how long it takes to break down in the environment.  When selecting a pesticide one should be chosen which will be effective in killing the pest and decompose readily so that it does not build up in the environment and negatively affect other organisms.  The physical properties of a pesticide, whether it is a solid, liquid, or gas, will determine its application method.

c. Toxicity to target and non-target organisms:  The chosen pesticide should be toxic to the target organism (the pest) but as non-toxic as possible to other organisms.  Toxicity is a big concern for worker and applicator safety.  Some pesticides are very general killers and others are more specific.  Pesticides should be chosen to be as specific as possible.  Unfortunately, more selective pesticides tend to be more expensive.

d. Environmental hazard:  Because of their chemical composition, pesticides pose a threat to both target and non-target organisms.  Pesticides can be ingested by non-target populations and be passed up the food chain in ever increasing concentrations (biological magnification) until top predators are negatively affected.  Pesticides can also contaminate soil and water systems.  To minimize these risks it is vital to select pesticides which can quickly decompose and are environmentally friendly.  Environmental impacts can be reduced by following the label found on the container or box.

e. Persistence:  As discussed previously, it is important to select a pesticide with a low level of persistence.  However, it is also important that the pesticide be persistent enough to effectively control the pest.

f. Selectivity:  In most cases, the more selective the pesticide the better.  This insures that only the target pest is affected by the pesticide.  Reviewing the label will provide the applicator with detailed information on selectivity.

Internet Link: http://www.ipm.ucdavis.edu/PMG/r107300811.html Further study material from UC Davis

33. Explain how the following factors affect pesticide selection

a. Pest resistance:  Pests can become resistant to a given pesticide though selection.  To avoid this it is wise to not always use the same pesticide.  Cycle the use of pesticides so that the pest does not develop resistance for a particular pesticide.  Also, consider using biological and cultural means of control.

b. Economics:  Pesticides can be expensive to apply.  Do not apply pesticides unless the loss from crop damage will exceed the cost of applying pesticides.

c. Application method:  When choosing a pesticide always look to see how it is to be applied.  If it is designed to be applied aerially, but you only need to spray one small field, then it might be best to choose another pesticide which can be applied from the ground.

d. Field history:  Knowing the history of the field can aid in selecting pesticides.  Know what pests have been problems in the past, what has been grown and what has been sprayed in a field.  Previous growing conditions will also aid in formulating an effective pest control plan.

e. Pest identity, stage and level:  It is vital that the pest species be correctly identified and that its stage in its life cycle be known.  Different pesticides will work only for specific species or species types and often the mode of action relates to the stage of the pest.

f. Environmental conditions:  Humidity, wind, rain, dew and temperature all affect how the pesticide should be applied and how it will function.  Keep these factors in mind while making your selection.

g. Crop growth stage:  Some crops in some stages of development are more sensitive to certain types of pesticides than others.  Pesticides should be chosen in a way that they won't harm the crop.  Pesticide labels are the best source of information for determining the crop growth stage during which certain pesticides can and should be applied.

h. Label restrictions:  Labels are legal documents, therefore warnings and restrictions should be strictly observed.  This may mean that the pesticide cannot be used in your given situation.  Restrictions include unapproved pests, unapproved geographical areas and unapproved crops or weeds.

g. Pre-harvest intervals:  Pesticide application is restricted when harvest time nears.  Due to residual toxins on the plant the closer the time to harvest the more limitations are placed on application.  Read the label and note the specific state time-to-harvest restrictions.

|38. Describe how a pest population develops resistance to pesticides

39. Distinguish contact and translocated pesticides

Contact (non-systemic) pesticides are those where the pesticide enters through the body wall of the insect or comes in direct contact with the plant tissue.  By completely covering the leaf tissue with contact herbicide, plants are burned, stunted and/or killed.  Insects can be affected by the insect walking through the pesticide or inhaling the pesticide.

Systemic (translocated) pesticides are those that move inside the plant causing injury to many areas throughout the plant.  The growing points are usually the most affected plant parts.  Insecticides can also be classified as systemic when they move inside an insect's system.

Internet Link: http://ianrwww.unl.edu/ianr/pat/priv1a.htm Further study material from University of Nebraska-Lincoln

40. Describe how the following affect pest resistance

a.  selection pressure

Selection pressure is when naturally resistant individuals in a pest population are able to survive pesticide treatments. The survivors breed and pass on the resistance trait to their offspring. With each passing generation, the pest population becomes more difficult to control with the same pesticides as compared with earlier generations. Reducing pesticide use and alternating among classes of pesticides with different modes of action can help to lessen the possibility of pest resistance. Managing pest resistance is very important in helping to prolong the effective life of needed pesticides.

Internet Link: http://txipmnet.tamu.edu/overview/pesticides.html

b.  resistance mechanisms

Plants have natural pest resistant mechanisms.  Natural pest resistance mechanisms occurring in higher plants can be classified into preformed resistance mechanisms and inducible resistance mechanisms. Pests and pathogens likewise have developed mechanisms to compromise plant resistance mechanisms.  This evolutionary game leads scientists to work to foster natural resistance.  Some of its advantages over the use of chemical pesticides include permanency, lower costs, and fairly high efficacy. The major limitations of fostering natural pest resistance is developmental costs and that pest population survivors breed and pass on traits to their offspring that may eventually limit the effectiveness of the natural resistant mechanisms.

Internet Link: http://www.isb.vt.edu/proceedings99/proceedings.keen.html Additional information

c.  pest reproduction methods

If a pest reproduction is understood various methods can be used to control the pest.  An example is the use of pheromones to attract insect pests into traps.  In addition, new research in genetic manipulations of pests has lead to the possibility of releasing into pest populations modified individuals that interfere with the pest's reproduction or impact.  In any case understanding the pest’s reproduction cycle, influencers, and methods are important factors in pest resistance.

41. Describe how adjuvants influence spray droplet retention, deposition and absorption, and degradation

Adjuvants are chemicals added to herbicides to enhance their effectiveness.  They can aid in defoaming, thickening, increasing droplet size, reducing surface tension and in penetrating waxy and hairy plant surfaces.  Stickers and spreaders are two of the most common adjuvants.  Care should be taken to use adjuvants only when necessary.  When used improperly, adjuvants can decrease the effectiveness of the herbicide and may also harm unspecified plants.

Spray droplet retention is the spray droplets ability to hold onto the plant.  Adjuvants help the liquid chemical adhere to the plant surface in order to effectuate the chemical properties to the pest.

The fluids ability to be deposited to the plant and absorbed is influenced by the chemicals physical properties.  Adjuvants can assist in the deposition and absorption of the chemical by altering its physical properties without changing or degrading the chemical’s pest toxicity.

Internet Link: http://www.cas.psu.edu/docs/CASDEPT/hort/TFPG/part3/part34a.htm Text on adjuvants and a list of the different types and what they do.

Internet Link: http://hermes.ecn.purdue.edu:8001/water_quality/documents/c-715.ks.ascii General herbicide text with information and a paragraph on adjuvants

42. List factors that increase the risk of crop injury from pesticides

Factors that may affect the risk of crop injury from pesticides may include:  1. soil conditions such as pH levels, nutrient levels, and drainage conditions  2. moisture conditions such as rainfall, humidity and dew  3. variety or hybrid selection  4. crop sensitivity  5. Uneducated use of adjuvants  5. Contamination in spray tank from previous use  6. Using pesticides that are incompatible

43. Explain how the following factors affect spray drift

a. Wind speed:  Increased wind speed will increase drift.  Even seemingly weak winds can carry droplets a considerable distance.

b. Nozzle characteristics:  Select a nozzle that will give you adequate coverage and  maximize droplet size.  Larger droplets tend to drift less than small droplets.  Nozzles come in different shapes, sizes and materials.  Excellent nozzles that drastically reduce drift have been introduced in the last few years.

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch5.htm#ITEM5A Nozzle selection- Article about spraying

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch5.htm#ITEM5B Nozzle material

c. Boom height and configuration:  The higher the boom height the more likely drift will occur.  Chose the minimum necessary height necessary for proper coverage.  For most field crops the boom must clear plant tops to avoid burning and uneven pesticide distribution.

d. Evaporation rate:  Choose a pesticide with a low evaporation rate.  When the pesticide evaporates it can be carried by the wind to other areas.  A low evaporation rate will reduce drift.

e. Spray viscosity:  An increase in spray viscosity (thickness) will reduce the number of small droplets and thus reduce the amount of drift.

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch5.htm#ITEM5C Further study material from University of Nebraska-Lincoln

f. Spray pressure:  The lower the pressure the larger the droplets will be which will reduce spray drift.  However, large droplet size also reduces coverage.  A constant pressure can minimize drift and still ensure proper coverage.

g. Ground speed:  The slower the vehicle the more dense the spray coverage; the faster the vehicle the more sparse the spray coverage.  Proper ground speed ensures correct coverage and helps minimize drift.

Internet Link: <HT{icon}{~HTTP~}{ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch5.htm#ITEM5E}> How spray pressure interrelates with other factors

Internet Link: http://ianrwww.unl.edu/ianr/pat/catmans/agplant.skp/agplch5.htm Further study material from University of Nebraska-Lincoln

44._List advantages and limitations of ground vs. aerial application methods

Ground pesticide application has the advantage of being directly applied to the desired location.  This reduces wind drift and enhances the chemicals per unit effectiveness.  The limitations to ground application are largely time and breadth of application.  The main advantage of aerial application is it takes much less time and in certain cases broad application is required to minimize a pest population.  The limitations of aerial application are largely its inability to be directly applied to the pest and the associated wind drift problems.  Aerial spray conditions are more exacting than ground spray conditions.  This problem gives rise to increased regulation and liability concerns which may require additional insurance needs.  Aerial application can be hazardous to people, livestock, other crops, and the environment.  Other factors that limit the use of aerial application include weather conditions, fixed obstacles such as power lines, field size, and the distance from the landing strip to the target.

45. Explain how the environment affects herbicide uptake, movement, selectivity, and carryover

Environmental factors greatly affect herbicide uptake.  Cool and dry conditions limit herbicide effectiveness the most.  If the soil is moist the plants tend to take up the herbicide more, because it is not stuck to the soil.  Ideal moisture, humidity, sunlight, and temperature conditions make for rapid uptake and movement.  Carryover is usually greatest in dry conditions.

Internet Link: http://hermes.ecn.purdue.edu:8001/water_quality/documents/c-715.ks.ascii info dealing with uptake in one section

46. Explain how plant type and growth stage affect herbicide uptake, movement, selectivity, and carryover

Young growing plants are more likely to uptake herbicides from the soil as they do not yet have hard outer surfaces and waxy coverings which limit the uptake of herbicides.  The type of plant, usually divided into broadleaf or grass, also affects uptake.  Broad-leafed plants have more leaf surface area and are more likely to take up the herbicide.  Upright grasses with thin leaf area are less likely to receive enough pesticide.  Larger plants are hard to kill due to their energy reserves, hairy leaf surfaces, thick leaf cuticles and multiple growing points.

Internet Link: http://hermes.ecn.purdue.edu:8001/water_quality/documents/c-715.ks.ascii Deals with uptake in one section

47. Explain how application methods affect herbicide uptake, movement, selectivity and carryover

Herbicide application can be divided into the following groups: Fall post-harvest, early preplant, preplant incorporated, pre-emergence, early post-emergence, and post-emergence.  Herbicide formulations exist with liquid carriers or solid carriers.  Water is the normal liquid carrier.  Solid carriers may be either dusts or granules.  Granules are widely used for soil-applied herbicides as they facilitate accurate placement in a band.  If a narrow band of material can control the weeds, plus cultivation, herbicide costs can be reduced.  Several factors influence distribution of herbicides on foliage or in soil.  Weed control is most effective when target plants or soil areas are reached by, and retain , an optimum dose of herbicide.  Thus, it is important that sprayed liquid is distributed uniformly.  The degree of uniformity depends on such factors as the mode of action of the herbicide, the size, nature and attitude of the targets, the interception of spray by non-target surfaces, and environmental conditions.  Uniformity of deposits is an important objective to achieve success with all herbicides.  Foliar applied herbicides are also subject to drift.  Granular applications have several advantages in comparison with sprays or dusts: 1) convenient to handle, 2) do not give rise to serious drift, 3) can be accurately placed, 4) tend to bounce of foliage, thus the majority of the herbicide will penetrate the soil, and 5) granule properties can be varied so that the rate at which the active ingredient is released can be controlled.  Carryover of herbicides is largely due to the persistence qualities of each herbicide. Ref: Roberts, H.A.  1982.  Weed Control Handbook: Principles, 7th ed., (issued by the British Crop Protection Council), Blackwell Scientific Publications, pg. 158-218.

Internet Link: http://hermes.ecn.purdue.edu:8001/water_quality/documents/c-715.ks.ascii Contains a section dealing with uptake

48. Identify plant injury symptoms caused by the following herbicide mode-of-action groups

a. Photosynthesis inhibitors:  Cause plants to turn yellow, then brown with necrotic spots.  Can cause uneven plant height.

Internet Link: http://www.psu.missouri.edu/agronx/weeds/Web%20Resources/herbinjsymptoms/Photoinh.html Has five different families of photosynthesis inhibitors and pictures and descriptions of the damage caused.

b. Cell membrane disrupters:  Turn the plant yellow/brown.  Very cool or warm temperatures will help cell membrane disrupters perform well.

Internet Link: <HT{icon}{~HTTP~}{www.psu.missouri.edu/agronx/weeds/Web%20Resources/herbinjsymptoms/Cellmem.html}> Describes and provides photos of different families of cell membrane disrupters

c. Growth regulators:  Cause stem twisting and epinasty.  The early petioles are turned down, and leaves cup upward.

Internet Link: <HT{icon}{~HTTP~}{www.psu.missouri.edu/agronx/weeds/Web%20Resources/herbinjsymptoms/growreg.html}> Describes and provides photos of different families of growth regulators

d. Pigment inhibitors:  Cause the plant to sprout, turn yellow/white and die.

Internet Link: <HT{icon}{~HTTP~}{www.psu.missouri.edu/agronx/weeds/Web%20Resources/herbinjsymptoms/Pigment.html}> Describes and provides photos of different families of pigment inhibitors

e. Root/shoot growth inhibitors:  Stunts and inhibits growth.  Seedlings will be short with wrinkly leaves and will die shortly after application.

Internet Link: <HT{icon}{~HTTP~}{www.psu.missouri.edu/agronx/weeds/Web%20Resources/herbinjsymptoms/Seedgrow.html}> Describes and provides photos of different families of seedling growth inhibitors

f. Amino acid synthesis inhibitors:  Amino acid synthesis inhibitors tend to kill a plant slowly.  The plant may be stunted in growth and will be chlorotic or purple.

Internet Link: <HT{icon}{~HTTP~}{www.psu.missouri.edu/agronx/weeds/Web%20Resources/herbinjsymptoms/AASyn.html}> Describes and provides photos of different families of amino acid synthesis inhibitors

49. Explain the importance of the following when applying herbicides to herbicide-resistant crops

a. Identifying the field:  When spraying any pesticide it is important to make sure you are spraying it on the correct field, but in the case of spraying herbicide-resistant crops it is crucial.  If a field, which is not resistant to the herbicide, is accidentally sprayed the crops will die or be severely affected by the herbicide.

b. Matching the correct herbicide with the hybrid/variety:  It is important to make sure you know what herbicide the crop is resistant to.  If the herbicide and crop are not correctly matched the results could be disastrous.  Just because a crop is herbicide-resistant doesn't mean that it is resistant to all herbicides.

Internet Link: http://spectre.ag.uiuc.edu/cespubs/pest/articles/v972h.html Basic info on herbicide-resistant crops, talks about what different abbreviations mean and what herbicides can be used on certain plants

c. Scouting and monitoring: Scouting and monitoring herbicide resistant crops is important during pre assessment, spray, and post spray periods.  Herbicide resistant crops may be affected by herbicides if the herbicide is sprayed incorrectly.  Careful application and monitoring are important factors in establishing a production plan for this generally more expensive seed.

50. Describe the toxicity and persistence of the organophosphate, carbamate, and synthetic pyrethroid insecticide families.

Organophosphates:  This class of insecticides is generally quite unstable, thus they replaced the persistent organochlorine compounds.  Organophosphates are more toxic to vertebrates than most other insecticides.  They are also chemically unstable or nonpersistent and break down rather quickly and easily.  It is the latter characteristic that brings them into general agricultural use.  This class of compounds is derived from phosphoric acid.

Carbamates:  The most commonly used carbamate (Sevin) has very low mammalian oral and dermal toxicity.  Sevin, or carbaryl, is a representative of this class, and is probably the most widely used insecticides ever produced.  It was developed in the 1956 and is still widely used today.  More Sevin has been used world wide than all other carbamates combined.  Carbofuran, another widely used carbamate, is highly toxic to humans.  The persistence of this class of compounds is similar to the organophosphates.

Synthetic pyrethroids:  Pyrethrum was seldom used in agriculture because of its cost and instability in sunlight.  Beginning in the 1980s, several pyrethrin-like materials were developed and have become available for use in agriculture, especially around the home.  Most of these are now quite stable in sunlight and are relatively safe to use around pets and humans.  They are effective across a broad range of insect and mite pests.  These compounds are effective at very small doses.  The mammalian and dermal toxicities are low.  Though the pyrethroids are more stable in sunlight, they still only persist from 4 to 7 days.

Ref: Ware, G. W.  1996.  Complete Guide to Pest Control, 3rd ed., Thompson Publications, Fresno, California, pg. 15-44.

Ref: Pedigo, L. P.  1999.  Entomology and Pest Management, 3rd ed., Prentice Hall, pg. chapter 11.

Ref: Pacific Northwest, 1998 Insect Control Handbook.  Oregon State University (revised annually), pg. 4-10.

Internet Link: http://www.vet.purdue.edu/depts/bms/courses/chmrx/pesticid.htm Further study material from Perdue University

51. Recommend insecticide timing and placement based on the following types of insecticide activity

a.  Contact:  Contact insecticides enter the insect through the body wall and proceed to disrupt their system.  This type of insecticide should be used in areas and at times when insects will be active.  It is also essential to apply pesticides at the proper stage of growth for each insect that will have the maximum effect on the pests.

b.  Stomach poison:  Stomach poisons are eaten by the insect and should be applied where the insects feed and when they are in a stage when they are actively feeding, generally the larval stage.

c.  Systemic:  Systemic  insecticides are ones which are incorporated by the plant and poison insects feeding on the plant.  They are especially effective with piercing-sucking insects.  These pesticides should be applied at or just before the insects active feeding state.

d.  Ovicidal:  Ovicidal pesticides kill the insects eggs.  These pesticides should be applied after all the eggs are laid and before they start to hatch.

e.  Juvenile hormone:  Juvenile hormone insecticides interfere with metamorphosis, preventing proper growth and development of insects.  Juvenile hormones are also known as Insect Growth Regulators (IGR).

52. Describe how the following fungicide characteristics affect use

a. Contact vs. locally systemic vs. systemic:  Contact fungicides kill fungi which come in contact with the fungicide.  This limits their effectiveness and means the plants have to be thoroughly sprayed so that all surfaces are covered.  Locally systemic fungicides are absorbed into the plant and will combat fungi in that particular area of the plant.  Systematic fungicides will spread throughout the plant and protect it for a given period of time from fungi.

b. Protective vs. curative:  Protective applications are when fungicides are applied before a fungi problem exists.  This is much more effective than a curative approach where the fungicide is applied to kill established fungi.

c. Seed vs. soil vs. foliar applied:  Fungicides can be coated on seeds before they are planted.  This protects the seed and young plant from being attacked by fungi before they are established.  Fungicides can also be applied to the soil.  Soil application kills the fungi that are found in the soil so that they do not have the opportunity to infect the plant.  The third method is to apply the fungicide directly to the plant (foliar). Foliar application directly kills fungi that affect leaves, stems, and flowers.

d. Broad spectrum vs. narrow spectrum:  Most fungicides have a narrow spectrum, that is they retard only specific fungi.  This makes it necessary to correctly identify and predict what fungi should be targeted.  Broad-spectrum fungicides kill a wide range of fungi.

e. Mode of action:  Fungicides disrupt at least one metabolic pathway of the fungus which can either kill it or slow its growth and reproduction. Ref: The standard pesticide user's guide, 1997, p44-49.

ENVIRONMENTAL STEWARDSHIP

53. Read and follow pesticide label instructions

The pesticide label provides important information on safety, application, mode of action, active ingredients, special precautions and environmental and safety hazards.  Be sure to read the label carefully before buying a pesticide, mixing it, applying it, and storing or disposing of it.  The label will provide important information for each of these steps. Bohmont, Bert L.  1997.  The standard pesticide user's guide.  Pp. 140-151

Internet Link: http://www.ianr.unl.edu/pubs/Pesticides/g937.htm#labing This site describes in more detail what is found on pesticide labels

Internet Link: http://entweb.clemson.edu/pesticid/document/labels/labeling.htm/htm Clemson University

54. Describe pesticide characteristics that endanger soil and water quality

Some pesticides are not biodegradable.  That fact combined with over-treatment can lead to an accumulation of pesticides in the soil.  The pesticides may bind with cation exchange sites in the soil, enhancing the contamination in the soil.  This can harm or limit the other types of crops that can be planted.  Pesticides can also run off the soil and accumulate in the ground water or local water sources (lakes and streams).  Labels on pesticides will describe the duration of the pesticide and its length of phytotoxicity.

55. Evaluate a site's vulnerability to soil and water contamination

If there is a large amount of runoff through a piece of land, the water can carry chemicals and soil that may settle on the site and cause contamination.  If the site is in a low-lying area, water and soil might run there and a build up of contaminants may occur.  Due to large pore spaces, sandy soils usually have the highest rate of pesticide movement through the soil.  Irrigation water can attribute to the leaching of pesticides into groundwater or the accumulation of pesticides in streams, rivers, or lakes.  The adsorption rate of pesticides on cation exchange sites also will determine if pesticides will leach into groundwater or remain in the soil.

56. Describe the following Worker Protection Standards or provincial equivalents for handling pesticides

a. Re-Entry Interval (REI):  Re-entry interval concerns the amount of time which needs to pass after an area has been sprayed before re-entry into the area is allowed.  While there are exceptions to this rule (early-entry and early-entry no contact) the basic rule is that no one should be in the area for the time specified on the label of the pesticide.  When two or more chemicals are sprayed on an area, the longest specified re-entry interval should be the one followed.

Internet Link: http://ipmwww.ncsu.edu/safety/epawps4a.html#46 Info on REI

b. Information exchange requirements:  This refers to the information that needs to be passed on between a commercial sprayer and customer and between an employer and employee.  This information concerns the chemicals being used, where, when and what the re-entry interval is.  Also, information concerning the re-entry interval should be posted or passed on orally to those who will be in the area.

Internet Link: http://ipmwww.ncsu.edu/safety/epawps6.html#92 Further study material from North Carolina State University IPM Network

Internet Link: http://ipmwww.ncsu.edu/safety/epawps3.html#33 Further study material from North Carolina State University IPM Network

c. Personal Protective Equipment (PPE) required by law:  The minimum personal protective equipment required by law when working with chemicals which have a low toxicity are long sleeved shirts, long pants, socks, shoes, gloves, eye protection and aprons while mixing or loading.  When working with more toxic chemicals always wear coveralls and protective face and head gear.  A chemical resistant apron will be necessary in some instances.  In all cases follow the protective requirements specified on the label and remember that it is better to be safe than sorry.

Internet Link: http://ianrwww.unl.edu/ianr/pat/pat7.htm#item7a Gives info about PPE

Internet Link: http://hammock.ifas.ufl.edu/txt/fairs/29557 Brief overview of requirements

d. Emergency assistance requirements:  If an employee is poisoned by a chemical, the employer is responsible to see that some means of transportation is provided to take the employee to receive medical attention.  Employers should also provide product names, EPA registration number, first aid information, eye-wash kits, first-aid kits and general medical information in an area easily accessible to employees and preferably close to where chemicals are handled and mixed.  All information should be provided in both English and Spanish when available.

Internet Link: http://ipmwww.ncsu.edu/safety/epawps3.html#35 Further study material from North Carolina State University IPM Network

e. Oral and posted warning requirements:  Some chemicals require both oral and posted warning requirements, but most require only one or the other.  The employer should chose one method or the other.  Oral warnings should be given to anyone who is not aware of the information and who may be in the area.  The oral warning should include information on what is being sprayed, where, when, and with instructions to stay out of the area until after the re-entry interval.  Posted warnings should be at all usual entrances to the area being sprayed with information on the time of spraying and the re-entry interval.  Signs should be posted in English and Spanish if necessary.

Internet Link: http://ipmwww.ncsu.edu/safety/epawps4a.html#41 Further study material from North Carolina State University IPM Network

Internet Link: http://ipmwww.ncsu.edu/safety/epawps4a.html#44 Further study material from North Carolina State University IPM Network

f. Site decontamination procedures:  The decontamination site for early-entry personal should be within 1/4 of a mile from where they are working.  It should be provided with soap, towels and plenty of fresh water.  Workers should also be provided with a pint of water that is readily accessible for emergency eye flushing.

Internet Link: http://ipmwww.ncsu.edu/safety/epawps4c.html#DECON Further study material from North Carolina State University IPM Network

57. Define the following terms associated with pesticide use

a. Point source pollution:  Point source pollution is pollution which comes from a single identifiable source such as a factory.

Internet Link: http://www.netpci.com/~adavis/CRP/node20.html Basic definition of point and non-point source pollution

b. Non-point source pollution:  Non-point source pollution is the pollution caused by multiple non-identifiable sources.  One of the major contributors of non-point source pollution is runoff.  Water runoff often contains household chemicals, automotive wastes, fertilizers and pesticides.  These contaminants enter the water system and can contaminate millions of gallons of water.

Internet Link: http://waterknowledge.colostate.edu/qa.htm Basic detailed description of non-point source pollution

c. Maximum contaminant level:  The maximum amount of contaminates public drinking water may contain.  Limit set under the Safe Drinking Water Act.

Internet Link: http://www.oneplan.state.id.us/Glossary/glos13.htm Definition of the term

d. Parts per million and parts per billion:  Parts per million (ppm) and parts per billion (ppb) refer to how much of an actual chemical is present with respect to other substances.  For example, if something is toxic at a level of 4 parts per million in water, then when four molecules of the chemical are found in every million water molecules the water is considered contaminated.

e. Pesticide residue tolerance in the crop:  Pesticide tolerant crops are those that withstand damage from a given pesticide either due to natural tolerance or genes that have been genetically altered.

f. Best management practices:  Best management practices preserve water resources and make good use of irrigation water and chemicals.  Best management practices benefit not only the environment but also are also economically beneficial.

Internet Link: http://hammock.ifas.ufl.edu/txt/fairs/wq/18593.html Further study material from the University of Florida

Internet Link: <HT{icon}{~HTTP~}{dbdec.nrc.state.ne.us/tpnrd/best.htm}> Definition of various management practices

g. Total maximum daily load (TMDL):  A TMDL or Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources.  Water quality standards are set by States, Territories, and Tribes. They identify the uses for each waterbody, for example, drinking water supply, contact recreation (swimming), and aquatic life support (fishing), and the scientific criteria to support that use.  A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The calculation must include a margin of safety to ensure that the waterbody can be used for the purposes the State has designated. The calculation must also account for seasonal variation in water quality.

The Clean Water Act, section 303, establishes the water quality standards and TMDL programs.

Internet Link: http://www.epa.gov/owow/tmdl/intro.html Additional information

HEALTH AND SAFETY

Internet Link: http://ianrwww.unl.edu/ianr/pat/pat.htm "Applying Pesticides Correctly":  Many different pesticide topics and quiz questions dealing with every section.

58. List pesticide mode of entry into the human system

Pesticides may enter the human body in many different ways.  First, they may be absorbed though the skin.  Different areas of the body have different rates of absorption and care should be taken to cover all areas of the body which may possibly come in contact with the pesticide.  Never use the bathroom after handling pesticides without first washing hands and arms thoroughly.  Cuts and wounds are also possible areas of skin absorption.     Inhalation is another way pesticides enter the body.  The lungs absorb the pesticide very quickly causing many harmful effects.  The third way of absorption is by swallowing the pesticide.  One easy way to avoid this type of poisoning is to never store pesticide in anything but its original container and to always keep chemicals out of reach of children.

Internet Link: http://hammock.ifas.ufl.edu/txt/fairs/26596 How pesticides can poison and some basic first aid

Internet Link: http://www.aginfonet.com/agricarta/content/sk_safety_council/pesticide_poisonings.html Information on how pesticides enter the body and information on different families of poison and their short term and chronic effects

Internet Link: http://www.aginfonet.com/agricarta/content/sk_safety_council/pesticide_poisonings.html Information on how pesticides enter the body and information on different families of poison and their short term and chronic effects (this information was used to answer questions 53-55)

<i>Bohmont, Bert L.  The standard pesticide user's guide (1997)  p 199 was used to answer questions 53-55</i>

59. Define chronic and acute pesticide poisoning

Acute poisoning is when a person is exposed to a pesticide in a high enough dose that poisoning symptoms are immediately visible.  Chronic poisoning is when a person is exposed to low levels of pesticide over a period of time.  With chronic poisoning, eventually the pesticide builds up in the body and causes poison symptoms.

60. Recognize symptoms of acute pesticide poisoning

The symptoms of acute poisoning may include: dizziness, nausea, vomiting, diarrhea, cramps, sweating, burning sensation on the skin or eyes, rashes, headaches, weakness, irritated skin, throat or eyes and possibly a stroke or death.

Internet Link: http://hammock.ifas.ufl.edu/txt/fairs/26594 A short table listing some of the symptoms of poisoning

61. List possible chronic effects of pesticide poisoning

Chronic effects of pesticide poisoning include all of the symptoms of acute pesticide poisoning.  In addition, due to the long-term exposure, chronic effects can include cancer and tumors, damage to internal organs and the nervous system, sterility and birth defects.

62. Describe what procedures to follow if a pesticide gets on skin, in eyes, mouth or stomach, or is inhaled

Protect yourself and remove the person from the cause of exposure.  Call a doctor or ambulance.  For specific information on treatment, refer to the directions given on the pesticide label.  In general if pesticide gets on the skin or in the eyes, flush the exposed surface with clean water for fifteen minutes.  If material is ingested, follow the emergency directions on the label.  In some cases it will be necessary to induce vomiting, in others to drink milk or other liquids.  For inhalation it is important to get out of the area, lay still and call a physician if necessary.  Bring the label to the doctor's office.  It contains information, such as the name of the chemical and antidotes, which will help in the treatment.

Internet Link: http://www.aginfonet.com/agricarta/content/sk_safety_council/first_aid.html Basic first aid for pesticide exposure

Internet Link: http://muextension.missouri.edu/xplor/agguides/agengin/g01915.htm Further study material from University of Missouri Extension

63. Describe protective gear to use while mixing and applying pesticides

The goal of protective clothing is to minimize exposure to the pesticide.  The first step in determining what protective gear to wear is to read the instructions on the label.  The label will give basic instructions on what type of protective clothing and equipment to use. Long pants, long sleeved shirts, gloves and coveralls should ALWAYS be worn when dealing with pesticides.  When mixing pesticides, wear protective equipment that protects against splashes and/or dust and fumes.  This may include a face shield, goggles, respirator and protective apron.  The type of protection needed is also based on how long you will be exposed to the pesticide and what type of pesticide you are using.  Some protective clothing will protect longer than others.

Internet Link: http://ianrwww.unl.edu/ianr/pat/pat9.htm#item9a Protective gear to be used when mixing pesticides

Internet Link: http://www.ag.ohio-state.edu/~ohioline/b750/b750_2.html Types of protective clothing needed, including drawings of someone properly clothed.

64. Describe proper cleanup procedures for application equipment and protective gear

All equipment and protective gear should be cleaned thoroughly and promptly.  Applicators should attempt to clean out spray tank the best they can in the field over the sprayed crop before returning to inhabited areas.  This can be accomplished by rinsing the tank in the field and disposing of the rinse water on the crop that has just been sprayed.

Internet Link: http://www.ag.ohio-state.edu/~ohioline/b750/b750_3.html Directions for cleaning protective clothing

Internet Link: <HT{icon}{~HTTP~}{muextension.missouri.edu/xplor/agguides/agengin/g01916.htm}> Pesticide Application Safety (the fifth section discusses equipment clean up and storage).

65. Describe proper ways for disposing of pesticides and containers

The best way to dispose of pesticides is to use them as directed and not to create a surplus.  Only mix up as much pesticide as will be needed.  If there are excess pesticides that are still usable, use them at another approved site, or see if anyone else, who is authorized, can use them.  If there are pesticides which cannot be used, check with local authorities to see if there is a local hazardous waste disposal site where they can be disposed of properly.   Empty containers need to be thoroughly rinsed three times to be considered clean.  The rinse water should be emptied into the spray tank to avoid contaminating the soil or water sources.  Containers that have been rinsed should be labeled "rinsed" and may be recycled or disposed of in a sanitary landfill.  Containers and pesticides should never be burned or dumped on private property.

Internet Link: http://www.ag.ohio-state.edu/~ohioline/b750/b750_4.html Disposal of pesticides and  containers

Internet Link: http://muextension.missouri.edu/xplor/agguides/agengin/g01916.htm Pesticide Application Safety (the sixth section discusses methods for cleaning and disposing of  pesticide containers)

Internet Link: http://ianrwww.unl.edu/ianr/pat/pat11.htm#item11c Pesticide disposal

66. Describe how to store pesticides safely and securely

Pesticides should be stored separately from other products.  The storage area should be located away from children, domestic animals and untrained personnel.  The storage unit should be locked and clearly labeled as containing pesticides.  Storage areas should be well ventilated, insulated and/or have climate control.  The pesticides should not be exposed to extreme heat or cold as that could cause the bursting of containers and the loss of potency.  There should also be adequate lighting.  Materials to contain and clean up spills should be stored with the pesticides as well as a water source to be used to rinse the skin or eyes in case of accidental exposure.  Measures should be taken to make sure that there is no run off from the storage unit and that all pesticides are stored in nonporous containers and do not get damp.

Internet Link: http://muextension.missouri.edu/xplor/agguides/agengin/g01916.htm Pesticide Application Safety (the first section discusses pesticide storage).

Internet Link: http://ianrwww.unl.edu/ianr/pat/pat11.htm#item11b Pesticide storage

67. List procedures for handling a pesticide spill

There are four C's for handling a pesticide spill: control, contain, clean and call.  Before trying to control the spill make sure to put on appropriate protective gear.  If there is a leak or spill contain it by stopping it at the source.  This could mean picking up a tipped over jug or turning off a faucet.  The goal is to keep the spill from getting worse.  The second step is to contain the spill and stop it from spreading.  If it is a powder, cover with plastic or a sweeping compound.  If it is a liquid, stop it from spreading by blocking its path with absorbent materials or create a dike by spading up earth.  The third C is clean.  Liquids can be cleaned by covering them with absorbent materials such as sawdust, cat litter, fine sand, shredded newspapers etc.  Carefully pick up the material and store it in a plastic container until it can be disposed of safely.  Do not rinse area with water as that will spread the pesticide.  Instead if the surface is nonporous wash with detergent and water, however, do not let any of the soapy water run from the area.  Absorb the water with absorbent material and dispose of it in the same way you did the pesticide.  Be sure to clean all equipment that came in contact with the pesticide as well as yourself.  Then, if necessary, call and report the spill to local authorities.  They may also be able to provide directions for cleaning and decontaminating the area.

Internet Link: http://muextension.missouri.edu/xplor/agguides/agengin/g01916.htm Pesticide Application Safety (the last section discusses how to handle a pesticide spill)

Internet Link: http://ianrwww.unl.edu/ianr/pat/pat11.htm#item11d What to do if pesticides are spilled

Pest Management Glossary

Abiotic: Non-living, physical or chemical, includes solar radiation, temperature, humidity, and pH; used in context of an effect, such as abiotic injury.

Action threshold: The pest density at which a pest management tactic must be implemented in order to avoid economic loss.

Active ingredient: The chemical in a formulated product that is responsible for the herbicidal/insecticidal/fungicidal effects as indicated on the product label.

Acute exposure: Contact with a pesticide or toxin over a short period of time.

Adjuvant: Substance that enhances the effectiveness of a pesticide.

Bacteria: Unicellular organisms that include free living, saprophytic, and parasitic forms.

Banded pesticides: Pesticide application either over the rows or in-between the rows to reduce the overall application rate per acre.

Beneficial organisms: Organisms that reduce pest numbers or improve soil or plant quality.

Best Management Practice (BMP): Also called Good Farming Practices. Practices recognized as effective and practical means for producing a crop in an economically and environmentally sound way.

Biological pest control: The process of conserving, augmenting or introducing beneficial living organisms to reduce a pest population or its impacts. It includes the use of insects, nematodes, mites, fungi, bacteria, viruses, plants, vertebrates, and other living organisms.

Biological pesticides: Pesticides derived from living organisms such as Bt (Bacillus thuringiensis).

Biotic: Pertaining to living organisms.

Broad-spectrum pesticide: Pesticides that are toxic to a wide range of organisms.

Carcinogen: Substance that may initiate cancerous tumor formation in animals.

Chemical pest control: The use of pesticides to reduce a pest population or its impacts.

Chronic exposure: Contact with a pesticide or toxin over a long period of time, usually at low levels.

Common pesticide name: Name given to a specific pesticide active ingredient. Many pesticides are known by a number of trade or brand names, but have only one recognized common name.

Contact pesticide: A pesticide that is toxic to an organism by contact rather than a result of translocation or ingestion.

Cultural pest control: The use of practices other than chemical and biological controls to reduce a pest population or its impacts. Such practices include tillage, row spacing, irrigation, fertility, timely harvest, and all forms of mechanical pest control.

Economic Injury Level: The pest damage level at which the cost of controlling the pest population equals the value of the crop lost.

Economic Threshold (Action Threshold): Pest density at which control measure should be taken to avoid crop value loss from reaching the Economic Injury Level. By implementing a management strategy when Economic Threshold is reached and keep pest populations from reaching the Economic Injury Level.

Fumigant: Gaseous phase of a pesticide used to destroy insects, pathogens, weed seeds, or other pests in soil or grain bins.

Fungi: Organisms which lack chlorophyll and vascular tissue and range in form from a single cell to a body mass of branched filamentous hyphae that often produce specialized fruiting bodies. Fungi cannot produce their own food.

Genetic resistance: Genetically based mechanisms within host plants which hinder pest development.

Good Farming Practices: See BMP

Herbicide carryover: Occurs when a herbicide does not break down during the season of application and persists in sufficient quantities to injure succeeding crops.

Host: A living organism serving as a food source and refuge for a parasite.

Integrated pest management (IPM): A sustainable approach that combines the use of prevention, avoidance, monitoring and suppression strategies in a way that minimizes economic, health, and environmental risks.

LD50 or LC50: The lethal dose of a substance that kills for 50% of the test organisms expressed as milligrams (mg) per kilogram of body weight. It is also the concentration expressed as parts per million (ppm) or parts per billion (ppb) in the environment (usually water) that kills 50% of the test organisms exposed.

Mechanical pest control: A component of cultural pest control that uses physical methods to reduce a pest population or its impacts. Mechanical controls include cultivation, hoeing, hand weeding, mowing, pruning, or vacuuming.

Mode of action: The mechanism by which pesticides affect target organisms.

Narrow-spectrum pesticide: Pesticides that act on a limited range of species.

Non-point Source (NPS) Pollution: Contamination derived from diffuse sources such as construction sites, agricultural fields, and urban runoff.

Parasite: An organism which lives on or in another living organism and obtains part or all of its nutrients from that other living organism.

Parasitoid: An insect that feeds on and develops in another insect, and causes death in the host insect.

Parts per billion (ppb)/ Parts per million (ppm): A means of expression concentration: parts of analyte per billion/million parts of sample.

Pathogen: Living agents that cause diseases in plants and animals.

Pest: Organism that directly or indirectly causes damage to crops.

Pest density: The number of pests per unit area or plant structure.

Pesticide resistance: The inherited ability of an organism to survive and reproduce following exposure to a dose of pesticide normally lethal to the wild type.

Persistence: Ability of a pesticide to resist degradation as measured by the period of time required for breakdown of a material. Depends on environmental conditions and chemical properties.

Personal Protective Equipment: Clothing and protective devices required by EPA to be worn by users of pesticide products.

Phytotoxic: Injurious or toxic to plants.

Plant disease triangle: Diagrammatic representation of the three key factors contributing to plant diseases: 1) susceptible hosts, 2) pathogen presence, 3) proper environmental conditions.

Plant parasitic nematodes: Microscopic, non-segmented roundworms that usually survive in soil, and invade plant roots.

Point source pollution: Contamination from specific identifiable source.

Postemergence: Applied after emergence of the specified weed or planted crop.

Preemergence: Applied to the soil surface prior to emergence of the specified weed or planted crop.

Preplant incorporated (PPI): Applied and tilled into the soil before seeding or transplanting.

Race or strain: Organisms of the same species and variety that differ in their ability to parasitise varieties of a given host, or that differ in their reaction to pesticides.

Reduced-risk pesticides: These are pesticides which: 1) reduce pesticide risks to human health; 2) reduce pesticide risks to nontarget organisms; 3) reduce the potential for contamination of valued, environmental resources.

Re-entry interval: A time period set by EPA that restricts individuals from entering a pesticide-treated area.

Refugia: Areas, untreated with pesticides, provided to preserve susceptible populations of pests.

Sampling: Any valid method to determine a representative value for a field parameter.

Scouting: Sampling or observing crops to determine levels of pest populations and disease; also used to assess crop health and yield potential, and levels of beneficial insects.

Selectivity: Pesticides that are toxic primarily to the target pest (and perhaps a few related species), leaving most other organisms, including natural enemies, unharmed.

Selection Pressure: An action, event, or chemical that preferentially allows survival of one group over another.

Setback: The distance from sensitive areas, such as surface water, wetlands, or tile drain inlets, where no pesticides are to be applied.

Spray drift: Movement of airborne spray droplets of a pesticide outside the intended area of application.

Surfactant: A material that favors or improves the emulsifying, dispersing, spreading, wetting, or other surface modifying properties of pesticides in solution.

Systemic: Not localized; movement away from the area of application to other plant tissues through translocation.

Tank mix: A mixture of two or more compatible pesticides intended for simultaneous application.

Tolerance: The inherited ability of a species to survive and reproduce after pesticide treatment. Also refers to the ability of a crop to yield satisfactorily in presence of pests or adverse environmental conditions.

Toxicity: Degree to which a pesticide is poisonous; the ability of a substance to interfere adversely with the vital processes of an organism.

Trade name: Name given to a product sold by a company to distinguish it from similar products made by other companies.

Transgenic resistance: An organism whose genome has been modified to incorporate pest resistance by the introduction of external DNA sequences into the germ line or gene transfer from outside the normal range of sexual compatibility.

Transgenics (bioengineered organisms): Plants or animals that contain DNA derived from a foreign plant or animal.

Translocation: Actively moved within and between plant tissues and organs.

Trap crop: A crop that attracts and concentrates insect pests.

Vapor drift: The movement of chemical vapors from the area of application.

Viruses: Non-cellular parasites/pathogens comprised of a protein shell and a simple genetic core, usually RNA in plant viruses.

Worker Protection Standard: EPA regulations requiring protective clothing and practices designed to protect users of pesticides by reducing pesticide exposure.

CROP MANAGEMENT

CROPPING SYSTEMS

1. List advantages and limitations of monoculture crop and crop rotation systems

The chief advantage of monoculture/single crop systems is the simplicity of management.  Crop rotation systems can be used to maintain or improve chemical, biological, and physical conditions in the soil.  Yield advantages are higher for rotated crops than that of single crops.  Crop rotations can help to control insects, diseases and weeds, while continuous cropping increases the potential for infestations.  Grasses and legumes may be included in rotations to improve soil structure and reduce erosion.  Legumes may also reduce or eliminate the need for nitrogen fertilizers in rotated crops.  Disadvantages of crop rotation systems may include increased equipment use and high levels of management.

Internet Link: http://abe.www.ecn.purdue.edu/~agen521/epadir/erosion/reasons.html Further study material from Purdue University

Internet Link: http://www.al.nrcs.usda.gov/bmp/rotation.html Further study material from USDA

Internet Link: http://www.dpi.qld.gov.au/dpinotes/fieldcrops/genmanage/fs99332.html Further study material from Queensland Farming Systems Institute, Australia

2. Describe the role of the following in a cropping system

a. fallow

Fallow land allows for possible increased organic material, increased microbiological activity, and possible pests may run their lifecycle without increased food sources which may reduce future pests or density of pests.

b. green manure crops

Green manure crops are those grown to be incorporated into the soil while still green.  Green manure crops increase the nitrogen and organic matter content of the soil as well as provide cover, thus preventing wind and water erosion. 

c. cover crops

Cover crops are grown for the purpose of preventing soil erosion and suppressing weeds and insects.  Cover crops and green crops are annual or perennial plants grown during part or all of the year.

d. trap crops

Trap crops protect the main crop from a pest or a complex of pests. The trap crop can be a different plant species, different variety, or even a different growth stage of the same species.  Trap cropping is most effective on pests that are abundant and insects of intermediate mobility rather than those, like aphids, passively dispersed by air currents or strong fliers that descend on a crop from higher elevations.

e. companion crops

Companion crops are grown simultaneously  with a main crop to provide weed and insect control, and to help reduce erosion.  Companion crops usually are salable products.

Internet Link: http://echonet.org/Technotes/GreenManureCrops.html Further study material on green manure crops

3. Describe how cropping sequence in a rotation influences the following

a. tillage options: Tillage requirements may vary depending on the crop just grown and the crop to be planted.  The timing of tillage is also dictated by the crop being grown, when it is to be harvested and how much residue is on the surface.  When the next crop must be planted (fall or spring) enters into the tillage equation. [Ref.  Phillips, R.E, and S. H. Phillips (ed.)  1984.  No-Tillage Agriculture: Principles and Practices.  Van Nostrand Reinhold Company, New York.]

b. residue management: Cropping systems or rotations can influence the amount of residue on the soil surface.  Silage corn leaves very little residue, but a following crop of wheat would have considerable stubble and straw residue that could be worked into the soil or left on the surface.  In semiarid areas where wind is a problem, the cropping sequence should leave considerable surface stubble and residue which can reduce wind erosion significantly.  Hilly land also requires the same consideration.  Equipment and available resources would dictate how this residue is managed; no-till would require different planting and tillage equipment than would clean tillage. [Ref.  Unger, P.W.  (ed.)  1994.  Managing Agricultural Residues.  Lew Publishers, Boca Raton, FL.]

c. moisture availability: Moisture availability is closely related to the type of tillage system employed, the class of land being used for agricultural production, climate (especially precipitation), irrigation (as a supplement or the total source of water for the growing crop, as is the case in arid areas), the crops being grown and the order in which they are grown.  Certain crops encourage better infiltration of moisture into the soil than do others.  Soils susceptible to erosion must have cropping sequences that limit erosion.  Both of these conditions will influence moisture availability.  In semiarid areas the cropping sequence, to assure available moisture, may require a fallow-crop sequence.  Crops that leave a considerable amount of residue on the surface will enhance moisture availability because of increased infiltration and reduced runoff and erosion.  [Ref.  Hatfield, J.L., and D.L. Karlen.  (ed.) 1993. Sustainable Agricultural Systems.  p. 21-46.  Lewis Publishers, Boca Raton, FL; Phillips, R.E, and S. H. Phillips (ed.)  1984.  No-Tillage Agriculture: Principles and Practices.  p.  66-86.  Van Nostrand Reinhold Company, New York.]

d. pest management: Cropping sequence is effective in interrupting the life cycle of insects, plant pathogens, nematodes, and weeds.  Thus crop rotation is one of the most effective means of cultural control for pest problems.  This is especially so with insects, diseases, and weeds.  In the case of nematodes, crop rotation may be the only way to control a particular nematode in a given crop.  Where it is critical to eliminate the incidence of pest infestation in a given crop, it may be necessary to interrupt the growth of that crop by two or three other crops before it is grown again.

e. Yield potential: Because cropping sequence in a rotation helps in pest management, tillage, and the other items mentioned above, yield potential is increased.

[Ref.  Edwards, C.A., R. Lal, P. Madden, R.H. Miller, and G. House.  (ed.)  1990.  Sustainable Agricultural Systems.  p.  107-122.  Soil and Water Conservation Society, 7515 Northeast Ankeny Road, Ankeny, IA 50021;  Francis, C.A., C.B. Flora, and L.D. King.  1990.  Sustainable Agriculture in Temperate Zones.  John Wiley & Sons, Inc.  New York.  This book is an excellent source of information about tillage systems and sustainable agricultural practices; Ref.  Phillips, R.E, and S. H. Phillips (ed.)  1984.  No-Tillage Agriculture: Principles and Practices.  p.  152-186.  Van Nostrand Reinhold Company, New York.]

4. Compare clean-till and high surface residue management systems for the following

High surface residue management is a year-round system beginning with the selection of crops that produce sufficient quantities of residue and may include the use of cover crops after low residue producing crops. High surface residue management includes all field operations that affect residue amounts, orientation and distribution throughout the period requiring protection.  Tillage systems included under this type of management are no-till, ridge-till, mulch-till, and reduced-till.  Clean-till is a system that leaves less than 15 percent residue cover after planting, or less than 500 pounds per acre of small grain residue equivalent throughout the critical wind erosion period.  Clean-till generally involves plowing or intensive tillage.

Internet Link: http://www.ctic.purdue.edu/Core4/CT/CRM/TillDefine.html Further study material from Purdue University

a. crop rooting patterns:  Plowing can create a hard pan level restricting deep root growth, whereas plowing can loosen surface soil allowing for better root growth.  Plowing can also turn under diseased residue, venting the soil and minimizing disease.

b. seed placement:  Planting in surface residues requires special equipment including seed drills that will penetrate residue and deposit seeds into the soil.  Clean-tillage makes it possible to create a fine seedbed in which seeds can be planted to more exact specifications.

Internet Link: http://www.ctic.purdue.edu/Core4/CT/CRM/TillDefine.html Further study material from Purdue University

c. pest management:  Insect and weed control with conservation tillage requires knowledge of insect dormancy habits and different weed stages.  In many cases, pesticides and herbicides must be applied to control pest and weed growth.  Clean-tillage generally helps with weed and insect control.

Internet Link: http://www.agric.wa.gov.au/agency/ Further study material from Western Australia

d. stand establishment:  With clean-tillage, prior to seedling emergence, intense wind can damage the seedbed and uncover the seed.  After emergence, high wind can cause blowing sand to cut off or sting the young seedlings.  Conservation tillage prevents these problems.  Clean-tillage can also make the soil susceptible to soil crusts, making seedling emergence difficult.

e. fertilizer placement:  Fertilizer is easily applied in a clean-tillage field through broadcast or banding.  Fertilizer application in a no-till field cannot be easily applied through banding.  Fertilizer must be broadcast with no-till and cannot be incorporated.

Internet Link: http://www.mandakzerotill.org Further study material from The North Dakota Zero-Tillage Farmer's Association

5. Describe how the following factors affect the conversion of non-cropland to cropland

a. existing vegetation

Non-cropland vegetation can vary from large trees to small brush and may contain toxic plants.  The root structures of the existing vegetation may be deep or difficult to remove when converting the area to crop land.  And if it is a bog area containing water, the vegetation may have some aquatic features and will need to be drained.

b. pest management

Non-cropland pests will likely be a function of the existing vegetation and water availability.  Once the area is cleared and prepared for crop production many of the pests will also be minimized.

c. nutrient availability

Test for nutrient availability in the soil prior to planting.  Some non-cropland can have increased fertility due to its fallow nature, but most non-cropland will have poor nutrients and high acidic or alkaline soils.

d. yield potential

Yield potential varies widely in non-cropland areas and will likely need to be helped.  Conversion of the land may require a great deal of effort depending on the circumstances.  Leveling, drainage, pest control, and nutrient management are all costly issues that factor into the yield potential of the new crop land.

e. erosion potential

If the non-cropland area has signs of erosion (which should be clearly evident due to years of natural erosion effects), the area should be prepared to prevent erosion prior to planting.

f. environmental impacts

Prior to any conversion, a walk-through should be done to determine any environmental impact.  A history of the area should be considered and discussions with prior owners should be conducted to determine the impact of conversion to crop land on wildlife, vegetation, and neighboring drainage areas.

6. Define allelopathy

Suppression of growth of a plant by a chemical toxin released from a nearby plant.  Some examples are rye and some small grains.

Internet Link: http://www.univ-savoie.fr/labos/ldea/alelodef.htm Definition and information regarding allelopathy

HYBRID AND VARIETY SELECTION

7. Define cultivar or variety, and hybrid

Hybrids are the offspring of two plants of different races, breeds, varieties, or species while a cultivar or variety is a plant having minor characters or variations which separate it from the type species.

Internet Link: http://www.orchidlady.com/glossary.html Online glossary of botanical terms

8. Differentiate hybrid and open pollinated variety

Hybrids are created by looking for the right combination of parent lines to cross to produce plants with the desired special characteristics. This cross-pollination is done by hand to ensure that only the designated partners are crossed. Open pollinated varieties are seeds harvested from plants pollinated by wind or insects.  Hybrid plants usually loose some of the traits of the original parents in an effort to enhance a selected trait.  Open pollinated selection processes usually retain much of the traits of the original parent plants, but do not always enhance a selected trait.

9. Describe how the following influence hybrid or variety selection

a. maturity:  cultivars selected for a given area must mature in the time provided by the growing season.  In more northerly climates, this becomes a very significant consideration.  On the other hand, cultivars should be selected that will also utilize the major part of the growing season.

b. yield potential: choose cultivars with the highest yield potential, but also make sure selections have shown yield stability in a wide variety of climatic environments.  Market demand should also be considered when choosing a cultivar with high yields.  If there is no demand for the crop even though the yield potential is high, one would not plant it.

c. adaptation to soil and climatic conditions:  poorly drained soils restrict crop choices since most crops require well-drained soils.  Soils that are deep and well drained allow farm managers to choose the best cultivar for that particular area.  Climatic conditions such as frosts, high temperatures, lack of precipitation, etc., dictate that cultivars be chosen that match the specific conditions expected.

d. yield stability among years and locations:  growers should research which varieties have been grown successfully in locations similar to their area.  Good cultivars have also been successfully grown for a number of years with good results.

e. pest resistance and tolerance:  the best way to avoid losses due to pests is to choose cultivars that show resistance, or at least some tolerance, to a particular pest.  This should be done regardless of the crop being grown.  Determine the potential pest problems, and then chose cultivars, if they are available, that reduce the losses that these pests can cause.

f. herbicide sensitivity:  herbicide resistance becomes a factor when a crop is being planted, following another crop on which a herbicide was used that leaves a residual effect in the soil.  If an atrazine type herbicide was used on corn, one would not plant a crop that was sensitive to atrazine carryover.

h. harvestability:  lodging or failure of the grain to dry down (in corn) can make the crop largely unharvestable and will result in yield losses.

h. end use:  this is usually where the cultivar is chosen because it possesses certain attributes desired by the end user high protein, high oil, specific amino acids, certain aromatic compounds, etc.

i. value added trait:  if a specific trait is desired it maybe advantageous to select a hybrid which focuses on that specific trait.  These value added traits may be related to yield increase through pest management or plant vigor.

10. Define genetically modified (GM)

A GMO is an organism that has been genetically modified by receiving DNA from another organism.  Organisms are genetically modified to inherit beneficial traits that other organisms possess.

Internet Link: http://www.agrisk.umn.edu Further study material from The University of Minnesota

11. List advantages and limitations of growing GMs

GMOs have beneficial traits that non-GMO plants or animals simply do not have.  GMOs can be manufactured to have a variety of useful characteristics.  Transgenic crops can be engineered to be resistant to certain diseases, herbicides, or detrimental insects, increasing the grower's options for pest control and reducing possible damage to the environment.  Crops can also be genetically engineered to improve appearance, shelf life, and nutritional value.  Concerns over GMOs include the possibility that insects will mutate and become resistant.  Some weeds may develop a tolerance to a herbicide if it is repeatedly applied to a crop that is engineered to be tolerant to that herbicide.  Dependence on a few GMOs with a narrow genetic base could also increase the chance of total crop failure.   Finally, genetically altered crops may be morally unacceptable to some people and growers may find a smaller market base for GMOs.

Internet Link: http://www.agrisk.umn.edu/ Further study material from The University of Minnesota

12. Explain why randomization and replication are important in field trials

A well designed field trial occurs when all varieties are sown under identical conditions in plots or nursery rows of uniform size.  The experimental field should be uniform in topography and soil character.  Soil preparation, crop sequence, and fertilization should be identical for the entire field that is included in the experiment.  Seeding of all the varieties should be carried out at the same time.  It is also important to replicate the experiment in three to ten plots or rows to eliminate variations due to differences in soil depth, origin, topography, standing water, runoff, soil compaction, and animal excretions.  When one variety consistently outyields another by a margin of 19-1, then it is assumed that this variety is superior.  Any difference smaller than 19-1 is largely due to chance and considered insignificant.  In order to develop a well-designed field trial it is essential to incorporate all of these elements.  A poorly designed field trial will not contain replication and the results therefore will be indistinguishable from the background variation that is always inherent in a field.  One would not be able to tell whether or not the result was due to the cultivar, fertilizer treatment, herbicide, insecticide, etc., or whether it was due to variation in the soil or drainage patterns.

13. Use least significant difference (LSD) and multiple range test (MRT) values to interpret differences among varieties or hybrids

LSD:  Basically if two responses, yield, etc, differ by a value greater than the LSD value provided, those two responses are considered to be significantly different at the 5% level, e.g., 95% of the time one would expect differences of that size to be due to the treatments and not due to chance.  5% of the time such differences would be due to chance.

MRT:  In a MRT, values listed in a tabular manner will be followed by letters.  At the bottom of the table, a statement will say: "Values within columns followed by the same letter do not differ significantly at the 5% level."  Part of this statement will usually be an indication of the MRT used.  For example:  Waller-Duncan or SNK (Student-Newman-Kuhls) are the two most commonly used.  They are named after their developers.  Again the interpretation is the same as for the LSD given above.

CROP ESTABLISHMENT -- SEED QUALITY

14.  Use seed tag information to determine seed quality

Seed tags contain:  seed grade, bag weight, lot number, kind & variety name, pure seed (%), inert material (%), weed seed (%), noxious weed content (must be none), origin of the seed (where it was grown), germination (%), hard seed(%) where applicable, dormant seed (%), total germination (%), and date the germination test was run (month and year).

Internet Link: <HT{icon}{~HTTP~}{frost.ca.uky.edu/agripedia/agmania/seedtag/reveal.htm}>  Seed tag info

Internet Link: http://www.ext.nodak.edu/extpubs/plantsci/crops/a353w.htm Seed tag info

15.  Describe how pre-harvest and harvest conditions influence seed quality

Harvest conditions that affect seed quality include seed maturity, seed viability, and seed moisture content.  Harvesting too early reduces yield and diminishes seed viability.  Harvesting too late results in yield loss due to shattering, lodging, and mechanical seed damage.  Harvest must be timed so that the seed has reached full maturity and the seed moisture content has declined to levels that allow safe storage.  Seed harvested at higher moisture levels tend to deteriorate quickly and seed that is too dry tends to be fragile and easily damaged during threshing.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. p34, 59.

16.  Describe how storage time, handling, and storage conditions affect seed quality

Storage time:  Most seeds can be stored a relatively short period and still maintain high germination.  The more deleterious the conditions under which the seed is stored (high temperature and humidity), the shorter the period it can maintain viability.  Seed stored for over one year should be evaluated for germination before determining the amount of seed required to obtain the desired stand.  Seeds differ greatly in their storage time ranging from of few months to many years.

Handling:  Through impact or undue pressure, the physical quality of the seed can be damaged.  Heavy seeds like those of peas, corn, and soybean can be fractured if they strike or are struck by a hard object or film surface, thus degrading seed quality.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p528.

Storage Conditions:  Factors such as seed moisture content, storage temperature, initial seed quality, damage caused by rough handling, insect damage, and the extent of cleaning all influence seed quality during storage.  Some general rules in managing stored seed are:

1. The seed stocks should be kept under continuous observation

2. Seeds should be fumigated between outgoing and incoming stocks

3. Floors should be swept thoroughly and rubbish burned

4. Ventilation should be encouraged within and between stocks

5. Seed should not be piled against a wall

6. The storage building should be repaired and kept in good condition

7. Seeds showing the best storage potential should be selected for carrying over from one season to the next

8. Seeds stored in bulk require frequent turnings to prevent deterioration due to heating

   *Following these rules will help maintain seed quality during storage.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p542-3.

Internet Link: http://www.goldsmithseeds.com/column/mar2897.htm General info on seed storage

Internet Link: http://www.sproutpeople.com/storage.html Info on seed storage

17. Describe the advantages and limitations of seed treatments

Seed treatments are done for several purposes:  1. Seed disinfection/disinfestation to combat seedborne diseases and insect pests  2. Protection of seeds against diseases and pests that may be present in soil or be airborne when seedlings emerge  3. Specialized seed treatments such as coating, pelleting, scarification, decortication, irradiation, blending, delinting (cotton), etc., to protect seeds against pests or aid in germination.  Also important, and beneficial, is the placement of a coating around the individual seeds of legumes that contains the specific Rhizobia spp. required to effect optimum dinitrogen fixation.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p503.

Seed Coating/pelleting:  Advantages: 1. Creates uniform size for precision machinery  2. Reduces environmental stresses like drought and flooding. Disadvantages: Seed may cost a little more and the apparent seeding rate must be adjusted to account for the fewer number of seeds per pound of seed.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p515.

Scarification:  Advantages: 1. Allows water to pass through hard seed  2. More uniform germination.  Disadvantages: 1. Possible damage to seed quality.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p517.

Decortication:  Advantages: 1. Creates more uniform size in seeds and 2. Reduces germs in seedball. Disadvantages: 1. Possible damage to seed quality.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p517.

Irradiation:  Advantages: 1. Increases water absorption and 2. Reduces the proportion of hard seeds.  Disadvantages: 1. May sterilize some seeds.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p517.

Delinting:  Advantages: 1. more uniform planting  2. free from certain lintborne pathogens.  Disadvantages: Delinting is an extra expense that will be added onto the cost of the seed.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p516.

Internet Link: http://www.ipm.iastate.edu/ipm/icm/1997/4-21-1997/onfarmseed.html Information regarding seed treatments

18. Describe advantages and limitations of bacterial inoculants

By using bacterial inoculants, the nitrogen-fixing potential in the roots of legumes can be increased. Using seed inoculants is also cheaper and more effective than mid-summer direct applications of nitrogen.   However, the effectiveness of seed inoculants may be limited by seed treated with insecticides and fungicides.  Factors that affect the degree of damage inflicted on the inoculant include toxicity of seed treatments and length of time inoculant is in contact with seed treatments.  Storage and shipping may also affect the viability of the bacterial inoculants.

Internet Link: http://www.aes.purdue.edu/AgAnswrs/1997/9-26Seed_Inoculation.html Further study material from Purdue University

Internet Link: http://www.aes.purdue.edu/AgAnswrs/1998/1-9Seed_Inoculation.html Further study material from Purdue University

Internet Link: http://www.ksu.edu/plantpath/extension/alert-98/98-07.html Further study material from Kansas State University

19. Describe how storage time, handling, and storage conditions affect quality and use of bacterial inoculants

storage time: if storage time is projected to be short then bacterial inoculants may be minimized.  If the storage time is projected to be long then bacterial inoculants may need to be increased or used multiple times depending on the label, restrictions, and manufactures recommendations.

handling:  if crop handling is minimized and containers and transfer mechanisms are cleaned, the use of bacterial inoculants may be minimized.  Also, because moisture from broken crops increases bacterial growth it is important to keep breakage to a minimum. 

storage conditions:  if the conditions are moist then the effect of bacterial inoculants may be compromised.  Fans, blowers, and exhaust systems can be effectual in minimizing the use of bacterial inoculants.

20. Describe uses and limitations of the standard germ test

Standard germination test:  This test is valuable in providing germination and purity of seed lots.  It is used on all seed that is sold.  Vigor tests are much more specific in that they provide an idea of what kind of germination and emergence one would expect from a crop planted under adverse conditions such as cool or cold and wet soils (cold germination test).  Vigor tests are more expensive and thus are not used on a daily basis as is the standard test, but can provide valuable information about a seed lot.  Other vigor tests include the accelerated aging test (tests viability) and the tetrazolium test.  The tetrazolium test is used to test viability and works by identifying the approximate germination percentage.

21. Define Pure Live Seed (PLS)

Pure live seed (PLS) refers to the ratio of the seed in a lot that will germinate.  PLS is calculated as shown below:

PLS = purity ratio X germination ratio

22. Use purity and germination information to calculate a seeding rate

Suppose you have seed with the following characteristics:

      Purity or pure seed content = 95%       germination percent = 93%

Thus  (95/100) X (93/100) = .8835

    PLS = .8835 X 100 = 88.35%

Thus, if the recommended seeding rate for a crop is 60 pounds per acre, then the amount required to achieve 60 pounds of viable seed per acre would be

Seeding Rate = Recommended Rate / PLS

 = 60lb / 0.8835

 = 67.99 lb or 68 lb

23. Explain the role of Plant Variety Protection (PVP) laws in maintaining seed purity

Plant Variety Protection laws were implemented to protect growers and maximize seed purity.  These laws not only protect growers with regard to seed purity but also help the seed industry.  In the absence of Plant Variety Protection (PVP) laws, firms can copy technologies developed by others with impunity, to the extent that prospective innovators in the private sector would cease to undertake such beneficial activities. PVP laws are governed by policies that relate to Intellectual Property Rights (IPR) in general. PVP laws determine the ability of individuals or firms to claim exclusive ownership rights over certain plant varieties or components of plant varieties (Pray and Tripp, 1998). 

CROP ESTABLISHMENT -- PLANTING PRACTICES

24.  Describe how the following factors affect seed germination

a.  soil temperature: The extreme temperature range for the germination of field crop seeds is from 32°F-120°F. Cool season crops germinate at lower temperatures than warm season crops.  At temperatures too high for germination, the seeds may be killed or merely forced into secondary dormancy.  Oil content is enhanced in soybean and rapeseeds when the temperatures are above average during the last five weeks of maturation.  In contrast, oil content is greater in flax and sunflower seeds when plants are exposed to low temperatures (13-18°C, 55 to 65°F).  High temperatures and delayed harvest due to wet weather may cause increased free fatty acid levels in certain oilseeds (e.g., rapeseed) which lowers overall seed quality.  High night temperatures enhance seed development in rice by increasing the size of the aleurone and bran layers.  Temperature during seed development also has an important role in the expression of seed dormancy.  High temperatures are generally associated with increased hardseededness and dormancy in a number of crops.  High temperatures during the early stages of ripening of wheat seeds reduce the susceptibility of seeds to preharvest sprouting.  In other crops, such as Petkus winter rye and wheat, low temperatures during the latter stages of seed maturation fulfill the vernalization requirement to induce flowering.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. pg 27-28.

Ref: Martin, John H., et al. Principles of Field Crop Production, Third Edition, 1976, Macmillan Publishing Co., Inc. pg 178-9.

Internet Link: http://www.agric.gov.ab.ca/agdex/500/9000002.html Info on soil temperatures

b.  soil moisture: Abundant water is necessary for rapid germination.  Field crop seeds start to germinate when their moisture content (on a dry basis) reaches 26-75%.  Soil moisture status has a marked effect on seed quality because of its role in determining the solubility of essential elements necessary for growth of the mother plant.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. pg 27-28.

Ref: Martin, John H., et al. Principles of Field Crop Production, Third Edition, 1976, Macmillan Publishing Co., Inc. pg 178-9.

c.  seed/soil contact: Seed-soil contact:  Without good soil-seed contact the seed cannot imbibe enough water to germinate successfully, or it will not be able to take up enough water to keep the developing seedling alive.  With small-seeded crops, such as forage legumes and grasses, the lack of good soil-seed contact is the major reason for failure to establish stands required for high production.  Through good seed-soil contact the seedling is able to obtain, through the water, essential elements necessary for successful growth and development.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. p26.

Ref: Horrocks and Vallentine, 1999. Harvested Forages.  Academic Press, p136-154.

25.  Describe how depth of planting affects crop emergence

The optimum seeding depth varies according to crop and the environmental conditions at planting.  Planting one to one and one-half the seed's diameter is usually ideal for most crops as long as sufficient soil moisture is available to initiate germination.  Most plantings require at least a minimum of soil coverage.  Deeper planting in the soil minimizes the problems associated with decreased soil moisture, but it increases the likelihood that the seedling will not be able to sufficiently elongate to penetrate the soil surface.  Deeper plantings also result in cooler soil temperatures that may retard seedling growth.  Some of the grasses, notably corn, may be planted quite deep because of elongation of the coleoptilar node.

See Table 7-3 in Martin, John H., et al. Principles of Field Crop Production, Third Edition, 1976, Macmillan Publishing Co., Inc. pg 204 for crop specific information on planting depth.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. pg 27-28.

Internet Link: http://www.nk.com/nkwired/1998/01_06_depth.html Info on planting depth

26.  List conditions that alter recommended planting depth

Conditions that affect recommended planting depth are: available moisture, proper soil temperature, aeration, light intensity, avoidance of insect pests, avoidance of toxic amounts of salt, and the crop being planted where the planting depth is influenced by seed size.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p88.

27.  Identify factors that influence planting date

The factors that determine planting date are similar to those mentioned in question number 3.  The available moisture, soil temperature, and the avoidance of insect pests are major factors in determining planting date. The time of the year, which is related to soil moisture, soil temperature, etc., is also an important factor to consider in determining planting date.  Depending on whether the seed is a cold or warm season plant also will determine time of planting.

Internet Link: http://www.ipm.iastate.edu/ipm/icm/1999/5-3-1999/dateeffects.html Info on planting dates

28.  Identify limitations of seeding earlier or later than optimum

Some consequences of seeding too early or too late are possible damage and crop loss due to freezing, insufficient soil moisture, too high or too low soil temperature, exposure to pests and diseases, and the immaturity of crop at harvest time.  Harvesting the crop before it reaches full maturity and result in yield losses and reduce storage life.

Internet Link: http://www.ag.uiuc.edu/~ar-qssb/soy97/yield.htm General information on seeding schedules

29.  Describe how the following factors affect seeding rates

a.  planting practices

Many seeding rates of crops should be based on seed per foot of row, not pounds per acre.  In narrow rows, a slight shift in the number of plants per foot of row can result in excessive seeding rates.  Wide rows can accommodate more plants per foot of row and thus higher seeding rates. 

Internet Link: http://ext.msstate.edu/pubs/pub1194.htm Further study material from Mississippi State University

b.  soil tilth

Soil tilth is the physical condition of the soil as related to ease of tillage, fitness as a seedbed, and its impedance as to seeding emergence and root penetration.  A soil that has good tilth serves as a good seedbed and seeding rates can be increased.  Soils with poor tilth may have limited seeding rates due to restricted root growth, soil crusts or limited water infiltration.  Ref:Brady, N.C. 1990.  The Nature and Properties of Soils, Macmillan, pg. 118-120, 597.  

Internet Link: http://com.agronomy.wisc.edu/Publications/Aadvice/2000/ProvenCornManagementPractices.htm Further study material from The University of Wisconsin

c.  environmental conditions

Environmental factors that affect seeding rates are the availability of water, soil temperature, air temperature, and current weather conditions.  If conditions are especially dry or other factors exist that will affect seed germination, the seeding rate should be increased to compensate for the seeds that will not germinate.

d.  crop residue

Because conditions are often less optimal for seed placement, the seeding rate for no-till fields may need to be 10 to 15 percent greater than that for tilled soils.  An increased seeding rate is needed when poor stands could result from large amounts of residue, uneven residue distribution, or drills not being properly operated to penetrate residue.  However, seeding rate may not have to be adjusted when planting into soybean residue or where the corn residue level is light.  Seeding rates may not need to be increased if the drill operator has the drill properly adjusted and calibrated. 

Internet Link: http://frost.cu.uky.edu/pubs2/id/id136/id136.htm Further study material from The University of Kentucky

e.  seed size

Seed weights may vary considerably among varieties and production series.  This can affect seeding rates and final stands.  There are fewer large seeds per pound  than small size seeds.  As a result, more pounds of large seed per acre are required to equal the same seeding rate as smaller seed.  Seed tags may contain seed per pound information to aid in calculating proper seeding rates. 

Internet Link: http://www.ianr.unl.edu/pubs/fieldcrops/g1395.htm#t10 Further study material from Nebraska Cooperative Extension

30. Calculate plant population in a field

Plant population is determined by determining the desired target population.   Target population or intended plant stand is different from seeding rate.    Normally, you use a seeding rate greater than the target population since seed germination and plant survival will be less than 100%.  If you already know your target population goal, record that value in Step #1d below.  If not, enter values for the original seeding rate, seed germination percentage, and expected plant survival rate in #1a, #1b, and #1c, then calculate target population in #1 d.  Remember to convert percent to decimal numbers in #1b and #1c when multiplying (e.g., .90 rather than 90%).

a.   Original seeding rate (from your records):  26,600 seeds/a.

b.   Seed germination percentage (from seed tag):  95%

c.   Expected plant survival rate (use 95% if you're not sure):  95%

d.   Original target population (#1a x #1b x #1c):  24,006 plants/a.

When determining the plant population in the field, randomly pick 3 or 4 areas (in forages a 3-foot square area is sufficient; in row crops a 10-foot section of a row is sufficient), count and record the plants in these areas individually.  Multiply the width X the length to obtain the square footage of the area.  Since an acre contains 43,560 sq. feet, divide the square footage of the sampled areas into 43,560.  This provides a factor that when multiplied by the number of plants in the sampled area is equal to the plants per acre.

Internet Link: http://www.agcom.purdue.edu/AgCom/Pubs/AY/AY-264.html Info regarding calculation of plant populations

Internet Link: http://www.esso-farm-tek.com/Spring1995/page22.html Info regarding calculation of plant populations

31. Differentiate seeding rate, plant population, and harvest population

Plant population is the number of plants predicted to be in a certain area (or found in a certain area) and is determined by the crop produced, soil fertility, soil type, and the availability of moisture.  Seeding rate is the amount (usually by weight) of seeds that should be planted per acre in order to get a good stand.  Seeding rate is usually higher than plant population due to disease, insects and premature plant death.  Harvest population is the number of plants predicted to be in a certain area at time of harvest.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. p27-28.

Internet Link: http://www.modernforage.com/seedrate.htm Info on seeding rates

Internet Link: http://www.agric.gov.ab.ca/crops/seed01.html Info on calculating seeding rates

32. Describe advantages and limitations of applying fertilizer at seeding

The broad variety of fertilizer application technologies during seeding have tremendous advantages if applied correctly.  The fertilizer can help the seed from emergence to seedling and can be coupled with pest management practices to protect the seed from fungal and virus pests.  The main limitation is cost. 

CROP GROWTH, DEVELOPMENT AND DIAGNOSTICS

33. Describe characteristics of the following growth stages

a. germination and emergence:  The sequence of events in a viable seed starting with imbibition of water that leads to growth of the embryo and development of a seedling.  Emergence is when the coleoptile or hypocotyls poke through the soil surface.

Ref: Flocker, William J.,et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p644.

b. vegetative:  Referring to the asexual (stem, leaf, root) development in plants in contrast to sexual (flower, seed) development.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p653.

c. flowering:  The sexual development of floral leaves grouped together on a stem that, in the angiosperms, are adapted for sexual reproduction.  Pollination occurs and an ovule is fertilized.  Requires male and female plant parts working together.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p643.

d. seed development:  The step following flowering.  The period between the time of fertilization of the egg and maturity.  (i.e., when carbohydrates cease to be imported into the seed)

e. physiological maturity:  The final stage of development while the seed is still attached to the plant.  Includes cell enlargement plus the accumulation of carbohydrates and a decrease in acids.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p329.

34. Describe how temperature and moisture extremes affect crops at the growth stages listed in #33.

a. germination and emergence:  Extreme hot and cold temperatures can retard germination and emergence.  Extreme moisture can create molds, fungi, and viruses which will destroy the seed prior to germination and emergence.

b. vegetative:  Extreme hot and cold temperatures can destroy the cell structure of the plant which can open the plant to pests including viruses or could outright kill the plant.  Extreme moisture can cause root rot or could foster pests which can eventually kill the plant.

c. flowering: 

Under conditions of extreme hot or cold the flower of the plant could be destroyed which would minimize if not eliminate any seed development or fruit.

d. seed development: 

Because under conditions of extreme hot or cold the flower of the plant could be destroyed, this would minimize if not eliminate any seed development.

e. physiological maturity: 

The general growth of the plant will be retarded under conditions of extreme hot or cold or extreme moisture.  Besides the general limitations on growth, increases pest activity will also limit growth and physiological maturity.

35. Define growing degree unit

 Growing degree day (GDD) is the amount of temperature required by a plant to achieve various growth stages.  GDD is determined by subtracting the minimum temperature for growth for a specific type of crop from the daily average temperature.  The positive values (differences) are accumulated from a specific time at the beginning of the growing season throughout the growing season.  Negative values (differences) are ignored or dropped.  Warm-season crops and cool-season crops have different minimum and maximum temperatures between which growth will occur.

Ref: Copeland, Lawrence O. and McDonald, Miller B. Seed Production, Principles and Practices, 1997, Chapman & Hall, New York, NY. p265 and Table 14.1 for cotton example.

36. Use growing degree units to determine rate of crop development

Growing Degree Days are used to determine growth stages of plants, predict stage of development at a specific time of year, as well as predict eventual insect hatches that may affect a crop.

Internet Link: http://ceinfo.unh.edu/Agriculture/Documents/growdays.htm Information regarding growing degree days

Internet Link: http://classes.aces.uiuc.edu/CPSC121/gdd.htm Information regarding growing degree days.

37. Describe how day length affects flowering in short day, long day, and day neutral crops

Flowering in some crop plants is induced by change in day length (photoperiodism) and/or low temperatures (vernalization).  Plants like spinach, sugar beet, Hibiscus, coneflower, dill, Fuschia, henbane, and Sedum require long-days for flower induction (long-day plants), while others like Bryophyllum, Chrysanthemum, cocklebur, Cosmos, Kalanchoe, poinsettia, strawberry, tobacco, and Viola require shorter days for flowering (short-day plants).  Several plants like artichoke, balsam, Gardenia, cucumber, Comphrena, lima bean, cineraria, and tomato are not influenced by day length and are considered day-neutral plants.  Long-day plants are those that require day lengths longer than their critical day length, while short-day plants require days shorter than their critical day length.  This critical day length can vary slightly with the prevailing temperatures.  Vernalization is an induction or acceleration of flowering by low temperatures.  Crop plants are classified into (1) those that require low temperatures for flowering like winter wheat and rye, beets, Brussel sprouts, carrots, celery, cauliflower, and cabbage and (2) those in which low temperatures can induce early flowering like peas, lettuce, and spinach.

Ref: Desai, B.B., et.al. Seeds Handbook, Biology, Production, Processing, and Storage, 1997, Marcel Dekker, Inc., p9-11 and Figure 1 p10.

38. Locate the growing points in grasses and broadleaf plants

Monocot:  Stem growth originates from an apical meristem that produces vascular bundles scattered throughout the parenchyma.  The vascular bundles most frequently form near the epidermis.  Monocots have no continuous cambium and lack secondary growth.  The growing point in grasses is at ground level until the plant changes from the vegetative to the reproductive stage of development.  It is then elevated as the stem grows or elongates and it becomes the panicle or head (grain or seed-bearing, pollen-bearing in case of corn) structure in all small grains and forage grasses.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p30.

Dicot:  Cells and tissues in dicot plants originate from a terminal shoot meristem that forms primary tissue.  The vascular bundles of a herbaceous dicot plant remain separated and distinct.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p27-29.

39.  Describe how the following factors affect crop canopy closure

a.  row spacing:  Planting corn or soybean in row spacing less than 30 inches results in canopy closure earlier in the growing season.  The rapid canopy closure reduces problems associated with late emerging weeds.  Planting crops in narrow rows reduces the amount of sunlight transmitted through the canopy, which reduces the growth of weeds and the need to apply herbicides repeatedly.  More rapid canopy closure due to narrower rows also increases light interception by the crop.    

Internet Link: http://www.weeds.iastate.edu/mgmt/qtr97-2/rowspac.htm Further study material from Iowa State University

Internet Link: http://www.ianr.unl.edu/pubs/fieldcrops/g963.htm Further study material from The University of Nebraska

b.  plant population:  Optimum plant populations will result in faster canopy closure than below-optimum stands, and improve the crops ability to compete with weeds.  However, early dense canopy formation and high plant population may also increase disease incidence due to wet, cool conditions.

Internet Link: http://deal.unl.due/compro/html/prod_decisions/pdplantpop.html Further study material from The University of Nebraska

c.  plant growth habit:  Since plants show differing growth habits, rate and extent of crop canopy closure varies also.  Crops with bushy characteristics may experience canopy closure sooner and to a fuller degree than vine type crops.  Crops with rapid shoot development may also show canopy closer before slower maturing crops.

40.  Differentiate the following

a.  summer annual:  A summer annual is a plant that completes its life cycle of seed germination, vegetative growth, reproduction and death in a single growing season.  The life cycle of a summer annual usually starts in the spring and ends in the fall.

b.  winter annual:  A winter annual is a plant that completes its life cycle of seed germination, vegetative growth, reproduction and death in a single growing season.  The life cycle of a winter annual usually starts in the fall and ends in the spring.

c.  biennial:  A biennial is a plant having a life span of more than one year but not more than two years.

d.  perennial:  A perennial is a plant that lives longer than two years, and some may live indefinitely.  Some perennial plants lose their leaves and become dormant during winter, while others may die back and resprout from underground root structures each year.

41. Describe how the following soil factors affect crop root growth

a.  pH:  pH is a term that can be used to describe the acidity or alkalinity of a soil.  Soils with high pH values (8-14) are considered alkaline soils.  Soils with low pH values (1-6) are considered acid soils.  Two ions that highly influence acidity are the hydrogen and aluminum ions.  Al toxicity is probably the most important growth-limiting factor in many acidic soils.  The toxic effects of excessive Al on root growth can seriously influence plant growth and yield.  Excess Al interferes with cell division in plant roots, inhibits nodulation, and decreases root respiration.  Al toxicity results in short stubby roots.  For optimal root and crop growth, pH  should be regulated between 6.5 and 7.0.

Ref:  J.L. Havlin et. al.  Soil Fertility and Fertilizers.  1999.  pg. 52,60-62

b.  Moisture:  Water is a vital resource to roots and plants.  Generally, plant roots can extract water from the soil up to its permanent wilting point-somewhere around -.033Mpa.  Soil water deficiencies may lead to root clumping.  Roots in dry soil show very little growth.  High water tables restrict root development in many plants.  Since roots need oxygen to grow, a deficiency may result in waterlogged conditions and root growth may cease.  Waterlogged conditions may lead to decreased root conductivity to water, changes in phytohormone production by roots, and accumulation of toxins in the soil and roots.   Water saturation can also adversely affect soil structure, with the result that root development is restricted.

J. Janick  et. al.  Plant Science-An Introduction to World Crops. pg. 294

Internet Link: http://www.uoguelph.ca/~mgoss/83-410.html Further study material from The University of Guelph

c.  Texture and structure:  The structure of soil has a major effect on root development.  Roots may grow well in soils with many large pores, or if the soil can be easily deformed.  Roots may also grow well if there are sufficient cracks or biopores, even when soil bulk density is high.  Roots will not grow into rigid pores which are smaller in diameter than the apical meristem of the root.  They can, however, enlarge or create pores where the rooting medium is weak enough.  Soil texture has an equally important role in determining the viability of roots in soil.  Soil texture influences soil characteristics important to root growth such as infiltration, water storage, aeration, and fertility. Clay textured soils with high cation exchange capacities can provide ample nutrients to the roots.  Water is also retained longer in clay soils than in sandy soils, although drainage is more difficult.  Clay textured soils do not have good aeration characteristics required for good root growth.  Sandy soils do provide excellent aeration characteristics for root growth as well as better infiltration rates than clay soils.

Miller, R.W., Gardiner, D.T.  Soils in Our Environment.  1998.  pg. 64.

Internet Link: http://www.uoguelph.ca/~mgoss/three/410-N03f.html Further study material from The University of Guelph

d.  Nutrient status:  Nutrients can have specific effects on root development.  For example, root thickness, frequency of root branching, rate of lateral root growth, and root hair development are all influenced by the nutrient supply.  Nodulation is strongly influenced by the presence of NO3 in the soil.  In general, plants respond to nutrient deficiency by concentrating more resources on root growth, leading to increased root-shoot ratios.

Internet Link: http://www.iacr.bbsrc.ac.uk/res/corporate/meetings/tsessionB.html Further study material from The University of Aberdeen, UK

e.  Fertilizer placement:  Fertilizer materials vary in their soil reaction pH.  Phosphoric acid released from dissolving P fertilizers such as triple superphosphate (TSP) can temporarily acidify zones in proximity to the site of application.  TSP will reduce the pH to as low as 1.5, which can cause seedling injury and inhibit root growth.  Care must also be taken with row or seed placement of diammoniom phosphate since free ammonia can be produced and cause root damage.  Fertilizer banded directly below the seed or below and to the side of the seed provides excellent access for the first seminal root pair with little potential for foot damage.  Generally, nitrogen and phosphorus sources can be applied with the seed in a band to obtain favorable results. However, applying the crop's entire nitrogen and sulfur needs with the seed can cause excessive root or seedling injury, primarily through burning the seminal root tip.  A minimum separation of two inches is required between the seed and the fertilizer band in silt loam soils.  A wider separation may be needed in coarser textured soils when ammonium based fertilizers are used.

Ref:  J.L Havlin et. al.  Soil Fertility and Fertilizers.  1999.  pg. 46, 184.

Internet Link: http://www.montana.edu~wwwpb/ag/whe_fer2.html Further study material from Montana State University

f.  Soil borne insects and diseases:  Cultivated plants are subject to a wide array of plant diseases induced by bacteria, fungi, viruses and mycoplasma-like organisms.  Roots may be infected and damaged or killed by any number of soil-borne diseases and insects.

Ref:  H.T. Hartman  et. al.  Plant Science-Growth, Development, and Utilization of Cultivated Plants.  1988.  pg 242.

42. Describe how taproot and fibrous root systems differ in erosion control and nutrient uptake patterns

Erosion is reduced in areas where plants with fibrous root systems are abundant because the root systems hold the sediments in place.  Plants that have extensive, fibrous root systems are more dense and have more surface area available to adsorb soil particles and plant nutrients.   A strong positive relationship exists between plant root density and the soil's resistance to flowing water erosion.  Taproot systems are generally less effective at erosion control because they have less surface area available to attract soil particles and nutrients. 

Internet Link: http://pbisotopes.ess.sunysb.edu/esp.Science_Walks/Campus_hydrology/hydrology.htm Further study material on erosion control

Internet Link: http://www.nal.usda.gov//ttic/tektran/data/000008/79/0000087957.html Further study material on erosion control

43. Describe how nutrient uptake patterns differ between taproot and fibrous root systems

Taproot Systems are characterized by having one main root (the taproot) from which smaller branch roots emerge.  When a seed germinates, the first root to emerge is the radicle, or primary root.  In conifers and most dicots, this radicle develops into the taproot.   Taproots can be modified for use in storage (usually carbohydrates) such as those found in sugar beet or carrot.  Taproots are also important adaptations for searching for water, as those long taproots found in mesquite and poison ivy.

Fibrous Root System:  Characterized by having a mass of similarly sized roots.  In this case the radicle from a germinating seed is short lived and is replaced by adventitious roots. Adventitious roots are roots that form on plant organs other than roots.  Most monocots have fibrous root systems.  Some fibrous roots are used as storage; for example sweet potatoes form on fibrous roots.  Plants with fibrous roots systems are excellent for erosion control, because the mass of roots cling to soil particles.

Taproot systems are built for long term survival with a large deep taproot.  Nutrient uptake is generally stored in the long deep root and released as the plant needs it.  Fibrous root system are shallow, spreading systems which are very efficient at water and nutrient uptake making a layer just beneath or just at the soil surface.  Fibrous root systems have dense, shallow roots soluble nutrients are quickly washed away in high rain environments.  As a result many fibrous root systems are located in soils that are poor in nutrients.

44. Describe how the following affect the economics of replanting

a. expected date of replanting

The main economic issue in replanting is the price of the seed or start.  Because prices fluctuate across time the expected date of replanting should be during a time when expected prices are lower or when prices combined with expected production costs match expected profits.

b. population of surviving plants

The cost for replanting is reduced by the population of surviving plants.  If the surviving plant population is substantial then the costs are reduced.

c. pesticides applied

Existing pesticide application may reduce the need to use pesticides on replant population. 

d. stand uniformity

Stand uniformity can reduce costs in replanting by making it easier to identify surviving plants and by making it easier to replant.

e. pest pressure

If pest pressure is extreme then replanting may need to be delayed.  If replanting is done with resistant varieties then the replanting may survive.

45. List information needed to diagnose a crop production problem in the field

In diagnosing crop production problems, some general steps are:

      - Talk with farm manager about field crop history and any past problems in field

      - Scout field

      - Consult with neighboring farmers to learn of any similar problems

      - Determine whether the problem is soil, pest or water related

      - For soil related problems, take appropriate soil samples and have them tested

      - For pest related problems, scout for insect or weed suspects

      - Determine if problem is water supply related

      - Check water supply for salinity or pH problems

      - Check for signs or symptoms of soil compaction

      - Determine extent of injury

      - Examine which chemicals where used in the past

APPLIED INFORMATION TECHNOLOGIES

46. Differentiate precision and accuracy

Precision is the quality of being reproducible in amount or performance. 

Accuracy is the ability of a measurement to match the actual value of the quantity being measured; the quality of nearness to the truth or the true value.

47. Define the following precision agriculture terms

a.  global positioning system (GPS):  GPS is funded by and controlled by the U. S. Department of Defense (DOD).  While there are many thousands of civil users of GPS worldwide, the system was designed for and is operated by the U. S. military.  GPS provides specially coded satellite signals that can be processed in a GPS receiver, enabling the receiver to compute position, velocity and time.  Four GPS satellite signals are used to compute positions in three dimensions and the time offset in the receiver clock.

Internet Link: http://www.utexas.edu/depts/grg/gcraft/notes/gps/gps.html Further study material from The University of Texas

b.  remote sensing:  Remote sensing is the collection of data from a distance.  Data sensors can be hand-held units, mounted on aircraft or satellite-based.  Remotely sensed data provides a tool for evaluating  plant stress related to moisture, nutrients, compaction, crop diseases and other plant health concerns.

Internet Link: http://muextension.missouri.edu/xplor/waterq/wq0450.htm Further study material from The University of Missouri

c.  geographic information systems (GIS):  An information system used to work with data referenced by spatial or geographic coordinates.  GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for analyzing the data.

Internet Link: http://ag.arizona.edu/precisionag/ Further study material from The University of Arizona

d. variable rate technology (VRT):  the application of fertilizer, seed or chemicals at a variable rate determined by the interpretation of data in yield and soil maps.

Internet Link: http://www.bae.uga.edu/dept/research/precision/rough.html#desc Further study material from The University of Georgia

Internet Link: http://ag.arizona.edu/precisionag/ University of Arizona's precision ag page

e. crop management zone (CMZ):

A management zone is considered an area of the field that is 1) sufficiently homogeneous that crop input needs are not significantly different, and 2) can be economically managed independently from other areas of the field.  This means different inputs may have different management zones.  For example, from point 1, an insect infestation may impact an area of the field that includes different soil types with different nutrient needs.  That area of the field will become a single management unit with respect to insecticide application, but could be broken into several management units for nutrient application.  Or from point 2, a precision variable rate fertilizer applicator may be able to change rates and mixtures every 10 m in the direction of travel with a swath of 5 m, while it may be possible to control individual nozzles on an herbicide applicator every meter.

Barnes, E.M., and M.G. Baker. 1999.  Multispectral data for soil mapping:  possibilities and limitations.  ASAE paper 991138.

Colvin, T.S., D.B. Jaynes, D.L. Karlen, D.A. Laird, and J.R. Ambuel. 1996.  Six year yield variability within a central Iowa field.  In Proceedings of the 3rd International Conference on Precision Agriculture, ASA. page 581.

48. Describe how the following factors affect yield variability in a field

a.  soil texture:  Fields may show yield variability due to changes in soil texture within the parameters of individual fields.  Variation in soil properties that affect crop yields such as water-holding capacity, aeration, nutrient availability, and drainage may result from variation in soil texture within a field.

Ref:  H.T. Hartman et. al.  Plant Science-Growth, Development, and Utilization of Cultivated Plants.   1988.  pg. 173.

b.  soil organic matter:  As the organic matter content in soils increases, cation exchange capacity and  water holding capacity characteristics are increased.  Soil microorganism populations that promote good soil structure also proliferate more abundantly in regions where organic matter content is higher.  These factors may contribute to yield variability where organic matter contents change in different regions within a field.

Ref:  H.T. Hartman et. al.  Plant Science-Growth, Development, and Utilization of Cultivated Plants.  1988.  pg. 173.

c.  topography:  Diversity in topography leads to yield variability in a field.  Topography influences drainage and runoff.    Steep slopes allow water to flow faster downhill, with less infiltrating the soil.  Depressional areas may become highly leached or waterlogged, depending on internal drainage.  More water may collect in depressional zones than other areas of the field and increase or decrease yields.

Ref:  H.T. Hartman et. al.  Plant Science-Growth, Development, and Utilization of Cultivated Plants.  1988.  pg. 171-172.

d.  pest distribution:  Insects, diseases, and weeds are factors that affect yield variability in a field.  Each may prefer a specific type of microclimate in a field in order to develop and reproduce to their maximum potential.  Pests may thrive in certain areas of a field yet be severely limited in other areas where conditions are not ideal for their life cycles.

e.  previous management:  There are a number of management practices that growers use to produce a crop that can affect yield variability.  Some of these practices include tillage, planting population, irrigation, weed control, insect control, and fertilizer application.  For example, herbicide drift from an adjacent field will vary the yield on affected parts of the field.  Nonuniform irrigation applications will also affect yield variability.

f.  salinity:  If the field contains areas which contain saline soils, yields will likely be reduced in those sections.

g.  nutrient status and pH:  If the field contains variability in nutrients and pH, yields will likely be reduced in those areas.  Variable rate applicators can be useful in adjusting the variability of soil nutrients.

h.  drainage:  Field drainage is the most important variable in yield variability.  Standing water increases pest problems including fungus and virus pests.  Improved drainage systems can increase yields in affected areas.

Internet Link: http://www.arborday.org/programs/papers/PrecisionAg.html Further study material on precision ag

49. Use a map legend to identify information on a GIS map

Data showing the variability of yields at harvest can be used by producers to make more informed management decisions regarding the succeeding crop.  Yield maps provide feedback for determining the effects of variable inputs such as fertilizer and lime, seed and pesticides, and cultural practices such as tillage, irrigation and drainage.

Map legends show the yield rates as colors.

Internet Link: http://www.usda.gov/nass/aggraphs/cropmap.htm Further study material from USDA

50. Use geographical coordinates to locate a tract of land

AgExplorer has a complete section on satellite imagery.  Map Quest and other internet programs can help both demonstrate and utilize geographical coordinates.  Please note the following sources:

Internet Link: http://www.mapquest.com MapQuest

Internet Link: http://maps.yahoo.com Yahoo Maps

Internet Link: http://maps.google.com Google Maps

Internet Link: <HT{icon}{~HTTP~}{www.terraserver.microsoft.com

}>  Microsoft Maps

51. Explain why yield maps vary from year to year

Although yield variation within a field is usually the result of differences in soil types or soil properties, weather patterns usually have the largest effect on variability.  Soil fertility and weed pressure may also affect yields from year to year.

Internet Link: http://muextension.missouri.edu/xplor/waterq/wq0451.htm Further study material from The University of Missouri

52. Use a field map to devise a soil or pest sampling strategy

Where the topsoil has varying physical properties, such as soil type or soil depth, the yield potential will vary considerably throughout the field. Past management practices of uniform nutrient applications may have created excess nutrient accumulations in areas with low yield potential and nutrient deficits in areas with high yield potential. A variable rate application strategy will generally place higher rates of nutrients in areas with higher yield potential and lower rates of nutrients in areas with lower yield potential.  

Internet Link: http://muextension.missouri.edu/xplor/waterq/wq0451.htm Further study material from The University of Missouri

53. List advantages and limitations of yield monitor data

Yield monitor data can be very helpful in mapping field yield rates.  These monitors are expensive, but can be useful when used with variable rate applicators.  An additional limitation to yield monitor use is the time it takes to bring the data into a mapping tool and apply the data into the computer controlling the variable rate applicator.  Economies of scale dictate the economic advantage to the user of yield monitors.

HARVEST AND STORAGE

44. Describe how the following factors influence when to harvest

a.  crop moisture percentage:  Most crops experience a stage when the moisture content of the crop reaches a critical harvest point. This critical moisture level is highly subjective and depends on the variety of the crop, harvest methods and end use of the product. Cereal crops, for example, are generally harvested when seed reaches a low moisture content.  A high moisture content in cereal crops can lead to poor storage and spoilage.

Ref:  H.T. Hartman et. al.  Plant Science-Growth, Development, and Utilization of Cultivated Plants.  1988.  pg.  267-272.

b.  hybrid or variety characteristics:  New hybrids or varieties of crops may have physical or biological characteristics that differ from those of common varieties that alter the normal harvest date.  Hybrids may mature sooner or later than their counterparts thus changing the typical harvest date.

c.  end use:  Some crops are harvested at differing times due to the end use of the crop.  Some vegetables, such as peas, may be grown for seed or immediate human consumption.  When peas are grown for seed, the moisture content is very low at proper harvest time.  In contrast, peas produced for immediate human consumption must be harvested when the moisture content is high.

d.  weather:  Weather conditions may heavily influence the proper time to harvest.  Wet, muddy conditions severely limit the use of heavy machinery in fields.  Unusually hot and dry weather may speed up the ripening process of crops and force earlier than normal harvest dates.  Continuous cold or cloudy conditions may delay ripening and harvesting.

55. Describe how the following factors influence crop quality in storage

a. temperature: Cool-season crops are stored at cool temperatures, 0°C to 1°C (32°F to 34°F) while warm-season crops are stored at relatively warm temperatures of 10°C to 12°C (50°F to 54°F).  Storing crops at different temperatures can reduce quality and cause the spoiling of the crops.  Higher storage temperatures usually mean shorter storage time and decreasing crop quality.

Ref: Flocker, William J., et al. Plant Science; Growth, Development, and Utilization of Cultivated Plants, 1981, Prentice Hall Inc., p280.

b. moisture: Transpiration rates in stored crops are controlled by the relative humidity.  At a high relative humidity, stored fruits and vegetables are able to maintain weight, appearance, nutritional quality, and flavor.  Grains are stored at lower relative humidity rates and lower moisture content.

Moisture Tables:

Internet Link: http://ndsuext.nodak.edu/extpubs/plantsci/smgrains/ae701-1.htm#Moisture Further study material from North Dakota State University

Internet Link: http://www.oznet.ksu.edu/___library/hort2/mf978.pdf Further study material from Kansas State University

c. aeration: Aeration is important because it controls the temperature of the stored crop and allows the temperature to become uniform throughout the storage area and the crop itself.

Internet Link: http://ndsuext.nodak.edu/extpubs/ageng/grainsto/ae84-2.htm#Management Further study material from North Dakota State University

d. pests: Pests can affect the crop quality before and after harvest.  They are, however, a bigger problem before harvest.

e. crop condition and moisture at harvest: It is impossible to improve crop quality once it is stored so it is essential that stored crops be in excellent condition.

Internet Link: http://www.oznet.ksu.edu/___library/hort2/mf978.pdf Further study material from Kansas State University

f. post-harvest handling: Crops that are bruised or battered or otherwise damaged during sorting, grading or unloading have a decreased storage life.  Harvested crops need to be handled carefully and equipment should be maintained to avoid machinery damage to goods.  Most crops also need to be kept in cool, well-ventilated areas during post-harvest handling.

g. length of storage: Insect and disease monitoring must increase as storage time increases.  Generally as crops are stored longer, the likelihood of decreasing quality increases.

h. amount of foreign material: Foreign material may contain pests which can affect the storage capability of the crop.  Reduced foreign materials may increase the life of the stored crop.

i. sanitation of storage facilities:  It cannot be under estimated that a clean moisture free facility will increase the life of the stored crop.

56. List the consequences of not maintaining the purity of an identity-preserved (IP) crop

Identity-preserved crops contain value based on purity of the seed.  If the purity is compromised, even a little, the value of the seed is substantially reduced.

57. Describe how to maintain purity of an identity-preserved (IP) crop

Purity of IP crops is maintained by planting pure certified seed of a known variety. The seed is usually planted on land that has not produced that crop for at least a year. Fields are usually  isolated by a certain distances as part of the production plan.  Weeds must be closely controlled to prevent cross pollination with the IP crop.  All machinery used for harvest, transportation and storage should be thoroughly cleaned to avoid contamination.  Independent third party record keeping, field inspections and lab testing services should monitor the IP process.

Internet Link: http://www.dowagro.com/canada/agnetwork/article4e.html Further study material from Dow Agro

Internet Link: http://www.ohseed.org/identpreserved.htm Further study material from Ohio Seed

58. Recognize excessive crop loss or low quality factors in harvested product caused by improper harvesting procedures

Improper harvesting procedures can significantly reduce captured yields or cause excess broken and damaged crop.  His can reduce storage crop life and other factors prior to value adding.  Improper harvest equipment calibration and handling can leave much of the crop in the field or damaged during harvest reducing revenue.

MANAGING PRODUCTION RISK

59. Describe how to use the following to help reduce production risk

a. crop selection

In selecting the proper crops for the conditions, individuals can substantially lower production risks.  Factors to consider when choosing production crops include climate, soil type, topography, equipment and labor resources, previous crop selection and market forces.

By producing a crop with a good growth history for the region and with good potential economic return, production risks will be much lower for producers.  Crops that are new or exotic to the area may be more risky, but also provide higher income if prices or demand for the item are high.           

b. hybrid or variety selection

Proper variety selection is important in order to avoid unnecessary production risks.  A good choice could result in maximum satisfaction and increased profit.  The selection of a variety or hybrid should be based on research facts and grower experience.  Other aspects to consider when choosing hybrids or varieties include disease and insect resistance, length of time necessary for maturity, plant habit, cost and quality of seed, yield characteristics and quality of product. 

Internet Link: http://stephenville.tamu.edu/~nroe/ekind/ekindcm1.htm Further study material from Texas A&M University

Internet Link: http://ipmwww.ncsu.edu/grain/agronomy/smgrain2.html Further study material from North Carolina State

c. planting and harvest date

Crops planted on the proper planting date produce the most profitable yields.  Crops planted earlier than the optimal planting date may also have advantages.  For example, early planted corn usually results in earlier maturity in the fall with more time for field drying.  This translates into less dependence on artificial drying and reduced fuel consumption.  Early planting results in early ground emergence and crop cover to reduce erosion.  Late planting poses the risk of late season freezes or other adverse weather conditions that destroy the crop. 

Internet Link: http://deal.unl.edu/ Further study material from The University of Nebraska

d. crop insurance

Farming is commonly viewed as an inherently risky business.  In their operations, farmers are exposed to both production risks and price risks.  Farm production levels can vary significantly from year to year, primarily because farmers operate at the mercy of nature and frequently are subjected to natural disasters.  Producers can also experience wide swings in prices they receive for commodities they grow.  Because of the potential volatility of farm income, federal and private crop insurance companies are available to protect producers from unavoidable risks associated with adverse weather, plant diseases, and insect infestations.  Crop insurance can protect producers from the loss of a years income due to the various production risks of farming.  Crop insurance may also be beneficial in good years by allowing more aggressive marketing because of guarantee of a minimum yield.

60. Describe how the following affect crop management decisions

a. crop prices

Crop prices play an important part in guiding crop management decisions because they reflect consumer demand.  By examining commodity prices, producers can decide what crops might earn them the highest profits and which consumptive inputs should be altered.  If production of a product such as soybeans fails to expand as rapidly as the demand, prices will rise for soybeans.  Farmers will then find it more profitable to use their land to produce soybeans instead of their previous product, such as corn.  At the same time as prices rise for soybeans, farmers may wish to cut back on consumption of soybeans as sources of protein feed.   J. Janick et. al.  Plant Science-An Introduction to World Crops.  1981. pg. 743-744.

b. input costs

Whole-farm budgeting is used to summarize costs and returns to the total farm operation over a particular time period.  This type of budgeting allows the farmer to calculate input costs and expected returns.  Farmers may attempt to find alternative inputs with lower costs in order to increase profits.  Some crops may require high input costs such as fertilizer or special equipment, but have the incentive of high prices and potential high profits.  J. Janick et. al.  Plant Science-An Introduction to World Crops.  1981. pg. 743-744.

c. availability and skill of labor

Contempory farming operations typically range in size from a few hundred acres to many thousands of acres.  Such large operations require a mandatory labor base.  Some operations may require hundreds of workers to maintain them.  Some large farms may require many more laborers at harvest time.  With farming operations becoming increasingly complex, skilled labor such as mechanics and consultants are also necessary for survival.  The availability of skilled and unskilled labor can be a major factor in determining what type of farming operation can exist in a region.

d. equipment

Farm equipment represents a substantial capital investment.  In many cases, farmers are limited by what they can produce by the equipment available to them.  Farming is highly specialized in most regions and many crops require equipment made specifically for their production.  Farmers must decide on proper setup and operation of farm equipment to meet their needs.

e. weather

Mother Nature can be a farmer's best friend or worst enemy.  Farm management requires constant weather monitoring to be successful.  Many farming techniques must be altered to meet the conditions of the weather.  The weather affects planting dates by dictating when field conditions are suitably dry for heavy machinery to operate on.  Fertilizer types and rates must be adjusted to excessively wet or hot conditions.  Pesticides must be applied on calm, wind-free days.  Crop growth is totally dependant on the light received from the sun.  Any type of weather extreme may severely alter the yield of a crop.

Crop management decisions

f. cash flow

Cash flow is critical to economic variability in crop management.  The expenditures and interest expenses must be balanced with revenues and interest earnings.

g. crop insurance

Crop insurance is a management decision that is both risk based and economic based.  It is an essential hedging instrument for some and not even a thought for others.  The risk is historically based, but is weighted by the size of the potential economic loss.

h. farm programs

Additional federal and state farm programs may be available to help manage both input costs and reduce harvest risk.  Loan programs can help reduce interest expenses and county agents can help in giving an objective assessment to management decisions.

i. field proximity to sensitive areas

Proximity to sensitive areas has become an increasingly important management variable.  With new requirements for Crop Nutrient Management Plans, farm managers must be aware of water flows toward sensitive areas.  Pesticide and fertilizer use must be controlled and managed as urban creep and suburban expansion moves into previously farmed areas creating new neighbors to the farming community. 

Crop Management Glossary

Accuracy: The ability of a measurement to match the actual value of the quantity being measured.

Allelopathy: Any harmful effect of one plant or microorganism on other organisms through the production and release of chemical compounds into the environment.

Annual, summer: Plants whose seeds germinate in the spring, the plants produce seed and die the same fall

Annual, winter: Plants whose seeds germinate in the fall, the plants produce seed in the spring and die in the summer.

Anther: The pollen-bearing male portion of a stamen.

Anthesis: The time of flowering in a plant.

Applied Information Technology: Using advanced information technology to make better decisions in crop, soil, and environmental management systems.

Biennial plant: A flowering plant that takes 12-24 months to complete the life cycle. It grows vegetative the first year and reproduces the second year.

Biomass: The mass of a specific plant or plant part in a given area, usually expressed as weight or volume per unit area.

Boot stage: A grass growth stage when an inflorescence is enclosed by the sheath of the uppermost leaf, just prior to inflorescence emergence.

Clean till: Tillage where all plant residues are covered to prevent growth of all vegetation except that of the crop being produced.

Companion crop: A crop sown with another crop, especially one that will emerge and develop slowly. Also called a nurse crop.

Competition: The simultaneous demand by two or more organisms for limited environmental resources.

Continuous cropping: Growing a crop in a field every year.

Cover crop: A crop grown to: 1) protect the soil from erosion during periods when it would otherwise be bare; 2) scavenge excess nutrients from a previous crop to prevent nutrient loss; or both.

Crop management zone: A sub-region of a field that has a relatively uniform combination of yieldlimiting factors where a single level of crop management is appropriate.

Crop residue: Plant material remaining in the field after harvest.

Crop rotation: The practice of growing different crops in a planned regular sequence on the same land.

Cropping pattern: The yearly sequence and spatial arrangement of crops, or crops and fallow, in a given area.

Cultivar: A variety, strain, or race that has originated and persisted under cultivation, or was specifically developed for crop production.

Day neutral crop: A crop whose flowering is not influenced by day or night length.

Desiccation: The removal of moisture from a material.

Determinate plant: A plant that initiates flowering based on day length, with the change from vegetative to reproductive growth over a relatively short time.

Double cropping: The practice of consecutively producing two crops of either like or unlike commodities on the same land within the same year.

Dough stage: Stage of seed development at which the endosperm is pliable, like dough, defined as the time when 50% of the seeds on an inflorescence have dough-like endosperm.

Evaporation: The process in which a liquid is changed into a gas.

Evapotranspiration: The loss of water from a given area by both evaporation from plant and soil surfaces, and transpiration from plants.

Fallow land: Land not being used to grow a crop, but on which plant growth is controlled with tillage or herbicides. Used to store water, control weeds, and increase available soil nutrients.

Fibrous root system: A plant root system having a large number of small, finely divided, widely spreading roots, but no large individual roots; common with grass species.

Flag leaf: The uppermost leaf on a fruiting grass stem. The leaf immediately below the inflorescence.

Flowering stage: The physiological stage when anthesis occurs in a plant, or flowers are visible in nongrass plants.

Genetically Modified Organism (GMO/GM): See also transgenic. A living entity that has been modified or transformed through recombinant DNA technology.

Geographic coordinates: The system of latitude and longitude that defines the location of any point on the earth's surface.

Geographic Information Systems (GIS): A computer system for measuring and relating environmental and crop data to positions on Earth’s surface.

Germination: The resumption of growth of a seed embryo after a period of dormancy. Requires a favorable environment of adequate water, oxygen, and suitable temperature.

Germination test: A method to measure seed viability, when placed under favorable environmental conditions.

Global Positioning System (GPS): A system that uses a number of orbiting satellites to identify a location on Earth, based on longitude, latitude, and altitude.

Green manure: Living plant material incorporated into the soil while green for soil improvement.

Growing Degree Unit (GDU): Heat accumulation, calculated by subtracting a base temperature from an average of the maximum and minimum daily temperatures for an area.

Growth regulator: A substance that when applied to plants in small amounts either inhibits, stimulates, or otherwise modifies the growth process.

Harvest index: The quantity of harvestable biomass produced per unit of total biomass.

Harvest population: The number of harvestable plants per unit area remaining at the end of a growing season.

Heading: The developmental stage of a grass plant from initial emergence of the inflorescence from the boot until the inflorescence is fully emerged.

Hybrid: First generation progeny resulting from the controlled cross-fertilization between individuals that differ in one or more genes.

Identity-preserved (IP) crop: A crop in which specific genetic traits are known to exist.

Indeterminate plant: Plant whose flowering is not affected by day length, and continues vegetative growth after reproductive growth has begun.

Inflorescence: The flowering part of a plant or arrangement of flowers on a stalk.

Inoculant: A seed or soil additive, typically some type of bacteria or fungi, that enhances plant growth and development.

Intercropping: Growing two or more crops together in the same field at the same time.

Irrigation efficiency: The ratio of the amount of water actually consumed by a crop or stored in the root zone on an irrigated area to the amount of water applied to the area.

Least Significant Difference (LSD): A statistical range test used to determine true differences among treatment means.

Lodging, root: Condition in which stalks or stems fall due to a weak root system, root damage, or soil condition.

Lodging, stalk: Condition in which stalks or stems break or fall above the soil surface, because of weak stalk, damage, or weather events.

Long day crop: Crop in which flowering occurs when night length is less than the crop’s required critical length.

Maturity: The developmental stage when a plant reaches maximum dry matter production, yield, or desirable quality.

Milk stage: In grain, the stage of development following pollination in which the endosperm appears as a whitish liquid like milk.

Monoculture: Growing the same crop continuously in the same field, year after year.

Open pollinated: Plants pollinated by the wind, insects, birds or animals, and not by human manipulation.

Organic farming: Crop production systems that do not use synthetic pesticides or fertilizers

Panicle: A grass inflorescence, the main axis of which is branched, and whose branches bear loose flower clusters.

Perennial plant: Plants that have vegetative structures that allow them to live more than 2 years.

Photoperiodism: The growth and flowering response of plants in relation to changes in the length of daylight hours.

Physiological maturity: Plant growth stage representing the end of reproductive development, where the maximum dry weight has been accumulated.

Pollination: The transfer of pollen from the anther to the stigma of a flower.

Precision: The ability of a measurement to be consistently reproduced.

Precision agriculture: Using the best technologies to identify and manage in-field soil and crop variability to improve production and economic return.

Pure live seed: Percentage of pure germinating seed, calculated as: pure seed percentage x germination percentage/100.

Radicle: The first root of a plant that elongates during germination of a seed and forms the primary root.

Randomization: A random arrangement of treatments or plots, in order to obtain representative data for an experiment.

Relay cropping: A system in which one crop is planted into a standing crop prior to harvest of the established crop, which does not hinder the yield of either crop.

Remote sensing: The collection and analysis of data from a distance, often using sensors that respond to different heat intensities or light wavelengths.

Replication: Repeating plots or treatments in an experiment in order to increase precision.

Resistance, pest: Genetic ability to avoid, repel, or limit attack by a pest by genetic manipulation.

Resistance, pesticide: The inherited ability of an organism to survive and reproduce following exposure to a dose of pesticide normally lethal to the wild type.

Rhizobium: Bacteria which fix atmospheric nitrogen in nodules on the roots of legume plants.

Self pollinated: A plant pollinated by its own pollen.

Short day crop: A crop in which flowering is initiated when the crop’s critical night length is exceeded.

Stigma: The female part of a flower where pollen is deposited.

Taproot: The primary root of a plant formed in direct continuation with the root tip or radicle of the embryo. Forms a thick, tapering main root from which arise smaller, lateral branches.

Tilth: Physical condition of the soil that defines how easily it can be tilled, how good a seedbed can be made, and how easily seedling shoots and roots can penetrate.

Tolerance: The inherited ability of a species to survive and reproduce after pesticide treatment. Also refers to the ability of a crop to yield satisfactorily in presence of pests or adverse environmental conditions.

Transgenic: Plants or animals that contain DNA derived from a foreign plant or animal.

Variable Rate Technology (VRT): The ability to vary the application of crop production inputs based on criteria for crop response or soil conditions. Allows for the targeted application of inputs at varying rates across a field.

Variety: A taxonomic subdivision of selectively bred individuals that are distinct, uniform, and stable, that are often referred to as a cultivar when registered for use.

Vegetative: 1) The non-reproductive parts of plants. 2) The non-reproductive stage of plant development.

Vernalization: Exposure of germinating seeds or plants to low temperatures to induce flowering.

Viability: A measure of the potential for seeds to germinate, grow, and develop normally under favorable conditions.

Yield map: The pattern of crop yield in a field based on data collected using a yield sensor on a harvester, and geographic positioning of these yield values using a Global Positioning System.

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