TRI-STATE

FERTILIZER RECOMMENDATIONS

FOR

CORN,

SOYBEANS,

WHEAT

&

ALFALFA

TRI-STATE

FERTILIZER RECOMMENDATIONS

FOR

CORN,

SOYBEANS,

WHEAT

&

ALFALFA

Michigan State University

The Ohio State University

Purdue University

Extension Bulletin E-2567 (New), July 1995

Tri-state Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa

M.L. Vitosh, Michigan State UniversityJ.W. Johnson, The Ohio State University

D.B. Mengel, Purdue UniversityCo-editors

FOREWORDWhen fertilizer first became readily

available in the 1930s, universityresearchers began to conduct field stud-ies, develop soil tests and make fertil-izer recommendations. One of theearly publications in the tri-state regionwas “How to Fertilize Corn Effectivelyin Indiana” by G.D. Scarseth, H.L.Cook, B.A. Krantz and A.J. Ohlrogge,Bulletin 482, 1944, Purdue University,Agricultural Experiment Station. Sincethat time, many soil fertility scientistshave made significant contributions toour understanding of plant nutritionand the development of fertilizer rec-ommendations. We have learned agreat deal from this legacy and are verygrateful for their contributions.

In the past, universities have devel-oped fertilizer recommendations inde-pendently without much regard for dif-ferences that might have existedbetween states. We have reached a

time in our history when different rec-ommendations at the state boundaryline are being questioned. It is time tobreak with tradition and develop com-mon fertilizer recommendations thatwill serve more than one state. In thispublication, we have developed com-mon fertilizer recommendations for themajor crops in the tri-state region. Thetask has not been easy. We found thatsome changes and compromises werenecessary. This is our first attempt atdeveloping tri-state fertilizer recommen-dations for corn, soybeans, wheat andalfalfa. More work is needed on othercrops and has already begun. We lookforward to the continued developmentof these recommendations and are con-fident that they will be of great value tomany farmers, consultants andagribusiness associates in the tri-stateregion.

ACKNOWLEDGEMENTSThe editors would like to thank

those colleagues who have contributedgreatly to the writing of this publica-tion. They are D.R. Christenson andD.D. Warncke, Department of Crop andSoil Sciences, Michigan State Univer-sity; M.E. Watson, Research and Exten-sion Analytical Laboratory, and D.J.Eckert, School of Natural Resources,The Ohio State University; B.C. Joernand S.E. Hawkins, Department ofAgronomy, Purdue University. Wewould also like to thank G.N. Jacksonand S.A. Dlugosz from CountrymarkCooperative Inc. for their encourage-ment and help in facilitating the discus-sion that led to this publication. Inaddition, we would also like toacknowledge our department chairs,E.A. Paul, F.P. Miller and W.W. McFee,for their support and encouragement ofthis publication.

CONTENTSSAMPLING, HANDLING AND TESTING SOILS .............................................1

SAMPLING STRATEGIES......................................................................1Sample Distribution..........................................................................1Sample Depth...................................................................................1Time of Year to Sample ....................................................................1Intervals Between Samples ..............................................................2

SAMPLE HANDLING.............................................................................2SOIL TESTING PROCEDURES..............................................................2

SOIL pH AND LIME RECOMMENDATIONS..................................................3WEAKLY BUFFERED SOILS ..................................................................4

NITROGEN.................................................................................................4NITROGEN PLACEMENT ......................................................................4NITROGEN TIMING ..............................................................................5

Fall vs. Spring Applications ............................................................. 6Preplant vs. Sidedress Applications .................................................6Split or Multiple Applications ...........................................................7

NITROGEN LOSSES FROM SOILS........................................................7

SELECTING FORMS OF NITROGEN FERTILIZER..................................8N RECOMMENDATIONS FOR CORN.....................................................9N RECOMMENDATIONS FOR WHEAT ................................................10

PHOSPHORUS AND POTASSIUM .............................................................10PHOSPHORUS AND POTASSIUM FERTILIZER PLACEMENT AND TIMING .................................................................12

Starter Fertilizer ..............................................................................12Fertilizer with the Seed ...................................................................12

PHOSPHORUS RECOMMENDATIONS................................................13POTASSIUM RECOMMENDATIONS....................................................14

SECONDARY NUTRIENTS ........................................................................17MICRONUTRIENTS ..................................................................................17

DIAGNOSING MICRONUTRIENT DEFICIENCIES.................................18MICRONUTRIENT PLACEMENT AND AVAILABILITY..........................18SELECTING MICRONUTRIENT SOURCES ..........................................19MICRONUTRIENT RECOMMENDATIONS ...........................................20

The accuracy of a fertilizerrecommendation depends onhow well the soil sample onwhich the recommendationwas based represents the

area on which the recommendation willbe used. The physical and chemicalcharacteristics of soil in an area canvary considerably from place to placebecause of natural factors and the man-agement to which the area has beensubjected. Natural variation arises fromsoil-forming processes (such as mineralweathering and erosion) that lead toaccumulations or losses of nutrients atdifferent sites. Management factorsmight include tillage and fertilizationpractices, crop selection and irrigation. Itmay be necessary to take many samplesfrom a given area (at random or in asystematic manner) to assess its fertilityaccurately.

SAMPLINGSTRATEGIES

Four variables are generally consid-ered when taking soil samples:

1. The spatial distribution of samplesacross the landscape.

2. The depth of sampling.

3. The time of year when samples are taken.

4. How often an area is sampled.

Proper consideration of these vari-ables ensures that the sample accuratelyreflects the fertility of the area in ques-tion and allows for the best possible fer-tilizer recommendations.

Sample Distribution Sample distribution usually depends

on the degree of variability in a givenarea. In relatively uniform areas smallerthan 25 acres, a composite sample of 20to 30 cores taken in a random or zigzagmanner is usually sufficient. Largerareas are usually subdivided intosmaller ones. Non-uniform areas shouldbe subdivided on the basis of obviousdifferences such as slope position or soiltype.

Banding fertilizer creates zones ofvery high fertility in soils because thefertilizer is mixed with only a small por-tion of the soil. Samples taken in theband can greatly overestimate the over-all fertility of a site. Because the positionof fertilizer bands is rarely known withcertainty, one should take more randomsamples than usual in fields with fertil-izer bands and vary sampling positionwith respect to row location to ensurethat the bands do not bias test results.

For non-uniform sites, a systematicsampling approach is best. Sampling ina grid pattern can give an idea of vari-ability in a field and fertilizer applica-tion can be adjusted according to thedistribution of soil test results within thegrid. The grid spacing can vary from aslittle as 30 feet to several hundred feet.Often the grid spacing is some multipleof fertilizer applicator width. Grid geom-etry can be adjusted to account for char-acteristics of the site in question. Forexample, a rectangular grid may bemore useful than a square grid whenfertilizer applications have been primar-ily in one direction. Eight to 10 cores areusually taken and combined for analysisat each sampling point in the grid.

Sampling Depth Soil samples used for nutrient rec-

ommendations should be taken at thesame depth that is used in the researchgenerating the recommendations, nor-mally 0 to 8 inches. A major exceptioninvolves sampling sites subjected to lit-tle or no inversion tillage, includingthose in established forages, no-till andridges. In such cases, additional sam-ples should be taken at a shallowerdepth (0 to 4 inches) to assess acidifi-cation of the soil surface and makeappropriate lime recommendations.Surface soil pH may greatly affect her-bicide activity and/or carry-over prob-lems. Occasionally sampling the soilprofile in 4-inch increments also maybe useful for assessing the degree ofnutrient stratification in fields managedwith conservation tillage, but no recom-mendations are being made at this timebased on the results of such samples.

Time of Year to SampleSampling after harvest in the fall or

before planting in the spring is recom-mended. Fall sampling is preferred iflime applications are anticipated. Sam-pling during the growing season maygive erroneous results due to effects ofcrop uptake and other processes. In-season sampling should be used onlyto test soils for nitrate as a guide to sid-edressing additional N. Recommenda-tions for sampling soils for nitrate arenot consistent across Indiana, Michiganand Ohio, so those interested in suchtests should use in-state recommenda-tions.

Sampling should occur at the sametime of the year each time a particularfield is sampled. This allows better

1

SAMPLING, HANDLING AND TESTING SOILS

tracking of trends in soil test valuesover time, which may be as importantas the test values themselves.

Intervals BetweenSampling

Most sites should be sampled everythree to four years. On sites whererapid changes in fertility (particularlydecreases) are expected or when high-value crops are involved, shorter sam-pling intervals (1 to 2 years) are recom-mended. Regardless of the samplinginterval, records of changes in soil testvalues over time should be kept foreach site tested.

SAMPLE HANDLINGAfter the sample has been collected,

contamination must be avoided. Com-mon sources of contamination includedirty sampling tools, storage vesselsand surfaces on which soils are spreadto dry. Ashes from tobacco productscan cause considerable contaminationof soil samples. Soils should be shippedto the testing laboratory only in con-tainers approved by the lab.

Individual cores should be mixedthoroughly to form a composite sample.Moist cores should be crushed intoaggregates approximately 1⁄8 to 1⁄4inch across for optimum mixing. If themixed sample is to be dried, the dryingshould be done at temperatures nogreater than 120 degrees F (50 degreesC). After drying, a subsample of appro-priate size should be taken from thecomposite mixture and sent to the test-ing laboratory for analysis.

SOIL TESTINGPROCEDURES

Several tests are available to measurethe availability of individual nutrientsin the soil. The recommendations madehere are based on research conductedusing very specific tests, which areidentified for each nutrient. Producersand consultants should always be cer-tain their fertilizer recommendationsare based on research using the sameprocedures used to generate their soiltest results.

The specific procedures used to testsoils in Indiana, Michigan and Ohio are

described in NCR Publication 221, 1988,Recommended Chemical Soil Test Pro-cedures for the North Central Region,written by the USDA-sanctioned NorthCentral Regional Committee on SoilTesting and Plant Analysis (NCR-13)and published by the North DakotaAgricultural Experiment Station. Otherprocedures may yield results incompati-ble with the recommendations givenhere.

All soil test data in this publicationare reported as parts per million (ppm)rather than pounds per acre (lb/acre).The change to ppm is being madebecause it more truly represents what ismeasured in the soil. Soil test valuesare an index of availability and do notreflect the total amount of availablenutrients in soil. The use of lb/acre inthe past has also led to some confusionabout soil testing and the resulting fer-tilizer recommendations. Most commer-cial soil test laboratories are currentlyreporting soil test values in terms ofppm. To convert ppm to lb/acre, multi-ply ppm by 2.

2

Different crops require differ-ent soil pH levels for opti-mum performance; whenpH falls below these levels,performance may suffer

(Table 1). The pH of organic soils (morethan 20 percent organic matter) is gener-ally maintained at much lower levelsthan the pH in mineral soils (less than20 percent organic matter) to minimizechances of micronutrient deficiencies.The topsoil in fields with acid subsoils(most common in eastern Ohio) shouldbe maintained at higher pHs than thosefields with neutral or alkaline subsoils tominimize chances for nutrient deficien-cies associated with acid soil conditions.

Soil pH should be corrected by limingwhen the pH in the zone of samplingfalls 0.2 to 0.3 pH units below the rec-ommended level. The rates of applica-tion given in Table 2 are based on thelime test index obtained using the SMP-buffer lime requirement test and areapplicable to an 8-inch depth. For no-tilland established forages, lime recommen-dations are based on a 0- to 4-inchdepth, so the rates of application shouldbe one-half the values given in Table 2.These rates are for agricultural ground

limestone with a neutralizing value of90 percent. They should be adjusted ifother types of liming material are used.To adjust for a liming material with adifferent neutralizing value (nv), multi-ply the lime recommendation given inthe table by 0.90 and divide by the newneutralizing value.

Example: Lime recommendation= [(tons per acre x 0.90) /0.80] if nv is 80 percent.

The relative availability of theliming material is also affectedby the lime particle size. Forinformation on adjusting limerecommendations because ofdifferences in lime particle size,see in-state publications.

Lime rates also should beadjusted for other depths ofincorporation. To adjust for

other depths, divide by 8 and multiplyby the new incorporation depth.

Example: Lime recommendation =[(tons per acre / 8) x 10] if incorpora-tion depth is 10 inches.

Lime recommendations (LR) are cal-culated from the lime test index (LTI)for mineral soils and the soil pH fororganic soils using the following formu-las and rounding to the nearest tenth ofa ton:

Mineral soilsto pH 6.8: LR = 71.4 - 1.03 x LTIto pH 6.5: LR = 60.4 - 0.87 x LTIto pH 6.0: LR = 49.3 - 0.71 x LTIOrganic soilsto pH 5.3: LR = 32.9 - 6.31 x soil pH

These rates should raise soil pH tothe desired pH level, but the exact pH isnot always achieved. Applications of less

3

SOIL pH AND LIME RECOMMENDATIONS

Table 1. SOIL PH RECOMMENDED FOR

VARIOUS CROPS ON VARIOUS SOILS.Mineral soils with subsoil pH Organic

Crop > pH 6 < pH 6 soils—————— pH —————

Alfalfa 6.5 6.8 5.3Other forage

legumes 6.0 6.81 5.3Corn 6.0 6.5 5.3Soybeans 6.0 6.5 5.3Small grains 6.0 6.5 5.3Other crops 6.0 6.5 5.3

1 Birdsfoot trefoil should be limed to pH 6.0.

Table 2.TONS OF AGRICULTURAL LIMESTONE NEEDED TO RAISE THE

SOIL PH TO THE DESIRED PH LEVEL BASED ON THE SMP LIMETEST INDEX AND AN INCORPORATION DEPTH OF 8 INCHES.

Desired pH levels

Mineral soils Organic soils

6.8 6.5 6.0 Soil pH 5.3

tons agricultural limestone/acre2 tons/acre68 1.4 1.2 1.0 5.2 0.067 2.4 2.1 1.7 5.1 0.766 3.4 3.0 2.4 5.0 1.365 4.5 3.8 3.1 4.9 2.064 5.5 4.7 3.9 4.8 2.663 6.5 5.6 4.6 4.7 3.262 7.5 6.5 5.3 4.6 3.961 8.6 7.3 6.0 4.5 4.560 9.6 8.2 6.7 4.4 5.1

1Lime test index is the SMP buffer pH x 10.2These values are based on agricultural limestone with a neutralizing value of 90 percent (Indiana RNV = 65,Ohio TNP = 90+). Adjustments in the application rate should be made for liming materials with different particlesizes, neutralizing values and depths of incorporation.

Limetestindex1

than 1 ton/acre often may not be practi-cal and will not appear in computer-generated recommendations. When therecommendation is for 2 tons/acre orless, the application can be made anytime in a cropping sequence. When thelime recommendation exceeds 4 tons peracre, apply the lime in a split application— i.e., half before plowing and half afterplowing. Do not apply more than 8 tonsof lime in one season. Large applicationsof lime without thorough mixing maycause localized zones of high alkalinity,reducing the availability of some essen-tial nutrients. If the soil test indicatesmore than 8 tons per acre are required,retest two years after the application tosee if more lime is needed.

Surface applications of urea forms ofN fertilizer are not recommended onfields where lime has been surfaceapplied recently. The potential N loss byammonia volatilization is high whenurea reacts with unincorporated lime.Urea forms of N should not be surfaceapplied within one year of the limeapplication. Surface applications ofammonium nitrate, ammonium sulfate,or injected 28 percent N or anhydrousammonia are preferred when lime is notincorporated.

WEAKLY BUFFEREDSOILS

Because sandy soils are often weaklybuffered, there is concern about lime

requirements determined by the SMPlime test. These soils may have a soilwater pH below the desired pH rangefor optimum crop growth but the limeindex test does not indicate a need forlime. This occurs because weaklybuffered soils do not have sufficientcapacity to lower the pH of the SMPbuffer solution. When this situationoccurs, growers may want to considerusing 1 ton of lime per acre when thesoil water pH is more than 0.3 pH unitsbelow the desired soil pH and 2 tons peracre when the soil water pH is morethan 0.6 pH units below the desired soil pH.

4

Profitability, concern forgroundwater quality andconservation of energy aregood reasons to improvenitrogen use efficiency.

Placement of fertilizer nitrogen andtiming of application affect nitrogen useefficiency. Placement and timing ofnitrogen application are managementdecisions within a producer’s produc-tion system. Soil characteristics, rainfalland temperature, tillage system and fer-tilizer source affect the efficacy ofapplication. Because of our inability topredict the occurrence and amounts ofrainfall for a specific year, nitrogenplacement and timing should be basedon conditions that most frequentlyoccur. Most of the fertilizer nitrogenapplied in the eastern Corn Belt is usedon corn, so most of the discussion hereis on nitrogen management practicesfor corn.

NITROGENPLACEMENT

Tillage system and fertilizer sourceaffect proper placement of fertilizernitrogen. The most satisfactory way toapply anhydrous ammonia is by injec-tion in a band. Knife spacing providesan application option for anhydrousammonia. Injection into the soil byknives or spoke injector, spraying onthe surface and surface banding aretechniques used to apply fertilizer Nsolutions. Dry sources can be broadcastor placed in a band. The need to incor-porate N sources placed on the surfacedepends on the tillage system andwhether the N source contains urea.

The enzyme urease hydrolyzes ureato ammonia and carbon dioxide(NH2CONH2 + H2O - - -> 2NH3 +CO2). The ammonia vaporizes and islost if this occurs at the soil surface.

Urease is an enzyme common to soilorganic matter and plant residue. Fac-tors that enhance ammonia volatiliza-tion losses are: soil factors — high soilpH and low buffering capacity; envi-ronmental factors — warm tempera-ture, moist soil surface that is dryingand rapid air movement; managementfactors — surface application of highrates of urea-containing fertilizer,broadcast application, liquid fertilizerand crop residue on soil surface. Inject-ing or incorporating urea-containingfertilizer or receiving 1⁄2 inch or more ofrainfall before hydrolysis occursreduces or eliminates volatilizationlosses. Data shown in Tables 3 and 4illustrate the effect of applicationmethod in no-tillage for various Nsources. Dribble or band application ofurea-ammonium nitrate (UAN) solutionconcentrates the N solution, whichreduces contact with urease enzyme.This application technique slows the

NITROGEN

conversion of urea to ammonia and car-bon dioxide and lengthens the time Nsolutions can remain on the surfacewith minimum losses. Urease inhibitorsshow some promise in reducingvolatilization losses. Though there is anadvantage to soil incorporation on somesoils, incorporating fertilizers containingurea conflicts with the objectives ofmaintaining crop residues on the surfaceand reducing tillage operations. Thedevelopment of the spoke-wheel andhigh-pressure liquid applicators providesa method of injecting urea-ammonium

nitrate solutions into the soil with mini-mum disturbance of crop residue andcontrolling the placement relative to thecorn row.

Knife spacing is a consideration forsidedressing ammonia and in controlledtraffic such as ridge-tillage systems. Data

in Table 5 show that an ammonia bandbetween every other pair of rows is sat-isfactory compared to injecting in themiddle of every inter-row. Ammoniaapplied preplant diagonally will result incorn roots reaching the N band at differ-ent times. This may result in a rollingappearance to the cornfield. The use of20 to 40 pounds of N per acre applied asstarter fertilizer with the planter or as apreplant broadcast application will mini-mize the rolling appearance of corn.This practice will also ensure adequateN nutrition early in the season beforethe corn roots reach the N in the ammo-nia band.

NITROGEN TIMINGThe timing of N fertilizer applications

is an important factor affecting the effi-ciency of fertilizer N because the inter-val between application and crop uptakedetermines the length of exposure of fer-tilizer N to loss processes such as leach-

5

Table 3.THE EFFECT ON GRAIN YIELD

OF NO-TILL CORN BY NSOURCES AND METHOD OFAPPLICATION IN INDIANA.1

Average grain yieldN treatment bu/acre at 15.5% water

NH3 injected 139UAN injected 135UAN surface 118urea surface 1231Adapted from D.B. Mengel et al. 1982. Placementof nitrogen fertilizers for no-till and conventionalcorn. Agron. J. 74:515-518.

Table 5.EFFECT OF KNIFE SPACING OF AMMONIA APPLIED AT VARYING

RATES OF N ON CORN YIELD AT DEKALB, ILL.1

lb N/acre120 180 240

—————————bu/acre—————————Sidedress — 1985-1986 av.

30 171 176 18260 170 171 182

Preplant — 19862

30 159 178 19060 166 179 1801 Adapted from R.G. Hoeft. 1987. Effect of ammonia knife spacing on yield. In Proceedings of the

Seventeenth North Central Extension-Industry Soil Fertility Workshop. St. Louis, Missouri.2 Applied beneath the planted row.

Table 4.CORN GRAIN YIELDS AS AFFECTED BY SEVERAL

N MANAGEMENT STRATEGIESAT WOOSTER AND SPRINGFIELD, OHIO, 1984-1985.1

N Application Corn following

Rate Source2 Time Method Corn Soybeanlb/acre ——bu/acre——0 86 97150 AA Preplant Knife 154 162150 UAN Preplant Broadcast 145 154150 UAN Preplant Dribbled 154 155

(30” spacing)150 UAN Split Dribbled 150 157

1⁄3 preplant2⁄3 sidedress

150 UAN Split Dribbled 151 1562⁄3 preplant

1⁄3 sidedress1Adapted from D.J. Eckert. 1987. UAN management practices for no-tillage corn production. Journal ofFertilizer Issues. Vol 4:13-18.2AA = anhydrous ammonia; UAN = urea ammonium nitrate solution.

Knife spacing(inches)

ing and denitrification. Timing N appli-cations to reduce the chance of N lossesthrough these processes can increase theefficiency of fertilizer N use.

Ideally, N applications should coin-cide with the N needs of the crop. Thisapproach requires application of most ofthe N requirement for corn during aperiod 6 to 10 weeks after planting.Application of N during the period ofmaximum crop demand may not bepractical or possible; other methods andtimes of application may be equally effi-cient and appropriate. The efficacy oftime of application depends on soil tex-ture, drainage characteristics of the soil,amount and frequency of rainfall or irri-gation, soil temperature and, in somesituations, the fertilizer N source. Nitro-gen timing options usually include fallapplications, spring preplant applica-tions, sidedress or delayed applicationsmade after planting, and split or multi-ple treatments added in two or moreincrements during the growing season.

Fall vs. Spring ApplicationsFall applications of N are feasible only

in areas where low winter soil tempera-tures retard nitrification of ammonium.This limits fall application to the north-ern portion of the United States. Theconcern with fall application is thatlosses of N will occur between applica-tion and crop uptake in the next growingseason. This may lower crop yield andrecovery of applied N, compared withspring applications. Recommendationsfor fall applications are to use an ammo-nium form of N, preferably anhydrousammonia, and delay application untilthe soil temperature is below 50 degrees F.

Considerable year-to-year variation in theeffectiveness of fall N application occurs,as shown in Table 6.

These data illustrate that fall N appli-cations are usually less effective thanspring applications. In general, fall-applied N is 10 to 15 percent less effec-tive than N applied in the spring. HigherN application rates should not be usedin the fall to try to make up for potentialN losses. Use of a nitrification inhibitorwith fall-applied N can improve theeffectiveness of these treatments. Moststudies show, however, that spring-applied N is more effective thaninhibitor-treated fall N when conditions

favoring N loss from fall applicationsdevelop. In Table 7, inhibitor-treatedanhydrous ammonia was superior toanhydrous ammonia when applied inthe fall, but not when applied in thespring. Spring-applied anhydrous ammo-nia, however, was on the average betterthan the fall inhibitor-treated ammonia.To increase the effectiveness of fall-applied N with an inhibitor, delay theapplication until soil temperatures arebelow 50 degrees F.

Preplant vs. SidedressApplications

Benefits from delayed or sidedress Napplications are most likely where thereis a high risk of N loss between plantingand crop N use. Preplant N losses occurfrom sandy soils through leaching andfrom poorly drained soils through deni-trification.

Sidedress applications of N on irri-gated sandy soils produce consistentlygreater yields than a preplant applica-tion, as shown in Table 8. In areaswhere rainfall greatly exceeds evapotran-spiration, the same results are expected.Sidedress applications on coarse-textured/low CEC soils are usually moreeffective in increasing corn yields than

6

Table 6.YIELD OF CORN AS AFFECTEDBY NITROGEN RATE, TIME OFNITROGEN APPLICATION AND

SOIL TYPE IN MICHIGAN,1977-1984.1

Time of applicationNitrogen rate Fall Springlb/acre —-—-——--bu/acre—-—-——--

Loamy soils (5 experiments)

100 118 133150 127 154

Irrigated sandy loam soils (6 experiments)

100 162 172150 176 1811Adapted from M.L. Vitosh. 1985. Nitrogenmanagement strategies for corn producers.Michigan State University Extension BulletinWQ06.

Table 7.EFFECT OF N RATE, TIME OF APPLICATION, N SOURCE ANDNITRIFICATION INHIBITOR ON 8-YEAR AVERAGE CORN YIELD

IN OHIO.1

Fall-applied Spring-appliedN rate Urea AA AA+NI Urea AA AA+NIlb/acre ——-—-—-—-—-—--—-—-—-—----—-—-bu/acre-—-—-—-—-—-—-—-—-—-—-—-—-

0 5680 85 94 111 101 116 117

160 111 127 133 125 139 140240 — — — 139 — —320 — — — 139 — —

1 Adapted from R.C. Stehouwer and J.W. Johnson. 1990. Urea and anhydrous ammonia management forconventional tillage corn production. J. Prod. Agri. 3:507-513.

preplant treatments containing a nitrifi-cation inhibitor.

For medium- and fine-textured soils,yields seldom differ between preplantand sidedress application. Occasionally,sidedress application can be superior topreplant application when early seasonrainfall is excessive. The advantage todelaying N application is to assess cropneeds based on soil moisture and cropconditions. The disadvantages of delay-ing the major fertilizer N application are:the crop may have been under N defi-ciency stress before fertilizer N isapplied, resulting in a yield loss; wetconditions during the sidedress applica-tion period can prevent application, andlater additions may not be possiblebecause of corn growth; and dry condi-tions at and after sidedressing will limitN uptake.

Split or MultipleApplications

Application of N fertilizer in severalincrements during the growing seasoncan be an effective method of reducingN losses on sandy soils with high poten-tial for N loss through leaching. Irriga-tion systems equipped for simultaneous

application are often used to apply N inmultiple applications. The timing anddistribution of N additions in a multipleapplication system are important. Tomatch N uptake by corn, application ofsome N must occur by the sixth weekafter planting and most of the N require-ment should be applied by the tenthweek after planting. Research data sug-gest that a well timed sidedress applica-tion can be as effective as multipleapplications in irrigated corn produc-tion. A combination of sidedress appli-cations and N additions in irrigationwater may be needed to maximize cornyields on some sandy soils. Preplantadditions of one-third to two-thirds ofthe total N requirement, with theremainder applied later, are not as effec-tive as sidedress applications on irri-gated sandy soils.

On adequately drained medium- tofine-textured soils, the potential for Nloss is low and the use of delayed ormultiple N applications usually will notimprove corn yields. Adjusting the side-dress fertilizer N rate using the pre-sidedress or late spring soil nitrate test isan advantage to a split application onthese soils. This approach would permitadjusting for factors that affect N loss orgain and cannot be predicted.

NITROGEN LOSSESFROM SOIL

Nitrogen (N) can be lost from thefield through three principal pathways:denitrification, leaching and surfacevolatilization.

The form of N a farmer choosesshould depend on how serious a prob-lem he has with the above N losses.Cost of N, labor, equipment and poweravailability are other considerationswhen choosing a fertilizer source.

Denitrification occurs when nitrate N(NO3

-) is present in a soil and notenough oxygen (O2) is present to supplythe needs of the bacteria and microor-ganisms in the soil. If O2 levels are low,microorganisms strip the oxygen fromthe nitrate, producing N gas (N2) ornitrous oxide (N2O), which volatilizesfrom the soil. Three conditions that cre-ate an environment that promotes deni-trification are wet soils, compaction andwarm temperatures.

Leaching losses of N occur when soilshave more incoming water (rain or irri-gation) than the soil can hold. As watermoves through the soil, the nitrate(NO3

-) that is in soil solution movesalong with the water. Ammonium(NH4

+) forms of N have a positivecharge and are held by the negative siteson the clay in the soil; therefore, NH4

+

forms of N leach very little. In sandswhere there is very little clay, ammo-nium forms of N can leach. Coarse-textured sands and some muck soils arethe only soils where ammonium leach-ing may be significant.

One way to minimize N leaching anddenitrification is to minimize the timethe N is in the soil before plant uptake.This cuts down on the time when condi-tions are favorable for losses. Most ofthe N is needed by corn after the plantis 3 to 4 weeks old (June 1).

Surface volatilization of N occurswhen urea forms of N break down andform ammonia gases and where there islittle soil water to absorb them. Thiscondition occurs when urea forms of Nare placed in the field but not in directcontact with the soil. This situation canoccur when urea is spread on cornresidues or 28 percent is sprayed onheavy residues of cornstalk or covercrop.

7

Table 8.EFFECT OF N RATE AND TIME

OF APPLICATION ON CORNYIELD FOR AN IRRIGATED

MCBRIDE SANDY LOAM SOILIN MICHIGAN.1

Time of applicationN rate Preplant Sidedresslb N/acre ———-bu/acre———-

0 75 75120 149 155180 155 161240 157 167

1 Adapted from M.L. Vitosh. 1969-72 MontcalmFarm Research Reports.

The rate of surface volatilizationdepends on moisture level, temperatureand the surface pH of the soil. If the soilsurface is moist, the water evaporatesinto the air. Ammonia released from theurea is picked up in the water vapor andlost. On dry soil surfaces, less urea N islost. Temperatures greater than50 degrees F and a pH greater than 6.5significantly increase the rate of ureaconversion to ammonia gases. Applyingurea-type fertilizers when weather iscooler slows down N loss. If the surfaceof the soil has been limed within thepast three months with 2 tons or moreof limestone per acre, DO NOT applyurea-based fertilizers unless they can beincorporated into the soil.

To stop ammonia volatilization fromurea, the urea must be tied up by thesoil. To get the urea in direct contactwith the soil requires enough rain towash the urea from the residue or place-ment of urea-based fertilizer in directcontact with soil by tillage, banding ordribbling. If the residue is light (lessthan 30 percent cover), 0.25 to 0.5 inchof rain is enough to dissolve the ureaand wash it into the soil. If the residueis heavy (greater than 50 percent cover),0.5 inch or greater of rainfall is required.

Ammonia volatilization of N mayalso occur when ammonium forms of N— ammonium sulfate (AS), ammoniumnitrate (AN), diammonium phosphate(DAP), monoammonium phosphate(MAP) and ammonium polyphosphate(APP) — are surface applied to calcare-ous soils (soil pH greater than 7.5). Theextent of loss is related to the reaction

products formed when ammonium fer-tilizers react with calcium carbonate.Ammonium fertilizers that form insolu-ble precipitates (AS, DAP, MAP andAPP) are subject to greater ammoniavolatilization losses than AN, whichforms a soluble reaction product. To pre-vent ammonia volatilization, ammoniumfertilizers should be knifed in or incor-porated on calcareous soils.

SELECTING FORMS OFNITROGENFERTILIZER

The common N fertilizers are anhy-drous ammonia (82 percent N), urea (46percent N), solutions (28 to 32 percentN), ammonium sulfate (21 percent N)and ammonium nitrate (34 percent N).

Anhydrous ammonia (82 percent) isthe slowest of all N fertilizer forms toconvert to nitrate N. Therefore, it wouldhave the least chance of N loss due toleaching or denitrification. It must beinjected into the soil; therefore, it wouldhave no loss due to surface volatiliza-tion. The disadvantage of anhydrousammonia is that it is hazardous to han-dle. It must be injected into the soil, and on steep slopes erosion can be aproblem.

Urea (46 percent) converts to nitrateN fairly quickly, usually in less than twoweeks in the spring. Denitrification onwet or compacted soils can be serious.Leaching can be a problem in coarsesoils. In no-till situations, surfacevolatilization can be a problem if theurea is not placed in contact with the

soil and the weather is dry for severaldays after spreading.

UAN solutions (28 to 32 percent N)are usually made up of urea and ammo-nium nitrate. The nitrate in this productis subject to leaching and denitrificationfrom the time it is placed in the field.The urea components are subject to thesame loss mechanisms as urea. Nitrogensolutions can be banded on the soil sur-face easily by dribbling. This method ofapplication minimizes the amount thatsticks to the residue and, therefore, min-imizes surface volatilization but may noteliminate it.

Ammonium sulfate (21 percent) is anitrogen source with little or no surfacevolatilization loss when applied to mostsoils. Ammonium sulfate is a goodsource of sulfur when it is needed. Itsdisadvantage is that it is the most acidi-fying form of N fertilizer — it requiresapproximately 2 to 3 times as muchlime to neutralize the same amount ofacidity as formed by other common Ncarriers.

Ammonium nitrate (34 percent) is 50percent ammonium N and 50 percentnitrate N when added to the soil. Theammonium N quickly converts to nitrateN. For soils subject to leaching or deni-trification, ammonium nitrate would notbe preferred. Ammonium nitrate has nourea in it; therefore, it would be a goodchoice for surface application whereammonia volatilization is expected.

8

NITROGENRECOMMENDATIONSFOR CORN

The following N recommendations(Table 9) for corn assume the crop isplanted during the optimum plantingperiod on mineral soils with either goodnatural or improved drainage.

9

Table 9.NITROGEN RECOMMENDATIONS FOR CORN BASED ON YIELD POTENTIAL AND PREVIOUS CROP.

Previous crop Corn yield potential (bu per acre)

80 100 120 140 160 180+pounds N to apply per acre

Corn and most other crops 80 110 140 160 190 220Soybeans 50 80 110 130 160 190Grass sod 40 70 100 120 150 180Established forage legume1

Average stand (3 plants/sq ft) 0 10 40 60 90 120Good stand (5 plants/sq ft) 0 0 0 20 50 80

Annual legume cover crop2 50 80 110 130 160 1901Any legume established for more than one year.2Any legume or legume-grass mixture that has been established for less than one year. Nitrogen credit may be more or less (0 to 100 lb/acre), depending on plantspecies, stand, growing conditions and date of destruction.

ADDITIONAL COMMENTS

1. N fertilizer rates are based on the following relationship:

N (lb/acre) = -27 + (1.36 x yield potential) - N credit

or 110 + [1.36 x (yield potential - 100)] - N credit

N credits: Soybeans 30

Grass sod/pastures 40

Annual legume cover crop 30

Established forage legume 40 + 20 x (plants/ft2)to maximum of 140

Corn and most other crops 0

Organic waste Consult individual staterecommendations

2. For corn silage, assume 1 ton/acre is equivalent to 6 bu/acre of grain.

3. For inadequately drained soils with high denitrification potentials, N should be either:

• Applied in a split application.

• Applied as anhydrous ammonia with a nitrification inhibitor.

• Or concentrated in a band to minimize soil contact.

4. Corn grown on coarse-textured/low CEC soils with high leaching potentials may benefit from split or multiple N applications.

5. For soils with greater than 30 percent residue cover, the majority ofapplied N should be either:

• Injected below the soil surface.

• Dribbled in bands using N solutions.

• Or broadcast only if the material contains no urea (i.e., ammoniumnitrate or ammonium sulfate).

6. No-till corn, corn planted into cold, wet soils, corn following anhydrousammonia applied less than 2 weeks prior to planting, and corn follow-ing spring-tilled legumes or cover crops should receive some N atplanting, either:

• 20 to 40 lb N/acre banded near the row.

• Or 40 to 60 lb N/acre broadcast.

7. For organic soils with greater than 20 percent organic matter, adjustrates using a pre-sidedress N soil test (consult individual state recom-mendations) or reduce N rates by 40 lb/acre.

8. For fall applications (after October 20, well drained soils only) or earlyspring applications (before April 15) on wet soils, use only anhydrousammonia with a nitrification inhibitor. Fall applications of N are not rec-ommended on coarse-textured soils in the tri-state region. In addition,fall N is not recommended on any soil in Michigan and south of U.S. 40in Indiana.

9. If planting is delayed past the optimum planting period, reduce N rate toreflect loss of yield potential.

10. When soils are limed and the lime is not incorporated, surface applica-tion of urea forms of nitrogen fertilizer are not recommended within oneyear of the lime application. Ammonium nitrate, anhydrous ammonia,ammonium sulfate or injected 28 percent solutions are suitable materi-als for this case.

11. Incorporation of materials with a high carbon:nitrogen ratio, such assawdust and leaves, can cause a temporary shortage of N due to immo-bilization.

Tri-state phosphorus (P)and potassium (K) fertil-izer recommendations arebased on the nutrientneeds of the crop to be

grown and the quantity of those nutri-ents available in the soil as measured bya soil test. In the tri-state region, theBray P1 test is used to estimate P avail-ability and the 1 normal ammoniumacetate test is used to estimate K avail-ability. Tri-state recommendations aredesigned to provide adequate nutritionfor the crop, and to create or maintain asoil capable of providing sufficient nutri-ents without fertilizer addition for oneor more years. Thus, the tri-state recom-mendations utilize a buildup and main-tenance approach to fertilizer manage-ment.

The key to these recommendations isfield calibration and correlation studiesthat have been conducted over the past 40years. The conceptual model for these rec-ommendations is illustrated in Figure 1.The fundamental component of the modelis the establishment of a “critical level” —the soil test level above which the soil cansupply adequate quantities of a nutrient to

support optimum economic growth. Thecritical level is determined in the field andrepresents the results of hundreds of fieldexperiments. There are two important con-cepts to keep in mind. First, some cropsare more responsive to a nutrient than oth-ers, so the critical level can vary betweencrops. In the tri-state region, research hasshown that wheat and alfalfa are moreresponsive to P than corn or soybeans.Thus, the critical P level for wheat andalfalfa is higher than the critical level forcorn and soybeans. Second, the criticallevel can vary between soils. Recentresearch has shown that some soils, espe-cially high clay soils in Ohio, requirehigher K levels to support optimum crop

growth than other lower clay content soils.This information has been incorporatedinto the recommendations and is seen asan increase in critical level for K as thecation exchange capacity (CEC) increases.

When soil tests are below the criticallevel, the soil is not able to supply the Pand K requirements of the crop. The tri-state recommendations are designed tosupply additional nutrients and to raisethe soil test to the critical level over afour-year period. Soil tests below thecritical level should be considered asindicating a soil that is nutrient defi-cient for crop growth. For deficientsoils, recommended rates of fertilizer

should be applied annually.Placement techniques toenhance nutrient availability,such as banding or stripping,may also be beneficial onnutrient-deficient soils.Applying 25 to 50 percent ofthe recommended fertilizer ina band to enhance earlygrowth should be considered.

Above the critical soil testlevel, the soil is capable ofsupplying the nutrientsrequired by the crop and no

10

ADDITIONAL COMMENTS

1. Recommended N rate is based on the relationship:

N (lb/acre) = 40 + [1.75 x (yield potential - 50)]

2. No credits are given for the previous crop. Consultindividual state recommendations concerning creditsfor organic waste materials such as manure.

3. Apply 15 to 30 lb N/acre at planting and the remain-der near green-up in spring; or, apply all N at plantingas anhydrous ammonia plus a nitrification inhibitor,injected on 15-inch or narrower row spacing.

4. To prevent serious lodging on high organic mattersoils (greater than 20 percent organic matter), reducethe N rate by 30 to 50 lb N/acre.

PHOSPHORUS AND POTASSIUM

Critical Level Maintenance limit

Buildup range

Maintenance range

Drawdownrange

Fer

tiliz

er r

ate

Soil test level

Figure 1FERTILIZER RECOMMENDATION SCHEME

USED IN THE TRI-STATE REGION

Table 10. TOTAL NITROGEN

RECOMMENDATIONS FORWHEAT BASED ON YIELD

POTENTIAL.Yield potential Pounds N to apply

bu/acre lb N/acre

50 4070 7590+ 110

NITROGENRECOMMENDATIONSFOR WHEATThe following N recommendations forwheat (Table 10) assume that the cropis planted during the optimum plantingperiod on mineral soils with 1 to 5 per-cent organic matter and either goodnatural or improved drainage, and thatproper cultural practices are utilized.

Critical level Maintenance limit

response to fertilizer would be expected.The tri-state recommendations use amaintenance plateau concept to makerecommendations at or slightly abovethe critical level. The maintenanceplateau is designed to safeguard againstsampling or analytical variation.Recommendations for soil test values onthe maintenance plateau are designed toreplace the nutrients lost each yearthrough crop removal. Because the pur-pose of fertilizer applications in themaintenance plateau range is to main-tain fertility, no response to fertilizer inthe year of application would beexpected. Therefore, farmers maychoose to make multiple year applica-tions. No response to placement tech-niques such as banding or stripping orthe use of P and K starter fertilizerswould be expected in the maintenanceplateau region.

When soil test levels exceed themaintenance plateau level, the objectiveof the fertilizer recommendation is toutilize residual soil nutrients. Fertilizerrecommendations are rapidly reducedfrom maintenance levels to zero. There

is no agronomic reason to apply fertil-izer when soil tests are above the main-tenance plateau level.

Actual fertilizer recommendations arecalculated using one of three relation-ships — one applicable to buildup,another for maintenance and a third fordrawdown:

Tables 11 and 12 provide the criticalsoil test values and crop removal valuesused for calculating tri-state fertilizerrecommendations at various soil testlevels.

11

BUILDUP EQUATION

for P: lb P2O5/A to apply = [(CL - STL) x 5] + (YP x CR) for K: lb K2O/A to apply = [(CL - STL) x ((1 + (0.05 x CEC))] + (YP x CR) + 20

MAINTENANCE EQUATION

for P: lb P2O5/A to apply = YP x CRfor K: lb K2O/A to apply = (YP x CR) + 20 (for non-forage crops)

DRAWDOWN EQUATION

for P: lb P2O5/A to apply = (YP x CR) - [(YP x CR) x (STL - (CL + 15))/10]for K: lb K2O/A to apply = (YP x CR) + 20 - [((YP x CR) + 20) x (STL - (CL + 30))/20]

(for non-forage crops)

Note: The K maintenance and drawdown equation for forages, including corn silage, is:lb K2O/A to apply = [(YP x CR) + 20] - [((YP x CR) +20) x (STL - CL)/50]

where:CL = critical soil test level (ppm)STL = existing soil test level (ppm)YP = crop yield potential (bu per acre for grains, tons per acre for forages)CR = nutrient removed per unit yield (lb/unit)CEC = soil cation exchange capacity (meq/100g)

Table 12.NUTRIENTS REMOVED IN HARVESTED

PORTIONS OF AGRONOMIC CROPS.Crop Unit of yield Nutrient removed per unit of yield

P2O5 K2O

——— lb /unit———Corn

Feed grain bushel 0.37 0.27Silage ton 3.30 8.00

Soybeans bushel 0.80 1.40Wheat

Grain bushel 0.63 0.37Straw bushel 0.09 0.91

Alfalfa ton 13.00 50.00

Table 11.CRITICAL SOIL TEST LEVELS (CL) FOR VARIOUS AGRONOMIC CROPS.

Crop Critical soil test levelsP K at CEC1

5 10 20 30ppm (lb/acre) ————————— ppm (lb/acre)—————————

Corn 15 (30)2 88 (175) 100 (200) 125 (250) 150 (300)

Soybean 15 (30) 88 (175) 100 (200) 125 (250) 150 (300)

Wheat 25 (50) 88 (175) 100 (200) 125 (250) 150 (300)

Alfalfa 25 (50) 88 (175) 100 (200) 125 (250) 150 (300)

1 Critical level for ppm K = 75 + (2.5 x CEC) for all crops2 Values in parentheses are lb/acre.

Note:A CEC of 15 is used to calculate the K2O recommendation for calcareous soils (soils with pH equal toor greater than 7.5 and a calcium saturation of 80 percent or greater) and organic soils (soils with anorganic matter content of 20 percent or greater or having a scooped density of less than 0.8 gramsper cubic centimeter).

PHOSPHORUS ANDPOTASSIUMFERTILIZERPLACEMENT ANDTIMING

Most soil test report forms do notprovide information on how farmersshould apply their fertilizer. To be usedefficiently, P and K fertilizers should beapplied properly and at the appropriatetime. Because the choices of applicationdepend greatly on the fertilizer materialused and the equipment available, it isup to the farmer to see that the fertilizeris properly applied. When plants aresmall, soil test levels low, soil surfaceresidues high and soil temperaturescold, starter fertilizers become veryimportant for optimum plant growth.For well established crops such as foragelegumes, topdressing is the normal rec-ommended practice.

Starter FertilizersIn many instances, applying some or

all of the fertilizer needed with theplanting unit improves fertilizer effi-ciency. If starter fertilizer is used, apply20 to 40 lb of N, P2O5 and/or K2O peracre in a band 2 inches to the side and 2inches below the seed. The total amountof salts (N + K2O) should not exceed100 lb per acre for corn or 70 lb per acrefor 30-inch-row soybeans.

The amount of P2O5 added in theband is non-limiting except that most Pfertilizers are combined with N such asdiammonium phosphate (DAP),monoammonium phosphate (MAP) andammonium polyphosphate (APP). Whenthese fertilizers are used as a starter, donot band more than 40 lb N per acre oncorn and 20 lb N per acre on 30-inch-row soybeans. Nitrogen and P are themost important major nutrients for early

plant growth, particularly in no-till pro-duction systems. On high P testing soils(greater than 30 ppm P), N is the mostimportant nutrient for corn and shouldnot be omitted from the starter in highresidue no-till systems unless at least 40to 60 lb N per acre has been broadcastapplied prior to emergence. It is not nec-essary to include K in the starter fertil-izer unless the soil test K levels are verylow (less than 75 ppm K).

For drilled soybeans, wheat and for-age legumes, it is unlikely that any Pcan be banded beside and below theseed at planting time because most newdrills do not have fertilizer attachments.In this situation, all nutrients should bebroadcast before planting. Only onextremely low P testing soils (less than10 ppm P) will this create any signifi-cant P deficiency problems.

Fertilizer with the SeedThe general practice of applying fer-

tilizer in contact with seed is not recom-mended. Band placement to the sideand below the seed is usually superiorto any other placement. Some farmers,however, have grain drills or plantersthat place fertilizer in contact with theseed. In this case, caution should beused to prevent seed or seedling injuryfrom fertilizer salts. For corn, do notplace more than 5 lb N +K2O per acrein contact with the seed on low CECsoils (CEC less than 7) and no morethan 8 lb N + K2O per acre when theCEC is greater than 8. Soybean seed isvery sensitive to salt injury; conse-quently, all fertilizer for drilled soybeansshould be broadcast before planting. Forsmall grain seedings, do not drill morethan 100 lb of plant nutrients (N + P2O5

+ K2O) per acre in contact with theseed. Do not apply more than 40 lb Nper acre as urea in contact with small

grain seed. Young germinating seeds andseedlings are very sensitive to saltinjury. Dry weather will accentuate theinjury.

When seeding forage legumes, do notplace more than 100 lb P2O5 and 50 lbK2O per acre in contact with the seed. Ifthe fertilizer is placed 1 to 11⁄2 inchesbelow the seed, the seeding time fertil-izer may include all of the P and up to150 lb K2O per acre. Broadcast andincorporate any additional fertilizerrequirements before seeding. For estab-lished legumes, all fertilizer require-ments should be topdressed in the fallbefore plants go dormant (approxi-mately October 1) or after the first cut-ting in the spring.

12

13

Table 13.PHOSPHATE (P2O5) RECOMMENDATIONS

FOR CORN.Yield potential — bu per acre

100 120 140 160 180

———lb P2O5 per acre——-

85603520

0

957045200

1007550250

110856030

0

1159065350

05 (10)1

10 (20)15-30 (30-60)2

35 (70)40 (80)

Soil test

ppm (lb/acre)

1 Values in parentheses are lb/acre.2 Maintenance recommendations are given for this soil test range.

TABLES 13-17 PROVIDE ACTUAL P2O5 FERTILIZER RATE RECOMMENDATIONSDERIVED FROM THE EQUATIONS GIVEN ON PAGE 11.

Phosphorus Recommendations

Table 16.PHOSPHATE (P2O5) RECOMMENDATIONS

FOR WHEAT.Yield potential — bu per acre

50 60 70 80 90

———lb P2O5 per acre——-

805530150

906540200

957045200

1007550250

1058055300

15 (30)1

20 (40)25-40 (50-80)2

45 (90)50 (100)

Soil test

ppm (lb/acre)

1 Values in parentheses are lb/acre.2 Maintenance recommendations are given for this soil test range.

Table 17.PHOSPHATE (P2O5) RECOMMENDATIONS

FOR ALFALFA.Yield potential — tons per acre

5 6 7 8 9

———lb P2O5 per acre——-

1159065350

13010580400

14011590450

155130105500

165140115600

15 (30)1

20 (40)25-40 (50-80)2

45 (90)50 (100)

Soil test

ppm (lb/acre)

1 Values in parentheses are lb/acre.2 Maintenance recommendations are given for this soil test range.

Table 14.PHOSPHATE (P2O5) RECOMMENDATIONS

FOR CORN SILAGE.Yield potential — tons per acre

20 22 24 26 28

———lb P2O5 per acre——-

1159065350

12510075400

13010580400

13511085450

14011590450

05 (10)1

10 (20)15-30 (30-60)2

35 (70)40 (80)

Soil test

ppm (lb/acre)

1 Values in parentheses are lb/acre.2 Maintenance recommendations are given for this soil test range.

Table 15.PHOSPHATE (P2O5) RECOMMENDATIONS

FOR SOYBEANS.Yield potential — bu per acre

30 40 50 60 70

———lb P2O5 per acre——-

755025100

805530150

906540250

1007550250

1058055300

05 (10)1

10 (20)15-30 (30-60)2

35 (70)40 (80)

Soil test

ppm (lb/acre)

1 Values in parentheses are lb/acre.2 Maintenance recommendations are given for this soil test range.

14

TABLES 18-22 PROVIDE ACTUAL K2O FERTILIZER RATE RECOMMENDATIONSDERIVED FROM THE EQUATIONS GIVEN ON PAGE 11.

Potassium Recommendations

Table 18.POTASH (K2O) RECOMMENDATIONS FOR CORN

AT VARIOUS YIELD POTENTIALS, CATIONEXCHANGE CAPACITIES (CEC’S)

AND SOIL TEST LEVELS.

bu/ acre 100 120 140 160 180

—————lb K2O per acre————

CEC ——————5 meq/100g——————12595654520

0

1301007050200

135105756020

0

1401108065250

145115857025

0

025 (50)1

050 (100)075 (150)

0088-118 (175-235)2

130 (260)140 (280)

CEC —————10 meq/100g—————160120854525

0

1651259050250

170135

9560300

17514010065300

180145105

70350

025 (50)050 (100)075 (150)

0100-130 (200-260)2

140 (280)150 (300)

CEC —————20 meq/100g—————195145954525

0

20015010050250

210160110

60300

21516511565350

220170120

70350

050 (100)075 (150)100 (200)

0125-155 (250-310)2

165 (330)175 (350)

CEC —————303 meq/100g—————235170110

45250

24017511550250

245185120

60300

2501901256530

0

25519513070350

075 (150)100 (200)125 (250)

0150-180 (300-360)2

190 (380)200 (400)

Yield potential

Soil test K

1 Values in parentheses are lb/acre. 2 Maintenance recommendations are given for this soil test range.3 For Michigan, do not use CEC’s greater than 20 meq/100g.

ppm (lb/acre)

Table 19.POTASH (K2O) RECOMMENDATIONS FOR

SOYBEANS AT VARIOUS YIELD POTENTIALS,CATION EXCHANGE CAPACITIES (CEC’S)

AND SOIL TEST LEVELS.

bu/ acre 30 40 50 60 70

——————lb K2O per acre—————

CEC ——————5 meq/100g——————140110806025

0

1551259075300

1701351059035

0

180150120105400

19516513512045

0

025 (50)1

050 (100)075 (150)

0 88-118 (175-235)2

130 (260)140 (280)

CEC —————10 meq/100g—————1751351006030

0

19015011575400

2051651309045

0

215180140105500

23019515512060

0

025 (50)00050 (100)075 (150)

0100-130 (200-260)2

140 (280)150 (300)

CEC —————20 meq/100g—————2101601106030

0

22517512575400

2401901409045

0

255205155105500

27022017012060

0

050 (100)075 (150)100 (200)

0125-155 (250-310)2

165 (330)175 (350)

CEC —————303 meq/100g—————250185125

60300

26520014075400

280215155

90450

29023016510550

0

300245180120600

075 (150)100 (200)125 (250)

0150-180 (300-360)2

190 (380)200 (400)

Yield potential

Soil test K

1 Values in parentheses are lb/acre. 2 Maintenance recommendations are given for this soil test range.3 For Michigan, do not use CEC’s greater than 20 meq/100g.

ppm (lb/acre)

15

Table 20.POTASH (K2O) RECOMMENDATIONS FORWHEAT AT VARIOUS YIELD POTENTIALS,CATION EXCHANGE CAPACITIES (CEC’S)

AND SOIL TEST LEVELS.

bu/ acre 50 60 70 80 90

—————lb K2O per acre—————

CEC ——————5 meq/100g—————11585554015

0

120906040150

12595604515

0

130956550200

130100705520

0

CEC —————10 meq/100g—————150115754020

0

1551158040200

160120854525

0

1601258550250

165130905525

0

025 (50)050 (100)075 (150)

0100-130 (200-260)2

140 (280)150 (300)

CEC —————20 meq/100g—————190140904020

0

1901409040200

195145954525

0

20015010050250

2051551055525

0

050 (100)075 (150)100 (200)

0125-155 (250-310)2

165 (330)175 (350)

CEC —————303 meq/100g—————22516510040200

230165105

40200

235170110

45250

235175110

50250

240180115

55300

075 (150)100 (200)125 (250)

0150-180 (300-360)2

190 (380)200 (400)

Yield potential

Soil test K

1 Values in parentheses are lb/acre. 2 Maintenance recommendations are given for this soil test range.3 For Michigan, do not use CEC’s greater than 20 meq/100g.

ppm (lb/acre)

Table 21.POTASH (K2O) RECOMMENDATIONS FOR CORN

SILAGE AT VARIOUS YIELD POTENTIALS,CATION EXCHANGE CAPACITIES (CEC’S)

AND SOIL TEST LEVELS.

tons/ acre 20 22 24 26 28

—————lb K2O per acre3—————

CEC ——————5 meq/100g—————26022519518010025

0

275245210195110300

29026023021011530

0

300275245230125350

30029026024513535

0

CEC —————10 meq/100g—————29525522018011035

0

300270235195120400

30028525021012540

0

300300265230135450

30030028024514550

0

025 (50)050 (100)075 (150)

0100 (200)2

120 (240)140 (280)150 (300)

CEC —————20 meq/100g—————30028023018011035

0

300295245195120400

30030026021012540

0

300300280230135450

30030029524514550

0

050 (100)075 (150)100 (200)

0125 (250)2

145 (290)165 (330)175 (350)

CEC —————304 meq/100g—————300300245180110350

300300260195120

400

300300275210125

400

300300290230135

450

300300300245145

500

075 (150)100 (200)125 (250)

0150 (300)2

170 (340)190 (380)200 (400)

Yield potential

Soil test K

1 Values in parentheses are lb/acre. 2 Maintenance recommendations are given for this soil test level.3 Potash recommendations should not exceed 300 lb per acre.4 For Michigan, do not use CEC’s greater than 20 meq/100g.

ppm (lb/acre)

025 (50)1

050 (100)075 (150)0088 (175)2

110 (220)130 (260)140 (280)

025 (50)1

050 (100)075 (150)

0 88-118 (175-235)2

130 (260)140 (280)

16

Table 22.POTASH (K2O) RECOMMENDATIONS FORALFALFA AT VARIOUS YIELD POTENTIALS,CATION EXCHANGE CAPACITIES (CEC’S)

AND SOIL TEST LEVELS.

tons/ acre 5 6 7 8 9

—————lb K2O per acre3—————

CEC ——————5 meq/100g—————30030028527015040

0

300300300300175500

30030030030020555

0

300300300300230650

30030030030026070

0

025 (50)1

050 (100)075 (150)088 (175)2

110 (220)130 (260)140 (280)

CEC —————10 meq/100g—————30030030027016055

0

300300300300190650

30030030030022075

0

300300300300250850

30030030030028095

0

025 (50)050 (100)075 (150)100 (200)2

120 (240)140 (280)150 (300)

CEC —————20 meq/100g—————30030030027016055

0

300300300300190650

30030030030022075

0

300300300300250850

30030030030028095

0

050 (100)075 (150)100 (200)125 (250)2

145 (290)165 (330)175 (350)

CEC —————304meq/100g—————300300300270160550

300300300300190

650

300300300300220

750

300300300300250

850

300300300300280

950

075 (150)100 (200)125 (250)150 (300)2

170 (340)190 (380)200 (400)

Yield potential

Soil test K

ppm (lb/acre)

1 Values in parentheses are lb/acre. 2 Maintenance recommendations are given for this soil test level.3 Potash recommendations should not exceed 300 lb per acre.4 For Michigan, do not use CEC’s greater than 20 meq/100g.

17

Calcium (Ca), magnesium(Mg) and sulfur (S) are thethree secondary nutrientsrequired by plants. They areless likely to be added as

fertilizer than the macronutrients (N-P-K). Most soils in Indiana, Michiganand Ohio will adequately supply thesenutrients for plant growth. The standardsoil test measures the relative availabil-ity of Ca and Mg in soils. There is noaccurate soil test for S at this time. Aplant analysis is the best diagnostic toolfor confirming S availability.

If the exchangeable Ca level is inexcess of 200 ppm, no response to Ca isexpected. If the soil pH is maintained inthe proper range, then the added Cafrom lime will maintain an adequatelevel for crop production.

The required soil exchangeable Mglevel is 50 ppm or greater. Low levels ofMg are commonly found in eastern Ohioand southern Indiana and on acid sandysoils in Michigan. High levels of

exchangeable K tend to reduce theuptake of Mg. Therefore, if the ratio ofMg to K, as a percent of the exchange-able bases, is less than 2 to 1, then Mgis recommended for forage crops. MostMg deficiencies can be corrected bymaintaining proper soil pH using limehigh in Mg. The ratio of Ca to Mgshould be considered when lime isadded to a soil. If the ratio, as a percentof the exchangeable bases, is 1 to 1 orless (less Ca than Mg), a highcalcium/low magnesium limestoneshould be used. Most plants grow wellover a wide range of Ca to Mg soilratios.

Excessive use of K fertilizers cangreatly reduce the uptake of Ca and Mg.High K/low Mg forages can cause grasstetany, milk fever, hypocalcemia andother health problems for ruminant ani-mals. For these reasons, the tri-state Krecommendations for alfalfa and cornsilage do not follow the maintenanceplateau concept above the critical K soiltest level. Potassium recommendations

above the critical level are less than cropremoval so as to discourage luxury con-sumption of K and improve Mg uptake.

Sulfur is taken up as sulfate byplants. Sulfate sulfur is supplied primar-ily by microbial decomposition of soilorganic matter. Sulfate is a negative ionand easily leaches in soils. Most soils inIndiana, Michigan and Ohio will ade-quately supply needed sulfur for plantgrowth. Sandy soils low in organic mat-ter that are subject to excessive leachingmay not supply adequate sulfur. Cropssuch as wheat and alfalfa that growrapidly at cool temperatures when min-eralization of S is slow are most likely tobe S deficient. If elemental sulfur isused, it should be applied at least 2months before the crop is planted. Thiswould allow time for the S to be con-verted to the plant-available sulfate formby the soil bacteria. Sulfur should beadded in the sulfate form if added lessthan 2 months before plant uptake.

SECONDARY NUTRIENTS

MICRONUTRIENTS

Micronutrients arerequired by plants insmall amounts. Thoseessential for plantgrowth are boron (B),

chloride (Cl), copper (Cu), iron (Fe),manganese (Mn), molybdenum (Mo)and zinc (Zn).

Most soils in Michigan, Indiana andOhio contain adequate quantities ofmicronutrients. Field crop deficiencies ofCl, Mo and Fe have not been observedin this region of the United States. Somesoils, however, may be deficient in B,Cu, Mn and Zn, and deficiencies can

Sandy soils or highlyweathered soils low inorganic matterAcid peats or mucks with pH < 5.3 and black sandsPeats and mucks with pH > 5.8, black sands andlakebed/depressional soilswith pH > 6.2Peats, mucks and mineralsoils with pH > 6.5Acid prairie soils

Alfalfa and clover

Wheat, oats, corn

Soybeans, wheat, oats,sugar beets, corn

Corn and soybeans

Soybeans

Table 23.CROP AND SOIL CONDITIONS UNDER WHICHMICRONUTRIENT DEFICIENCIES MAY OCCUR.

Boron (B)

Copper (Cu)

Manganese (Mn)

Zinc (Zn)

Molybdenum (Mo)

Micronutrient Soil Crop

18

cause plant abnormalities, reducedgrowth and even yield loss. Whencalled for, micronutrient fertilizersshould be used judiciously and withcare. Some micronutrient fertilizers canbe toxic if added to sensitive crops orapplied in excessive amounts. Table 23lists the soil and crop conditions underwhich micronutrient deficiencies aremost likely to occur.

DIAGNOSINGMICRONUTRIENTDEFICIENCIES

Both soil testing and plant analysiscan be useful in diagnosing micronutri-ent deficiencies. Soil testing formicronutrients has become a widelyaccepted practice in recent years.Micronutrient soil tests, however, arenot as reliable as tests for soil acidity(pH) or for phosphorus (P) and potas-sium (K). For this reason, plant analy-sis is also very important in diagnosingmicronutrient deficiencies. Combiningplant analysis with soil tests providesmore accurate assessment of themicronutrient status of crops and soils.

Plant analysis can be used in twoways. One is to monitor the crop’smicronutrient status; the other is todiagnose a problem situation. By moni-toring, plant analysis can point out anexisting or potential problem beforevisual symptoms develop. Table 24 is aguide to interpreting the adequacy ofprimary, secondary and micronutrientsin specific plant tissues sampled at thesuggested times. These sufficiencyranges should not be used when otherplant parts are sampled or when sam-ples are taken at different times.

If you suspect a nutrient deficiencyproblem, don’t wait for the suggestedsampling time to get a plant analysis.

Collect plant samples from both prob-lem and normal-appearing plants. Takewhole plants if the plants are small;take leaf samples if the plants are large.Corresponding soil samples should alsobe taken from each area to help con-firm the deficiency.

MICRONUTRIENTPLACEMENT ANDAVAILABILITY

Table 23 lists the soil and crop con-ditions under which micronutrient defi-ciencies are most likely to occur. Whenthese conditions exist and soil or planttissue analysis confirms a need,micronutrient fertilizers should be soilor foliar applied. Micronutrientsbanded with starter fertilizers at plant-ing time are usually more effective overa longer period of growth than foliar-applied micronutrients. Most soil-

applied micronutrients, with the excep-tion of boron for alfalfa and clover,should be banded with the starter fer-tilizer for efficient uptake. Boron appli-cations for alfalfa and clover should bebroadcast with other fertilizers orsprayed on the soil surface. Broadcastapplications of 5 to 10 lb Zn per acremay be used to alleviate Zn-deficientsoils. Broadcast applications of Mn,however, are not recommendedbecause of high soil fixation. Residualcarryover of available Mn in deficientsoils is very limited. Therefore, Mn fer-tilizers should be applied every year onthese soils. Foliar-applied micronutri-ents are more frequently used whendeficiency symptoms are present orsuspected and when banded soil appli-cations are not practical.

Soil acidification with sulfur or alu-minum sulfate to improve micronutri-ent uptake is usually not practical on

NitrogenPhosphorusPotassiumCalcium

MagnesiumSulfur

2.90-3.500.30-0.501.91-2.500.21-1.000.16-0.600.16-0.50

4.25-5.500.30-0.502.01-2.500.36-2.000.26-1.000.21-0.40

3.76-5.500.26-0.702.01-3.501.76-3.000.31-1.000.31-0.50

2.59-4.000.21-0.501.51-3.000.21-1.000.16-1.000.21-0.40

ManganeseIron

BoronCopper

ZincMolybdenum

20-15021-2504-256-2020-70

—

21-10051-35021-5510-3021-501.0-5.0

31-10031-25031-8011-3021-701.0-5.0

16-20011-3006-406-5021-70

—

Table 24.NUTRIENT SUFFICIENCY RANGES FOR

CORN, SOYBEANS, ALFALFA AND WHEAT.Element Corn

Ear leafsampled atinitial silking

SoybeansUpper fully

developed leafsampled prior toinitial flowering

AlfalfaTop 6 inches

sampled prior toinitial flowering

WheatUpper leaves

sampled prior toinitial bloom

———————————Percent (%)—————————————

——–——————Parts per million (ppm)————–——————

large fields. Some starter fertilizers areacid-forming and may improve theuptake of both applied and native soilforms of micronutrients when deficien-cies are slight. When micronutrient defi-ciencies are moderate or severe, starterfertilizers alone will not overcome thedeficiency.

SELECTINGMICRONUTRIENTSOURCES

The three main classes of micronutri-ent sources are inorganic, syntheticchelates and natural organic complexes.Inorganic sources consist of oxides, car-bonates and metallic salts such as sul-fates, chlorides and nitrates. Sulfates ofCu, Mn and Zn are the most commonmetallic salts used in the fertilizer indus-try because of their high water solubilityand plant availability. Oxides of Zn arerelatively water insoluble and thus mustbe finely ground to be effective in soils.Broadcast applications of Zn oxidesshould be applied at least 4 monthsbefore planting to be effective. Oxysul-fates are oxides that are partially acidu-lated with sulfuric acid. Studies haveshown granular Zn oxysulfates to beabout 35 to 50 percent water-solubleand immediately available to plants.Metal-ammonia complexes such asammoniated Zn sulfate are also used bythe fertilizer industry. Such complexesappear to decompose in soils and pro-vide good agronomic effectiveness.

Chelates can be synthetic (manufac-tured) or natural organic decompositionproducts such as organic acids andamino acids, but they all contain knownchemical bonds that increase micronutri-ent solubility. Synthetic chelates usuallyhave higher stability than naturalchelates. Chelates such as Zn-EDTA are

more stable in soils than Zn citrate orZn-ammonia complexes and thus aremore effective in correcting Zn defi-ciency.

Natural organic micronutrient com-plexes are often produced by reactingmetal inorganic salts with organicbyproducts, mainly those of the woodpulp industry. Lignosulfonates, phenolsand polyflavonoids are common naturalorganic complexes. These complexes areoften quite variable in their compositionand are less effective than the syntheticchelates.

Selecting a micronutrient sourcerequires consideration of many factors,such as compatibility with N-P-K fertiliz-ers, convenience in application, agro-nomic effectiveness and cost per unit ofmicronutrient.

Table 25 lists several commonly usedmicronutrient fertilizer sources. Theinorganic sulfates are generally preferredto oxide forms of micronutrients whenblending with N-P-K fertilizers becauseof their greater water solubility andgreater effectiveness. Zinc and Mn

oxides, however, are acceptable sourcesof micronutrients when finely ground.Finely ground materials may presentsegregation problems when used withgranular fertilizers, so the use of a fertil-izer sticker is highly recommended. ZincEDTA, a synthetic chelate, has beenfound to be more effective than Zn sul-fate in Michigan and Ohio field trialsand may be used at one-fifth the rate ofZn sulfate. Natural organic chelates andcomplexes such as Zn citrate or Zn lig-nosulfonate are considered less effectivethan true (100 percent) synthetic che-lates and should be used at the samerate as inorganic sources. Chelated Mnreactions in soil are quite different fromchelated Zn reactions. Manganese che-lates, when applied to soil, are usuallyineffective because of high levels ofavailable Fe in our soils (Fe replaces theMn in soil-applied Mn chelates). There-fore, they are unacceptable sources ofMn when soil applied. Foliar applica-tions of Zn chelates are effective sourcesand should be used at their labeledrates.

19

Boron (B)

Copper (Cu)

Manganese (Mn)

Zinc (Zn)

Table 25.MICRONUTRIENT SOURCES COMMONLY USED FOR CORRECTING

MICRONUTRIENT DEFICIENCIES IN PLANTS.Micronutrient Common fertilizer sources

Sodium tetraborate (14 to 20% B)Solubor® (20% B)Liquid boron (10%)

Copper sulfate (13 to 35% Cu)Copper oxide1 (75 to 89% Cu)

Manganese sulfate (23 to 28% Mn)Manganese oxysulfates (variable % Mn)

Zinc sulfate (23 to 36% Zn)Zinc-ammonia complex (10% Zn)Zinc oxysulfates (variable % Zn)Zinc oxide1 (50 to 80% Zn)Zinc chelate (9 to 14% Zn)

® Registered trade name of U.S. Borax.1 Granular oxides are not effective sources of micronutrients.

MICRONUTRIENTRECOMMENDATIONS

Tables 26-29 give recommended ratesof soil-applied inorganic sources ofmicronutrients based on soil type, soiltest and pH. These rates are recom-mended only for the responsive cropslisted in Table 23. The micronutrient soiltests recommended for use in Michigan,Ohio and Indiana are 0.1 N HCl for Mnand Zn and 1.0 N HCl for Cu using a 1to 10 soil-to-extractant ratio. Micronutri-ent availability in both mineral andorganic soils is highly regulated by soilpH. The higher the soil pH, the higherthe soil test should be before a defi-ciency is eliminated. The higher the soilpH and the lower the soil test, the moremicronutrient fertilizer is needed to cor-rect a deficiency. Copper deficiency inMichigan, Ohio and Indiana has beenobserved only on black sands andorganic soils. Because of the extremeMn and Cu deficiency problems andoften excess N mineralization in organicsoils, wheat and oat plantings are notrecommended on these soils.

Boron recommendations for Michi-gan, Ohio and Indiana are not based onany soil test — they are based on soiltype and the responsiveness of the crop.Boron is recommended annually at arate of 1 to 2 pounds per acre broadcastapplied on established alfalfa and clovergrown on sandy soils. Boron applica-tions on fine-textured high clay soilshave not proven to be beneficial.

Molybdenum deficiency of soybeanshas been found on certain acid soils inIndiana and Ohio. Most molybdenumdeficiencies can be corrected by limingsoils to the proper soil pH range. Therecommended molybdenum fertilizationprocedure is to use 1⁄2 ounce of sodiummolybdate per bushel of seed as a

20

Table 26.MANGANESE FERTILIZER RECOMMENDATIONS FORRESPONSIVE CROPS GROWN ON MINERAL SOILS.1

Soiltest Mn2

Soil pH

6.3 6.5 6.7 6.9 7.1 7.3 7.5+

ppm ————————- lb Mn per acre3 —————————-248

12162024

2200000

6543000

5430000

4320000

7754200

9865420

10986542

1 Recommendations are for band applications of soluble inorganic Mn sources with acid-formingfertilizers. Broadcast applications of Mn fertilizer are not recommended.

2 0.1 N HCl extractable Mn3 Recommendations are calculated from the following equation and rounded to the nearest pound:

XMn = -36 + 6.2 x pH - 0.35 x STWhere XMn = lb Mn per acre

pH = soil pHST = ppm Mn soil test

Table 27.MANGANESE FERTILIZER RECOMMENDATIONS FORRESPONSIVE CROPS GROWN ON ORGANIC SOILS.1

Soiltest Mn2

Soil pH

5.8 6.0 6.2 6.4 6.6 6.8 7.0+

ppm ————————- lb Mn per acre2 —————————-248

12162024283236

2100000000

4310000000

5532100000

7654310000

9876432100

101087654210

1211109865431

1 Recommendations are for band applications of soluble inorganic Mn sources with acid-formingfertilizers. Broadcast applications of Mn fertilizer are not recommended.

2 0.1 N HCl extractable Mn3 Recommendations are calculated from the following equation and rounded to the nearest pound:

XMn = -46 + 8.38 x pH - 0.31 x STWhere XMn = lb Mn per acre

pH = soil pHST = ppm Mn soil test

planter box treatment or 2 ounces ofsodium molybdate per acre in 30 gallonsof water as a foliar spray. Extreme careshould be used when applying molybde-num because 10 ppm of Mo in foragemay be toxic to ruminant animals.

Table 30 gives foliar micronutrientrecommendations for responsive cropslisted in Table 23. Foliar rates of sug-gested sources should be based on thesize of the plant — use higher rates forlarger plants and lower rates withsmaller plants. Use 20 to 30 gallons ofwater for sufficient coverage of thefoliage to ensure good uptake of themicronutrient. When foliar sprays ofchelates are used, follow the labeled rate— using too much can cause foliarinjury and reduced uptake. At reducedrates, chelate foliar sprays are usuallyless effective than the suggested inor-ganic sources.

21

Table 28.ZINC FERTILIZER RECOMMENDATIONS FORRESPONSIVE CROPS GROWN ON MINERAL

AND ORGANIC SOILS.1

Table 29.COPPER RECOMMENDATIONS FOR CORN

GROWN ON ORGANIC SOILS.1

Table 30.COMMON MICRONUTRIENT FERTILIZER SOURCES AND SUGGESTED

RATES FOR FOLIAR APPLICATION.1

Soiltest Zn2

Soil test Cu2Soil pH

6.6 6.8 7.0 7.2 7.4 7.6+

ppm ————————- lb Zn per acre3 —————————-12468

1012

1000000

2100000

3211000

4322100

5433210

6544321

1 Recommendations are for band applications of soluble inorganic Zn sources.Synthetic Zn chelates may be used at one-fifth this rate. For broadcast applications,use 5 to 10 lb Zn/acre.

2 0.1 N HCl extractable Zn3 Recommendations are calculated from the following equation and rounded to the

nearest pound:XZn = -32 + 5.0 x pH - 0.4 x ST

Where XZn = lb Zn per acrepH = soil pHST = ppm Zn soil test

Copper recommendation

ppm lb Cu per acre3

443210

1 Recommendations are for band applications of soluble inorganicCu sources. For broadcast applications, use 5 to 10 lb Cu/acre.

2 1.0 N HCl extractable Cu3 Recommendations are calculated from the following equation

and rounded to the nearest pound:XCu = 6.3 - 0.3 x ST

Where XCu = lb Cu per acreST = ppm Cu soil test

Boron (B)

Copper (Cu)

Manganese (Mn)

Zinc (Zn)

Molybdate (Mo)

0.1-0.3

0.5-1.0

1.0-2.0

0.3-0.7

0.01-0.07

Sodium borate (20 %B)Boric acid (17%B)

Copper sulfate (13 to 25% Cu)

Manganese sulfate (28% Mn)

Zinc sulfate (36% Zn)

Ammonium molybdate (49%)Sodium molybdate (46%)

Micronutrient lb of element per acre Common fertilizersources

1 Use sufficient water (20 to 30 gallons) to get good coverage of foliage.

1114181216120+

Michigan State University is an Affirmative Action/EqualOpportunity Institution. Extension programs and materi-als are open to all without regard to race, color, nationalorigin, sex, disability, age or religion.

Issued in furtherance of MSU Extension work in agricul-ture and home economics, acts of May 8 and June 30,

1914, in cooperation with the U.S. Department of Agriculture. Gail L. Imig, extensiondirector, Michigan State University, East Lansing, MI 48824-1039.

All information in these materials is for educational purposes only. References to com-mercial products or trade names does not imply endorsement by the MSU Extensionor bias against those not mentioned. This bulletin becomes public property upon pub-lication and may be printed verbatim with credit to MSU. Reprinting cannot be used toendorse or advertise a commercial product or company.

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