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Nutrient Management Module No. 2

Plant Nutrition

and Soil Fertilityby Clain Jones, Soil Chemist, andJeff Jacobsen, MSU Extension Soil Scientist

Introduction

This module is the second in a series of Extension materialsdesigned to provide pertinent information on a variety of nutrientmanagement, water management, and water quality issues toExtension agents, Certified Crop Advisers (CCAs), consultants, andproducers. We have included 15 questions at the back of thismodule that wil l make the learning active as well as offer thepotential for credits for CCAs in Nutrient Management (within thePlant Nutrition and Soil Fertility competency areas.) Inaddit ion, we have included a resource section of other Extension

materials, books, web sites, and professionals in the field.

Objectives

After reading this module, the reader should:1. Know the 17 elements essential for plant nutrition2. Know the macronutrients and micronutrients3. Be familiar with the function and mobility of nutrients within

plants4. Understand the forms of each nutrient that are taken up by

plants5. Be familiar with typical nut rient plant concentrations6. Be able to specify how nutrient needs change during the

growing season7. Understand the basics of nutrient uptake8. Know the basics of how nutrients are held or released by the

soil

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2/122 Module 2 Plant Nutrition and Soil Fertility

Background

Research has determined that plantsrequire 17 nutrients, also called essentialelements (Marschner, 1995). Eachnutrient assists with different plantfunctions that allow the plant to grow andreproduce. Each plant nutrient is needed

in different amounts by the plant, andvaries in how mobile it is within the plant.It is useful to know the relative amounts ofeach nutrient that is needed by a crop inmaking fertilizer recommendations. Inaddition, understanding plant functionsand mobility within the plant should proveuseful in diagnosing nutrient deficiencies.Factors affecting soil fertility are alsoimportant in making sound nutrientmanagement decisions, and are discussed

in the second section.

Plant Nutrition

ESSENTIAL ELEMENTS

There are over 100 chemical elements,yet scientists have found that only 17 ofthem are essential for plant growth (Table1). To be classified as essential, the

element needs to meet the followingcriteria:1. The plant cannot complete its life cycle

(seed to new seed) without it.2. The elements function cannot be

replaced by another element.3. The element is directly involved in the

plants growth and reproduction.4. Mostplants need this element to

survive.The fourth criterion is used because

some specific plants have been found to

ELEMENTCarbon (C)

Hydrogen (H)

Oxygen (O)

Nitrogen (N)

Phosphorus (P)

Potassium (K)

Calcium (Ca)

Magnesium (Mg)

Sulfur (S)

Boron (B)

Chlorine (Cl)Copper (Cu)

Iron (Fe)

Manganese (Mn)

Molybdenum (Mo)

Nickel (Ni)

Zinc (Zn)

ROLEIN PLANTConstituent of carbohydrates; necessary for photosynthesis

Maintains osmotic balance; important in numerous biochemicalreactions; constituent of carbohydrates

Constituent of carbohydrates, necessary for respiration

Constituent of proteins, chlorophyll and nucleic acidsConstituent of many proteins, coenzymes, nucleic acids and metabolicsubstrates; important in energy transfer

Involved with photosynthesis, carbohydrate translocation, proteinsynthesis, etc.

A component of cell walls; plays a role in the structure and permeabilityof membranes

Enzyme activator, component of chlorophyll

Important component of plant proteins

Believed to be important in sugar translocation and carbohydratemetabolism

Involved with oxygen production in photosynthesisA catalyst for respiration; a component of various enzymes

Involved with chlorophyll synthesis and in enzymes for electron transfer

Controls several oxidation-reduction systems and photosynthesis

Involved with nitrogen fixation and transforming nitrate to ammonium

Necessary for proper functioning of the enzyme, urease, and found to benecessary in seed germination

Involved with enzyme systems that regulate various metabolic activities

SOURCEAir

Water

Air/Water

Air/Soil

Soil

Soil

Soil

Soil

Soil

Soil

SoilSoil

Soil

Soil

Soil

Soil

Soil

Sou rce: Colorado St ate Univ. (www.colostate.edu/Depts/CoopExt/TRA/PLANTS/nut rient.ht ml)

Table 1. Essential element, role in plant, and source.

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3/123Module 2 Plant Nutrition and Soil Fertility

need certain elements. For example, somecrops will respond to silica (Si) whengrown on highly weathered soils. Inaddition, cobalt (Co) is required bybacteria responsible for nitrogen fixationin legumes; therefore, some consider Co tobe essential, while others classify it asbeneficial. Other beneficial elementsinclude sodium (Na) and vanadium (V).Essentiality is generally determined bygrowing plants in nutrient solutions withor without a specific element, andobserving differences in plant growth orfunction. Bear in mind that thedetermination of essentiality isproblematic for elements that may berequired in only trace amounts, due to thedifficulty in keeping allof a certain traceelement out of the seed-nutrient solut ion,especially when plant seeds havesubstantial amounts of many elements.Due to this fact, it is possible that otherelements essential for growth will bediscovered at some point.

A limited supply of one of the essentialnutrients can l imit crop yield, althoughother factors such as heat or water canalso limit yield. The concept that onefactor wil l generally limit yield, or the law

of the minimum, is il lustrated in Figure 1,where the height of water in the barrelrepresents crop yield. Essentially, thefigure shows that ni trogen is init ially thefactor that limits yield (a), but after N isadded, potassium levels control yield (b).

NON-MINERAL NUTRIENTS

Three elements, carbon (C), hydrogen(H), and oxygen (O), are considered to benon-mineral nutrients because they arederived from air and water, rather thanfrom soil minerals. Although theyrepresent approximately 95% of plantbiomass, they are generally given littleattention in plant nutrition because theyare always in sufficient supply.

Figure 1. The law of the m inimum .

From Brady (19 84)

ELEMENT

Nitrogen (N)

Phosphorus (P)

Potassium (K)

Calcium (Ca)

Magnesium (Mg)

Sulfur (S)

Boron (B)

Chlorine (Cl)

Copper (Cu)

Iron (Fe)

Manganese (Mn)

Molybdenum (Mo)

Nickel (Ni)

Zinc (Zn)

Table 2. Absorbed nutrient forms andconcentrations in dry plant tissue.

FORMABSORBED

NO3

-(nitrate)

NH4

+(ammonium)

H2PO

4-, HPO

4

-2

(phosphate)

K+

Ca+2

Mg+2

SO4

-2(sulfate)

H3BO

3(boric acid)

H2BO

3

-(borate)

Cl -(chloride)

Cu+2

Fe+2(ferrous)

Fe+3(ferric)

Mn+2

MoO4

-2(molybdate)

Ni+2

Zn+2

CONCENTRATION RANGEIN

DRY PLANT TISSUE

1 - 5%

0.1 - 0.5%

0.5 - 0.8%

0.2 - 1.0 %

0.1 - 0.4%

0.1 - 0.4%

6-60 ppm

0.1-1.0%

5-20 ppm

50-250 ppm

20-200 ppm

0.05 - 0.2 ppm

0.1-1 ppm

25-150 ppm

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dissolves, the nutrients can beimmediately available for uptake. Knowingwhat form of a nutrient the plant absorbshelps us to better focus on what controlsthe movement of that nutrient in soil.

Plant Uptake of Nutrients

Nutrient uptake by roots is dependenton both the abil ity of the roots to absorbnutrients and the nutrient concentrationat the surface of the root.

ROOTS

Roots are composed of both a maturezone near the shoot, and an elongationzone near the root tip, or cap (Figure 2).Nutrients and water move freely throughthis elongation zone into the center of theroot (the xylem), and then up into theshoot. It is more difficult for nutrients toenter the root through the more maturezone of the root due to a restriction calleda Casparian strip. Therefore, nutrientlevels in deep soil likely become moreimportant later in the growing season,especially for deep-rooted plants. Rootsspread out both laterally and vertically asthe plant grows to take advantage of areaswithin the soil that have more water andnutrients.

Figur e 2. Cross -section of lower

portion of root

Q&A #1Most producers

generally apply onlyN, P, and K. Why is it

important for me to

learn about the other

11 mineral nutrients?As Table 2 shows, all of the 14

mineral nutri ents are taken up bythe crop and then removed from thefield at harvest. If these nutrients

are not replaced by eithercommercial fertilizers or organicmaterials such as manure, theamount of each in the soil wil ldecrease, potentially limiting cropyield. In Montana and Wyoming,there are known cases of B, Cl, Cu,Fe, Mn, and S deficiencies. Byknowing the nutrients that couldpossibly affect yield, you can betterdiagnose and remedy crop nutrientdeficiencies.

MINERALNUTRIENTS

The 14 mineralnutrients are classified aseither macronutrients ormicronutrients based ontheir plant requirements.There are six

macronutrients: Nitrogen(N), phosphorus (P),potassium (K), calcium(Ca), magnesium (Mg),and sulfur (S). Themacronutrients, N, P, andK, are often classified asprimary macronutrients,because deficiencies of N,P, and K are morecommon than the

secondarymacronutrients, Ca, Mg,and S. The micronutrientsinclude boron (B),chlorine (Cl), copper (Cu),iron (Fe), manganese(Mn), molybdenum (Mo),nickel (Ni) and zinc (Zn).Most of themacronutrients represent0.1 - 5%, or 100-5000

parts per million (ppm),of dry plant tissue,

whereas the micronutrients generallycomprise less than 0.025%, or 250ppm, of dry plant tissue (Table 2,previous page). Note that Cl, amicronutrient, has plant tissueconcentrations similar to some ofthe macronutrients. Keep in mindthat the classifications of micro vs.macronutrient refer to plant needs

rather than plant uptake amounts.Each nutrient cannot be taken up by

plants in its elemental, or non-chargedform, but instead is taken up in an ionic,or charged, form (Table 2), with theexception of boric acid which isuncharged. Most fertilizers are made upof a combinations of these availablenutrient forms, so when the fertilizer

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NUTRIENTMOBILITYWITHINTHEPLANT

All nutrients move relatively easilyfrom the root to the growing portion ofthe plant through the xylem. Interestingly,some nutrients can also move from olderleaves to newer leaves if there is adeficiency of that nutrient. Knowing which

nutrients are mobile (i.e., able to move) isvery useful in diagnosing plant nutrientdeficiencies because if only the lowerleaves are affected, then a mobile nutrientis most likely causing the deficiency.Conversely, i f only the upper leaves showthe deficiency, then the plant is likelydeficient in an immobile nutrient, becausethat nutrient cannot move from older tonewer leaves. Table 3 lists the six mobileand eight immobile mineral nutrients.

Sulfur is one element that l ies betweenmobile and immobile elements dependingon the degree of deficiency.

TIMINGOF NUTRIENT UPTAKE

Nutrient uptake does not necessarilymatch plant growth. For example, when

corn biomass represents 50% of its totalmature biomass, it has accumulatedapproximately 100% of its mature K, 70%of its N, and 55% of its P (Figure 3).Therefore, supplying sufficient K and Nearly in a crops growing season is likelymore important than during the middle ofthe growing season. However, late in thegrowing season, nutrients accumulate inthe grain rather than in the leaves or stalk.Therefore, late season nutrient applicationmay increase both quality and grain yield if

other plant requirements are met, such aswater. For example, nitrogen topdressed attillering has been found to increase bothyield and protein of winter wheat grown inMontana, especially at low soil N levels(Lorbeer et al., 2000). Therefore, it isimportant to understand nutrient needsand timing of nutrient uptake for eachcrop that youre working with. See theReferences, Books, and Web Resources atthe end of this module for some resources

on some specific crops.

Soil Fertility

In the previous chapter, it was pointedout that nutrient uptake is dependent onboth the plants abil ity to absorb a nutrientand the nutrient level at the root surface.Most soils have far more nutrients than areneeded by a plant in a growing season, yet

Table 3. Mobile and immobile

nutrients in plants.

MOBILE NUTRIENTS

Chloride

Magnesium

Molybdenum

Nitrogen

Phosphorus

Potassium

IMMOBILE

NUTRIENTS

Boron

Calcium

Copper

Iron

Manganese

Nickel

Sulfur

Zinc

Figure 3.

Accum ulation of

potassium (K),

nitrogen (N),

phosphorus (P) ,

and dry m atter

(DM) in corn.

(From F oth and

Ellis 1997 ).

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Q&A #2What causes clays

to have negative

charges?The negative charge on layer

silicates is due to two differentprocesses. Much of the negativecharge originates when somecations such as Mg+2 replaceother cations such as Al+3 within

the layer sili cate structure. Thissubstitution of a smaller chargedion for a larger charged ionduring formation of the mineralleaves a net negative charge onthe soil particle. The secondsource of the negative chargeoriginates when a layer silicateparticle breaks, exposing edgesites that are mostly negativelycharged.

CATIONAND ANION EXCHANGE CAPACITY

Some soil particles calledaluminosilicates, or layer silicates, havea negative charge that attracts positivelycharged ions (cations) such as ammonium(NH

4+) in the same way that hair is

attracted to a balloon. Other soil particles,such as iron hydroxides (e.g. rust), have

positive charges that attract negativelycharged ions (anions), such as sulfate (SO

4-2).

Soils generally have much higher amountsof the layer silicates than metal hydroxides;therefore, soils generally have a net, orbottom line, negative charge.

The total negative charge on soil iscalled the cation exchange capacity, orCEC, and is a good measure of the abilityof a soil to retain and supply nutrients to acrop. Some typical values of CEC for

various soil textures are shown in Table 4.Note CEC is typically expressed in

terms of milliequivalents (or meq) ofnegative charge/100 g of soil. A meq isequal to 6 x1020 charges; therefore, a soilwith a CEC of 1 meq/100 g means thatthere are 6x1020 negative charges on 100 g(0.22 lb.) of soil. This is a very largenumber, but because atoms weigh so little,this 0.22 lb of soil would only be able to

often very li ttle of these nutrients are insolution. This section describes the factorsthat affect nutrient concentrations in thesoil solution and explain the process ofhow nutrients in the soil solution movetoward the root.

TEXTURESoil texture, or the relative

amounts of sand, silt, and clay,plays a very important role inplant nutrition due to its effecton the ability to retain bothwater and nutrients. Soils areclassified into textural classes bytheir percentages of sand, silt,and clay (Figure 4). Note that asoil with 20% clay and 45%sand would be classified as aloam. Sand particles are smaller than 2millimeters (the thickness of a nickel) andlarger than 0.05 mm (1/2 the thickness of apiece of paper), and have very little ability

to hold water or nutrientsdue to large pore spacesbetween particles and lowsurface area. Conversely, clayparticles are smaller than0.002 millimeters (invisibleto the naked eye), and canhold large quantities of waterand nutrients. Soilsdominated by clay have smallpores that prevent waterfrom draining freely and havevery high surface areas,ranging up to 90 acres perpound of soil. This highsurface area gives nutrientsnumerous binding places,which is part of the reasonthat fine textured soils havesuch high abilities to retainnutrients. The second reasonis that clays are often madeup of minerals that have netcharges on their surfaces(Q&A #2).

Figur e 4. Textur al tr iangle showing the

ran ge in san d, silt, and clay for each soil

textu ral class .

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Q&A #3How does CEC affect

nutrient availability?

Soils with high CECs holdmore positively chargednutrients such as Ca+2. Onemight think that i f the soil isholding, or binding thenutrients, that they are notavailable to plants. However,these attractions are weak,allowing an exchange betweennutr ients in the soil soluti on andnutrients on the soil surface, soas nutri ents are removed fromsolution by a plant, more leave

the soil surface and entersolution. Generally, there aremany more nutrients attached tothe soil than are in solution, sothat exchangeable nutrients area much better measure ofavailable nutrients than solelynutr ient concentrati ons insolution.

hold 0.023 grams or 0.0008 ounces ofsodium ions (2% of the weight of astandard paper clip). A CEC above about 15meq/100 g has a relatively high capacity tohold nutrient cations, which include Ca+2,Mg+2, K+, NH

4+, Cu+2, Fe+2, Mn+2, and Ni+2.

Soils that are high in clay generally havehigher CEC values, although the type ofclay can substantially affect CEC.Nutrients that are held by charges on a soilare termed exchangeable. Soil testing(NM Module 1) is often done forexchangeable nutrients, such as K, because ithas been found that exchangeable nutrientsare available to plants (Q&A#3).

Soils also have the ability to holdanions. This ability is termed the anionexchange capacity, or AEC. The AEC isgenerally smaller than the CEC, but ishigh enough in most soils to holdsubstantial amounts of some nutrientanions such as SO

4-2.

ORGANICMATTER

Organic matter, l ike clay, has a highsurface area and a high CEC, making it an

excellent supplier ofnutrients to plants. Inaddition, as organic matterdecomposes, it releasesnutrients that are bound inthe organic mattersstructure, essentiallyimitating a slow releasefertilizer. The CEC of organicmatter can be as high as 215meq/100 g, a much highervalue than for clay. However,the CEC of organic matterdrops substantially as pHdecreases as explained in thefollowing section. Organicmatter can also hold largeamounts of water, whichhelps nutrients move fromsoil to plant roots.

pH

The pH of a soil is ameasure of the soils acidity,or hydrogen (H+)concentration. By definition,

Table 4. Cation Exchange

Capacities (CEC) for a

range of soil textures(FROM BRADY, 1984).

SOIL TEXTURE

Sand

Sandy loam

Loam

Silt loam

Clay

CEC RANGE

(meq/100g soil)

2-4

2-17

8-16

9-26

5-58

Figure 5 .

Th e effect

of soil pH

on nu trient

availability.

Thicker

bars

indicate

higher

nutrientavailability.

(From

Hoeft et al.,

2000) .4.0 5.0 6.0 7.0 8.0 9

pH

Nitrogen

Phosphorus

Potassium

Sulfur

Calcium

Magnesium

Iron

Manganese

Boron

Copperand Zinc

Molybdenum

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pH = -log[H+], where [H+] = the hydrogenion concentration. Because of the negativesign in the definition for pH, acidic soilshave low pH values and alkaline soils havehigh pH levels. Soil pH affects theavailabil it y of all of the nutr ients (Figure5). For example, copper, iron, manganese,nickel, and zinc are all more available atlow pH levels than at high pH levelsbecause metals are bound very tightly tothe soil or exist in solid minerals at highpH. Conversely, the base cations (Na+, K+,Ca+2, Mg+2) are bound more weakly to thesoil, so can leach out of the surface soil,especially at low pH. Therefore, they areless available at low pH. In Montana andWyoming, there are many soils with pHlevels above 7.5; therefore, there is ahigher likelihood for iron, manganese,nickel, copper, zinc, and phosphorusdeficiencies than in states with lower pHvalues, although deficiencies of themicronutrients are not often observed. The

optimum pH appears to be near pH 7, butkeep in mind that every crop has differentnutrient needs, and hence optimum pHlevels. For example, sweet clover has beenfound to have maximum yields near pH7.5, whereas soybeans and corn grow bestnear pH 6.8 (Foth and Ellis, 1997).

Lower pH generally causes lower CEC,because the higher concentration of H+

ions in solution wil l neutralize thenegative charges on clays and organicmatter. Fertilizing with ammonia-basedfertilizers is one way that pH may decreaseover time. Figure 6 demonstrates how pHaffects the surface charge, and hence theCEC and AEC of both clay particles andorganic matter. The effect of pH on CEC ismore pronounced for soil organic matterthan for layer silicates, because all of theCEC on organic matter is dependent onpH. Note that the negative charges on theclay particle that are not on the edge of theparticle are not neutralized.

NUTRIENTMOBILITYINSOIL

The previous section discussed themobili ty of each nutrient within the plant.The list of mobile and immobile nutrientsis somewhat different in soil than in theplant, yet is very important inunderstanding why some nutrients limitgrowth more than others. Specifically,nutrient mobility affects how we fertilize.For example, N fertilizer can be broadcastor incorporated with fair ly similar resultsbecause it is quite mobile. However, Pfertilizer is generally either banded orapplied with the seed because it is quiteimmobile in most soils. Table 5 illustratesthe relative mobility of each of the 14essential mineral nutrients. The form ofeach nutrient is very important inpredicting its mobili ty; therefore, theactual ions are shown rather than just thegeneral nutrient. For example, plants cantake up N as either nitrate (NO

3-) or

ammonium (NH4+), but NO

3- moves freely

through the soil due partly to its negativecharge, whereas NH

4+ is held by cation

exchange sites and, therefore, is less

F igure 6 . E ffect of pH on CEC and AE C of clay

particles and soil organic matter. Note decreased pH

causes CEC to decrease and AE C to incr ease (m ore

positive charges).

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Q&A #4How do the

relatively immobile

nutrients ever

make it to the

plant roots?The plants create a zone

directly next to the root that hasvery low concentrations of theseimmobile nutrients. This allowsdiffusion to occur which pullsnutrients that are further awayfrom the root towards the root(described more below). This, inturn, pulls more of theseimmobile nutrients off the soilsurface to maintain a balancebetween nutrients in solutionand nutrients on the surface ofthe soil.

mobile. Keep in mind that this is ageneralized table, and the actual relativemobility of each nutrient will depend onpH, temperature, moisture and soilmakeup, including the amount of organicmatter, layer silicates, and metalhydroxides. For example, some of theimmobile nutrients are more mobile thanothers.

As a good general rule, NH4+, K+, Ca+2,

and Mg+2 are more mobile than the metals(Cu+2, Fe+2, Fe+3, Mn+2, Ni+2, Zn+2).Fert ilizing with any of the mobileelements generally needs to be done morefrequently than the immobile elementsbecause the mobile elements are readilytaken up or leached compared to theimmobile elements. With the exception ofNH

4

+, which is quickly converted to NO3

-,the immobile nutrients can be banked,meaning more can be applied than meetcrop needs as a way of storing them for thenext cropping cycle. Soil banking is also

referred to as a buildprogram (see NM Module 1).

NUTRIENT MOVEMENT

TO PLANT ROOTS

Roots come directly in

contact with some nutrients(called root interception) asthey grow; however, this onlyaccounts for approximately 1-2.5% of the total N, P, and Kuptake of a plant (Foth andEllis, 1997). Therefore, othermechanisms must cause themovement of nutrients to theplant.

Water moves toward and

into the root as the plant useswater, or transpires. Thisprocess, called mass flow,accounts for a substantialamount of nutrientmovement toward the plantroot, especially for the mobilenutrients such as NO

3-.

Specifically, mass flow hasbeen found to account forabout 80% of N movement into the root

system of a plant, yet only 5% of the moreimmobile P (Foth and Ellis, 1997). Thisimplies that P (and the other less mobilenutrients) are somehow moving muchmore quickly than the surrounding wateris moving towards the plant roots. It hasbeen found that diffusion accounts for theremainder of the nutrient movement.

Diffusion is the process wherechemicals move from an area of highconcentration to an area of low

concentration. For example, if you open abottle of ammonia in a closed room, youcan soon smell it at the other side of theroom because it has diffused from themouth of the bottle that had highammonia concentrations, to the areas ofthe room that previously had no ammonia,or very low concentrations. This sameprocess occurs in soil water, although it

Table 5. Mobility of

nutrients in soil.

MOBILE

H3BO

3o, H

2BO

3-

Cl -

NO3-

SO4-2

RELATIVELY

IMMOBILE

NH4+

Ca+2

Cu+2

Fe+2, Fe+3

Mg+2

Mn+2

MoO4-2

Ni+2

H2PO

4-, HPO

4-2

K+

Zn+2

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generally occurs much slower. Byferti li zing near the plant root, the plant isless dependent on exchange processes anddiffusion to uptake nutrients, especially P.The nutrients that are most dependent ondiffusion to move them toward a plant rootare relatively immobile (Table 5), have

relatively low solut ion concentrations, andyet are needed in large amounts by theplant, such as P and K. The secondarymacronutrients (Ca, Mg, S) often do notdepend on diffusion because their solutionconcentrations are fairly high in soilrelative to plant requirements.

Summary

Plants need 17 elements, called

nutrients, to grow and complete their lifecycle. Three of these nutrients come fromair or water, whereas the other 14 arederived from the soil. Each of thenutrients performs a specific function orfunctions within the plant, and theamount of each needed by the plantdepends largely on function. A limitationof one nutrient can prevent the uptake ofothers, and ult imately, impact crop yieldand quality. Plant uptake of nutrients is

dependent on both the ability of the rootsystem to absorb nutrients and thenutrient concentration in soil solution.Nutrient accumulation within the plant is

generally faster than biomassaccumulation, which is one reason thatfertilizing early in the growing season isadvantageous.

Soils have large quantities of mostnutrients, yet the majority of thesenutrients are not in the soil solution, butinstead are bound to the soil. Some ofthese nutrients are available to plantsbecause they are only weakly bound asexchangeable nutrients. The cationexchange capacity (CEC) is one measure ofthe total amount of exchangeable cationsthat can be held by the soil, and generallyis a good general indicator of soil fertility.CEC is higher in soils with high amountsof clay and organic matter, and is lower inacid soils. Soil pH strongly affects theplant availabil ity of each of the nutr ients,with pH levels near 7 generally havingoptimum availability.

Nutrients vary greatly in their relativemobili ty within a soil. For example, nitrate(NO

3-) is highly mobile, yet phosphate

(HPO4-2, H

2PO

4-) is relatively immobile.

These differences are key to developingeffective nutrient management programs,and explain why applying immobilenutrients such as P near the root system is

important for optimum nutrient uptake.Subsequent modules will address eachspecific nutr ient in more detail, withemphasis on factors affecting mobility,uptake, and fertilizer requirements.

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ReferencesBrady, N.C. 1984. The Nature and

Propert ies of Soil s. 9th Edit ion.Macmil lan Publishing Company. NewYork. 750 p.

Foth, H.D. and B.G. Ellis. 1997. SoilFertility. 2nd Ed. CRC Press. BocaRaton, Florida. 290 p.

Hoeft R.G., E.D. Nafziger, R.R. Johnson,and S.R. Aldrich. 2000. Modern Cornand Soybean Production. MCSPPublications. Champaign, IL. 353p.

Lorbeer, S.L. J. Jacobsen, P. Bruckner, D.Wichman, and J. Berg. 2000.Captur ing the genetic proteinpotential in winter wheat. FertilizerFact Number 23. July 2000. MontanaState University Extension Service andAgricultural Experiment Station.

Marschner, H. 1995. Mineral Nutr it ion of

Higher Plants. 2nd Ed. AcademicPress. London. 889 p.

Sparks, D.L. 1995. Environmental SoilChemistry. Academic Press. SanDiego. 267 p.

Resources

BOOKSWestern Fert ilizer Handbook. 8th

Edition. 1995. Soil ImprovementCommittee. Cali fornia Fert ili zer

Association. Thomson Publications.351 p. (http://www.agbook.com/westernfertilizerhb.htm) $35including shipping.

Plant Nutrition Manual. J. Benton Jones,Jr. 1998. CRC Press, Boca Raton,Florida. 149 p. Approximately $50.

Soil Fert ility. Foth and Ellis. 1997. CRCPress, Boca Raton, Florida. 290 p.

Soil Fer tility and F ertilizers, 6th Edit ion.J.L. Havlin et al. 1999. Upper SaddleRiver, N.J.: Prentice Hall. 499 p.

Approximately $100.

EXTENSION MATERIALSFertilizer Guidelines (EB104). Single

copy is free.

Obtain the above Extension publication(add $1 for shipping) from:

MSU Extension Publi cationsP.O. Box 172040Bozeman, MT 59717-2040

See Web Resources below for onlineordering information.

PERSONNELEn gel, Rick. Associate Professor.

Montana State University, Bozeman.(406) 994-5295. [email protected]

Jackson, Grant. Associate Professor.Western Triangle AgriculturalResearch Center, Conrad. (406) 278-7707. [email protected]

Jacobsen, Jeff. Extension Soil Scientist.Montana State University, Bozeman.(406) 994-4605. [email protected]

Jones, Clain . Soil Chemist. MontanaState University, Bozeman. (406) 994-6076. [email protected]

Westcott, Mal. Western AgriculturalResearch Center, Corvall is. Phone:(406) [email protected]

WEB RESOURCEShttp://www.montana.edu/publications

Montana State University Publicationsordering information on extensionmaterials including information onFertilizer Guidelines (EB104).

http://scarab.msu.montana.edu/Agnotesold/agnotes11b_toc.htm

MSU weekly Agronomy notes by Dr. JimBauder on range of i ssues, includingfertilizer management. Currentlythere are 23 notes on Fertilizer

Management, and over 300 AgronomyNotes total answering real lifequestions from producers, extensionagents, and consultants.

http://landresources.montana.edu/FertilizerFacts/

28 Fert ili zer Facts summari zing ferti li zfindings and recommendations baseon field research conducted inMontana by Montana State Universitpersonnel.

http://www.agr.state.nc.us/cyber/kidswrplant/nutrient.htm

A nice concise summary of each of theessential elements. Source: NorthCarolina Department of Agri culture.

http://www.ag.ohio-state.edu/~ohioline/b472/fertile.html

Information on macronutrients andmicronutrients. Has plant analysis asoil testi ng information. Source: OhState Universit y.

AcknowledgmentsWe would like to extend our

utmost appreciation to the followingvolunteer reviewers who providedtheir time and insight in makingthis a better document:

Ron Carlstrom, Gallatin CountyExtension Office, Bozeman, MT

Rick Engel, Dept. of Land Resourcesand Environmental Sciences,MSU, Bozeman, MT

Jeff Farkell, Centrol Inc., Brady, MT

Neal Fehringer, Western AgConsulting, Billings, MT

Grant Jackson, Western TriangleAgricultural Research Center,Conrad, MT

Kent Williams, Custer CountyExtension Office, Miles City, MT

Suzi Taylor, MSU CommunicationsServices, Bozeman. Layout anddesign.

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The programs of the MSU Extension Service are available to all people regardless of race, creed, color, sex, disability or national origin.Issued in furtherance of cooperative extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in cooperationwith the U.S. Department of Agriculture, David A. Bryant, Vice Provost and Director, Extension Service, Montana State University,

Bozeman, MT 59717.

Copyright 2001 MSU Extension ServiceWe encourage the use of this document for non-profit educational purposes. This document may be reprinted if no endorsement of a commercialproduct, service or company is stated or implied, and if appropriate credit is given to the author and the MSU Extension Service. To use these docu-ments in electronic formats, permission must be sought from the Ag/Extension Communications Coordinator, Communications Services, 416 Culbertson

Hall, Montana State University-Bozeman, Bozeman, MT 59717; (406) 994-2721; E-mail - [email protected].

Mt 44492

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