Corn Producion Technology

8/8/2019 Corn Producion Technology

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CornProduction

Handbook

Kansas State University

Agricultural Experiment Station

And Cooperative Extension Service


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Nutrient Management Photos

Photo 1. Nitrogen deficiency (left) through nitrogen

sufficiency (right).

Photo 2. Nitrogen sufficient (left) nitrogen deficient (right).

Photo 3. Early season phosphorus deficiency. Photo 4. Late-season phosphorus response.

Photo 5. Potassium deficiency. Photo 6. Potassium deficiency.

Photo 7. Iron deficiency. Photo 8. Iron deficiency.


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Insect Management Photos

Photo 9. Armyworm larva. Photo 10. Black cutworm larva.

Photo 11. Black cutworm damage. Photo 12. Chinch bugs.

Photo 13. Corn earworm larva.

Photo 15. Corn rootworm damage.

Photo 16. Goose-

necked corn from

corn rootworm injury

Photo 14. Corn rootworm beetle.


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Photo 24. Southwestern corn borer larva.

Photo 18. Fall armyworm larva.

Photo 19. Flea beetle. Photo 20. Differential grasshopper.

Photo 21. Maize billbug. Photo 22. Seed corn maggot.

Photo 23. Southwestern corn borer eggs.

Insect Management Photos

Photo 17. European corn borer eggs.


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Growth and Development StewartDuncan,NortheastAreaExtensionAgronomist,CropsandSoils DaleFjell,NortheastAreaExtensionDirector RichardVanderlip,ResearchAgronomist,CropProduction(Emeritus) 3____________________________________________________________________________________________________________

Select Hybrids Careully KraigRoozeboom,ExtensionSpecialist,CropProduction/CroppingSystems DaleFjell,NortheastAreaExtensionDirector 7____________________________________________________________________________________________________________

Optimum Planting Practices KraigRoozeboom,ExtensionSpecialist,CropProduction/CroppingSystems DanDevlin,ExtensionSpecialist,EnvironmentalQuality StewartDuncan,NortheastAreaExtensionAgronomist,CropsandSoils KeithJanssen,Research/ExtensionSpecialist,SoilManagementandConservationSpecialist BrianOlson,NorthwestAreaExtensionAgronomist,CropsandSoils CurtisThompson,SouthwestAreaExtensionAgronomist,CropsandSoils 10____________________________________________________________________________________________________________

Nutrient Management DaleLeikam,ExtensionSpecialist,NutrientManagement DavidMengel,Professor,SoilFertilityandNutrientManagement 14____________________________________________________________________________________________________________

Weed Management DavidRegehr,ExtensionSpecialist,WeedScience BrianOlson,NorthwestAreaExtensionAgronomist,CropsandSoils CurtisThompson,SouthwestAreaExtensionAgronomist,CropsandSoils 21____________________________________________________________________________________________________________

Insect Management JeffWhitworth,ExtensionSpecialist,Entomology

PhillipSloderbeck,ExtensionSpecialist,Entomology 23

____________________________________________________________________________________________________________Major Corn Diseases DougJardine,ExtensionSpecialist,PlantPathology 25____________________________________________________________________________________________________________

Irrigation DannyRogers,ExtensionSpecialist,Irrigation 30____________________________________________________________________________________________________________

Harvesting Suggestions RandyPrice,ExtensionSpecialist,FarmMachinery 36____________________________________________________________________________________________________________

Drying and Storing JoeHarner,ExtensionSpecialist,GrainandLivestockSystems PhillipSloderbeck,ExtensionSpecialist,Entomology 38

____________________________________________________________________________________________________________

Proit Prospects MichaelLangemeier,Professor,AgriculturalEconomist 42

Contents


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Growth and Development

That corn crop that youre planning to harvest next all,or the one you are reviewing to try to understand why yields

were less or greater than expected, started when the seed wasplanted and ended when the ear was successully harvested.

Beore planting, considerable planning and preparationgoes into corn production. The crop you hope to produce isdependent on the genetic and environmental characteristics in

which the plant was grown.I we understand how the corn plant grows, develops, and

produces grain, we have a better chance o knowing what willaect plant growth and consequently how to manage the cropor best production. Consider the age o the corn in termso plant development rather than in days. With inormationregarding speciic production practices, the other sections othis publication will be more easily understood.

Lets start with the seed. Corn seed is made up o three

primary parts (Figure ): the embryo rom which the newplant will develop; the endosperm or starchy part, the energysource or germination and emergence until the plant canunction on its own; and the pericarp, or seed coat, whichprotects both the endosperm and the embryo. We want tostart with seed that has a viable embryo, that contains sui-cient stored energy to get the plant established, and that hasan intact seed coat to prevent attack by disease organisms.

Generally, seed is planted in soil moist and warm (mid-5degrees Fahrenheit or higher) enough to allow rapid germina-tion and emergence. With increased adoption o no-tillageand reduced tillage arming, planting dates are earlier, on

average, than 2 years ago. The practice o planting earlyallows or more intensiied and potentially proitable crop-ping systems. As a result o planting early, however, corn seedis oten planted into very cool soils where the 2-inch depthtemperature is oten closer to the minimally acceptable (orgermination) 5 degrees Fahrenheit than the optimum mid-5 degrees Fahrenheit or greater. This results in an extendedtime period to achieve emergence. Regardless o planting

date, an average o 25 growing degree days are required oremergence (Table ). Growing degree days are calculatedby subtracting 5 degrees Fahrenheit rom the average dailytemperature, then adding the daily growing degree days over

time. The planting to emergence growing degree days shouldbe calculated rom soil temperatures at seed depth.Depth o planting inluences the amount o growth

necessary beore the seedling can emerge rom the soil suraceand aect the time required rom planting to emergence.Changes in planting depth aect the depth at which the seed(seminal) roots develop, but has little aect on the depth at

which the permanent (nodal) root system develops. Eventhough the seed roots anchor the plant and absorb water andnutrients or the irst 2 to weeks, the young plant is livingon reserves rom the kernel until the nodal roots develop romthe crown and take over.

When the collar o the irst lea (the round tipped, orthumb lea) emerges and is visible above ground, the plantis at stage V. At that time, the seminal roots quit growing,and the nodal root system begins development. Until tasselingthe growth stage o the plant is designated by the number oleaves with visible collars. Although six or seven leaves maybe visible on the corn plant when the collar o the ourthlea is visible, the plant has only developed to stage V4. Fromstages V to V, each new lea will ully emerge or every85 growing degree days. From V until inal lea emergencerequires about 5 growing degree days per ully emerged lea.

During the irst 4 to 5 weeks ater emergence, the plant

continually develops new leaves rom the growing point,which is below or at ground level or most o this period. Atotal o approximately 2 leaves will be developed. Duringthis time, root and lea development progress rapidly. Nutrientuptake also is occurring rapidly. Since the growing point is stillbelow the soil surace, a rost or hail may destroy the exposedlea area, but likely would not kill the plant. This could be

Pericarp

Embryo

Endosperm

Figure 1. The primary parts of a corn seed. Table 1. Approximate Growing Degree Days (GDD)required for a mid-season maturity corn hybrid to reachdifferent growth stages from the time of planting1.

Stage GDD

VE - Emergence 25

V - Tassel initiation 475

VT - Tassel emergence ,5

Silking ,4

R4 - Dough stage ,925

R5 - Dent stage 2,45

R - Physiological maturity or black-layer 2,71AdaptedfromR.G.Hoeft,etal.2000.ModernCornandSoybeanProduction.Page8.


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particularly important when determining whether or not toreplant ollowing a late-spring rost or hail storm.

At stage V5 to V, or about 475 growing degree days, allo the leaves the plant will produce have been started and thegrowing point dierentiates into the tassel (Table ). Earsare initiated shortly ater the tassel. By growth stage V, thenodal roots have become the main root system o the plant.

Within a ew days o tassel initiation, the stalk grows rapidlyand the growing point is elevated above the soil surace whereany damage could aect the growing point and kill the plant.During the ollowing 4 to 5 weeks, rapid growth occurs

with the remaining leaves increasing in size and orming theactory that produces the grain during the latter portion othe growth cycle.

During this period o rapid stalk growth, plant heightincreases dramatically, culminating in the emergence o thedeveloping tassel (,5 growing degree days - Table ) rom the

whorl. The tassel continues developing until pollination occurs.Rapid root development and nutrient uptake also occur duringthis stage. At tasseling, less than hal o the inal weight o the

corn plant has been developed. However, more than percento the nitrogen, 5 percent o the phosphorus, and 8 percento the potassium have already accumulated in the plant. Thegrain producing capability o the plant is determined during thisparticularly important time period.

During the lowering process, stress conditions have moreeect on the timing o silk emergence than they have ontassel development and pollen shed. Under hot, dry stressulconditions, the tassel may develop and shed pollen beore theear and silk ormation has been completed resulting in pooror incomplete pollination. Silks will grow slowly and ail toemerge in time to be pollinated as well as being too dry to

support pollen germination and the complete growth o thepollen tube. One day o moisture stress (Figure 2) within aweek ater silking (,4 growing degree days - Table ) canresult in up to 8 percent yield losses. A period o to 4 days osevere moisture stress at this time can easily reduce inal grain

yields by percent. The pollination process begins at the baseo the ear and progresses to the tip. By looking at pollination

problems on various ear sections/zones, the timing o pollina-tion problems can be determined, and in many cases the eventthat led to the poor timing is clearly identiied.

The inal stage o growth o the corn plant is one thatresults in grain production. Beginning at pollination, essen-tially all o the carbohydrates produced by the plant go intothe developing kernels. The amount o production that occursis determined by ) the potential set during the early stages odevelopment; 2) the size o the actory that developed duringthe middle portion o the growth o the plant; and ) theproduction o the plant during the inal stage o the growthcycle. Drought or nutrient deiciencies during this period willresult in unilled kernels and light, chay ears.

Approximately 5 to days ater pollination (2,7growing degree days - Table ) most corn hybrids will reachphysiological maturity or black-layer. The grain illingprocess ends and the dry weight o the grain no longerincreases. This does not mean that the grain is at a moisturecontent suitable or harvest. Physiological maturity occursin the 25 to 5 percent moisture range, depending on hybrid

and environmental conditions. Ater black-layer, grain dryingis entirely a matter o moisture loss. I you can use or markethigh-moisture grain, or you want to harvest early and dry thegrain, harvest can occur any time ater black-layer without anyreduction in total dry weight o grain harvested.

I you consider eects o various management practiceson each o the three major periods o corn plant development,

you will be able to see how these practices can aect the yieldo your corn crop. Similarly, i some unexpected problem arisesand you can relate this problem to the normal growth anddevelopment o the corn plant, you will have a better under-standing o how this might aect your inal yields.

Use o Growing Degree Unitsin Corn Production

For years, corn maturity has been labeled in days. A 2day variety would presumedly reach maturity 2 days aterplanting. This system does not take into account complicatedphysiological processes that control growth and development

o corn. The number o days required to reachmaturity depends on location and date oplanting, and the weather to which the plantis subjected in a particular growing season. Inmost years, the growing season will be more orless than 2 days. The decision as to whichhybrid to plant to attain maximum productionbased on maturity can be diicult. A delayedplanting might not provide the requirednumber o days or the selected hybrid to ullymature. Or, the selected hybrid may be at acritical developmental stage(s) during periodso environmental and/or climatic extremes.Early planting dates should allow your selectedhybrid to reach maturity with time to spare,

9

8

7

65

4

3

2

1

0%Y

ieldLossperDayStress

50

80

90

110

120

100

70

60

140

130

Days After Planting

Silking

Average yield loss

per day of stress

Range of measured

yield loss from stress

Figure 2. Corn yield loss due to one day of moisture stress.


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but again, i the plants are stressed during key reproductivestages yields may be devastated.

Each day does not contribute equally to the growth oplants. Growth is aster during the warm season than in cold

weather. On the other hand, summer temperatures can betoo high or optimum growth. Although actors other thantemperature enter into determining rate o growth, seedproducers use the temperature based growing degree daysconcept to express hybrid maturity. Over the years, manyheat-unit systems have been devised. The one currently inuse or corn was proposed by the Environmental Data Serviceo the National Oceanic and Atmospheric Administration(ormerly U.S. Weather Bureau).

In this system, 5 degrees Fahrenheit is the base tempera-ture. Growing degree days are calculated by subtracting thebase rom the average daily air temperature. Corn grows verylittle at temperatures below 5 degrees Fahrenheit. Untilthe leaves emerge rom the soil, use o the average daily soiltemperature at seed depth rather than air temperatures isrecommended to more accurately calculate growing degree

days. As the temperature rises, corn grows aster i moisture,and nutrients, are plentiul. However, at air temperatureshigher than 8 degrees Fahrenheit, plant roots have greaterdiiculty taking in water ast enough to keep the plantgrowing at ull speed. Growing degree days are calculated bythe ollowing equation:

GDD =Max Temp. + Min Temp.

5 F2

Minimum temperatures below 5 degrees Fahrenheit arecounted as 5 degrees Fahrenheit and temperatures above8 degrees Fahrenheit are counted as 8 degrees Fahrenheit

(Table 2).The average growing degree days accumulation beginning

on March or our sites are shown in Figure . Use the accu-mulations to understand how growing degree days can be usedto help plan your corn operation. Notice that the accumulationrate is very slow early in the season, then increases rapidly andinally slows down again near the end o the growing season.

This variable rate o accumulation is what makes maturityexpressed in days inconsistent. Planting week early mayresult in corn reaching maturity only day earlier.

The three curves in Figure represent the growingconditions throughout the state. Colby represents the highelevations in northwest Kansas that have a relatively shortgrowing season. The Garden City-Horton curve represents

the broad mid-range o conditions in the state. Interestingly,a northern station at a low elevation (Horton) has about thesame conditions or promoting growth as a southern stationat a higher elevation (Garden City). Elevation and latitudecombine to determine the length o the Kansas growingseason. Independence data represents the area o southeastKansas that has a relatively long growing season. Periods osummer heat are more critical or corn production in this areathan the chances o an early reeze.

Suppose you are considering selecting one o the twohybrids rated by the seed supplier as shown in Figure .Further, lets assume that soil temperatures will warm to avor-able planting levels at about 4 growing degree days aterMarch . By ollowing the Planting Date line, we can deter-mine the average date at each location when this will occur.Naturally, southeast Kansas (April 22) will reach the pointsooner than at Garden City (May ) or at Colby (May 7).

I you are able to plant when 4 growing degree dayshave accumulated, the seed supplier predicts that the earlyhybrid will silk ater ,9 additional growing degree dayshave accumulated (,79 total growing degree days). Theuller season hybrid will not silk until a ,9 total growingdegree days have accumulated. The silking stage is crucial or

Table 2. GDD accumulations calculated for selected highand low daily temperatures.

Daily Temperature, Degrees F

Minimum Maximum GDD

4 7 5

48 7 5

52 78 5

59 85 22

2 88 24

2 98 24

GDUs Required to Reach:

Early Season Variety

Full Season Variety

Silking Maturity

1,390 2,610

2,8301,560

4,000

3,500

3,000

2,500

500

1,000

1,500

2,000

Mar AugJulyJuneMayApr OctSept

Maturity (full)

Maturity (early)

Silking (full)

Silking (early)

Planting

Independence

Colby

Garden Cityand Horton

End of SeasonFigure 3.


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the production o high corn yields. You can reduce the risk oyour corn reaching silking at the time when moisture and hightemperature stress are most likely. Corn producers in your area,especially dryland growers, should pay particular attentionto select a hybrid rating and planting date that will it yourenvironment.

I we add the predicted number o growing degree daysneeded to reach maturity to our assumed planting dateaccumulation o 4 growing degree days, we can predict thetime when the crop will be ready or harvest. Earlier planting

dates, earlier maturing hybrids and the use ostarter ertilizer have all contributed to cropphysiological maturity and harvest being wellahead o the prospects o an early reeze, unlessplanting is abnormally delayed. In our example,however, the end o season mark on each curveindicates the date days prior to the average2 degrees Fahrenheit reeze date. Note thatneither hybrid utilizes the entire growingseason in southeastern Kansas. Perhaps youmight want to try a hybrid that requires almost, growing degree days to reach maturity.Remember however, mid-season hot spells aectpollination. In northwestern Kansas, and in

west central Kansas, ull season corn that has arequirement o 2,8 or more growing degreedays may not reach maturity beore a killingreeze. The early season hybrid certainly looks to

be more promising in this area.The example given above assumes a normal year, and

planting on schedule. What i your planting is delayed week,or even 2 weeks? Your decision will depend on your location,but you might want to change corn hybrids. Another actorto consider is that the curve represents normal (or average)conditions. As everyone knows, such conditions dont otenexist. These curves can still be useul i they are shited to

C he ye nn e R aw li ns D ec at ur Norton P hi ll ip s S mi th J ew el l R ep ub li c Was hi ng to n M ar sh al l N em ah a Br ow n

DO

Atchison

JacksonPottawatomieRileyClay

CloudMitchellOsborne

Dickinson Geary

Morris

Lyon

Wabaunsee

Ottawa

RooksGrahamSheridanThomasSherman

Wallace Logan Gove Trego E ll is R us se llLincoln

Saline

Ellsworth

BartonRushNessLaneScottWichitaGreeley

Hamilton Kearny Finney

Gray

HodgemanPawnee

Edwards

Stafford

Rice

Reno

McPherson MarionChase

Harvey

Butler

Shawnee

Jeerson LV

WY

Douglas Johnson

MiamiFranklin

Osage

LinnAnderso nCoffey

Bourbon

Crawford

Cherokee

Allen

Neosho

Labette

Wilson

Montgomery

WoodsonGreenwood

Sedgwick

Elk

Chautauqua

CowleySumner

Kingman

Harper

Pratt

Barber

Kiowa

Comanche

Ford

ClarkMeadeSeward

HaskellGrant

StevensMorton

Stanton

5 5 10 10 10 15

20

25

25

25

252025252525 20

20

15

10

Figure 4. Average date of first 32 degree Fahrenheit freeze in fall. All datesare in October

Table 3. Growing degree units from this date to end of season

11-April 18-April 25-April 2-May 9-May 18-May 23-May End o

Season*

Ashland ,82 ,747 , ,57 ,47 ,59 ,24 Oct. 4

Belleville ,4 ,4 , ,254 ,8 ,8 2,959 Oct.

Burr Oak ,24 ,9 , ,57 2,958 2,8 2,75 Sept. Colby 2,98 2,94 2,872 2,88 2,7 2,5 2,5 Sept. 28

Elkhart ,554 ,48 ,99 , ,25 , , Oct. 8

Emporia , ,599 ,57 ,42 ,5 ,22 ,7 Oct.

Garden City ,42 ,5 ,279 ,2 ,5 ,2 2,98 Oct. 7

Hays ,87 , ,259 ,8 , ,8 2,95 Oct. 5

Horton ,45 ,95 , ,2 ,4 ,4 2,9 Oct.

Hutchinson ,794 ,729 ,48 ,54 ,48 ,4 ,247 Oct.

Independence 4, ,955 ,8 ,7 ,55 ,542 ,4 Oct. 7

Iola ,94 ,892 ,799 ,72 ,595 ,482 ,54 Oct. 5

Larned ,7 ,7 ,58 ,498 ,42 ,297 ,82 Oct.

Leoti , ,77 ,9 2,98 2,855 2,7 2,7 Oct.

Manhattan ,5 ,59 ,57 ,42 ,2 ,25 ,98 Oct. 7McPherson ,794 ,728 ,44 ,559 ,4 ,58 ,24 Oct. 2

Medicine Lodge 4, ,99 ,844 ,747 ,7 ,52 ,97 Oct. 7

Minneapolis ,72 ,5 ,582 ,495 ,4 ,29 ,7 Oct. 8

Ottawa ,754 ,88 ,4 ,54 ,44 ,5 ,85 Oct. 2

Quinter ,74 ,2 ,57 2,99 2,94 2,8 2,7 Oct.

St. Francis ,55 2,994 2,924 2,85 2,79 2,8 2,58 Sept. 25

Syracuse ,57 ,28 ,2 ,8 ,2 2,92 2,8 Oct.

Tribune 2,984 2,92 2,857 2,78 2,75 2,7 2,525 Sept.

Wineld 4,72 ,992 ,895 ,79 ,85 ,57 ,44 Oct.

*Endofseasondateisdefinedas10daysbeforetheaveragedateoffirst32-degreeFahrenheitfreezeinfall.Thereisa20percentchancethatafreezewilloccurbeforethisdate.


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it the actual conditions on a particular date. For example,Figure shows that between March and May 27, ,growing degree days accumulation at Independence is normal.

What i the spring is cool and growing degree days doesntreach , until June 7? I you assume normal conditions therest o the year by shiting the curve so that the , growingdegree days level is reached on June 7, you will again have aprediction o the growth and development o your corn cropor that particular year.

Table lists the number o growing degree days that willbe available on average or various planting dates or a numbero Kansas locations. We assume that the growing season ends days prior to the average date o the irst reeze in the all.

The probability that a reeze will occur beore that date is only

one in ive or 2 percent. Figure 4 shows the average date othe irst 2 degrees Fahrenheit reeze across Kansas.

I you plant corn in the Tribune area on May 2, you canexpect to have a seasonal total o 2,78 growing degree daysor your crop. You should select a hybrid that has a require-ment less than this. Keep in mind that the number o growingdegree days will vary rom year to year. The totals will be

within 5 growing degree days above or below the valueslisted in Table in 7 percent o the years.

The growing degree days rating placed on corn hybridsby seed producers can give you a great deal o insight into thegrowth and development o your crop. Getting amiliar with, andusing the growing degree days system will be worth your eort.

Hybrid SelectionHybrid Development and Marketing

Private irms market nearly all hybrid seed sold to cornproducers. Some o the larger companies have highly trainedbreeders and actively develop unique inbred parent lines.Many other irms use inbreds released by public institutionsand/or parent lines and crosses provided by private seedproduction specialists. As a result, the same or very similarhybrids may be marketed by several companies.

During the past decade, a number o novel traits havebeen incorporated into hybrids. Some o these traits wereintroduced using traditional plant breeding methods. Others

were transerred rom other species using genetic transorma-tion techniques. Currently, the most important o these novel

traits are related to insect resistance and herbicide tolerance.Most seed companies have suites o these traits available aloneor stacked in various combinations in a range o geneticbackgrounds. Be aware o potential market restrictions associ-ated with some traits.

Few, i any, public institutions actively develop hybridsor public use, but several have research programs that urnishindustry with basic research inormation, diverse gene sources,and improved inbred lines. Public scientists oten have skillsand resources unavailable to private irms, while industry canproduce and market quality seed in a much more eicientmanner than public agencies. Intense market competition

ensures the steady introduction o improved hybrids developedby the combined eorts o private and public scientists.

Importance o Choosingan Appropriate Hybrid

Choosing an appropriate hybrid is essential or successulcorn production. University hybrid tests oten have a yieldspread o 25 to bushels per acre between the top-yieldinghybrids and the test average. Poorly adapted hybrids may yield5 or more bushels per acre less than the best hybrids. Eachield has unique limitations (soil ertility, moisture intake and

storage capacity, slope, insect and disease potentials, etc.),and each manager has unique inancial, labor, and equip-

ment resources available to address these limitations. Otherproduction decisions also play a role in determining whatkind o hybrid is needed. For example, an early maturinghybrid may give disappointing yields under ull irrigation,heavy ertilization, and a long growing season. Conversely, aull-season hybrid may not do well on a nonirrigated site withlower potential ertility that tends to run out o soil moisturein August. The corn producers challenge is to choose hybridsappropriate or each management situation, keeping in mindrisks associated with potential weather extremes.

Inormation SourcesPersonal experience with a hybrid is the inal test osuccess; however, narrowing the list o available hybrids tothose best suited or your unique situation requires sitingthrough a large amount o inormation. Corn producersshould use all available inormation when selecting hybrids.Seed companies oten do a good job o characterizing theirhybrids, especially in comparison with other hybrids in theirproduct line. Company strip tests can be powerul when directcomparisons are made over a large number o tests.

University perormance tests provide the opportunityor a large number o direct comparisons between hybrids

rom a wide range o companies at a number o locationsacross the state. K-State Research and Extension publishesan annual Report o Progress including detailed results rommore than 2 Kansas Corn Perormance Tests conducted atseveral sites. The same inormation is available electronicallyat http://kscroptests.agron.ksu.edu. Oten, test results are postedon line within a ew days o harvest. Seed companies partici-pate voluntarily on a cost-sharing basis by paying a ee oreach hybrid entered in each test. The program has evaluatedseveral thousand dierent hybrids since its inception in 99.

Tests do not include all hybrids grown in the state and do notinclude the same set o hybrids at all test sites because entrants


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choose where to enter their hybrids. However, test resultscontaining current-year summaries and multi-year averagescan provide considerable guidance toward wise hybrid choices.

Hybrid Responseto Changing Environments

Corn production in Kansas encompasses a wide range oenvironmental conditions. A strong rainall gradient exists gener-

ally east to west across the state. Soil texture varies rom heavyclays to loose sands. Soil depth changes dramatically rom onearea to another. Length o growing season generally decreasesrom south to north and east to west due to latitude and elevationchanges. Cropping system actors such as irrigation, tillage, croprotation, and ertility regimes come into play as well.

Analysis o corn yields over multiple locations and manyyears reveals that the greatest underlying reason or observedyield dierences is location (soils, ertility, weather, manage-ment). In other words, changing environmental and/ormanagement conditions rom location to location have thelargest eect on corn yields compared to the eect o year

(precipitation and temperature patterns) or hybrid (geneticdierences). However, i the data are sorted into sets o loca-tions representing similar environments (e.g. eastern dryland,

western dryland, irrigated, etc.), year oten becomes the largestsource o yield dierences. Yield dierences due to hybridare generally much smaller than those due to either locationor year. Additionally, hybrid yield dierences usually change

with changing environmental and management conditions.This is reerred to as hybrid by environment interaction. Somehybrids respond dramatically to changing environmentalconditions; others are more stable. Obviously, selecting hybridsin a situation where location and year have such a large impact

on hybrid perormance is a challenge.The most important strategy to help overcome this chal-

lenge is to use results rom more than one year and more thanone location. Results rom a single location in a single yearrelect how those hybrids perormed under that particular seto conditions. There is no guarantee that conditions will besimilar in uture years or at other locations. However, i a hybridis tested at several locations over multiple years, one can havea better idea o how it responds to changing environmentalconditions and under what conditions it perorms best.

When examining results rom multiple locations, useresults rom test locations similar to your situation. It is notnecessary or the tests to be in your immediate geographic areaas long as the management and climatic actors are similar.

The KansasCornPerformanceTest reports contain tables andgraphs summarizing inormation rom sets o tests relectingthe various corn growing regions o Kansas.

Unortunately, the rate o hybrid turnover on the marketand in perormance tests has accelerated in recent years,reducing the availability o multi-year test results. In 99,roughly hal o the hybrids submitted to the K-State peror-mance tests were new entries. In 2, 75 percent were newentries; only 25 percent had been tested in previous years. With

so ew hybrids tested in more than one year, it becomes diicultto accumulate the inormation needed to make inormed selec-tion decisions. This rapid turnover underscores the need orannual examination o hybrid perormance at several locations.

Traits o InterestYield and Lodging All other things being equal, a

corn producer wants the highest yielding hybrids available.Lodging can severely decrease yields under certain conditions.I so, high yielding hybrids with superior stalk quality understress conditions are most desirable.

Maturity Choosing the appropriate maturity oreach situation is undamental to choosing the right hybrids.Relative maturity is rather clearly deined and predictablebased on either private company or experiment station inor-mation. Problems may arise when comparing similar hybridsrom dierent companies using their maturity ratings becausethe industry has no standardized maturity reporting system.State trials are a good source o inormation on relativematurity by reporting silking dates and harvest moisture or al

entries in a given test. Once you choose the desired maturity early, midseason, or ull-season (or your area) you cansort among hybrids within that class or other characteristicsthat it the intended purpose.

A hybrid attains physiological maturity when dry matterstops accumulating in the grain (somewhere between the 25percent and 5 percent grain moisture levels). Sae storagerequires urther drying. To lower the risk o experiencing sotcorn and yield reduction problems when using ull-seasonhybrids, choose those that reach physiological maturity at least or 2 weeks beore the average date o the irst killing rost in

your area.

Deciding which maturity class to plant depends on anumber o actors unique to each ield. With avorable mois-ture, temperatures, and ertility, ull-season hybrids generallyproduce the highest yields. However, early and midseasonhybrids may be a wise choice i some o the production actorsare limiting, or example on non-irrigated, upland sites withpoor water-holding capacity. Many mid-maturity hybridshave excellent yield potential under avorable conditions. Earlymaturing hybrids are useul or later plantings, or ields that

you wish to all-pasture or till beore winter, or or other specialsituations. Early maturing corn may be an alternative to grainsorghum or other crops on somewhat marginal land i it can

be planted early, i it can set and ill seed beore late summerheat and drought stress become severe, and i the producer is

willing to assume a slightly greater risk. Harvesting these plant-ings promptly will minimize lodging losses. Plant populationsshould be adjusted to match the requirements o each hybrid.Early hybrids oten perorm better when planted at popula-tions higher than those normally used or ull-season hybrids.Planting several maturities over a several-week period providesinsurance against severe weather losses, and i done careully,spreads harvest over a longer period.


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Other Characteristics Many other characters maybe important hybrid selection criteria, e.g., insect and diseaseresistance, tolerance to herbicides and drought, quick-dryingears, low ear-dropping tendency, and tendency to tiller orhave more than one ear per stalk. Be aware o particularhybrid sensitivities to certain classes o pesticides. Severalevents incorporating insect resistance genes rom Bacillusthuringiensis have greatly increased the options availableor producers acing problems with a range o insect pests.An array o herbicide tolerance traits provides options ormanaging particular weeds or cropping systems. See the InsectManagementandWeedManagementsections o this handbookor additional inormation on these traits. Seed companyrepresentatives can usually provide accurate inormationon these characters, and state yield trials occasionally revealdierential hybrid responses to some pest or stress.

Commercial hybrids normally are well-screened beorereaching state tests, and are generally well adapted to Kansas,including the heat and occasional drought experienced indryland systems. Examination o relative hybrid perormance

in tests subjected to stress conditions provides the best indica-tion o adaptability to such situations. The threat o poor seedset because o prolonged high temperatures and low humidi-ties killing pollen is real, but, ortunately, rare in Kansas.Drought and heat will sometimes disrupt lowering so that allpollen has developed and disappeared by the time silks appear.

Relationships o Yield with Other TraitsCorrelation analysis can reveal associations between

yield and other traits o interest in corn hybrids. Correlationso yield with measures o maturity (days to silk and harvestmoisture) and other traits rom corn perormance test results

over the past 2 years reveal some interesting patterns: In dryland tests in eastern Kansas, higher yield tended to

be associated with later maturity in years with avorableprecipitation patterns. The opposite tended to be true in

years when moisture was more limiting. In dryland tests in northwestern and west central Kansas,

higher yield was associated with early maturity more otenthan with late maturity.

In irrigated tests, higher yield usually was associated withlater maturity. The exception was or irrigated tests innorthwest Kansas where later maturity was oten associated

with lower yield.

Yield maturity relationships were not entirely consistent.Oten, there was no detectable association o yield withhybrid maturity.

High yields requently were associated with low grainprotein and oil levels, but not exclusively. Occasionally,high yields were associated with high protein and oil levels.Other research has shown that adequate ertilization canovercome the dilution eect observed with high yields.

Lodging was not always associated with lower yields.Lodging is notoriously variable and can result rom high

winds or other actors not related to hybrid characteristics.

In some years at some locations, a very strong relationshipbetween high yields and high lodging were observed. Inother years and locations, just the opposite was observed.Obviously one must use lodging inormation careully.

Unusual Types Yellow dent corn or eed grainproduction is the predominant type grown in Kansas, butsome white corn acreage is planted each year. White corn isgrown primarily or sale to industry or human ood purposes,but can be ed satisactorily to livestock i supplemented withVitamin A. The primary reason or interest in white corn isthe potential or adding value to corn production.

Several actors, including relatively small demand and widelyluctuating supply due to weather and acreage extremes, resultin considerable instability in price and proits rom white cornproduction. A substantial premium or white over yellow cornin one season may stimulate excess production in the ollowing

year, resulting in no premium or even a discount or white grainthat year. Yield-adjusted price premiums were close to $. perbushel in 22 according to a report prepared or the Agricultural

Marketing Resource Center. This is similar to the premiums inthe mid 99s, but down rom the peak o $.45 per bushel in998. July, 2 cash grain prices in northeast Kansas exhibitedup to a $.25 per bushel premium or white corn.

Historically, commercial, white hybrids were similar to,but oten later-maturing, slower-drying, lower yielding, andless stress-tolerant than the yellow endosperm types. Plantbreeders and geneticists have expended much less breedingeort on white corn than on yellow corn. However, white corn

yields have increased in recent years, reaching 98 to 99 percento yellow corn yields in recent years according to a reportpublished by the Agricultural Marketing and Resource Center

Forage A good proportion o the yellow corn grownin Kansas is used or silage. Successul silage hybrids also areheavy grain producers but can be somewhat later maturingthan those grown solely or grain. Yield and maturity datarom Kansas Corn Perormance Test results provide a goodsource o inormation or choosing silage hybrids, even thoughno orage yields are available.

Checklist or Choosing Hybrids Look or improved hybrids or each management situation

on your arm. This could potentially make you more moneythan anything else you could be doing.

Try to avoid settling on one brand or one avorite seedcompany representative or several years. You may bemissing something.

Take the trouble to learn or write down the good hybridnumbers that come to your attention. Follow up byobtaining as much inormation on each hybrid rom asmany sources as possible. Never select a hybrid based onsingle-year, single-location results.

Try several promising hybrids on a small scale each yearand keep harvest records or each.


14/52

Optimum Planting PracticesSeedbed Preparation and Planting Practices

Corn kernels need a soil that is warm, moist, well suppliedwith air, and ine enough to give good contact between seedand soil or rapid germination. A number o dierent tillageand planting systems can be used to produce corn. These

systems may involve primary and/or secondary tillage, or nopreplant tillage operations. An ideal seedbed should accom-plish the ollowing: control weeds, conserve moisture, preserve or improve tilth, protect water quality, control wind and water erosion, and be suitable or planting with your equipment.

One goal o seedbed preparation is to provide a meanso proitable corn production, while minimizing soil erosion

due to wind and water. Tillage and planting systems thataccomplish this goal are oten described as conservation tillagesystems. These systems, reerred to as no-till, reduced-till,mulch-till, ridge-till, or strip-till have been rapidly adoptedby Kansas armers. Corn acres planted no-till have increasedrom less than 5 percent o the planted acres in 99 to almost percent o the planted acres by 24 (Figure 5). Otherconservation tillage systems have declined in recent years,although estimates o strip-till acres are not available and maybe included in the conventional-till values. Conservation-tillage systems have advantages over ull tillage in that theyminimize adverse impacts on water quality; conserve soilmoisture; reduce soil erosion; and reduce labor and energyrequirements.

In conservation tillage, the soil surace is protected romthe erosive eects o wind, rain, and lowing

water. Resistance to these erosive agents isachieved either by protecting the soil surace

with crop residue or growing plants, or byincreasing the surace roughness or soil perme-ability. Water erosion losses or dierent tillagesystems are shown in Table 4.

A common goal o conservation tillage

systems is to reduce soil erosion losses belowsoil loss tolerance or T value. Soil loss toler-ance is an estimate o the maximum annual rateo soil erosion that can occur without aectingcrop productivity over a sustained period. Soilloss tolerances or Kansas cropland are normallyin the range o 4 to 5 tons per acre per year.Soil loss tolerances or speciic soil mappingunits can be ound in soil surveys or romUSDA Natural Resources Conservation Servicepersonnel.

The amount o residue necessary or erosion protectiondepends on several actors such as climatic conditions andpatterns, soil erodibility, surace roughness, ield length, lengthand steepness o slope, cropping practices, and other conserva-tion practices. A rule o thumb is to leave percent residue

cover on the soil surace ater planting where water erosionis the primary concern. Relatively lat ields can be protectedagainst water erosion with as little as 5 to 2 percent residuecover. Fields with steeper or longer slopes may requirehigher amounts o surace residue. Where wind erosion isa concern, , pounds per acre o lat small grain residueor its equivalent (roughly pounds per acre o -inchstanding wheat stubble, ,7 pounds o standing sorghumstubble, or , pounds o lat corn stalks) is required on thesoil surace during the critical wind erosion period. Standingstubble provides the added beneit o capturing snow duringthe winter months. In certain situations, conservation tillage

alone may not adequately protect the soil surace rom erosionlosses. In those situations, conservation tillage can be inte-grated with other conservation practices, such as terracing,contouring, strip cropping, or windbreaks to provide necessaryprotection.

Long-term research in Kansas has shown that corn can begrown successully in conservation tillage systems (Table 5).Careul management and planning are important. Uniormresidue distribution, eective weed control, proper seed place-ment, correct planter adjustment, soil testing, and ertilizermanagement are all important in conservation tillage cornproduction.

Many producers trying no-till corn or the irst time do soollowing a soybean crop in central and eastern Kansas. Fewerplanting problems are encountered in this sequence because

0%

5%

10%

15%

20%

25%

30%

35%

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

No-Till

Ridge-Till

Mulch-Till

Reduced-Till

Conv-TillPercentofKansascorn

acres

Figure 5. Percent of corn acres in various tillage systems in Kansas. FromCTIC Crop Residue Management Survey; 1999, 2001, and 2003 interpolated.


15/52

soybeans produce less residue than other crops, the residueis easily managed, and the soil is generally loose and mellow.Soybeans typically produce 45 pounds o residue per bushel ograin, whereas corn, grain sorghum, and wheat produce , ,and pounds o residue per bushel o grain, respectively.

No-till corn planting is best suited to soils that aremoderate to well-drained. Soils oten remain cooler and

wetter throughout the growing season under no-till condi-tions. This is particularly true in heavy residue conditions.

While wetter soils are an advantage during dry periods, atplanting time it can mean later planting, slower seed germina-tion, delayed maturity, and a longer period when seeds aresusceptible to pests. These conditions can result in reduced

yields in no-till situations, particularly in cool, wet springs, andon poorly drained soils. For example in Table 5, no-till yieldsare equal to or greater than those with more tillage on manysoils, but are less on the poorly drained Parsons and Woodsonsilt loams. Under these conditions, other conservation tillage

systems, such as strip-till, reduced-till, or ridge-till might bebetter choices.

Strip-till provides some o the beneits and avoids some othe problems o both conventional and no-till systems. Tillingan 8- to -inch strip in either the all or spring providesa avorable early season environment or corn growth anddevelopment. With less residue over the row, the soil can dry

and warm more quickly in the typically cool, wet conditionso early spring. In years o experiments in north centralKansas with wheat residue, soil temperature was consistently4 to degrees Fahrenheit warmer in strip-tilled rows than inno-till rows. Early season crop growth, nutrient uptake, and

yield were greater or corn in strip-till than or corn in no-till. Residue preserved on the soil service in the untilled areabetween the rows conserves soil moisture and protects the soilrom wind and water erosion.

As with no-till, strip-till does not it every situation.Research conducted over years at seven locations in eastcentral and southeast Kansas indicated that roughly 5

Table 4. Soil losses for various tillage systems in soybean, corn, and wheat residue.

Corn Residue1 Soybean Residue1 Wheat Residue2

Tillage SystemCover

%Soil Loss

tons/aCover

%Soil Loss

tons/aCover

%Soil Loss

tons/a

Plow, disk, disk, plant 4 . 2 4. -- --

Chisel, disk, plant 8. 7 9. -- --

Disk, disk, plant -- -- 5 4. -- --

Disk, plant 5 . 9 . -- --

Plow, harrow, rod-weed drill -- -- -- -- 9 4.2

Blade (x), rod-weed, drill -- -- -- -- 29 .2No-till plant or drill 9 .2 27 5. 8 .21Siltyclayloam,5percentslope,twoinchesappliedwaterat2.5inches/hour.2Siltloam,4percentslope,threeinchesappliedwaterat2.5inches/hour.(DatafromE.C.Dickey,UniversityofNebraska-Lincoln).

Table 5. Yields of corn grown under various tillage systems. Yield (bu/a)

Location(Soil type) Rotation

Number oyears tested No-Till Strip Till

ReducedTill

ConventionalTill

Brown County(Grundy silt loam)

C-SBcont.

88

84 -- --

9887

Shawnee County(Eudora silt loam)

C-SB2cont.

88

77

--579

727

Riley County(Kenebec silt loam)

cont. 28 -- -- 9

Franklin County (Woodson)Southeast Multiple Sites

C-SBC-SB

7*

74

2545

----

--

Labette(Parsons silt loam) cont. 9 --Republic County(Crete silt loam)

C-SBcont.

44

555

-- --52

Republic County(Crete silt loam) W-C

4 4 -- --

Harvey County(Ladysmith silty clay loam)

W-C 8 9 -- 74 --

Staord County(loamy ine sand)

cont. 4 4 -- -- 72

Thomas County(Keith silt loam)

WCF5cont.

42

7527

--22

7--

72

1Irrigated,2Corn/Soybean,3Continuouscorn,4Wheat/Corn,5Wheat/Corn/Fallow,6LimitedIrrigation(9in.),*4sites,3years


16/522

percent o the time, strip-till corn perormed no dierentlythan corn with no tillage or conventional tillage. However,

with wet planting conditions, strip-till corn perormed betterthan that grown with no-till because the soil dried aster,resulting in better seed slot closure and improved plant stands.

With persistently dry conditions, strip-tilled corn perormedbetter than corn planted with conventional tillage because obetter soil moisture conservation. For more inormation onstrip-tillage, see K-State Research and Extension publication,ConsideringStrip-Tillage, MF-2.

Strip-till requires specialized equipment. Dierent conigu-rations are available rom the various equipment manuacturers.However, the basic design consists o coulters, residue managers,disks, and a sub-surace knie or injecting ertilizer.

Planting DatePlanting corn early is important to use the entire growing

season and maximize yield. Planting dates range rom lateMarch in southeastern counties to mid-May in northwestKansas (Figure ). Many producers use soil temperature to

determine planting time. Planting when the soil temperaturereaches 55 degrees Fahrenheit at a 2-inch depth at mid-day can be an excellent guide early in the planting season,provided the weather outlook or the ollowing weeks is avor-able. Late-planted corn is taller than corn planted at optimumtimes and oten is used or silage. Although taller, total drymatter production is lower with late plantings and producersneed to be aware o typically lower silage and grain yields.Hybrids respond dierently to varied planting dates. In high-

yielding environments, ull-season hybrids planted at datesto optimize use o the entire growing season typically havea greater yield potential than short-season hybrids. In mois-

ture-limited or high-stress environments, planting an early tomedium-maturing hybrid ( to 2 day relative maturity)at the extreme early end o the recommended planting

windows suggested in Figure may allow the corn to be in itsreproductive and grain illing stages beore heat and droughtstresses usually occur in Kansas. This strategy is eective onlyi temperatures allow germination and emergence to proceedsoon ater those earlier planting dates.

Plant PopulationsOptimum plant populations depend on the yields a

particular environment will permit. This explains the widerange in recommended plant populations across the state. Thedesired plant population or dryland corn in a wheat-corn-allow rotation in northwestern Kansas may be only , to2, plants per acre; whereas dryland corn in northeasternKansas may require 22, to 25, plants per acre or moreto maximize yield (Table ). Most irrigated corn plant popula-tions will range rom 28, to 4, plants per acre, withsome as high , plants per acre. I irrigation is limited,the desired plant population may range rom 24, to 28,plants per acre, depending primarily on soil type and amounto available water.

The picture is made more complex by the interaction oyield response to plant population with other managementpractices and environmental conditions. Dramatic changes in

temperatures and rainall resulting in erratic yield levels otenare observed rom one year to the next in a particular area.This is especially true or dryland corn in central and westernKansas. Populations somewhat lower than those listed in

Table may, in act, result in more consistent dryland yieldsin western Kansas. But with lower populations, yields may belimited i growing conditions are good. Optimal seeding ratesmay need to be adjusted or irrigated corn i ertilizer or irri-gation rates are sharply increased or decreased. For example,research at the Irrigation Experiment Field near Scandia hasshown that i ertilizer rates are increased, seeding rates alsoshould be increased to realize the maximum yield beneit.

The inal or harvest plant population is approximately 85percent o the planting rate. For example, i a harvest populationo 24, plants per acre is desired, the seeding rate should be28,2 seeds per acre to obtain that population (Table 7). Corncan compensate by producing larger ears i populations are toolow to use growing conditions. Table 8 shows the estimated

yield potential or dierent plant populations and ear weights.An average ear weight is near .5 pound, but smaller ears aremore likely with high populations or less avorable growingconditions. (See K-State Research and Extension publicationKansasCropPlantingGuide,L-88.)

Hybrids also respond dierently to plant populations.

When the population is too high, some hybrids will have barrenstalks and produce lower grain yields. Shorter-season hybridsshould have inal stands that are to 5 percent higher thanthose suggested or ull-season hybrids in the same environ-ment. In addition to yield dierences, the eect o populationon root and stalk lodging should be noted. Lodging increases aspopulations increase, but the problem is more severe with somehybrids. Consult seed company recommendations or desiredplant populations o speciic hybrids.

Zone April 25-May 5Zone 2 April 5-May Zone April -May 5Zone 4 March 2-April 25

Figure 6. Suggested corn planting dates.


17/52

Row SpacingNarrow rows can have an advantage under high-yielding

conditions (greater than 75 bushels per acre). Rapid canopyclosure with narrow rows can enhance weed control andreduce intra-row plant competition, which can allow theuse o higher seeding rates. Research in central and eastern

Kansas has demonstrated that high-yielding corn grown in2-inch and 5-inch rows has a 2 to 5 bushels per acre yieldadvantage over corn grown in -inch rows. One drawbacko narrow row corn production is the cost associated withplanting and harvesting equipment modiications or purchase.Unortunately, grain drills and air seeders do not meter seedsas precisely as row crop planter units and platorm headersdo not perorm adequately with high-yielding corn. Anotherconsideration is the use o narrow-proile tires or sprayingto minimize traic injury to young corn plants. Twin-rowplanting attempts to gain the advantages o narrow rows

without additional harvest equipment costs. Although twin-rows may have an advantage in high-yield environments,research in Kansas and other states has been inconsistent,oten showing little advantage or twin-row systems overtypical row spacings. The yield beneit rom narrow rowsdecreases as yields decrease. When yields are 2 bushels per

acre or less, planting corn in narrow rows can reduce yieldsby 8 bushels per acre or more compared to that grown in-inch rows. In moisture-limiting environments, corn shouldbe planted in -inch or wider rows. See MF-25,NarrowRowCornProductioninKansas, or more inormation aboutplanting corn in narrow rows.

Skip-row plantingmay minimize the yield variabilitytypically encountered with dryland corn production in westernKansas. In skip-row planting, rows o corn are skipped andnot planted, but the plants per acre are the same as i everyrow were planted. As a result, in a plant-one-skip-one pattern,the number o seeds dropped is doubled in the planted row.

Table 6. Suggested final corn populations.

Dryland

Area EnvironmentFinal Plant Population

(plants per acre)

Northeast - to 5-bushel potential 22,-25,

5+ bushel potential 24,-28,

Southeast Short-season, upland, shallow soils 2,-22,

Full-season, bottomground 24,-2,

Northcentral All dryland environments 2,-22,5

Southcentral All dryland environments 8,-22,Northwest All dryland environments ,-2,

Southwest All dryland environments 4,-2,

Irrigated

Environment Hybrid maturity Final Plant Population

Full irrigation Full-season hybrids 28,-4,

Shorter-season hybrids ,-,

Limited irrigation All hybrids 24,-28,

Table 7. Seed spacings required to obtain harvest populations of from12,000 to 36,000 plants per acre.

Harvestedpopulation

Seeds/acre1

planted

Row width, inches Row width, inches30 36 30 36

seed spacing, inches Seeds/10 t. o row

2, 4, 4.75 2.25 8

4, ,5 2.5 .5

, 8,8 . 9.25

8, 2,2 9.75 8.25 2 5

2, 2,5 9. 7.5 4

22, 25,9 8. .75 5 8

24, 28,2 7.5 .25 9

2, , .75 5.75 8 2

28, 2,9 .25 5.25 9 2

, 5, . 5. 2 242, 7, 5.5 4.5 22 2

4, 4, 5.25 4.25 2 28

, 42,4 5. 4. 24 291Assuminghighgerminationandthat85percentofseedsproduceplants.

Table 8. Yield potential of different corn plantpopulations at two average ear weights.

Plants/acre 0.4 lb ear 0.5 lb ear 0.6 lb ear 8, 4 57 9

2, 9 8

, 9 4 7

2, 4 4 7

24, 7 7 2

28, 2 24

, 7 24 257

2, 8 229 274

4, 94 24 29

, 2 257 9

AdaptedfromNebguideG79-487


18/524

Nutrient ManagementTotal ertilizer use on corn is greater than on any other crop

grown in the United States and is likely second only to wheat in

Kansas. Even with good overall crop management, ew Kansassoils will sustain proitable corn production without supple-mentation o several crop nutrients rom ertilizers, manures,and/or legume rotations. Typical symptoms or some o themost common nutrient deiciencies are illustrated in photos to 8. While estimates vary, each bushel o corn grain harvestedrom Kansas ields removes about .9 pounds o nitrogen (N),. pounds o phosphate (P

2O

5) and .2 pounds o potassium

(K2O) per acre. The approximate removal o these and other

nutrients by corn grain and stover or a 5 bushel per acre cropare given in Table 9. This data shows that harvesting only the

grain removes considerably less nutrients than i the entire cropis harvested or silage.

Determining Fertilizer NeedFertilizer and lime need can best be determined by using

several tools: soil tests, local research inormation, on-the-arm research trials, crop nutrient removal, plant analysis, pastexperience, or a combination o these. Soil test interpretationsare based on many years o research work conducted across thestate. Reliable interpretations can be made or the likelihoodo obtaining a response assuming that crop yield potential isnot restricted by actors other than the nutrient in question.

The most reliable means o determining ertilizer need is bysoil testing regularly with continual support rom the other

The inal stand will be similar to that or a ield with everyrow planted. Possible planting patterns can be quite diverse,but plant-one-skip-one, plant-two-skip-one, and plant-two-skip-two are the most common. Research coordinated by theUniversity o Nebraska with sites in Kansas, Colorado, andNebraska, indicates a beneit to skip-row corn i the yieldhistory or the ield is 9 to bushels per acre or less. In thelower yielding, dryland environment o western Kansas wheremoisture may be limiting during grain ill, skip-row plantinghas been beneicial because corn roots are able to grow into theskipped row area and use available soil moisture to completegrain ill. In extremely dry conditions with low yield potential,the plant-two-skip-two pattern is the most beneicial. Onlymarginal beneit was observed rom the plant-two-skip-oneplanting pattern compared to planting every row.

Adequate weed control is critical to the success o skip-rowcorn. Consider using glyphosate-resistant corn to allow theapplication o glyphosate, a broad spectrum postemergenceherbicide, to control late emerging weeds. I the ield is nottreated when the corn is approaching inches tall or the V-8

stage, weeds will lourish in the skipped row because no corncanopy is present to shade these weeds. Weeds in the skip willdeplete soil moisture beore the corn can use it or grain ill.

Be aware that questions about crop insurance coverageand enrollment in government programs have suraced withskip-row planting patterns. Producers should check with theirlocal insurance provider and Farm Service Agency to inquireabout appropriate rules and regulations i considering the useo a skip-row planting pattern or corn.

Planting DepthThe speed o germination and emergence depends on

planting depth and soil temperatures. Corn emergence at 5 to55 degrees Fahrenheit may take 8 to 2 days, while at to5 degrees Fahrenheit, corn emerges in 8 to days. Below 5degrees Fahrenheit little, i any, germination can be expected.Soils are colder at increased depths, which may slow germina-

tion and subject the seed to diseases or insects resulting in seedinjury. Early plantings will emerge quicker with planting depthso .5 to 2 inches than i planted deeper. Sandy soils warm morerapidly than ine-textured soils because they hold less water.Planting 2 to inches deep in sandy soils is necessary to preventdrying o the seed zone i dry conditions ollow planting.Planting depth more than .5 inches under any soil conditionmay cause emergence problems.

Planting seed deep does not mean corn roots will bedeeper. Roots that come directly rom the kernel are tempo-rary. Permanent roots develop at nodes above the seed andorm at the same soil depth regardless o planting depth.Planting too shallow may orce the crown to develop at thesoil surace, inhibiting development o the secondary andbrace root systems and limiting nutrient uptake. Careulplanter adjustment or speciic ield conditions will assureproper seed placement. This includes planting at the optimumspeed or your planting equipment. Research in northeastKansas has shown that increasing planter speed rom 4 to 8miles per hour increased the number o multiples and skips

and, more importantly, decreased inal stand, which can have anegative eect on yield.

Seed Size and ShapeHybrid seed corn is available in dierent seed sizes and

shapes. Seed location on the ear inluences seed size andshape; large round seed comes rom the ear base, small roundsrom the tip and lat seed rom the center. Research indingsindicate that yield potential is not inluenced by seed size andshape with equivalent inal plant populations. Small roundseed may have lower ield emergence in the cool conditionsassociated with very early planting, but this is due to seed

quality rather than seed size or shape. Obtain the cold germi-nation ratings or suspect seed lots to assure adequate seedquality. Planters should be adjusted appropriately or the sizeand shape o each seed lot to ensure accurate seed singulation,

which will minimize doubles and skips.


19/525

Table 9. Approximate amount of nutrients removed by 150 bushel corn crop per acre.*

Element

Quantity in

Element

Quantity in

Grain lbs Stover lbs Grain lbs Stover lbs

Nitrogen 5 8 Chlorine 4 8

Phosphorus (P2O

5) 5 8 Iron . .8

Potassium (K2O) 4 55 Manganese .5 .25

Calcium 5 Copper .2 .8

Magnesium 29 Zinc .7 .7

Sulur 8 Boron .4 .2

Molybdenum .5 .

*N,PandKestimatesadaptedfromK-Stateresearchandotherstatelandgrantuniversityinformation.SecondaryandmicronutrientestimateadaptedfromBarber,S.A.andR.A.Olson,1968.Fertilizeruseoncorn.InChangingPatternsinFertilizerUse.

methods listed. Remember, however, laboratory soil test resultsare no better than the sample collected in the ield.

In addition to guiding ertilizer needs or the current crop,soil test results have long-term value. In act, the value o along-term, sound soil testing program is increased immensely

when viewed in an historical context. By keeping soil testrecords over a period o years or an individual ield, theserecords become an excellent means o assessing the adequacyo the ertilizer program being ollowed. For example, anincrease in the soil test values in successive samplings or anutrient indicates that the application rate is in excess o theamount being used by the plants. I the soil test level or thenutrient is above the medium interpretation level ( ppmBray P or Mehlich extractions) then a reduction in rate orno application will likely not reduce corn yields. In contrast,a decrease in soil test values over time indicates that cropremoval has been greater than the application rate which maynot be in the producers best interest especially i the soiltest has dropped into the low interpretation level. Ater severalsuccessive soil samplings, monitoring soil test levels may

become the most important use o the soil test program.A complete set o Kansas State University recommenda-tions is provided in the publication SoilTestInterpretationsandFertilizerGuidelines, MF-258.

NitrogenNitrogen management decisions or corn are dependant

on several actors, including: water management i irrigated,soil texture, options available or nitrogen ertilizer applica-tion, manure application history, soil organic matter content,residual soil proile nitrate-N content, residue managementsystem, previous crop, and tillage system adjustments.

While nitrogen application rate is the irst thing thatoten comes to mind when discussing improved corn nitrogenuse eiciency, the time and method o nitrogen applicationare as important to eicient nitrogen use as nitrogen applica-tion rate. How the nitrogen is applied, how much nitrogen isapplied and when nitrogen is applied all have dramatic eectson nitrogen use eiciency by the corn crop.Additionally,or irrigated crop production, nitrogen management mustbegin with water management.

In Kansas, widely varying soils, climate, and culturalconditions have large eects on expected nitrogen use ei-ciency or a speciic nitrogen-management program. Much othe corn production in Kansas is on irrigated, coarse texturedsands where nitrogen leaching is the main actor reducingnitrogen-use eiciency. Minimizing the potential or nitrogenleaching loss is the most important actor or improved cropproduction proitability and environmental protection underthese conditions. This is especially important in areas with arelatively shallow aquier.

At the same time, there is signiicant irrigated acreage inKansas with medium-ine textured soils. Denitriication is themain cause or concern in these areas because there is minimalpotential or signiicant nitrogen leaching. The same is trueor dryland corn production on the claypan soils o southeastKansas and other scattered poorly drained soils in the centraland eastern parts o the state. For dryland production in the

western part o the state, timing applications so that N ismoved into the soil proile with limited precipitation is impor-tant or making most eicient use o applied nitrogen.

The nitrogen recommendation algorithm is based onexpected yield (YG), soil organic matter content (SOM),legume crop nitrogen credits, manure application/methodo application, nutrient credits, irrigation water nitrate-Ncontent, and the 24 inch residual soil proile nitrogen test.

Corn nitrogen Recommendation =(1.6 YG) (SOM 20) Profile N Legume N Other N Credits

For irrigated production, N guidelines are capped at pounds nitrogen per acre while dryland production is cappedat 2 pounds nitrogen per acre.

Suggested recommended nitrogen application rates aredirectly tied to yield goal. Yield records should be used to setindividual realistic, but progressive, yield goals or each ield.Appropriate yield goals or a speciic ield should be highenough to take advantage o high production years whenthey occur, but not so high as to jeopardize environmentalstewardship and/or proitability when environmental condi-tions are not so avorable. Appropriate yield goals all betweenthe average yield obtained in a ield over the past to 5 years


20/52

Table 11. Likelihood Of Significant Profile Nitrogen Carryover

Higher Probability O Signiicant Proile Nitrogen Proile Nitrogen Test More Valuable Lower Probability O Signiicant Proile Nitrogen Proile Nitrogen Test Less Valuable

Medium-Fine Textured Soils Sandy soils

Recent History O Excessive N Rates Appropriate N Rate History

Previous Crop Previous Crop

Lower than expected yield Soybeans (immediately preceding)

Drought aected Higher than expected yield history

Fallow Expected yields history

Previously destroyed stands o alala/clovers Excessive Precipitation

Manure Application or History No Manure or Biosolid Application History

Warm, Late Falls and/or Early, Warm Springs Increased Rotation Intensity

to near the highest yield obtained in a speciic ield. Theproducer should set the individual ield yield goals.

In Kansas or corn production, 2 pounds nitrogen peracre per year are credited or each percent soil organic matterin the surace to 7 inches soil depth. Previous-crop soybeansare credited at 4 pounds nitrogen per acre or a ollowingcorn crop. Alala is credited at rom to 2 pounds nitrogenper acre or a ollowing crop, depending on how good thealala stand is and how much grassy weeds have inested thestand. Sweet clover is credited at roughly the same amountas alala while red clover is credited rom to 8 poundsnitrogen per acre depending on the stand density (Table ).

Manure nitrogen credits depend on the method omanure application, time until manure is incorporated,organic and mineral nitrogen contents o the speciic manureused, and the number o years since the manure was applied.Speciic guidelines or crediting manure or nutrient applica-tion can be ound in the Kansas State University publicationEstimatingManureNutrientAvailability, MF-252.

While the proile nitrate-N test is strongly suggested or

developing nitrogen application rate guidelines, it is not neces-sarily suggested that it needs to be used on every acre, everyyear. It is strongly suggested that these proile soil samplesare collected or nitrate-N analysis when there is a relativelyhigher probability o signiicant proile nitrogen. There arealso conditions when the likelihood o signiicant nitrate-Naccumulation in the soil proile is relatively low. Table provides some general guidelines or the use o the soil proilenitrate-N test. I possible, proile nitrogen samples should becollected to a depth o 2 eet. For areas o the state where theproile depth is less than 2 eet (clay pan, rock, etc.), samplesshould be collected the depth o the existing proile.

Field comparisons conducted by Kansas State researchersindicate little agronomic dierence between nitrogen mate-rials when properly applied. Material selection should be onthe basis o cost (applied), availability o material, adaptabilityto arm operations, and available dealer services.

Nitrogen application or corn can be made at severaltimes with equal results on most land in Kansas. Nitrogenmay be applied beore planting, at planting time, and/or as

a sidedressing ater corn is up. The best time/method ornitrogen application depends on the individual ield likelihood

o signiicant nitrogen loss and the speciic production opera-tion, time, equipment and labor availability. Nitrogen uptakeby corn is quite rapid in a period starting about 25 days ateremergence and by the time o silking percent o the totalnitrogen has been taken up (Figure 7).

I the potential or signiicant nitrogen loss is present,nitrogen applications should be timed so that nitrogen isavailable when needed or this rapid growth. A small amounto nitrogen may be applied in a starter ertilizer to meet earlyseason needs. Preplant nitrogen applications, except on sandysoils, can be made in late all or spring with little concern orleaching loss. On sandy soils, preplant nitrogen applicationsshould be delayed until spring. Nitrogen application shouldalso be delayed on ine textured soils subject to standing wateror looding. I nitrogen is applied sidedress, the applicationsshould be made early (i.e. ive-lea stage) to avoid weatherconditions preventing application. With sprinkler irriga-tion on sandy soils, application o the nitrogen through theirrigation system has been quite satisactory. Application onitrogen through irrigation systems under other soil condi-

Table 10. Corn nitrogen credits for various previous cropsin rotation.

Previous Crop Corn N Credit

Corn, wheat, sorghum, sunlowers lbs N/A

Soybeans 4 lbs N/A

Alala > 5 plants/t2 2 lbs N/A

Alala 2-5 plants/ t2 8 lbs N/A

Alala -2 plants/ t2 4 lbs N/A Alala < 2 plants/ t2 lbs N/A

Red clover excellent stand 8 lbs N/A

Red clover air stand 4 lbs N/A

Red clover poor stand lbs N/A

Sweet clover excellent stand lbs N/A

Sweet clover air stand lbs N/A

Sweet clover poor stand lbs N/A


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tions is possible, but the ertilizer distribution is no better thanthe water distribution. Do not use any nitrogen material thatcontains ree ammonia when applying through a sprinklersystem unless special precautions are taken.

Kansas Nitrogen BMPs.Dryland corn production in Kansas reaches rom the

western Cornbelt o northeast Kansas that has the potentialor yields o 5 to 2 bushels per acre, to western Kansas

with an annual precipitation o 5 to 2 inches and whereyield potentials are typically bushels per acre or less tothe shallow clay-pan soils o southeast Kansas and that have

the potential or 5 bushel per acre corn but is oten aectedby high winter/early spring denitriication nitrogen losses ordrought conditions. The point is, there is no one BMP (bestmanagement practice) package or the state.

Following are a ew general nitrogen BMPs or cornproduction under various systems in Kansas. In general, thegreatest potential or nitrogen movement to groundwater is inour irrigated systems on sandy soils. Shallow aquiers in someo these areas greatly increases the risk o nitrate-N movementto groundwater. On medium-ine textured irrigated soils andpoorly drained and/or claypan soils, managing denitriication

loss is o greater importance than leaching.Nitrogen BMPs or Irrigated Sands Corn Production Implement irrigation scheduling/management program Manage other controllable actors (e.g. other nutrients,

weed management, etc.) Manage potential nitrogen leaching Split nitrogen application no all nitrogen application Include starter NP, NPS, or NPKS application Consider including to 4 pounds nitrogen per acre

starter applied (not with the seed)

Consider N-Serve with anhydrous ammonia or shallowaquier locations

Subsurace/knie nitrogen applications always good. Include some early nitrogen with preplant, pre-emerge

weed control program Apply split nitrogen applications through sprinkler system

i available Make sure adequate nitrogen is applied early in case irriga-

tion water not needed Make sure last nitrogen application is made by tasseling or

shortly ater (7 to 4 days)

Nitrogen BMPs or Irrigated Medium-Fine Textured Soils Implement irrigation scheduling/management program Manage other controllable actors (e.g. other nutrients,

weed management, etc.) Manage or potential nitrogen denitriication loss Split applications should be considered (all or spring

preplant, starter, sidedress) Anhydrous ammonia preerred or all application

Include starter NP, NPK, or NPKS application Consider including to 4 pounds nitrogen per acre

starter applied (not with the seed) Subsurace/knie applications always good. Make sure last nitrogen application is made by tasseling or

shortly ater (7 to 4 days)

Nitrogen BMPs or Dryland Corn Production No all N applications to clay-pan soils o southeast Kansas

or poorly drained central-eastern Kansas soils (denitriica-tion)

Avoid all nitrogen applications to bottomland soils

requented with waterlogged conditions (denitriication) Manage other controllable actors (e.g. other nutrients,

weed management, etc.) Include starter NP, NPK, or NPKS application Consider including to 4 pounds nitrogen per acre

starter applied (not with the seed) Include some early nitrogen with preplant, pre-emerge

weed control program Sidedress application desirable on requently waterlogged

soils Make sure adequate nitrogen is applied early in crop

growth and development For western Kansas, make applications early to improve

potential or movement into root zone Subsurace/knie applications always good I unincorporated nitrogen application, surace band appli-

cation preerred.

Phosphorus and PotassiumPhosphorus is required or many metabolic processes

within the plant. Photosynthesis, respiration, carbohydratesynthesis and utilization, cell division, reproduction, andenergy transer all require phosphorus within the plant. I

DRYMATTERANDNUTRIENTUPTAKE

(%OFTOTAL)

100

80

60

40

20

0

0 100755025

DAYS AFTER EMERGENCE

MATURITY115DAYS

POTA

SSIUM P

HOSPHORU

S

NITR

OGEN

DRY

MATTE

R

Tasseling

Silking

Figure 7. The uptake of nutrients by a corn plant and theincrease in dry matter n relation to the number of days afteremergence. (Source: Hanway, J.J. 1960. growth and NutrientUptake by Corn, Iowa State University Extension PamphletNo. 277).


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RelativeYield(%)

VL L M H V H

100 %

95 %

50 %

50 ppm

Crop Responsive Soil Test Range MaintenanceRange

ManureManagement Range

EnvironmentalRisk Range

EX

No ApplicationManure

Allocation

10 ppm 20 ppm 30 ppm

20 ppmCritical Value

30 ppmUpper Build

BuildRecommendation

SufciencyRecommendation

MaintenanceRecommendation

StarterStatement

StarterStatement

Bray 1 or Mehlich 3 Soil Test (ppm)

Nutrient Recommendation

UpperManure Limit

Figure 8. Phosphorus Management Model.

phosphorus becomes deicient, crop growth, grain production,and proitability all will suer. Phosphorus deiciencies in corninclude: small and stunted seedlings (Photo ), purplish leacoloration (especially seedlings in cold, wet years), delayedmaturity (delayed silking and tasseling) (Photo 4), thinstems and poorly developed root systems. While purpling o

young seedling leaves is the most oten mentioned deiciencysymptom in corn, anything that inhibits root growth maycause corn seedlings to become purple. Additionally, somehybrids are more prone to purpling o leaves than others.

Although less phosphorus is ound in plants than eithernitrogen or potassium, sizeable amounts are removed in theharvested portions o crops. For corn, regional estimates othe amount o phosphorus removed are in the range o .to .8 pounds o P

2O

5equivalent removal with each bushel

o corn grain. For Kansas, research indicates that about .pounds P

2O

5per bushel is contained in one bushel o corn.

Lower grain phosphorus values may result on low phosphorustesting soils, while higher grain phosphorus contents are likely

with high or very high phosphorus soil test values.

Kansas State University corn phosphorus recommenda-tions provide two main options or producers, depending oncircumstances or speciic ields and situations.Sufficiencyphosphorus ertility programs are intended to estimate thelong-term average amount o ertilizer phosphorus required to,on the average, provide optimum economic return in the yearo nutrient application while achieving about 9 to 95 percento maximum yield. In some years, greater amounts o nutrientare required or optimum yield and economic return, whilein other years less than recommended amounts o nutrient

would suice. There is little consideration o uture soil testvalues and soil test values will likely stabilize in the low, crop

responsive range. Figure 8 presents the general model used orphosphorus management by Kansas State University.Build-maintenancerecommendations are intended to

apply enough phosphorus to build soil test values to a targetsoil test value over a planned time rame (typically 4 to 8

years) and then maintain soil test values in a target rangeuture years. I soil test values exceed the target range, nophosphorus is recommended with the exception o low starterapplied rates i desired. Build-maintenance ertility programsare not intended to provide optimum economic returns ina given year, but rather attempt to minimize the probabilityo phosphorus limiting corn yields while providing or near

maximum yield potential.Both suiciency and build-maintenance programs have

advantages and disadvantages, depending on the needs andexpectations o speciic producers, ields and situations. Bothapproaches are based on identiying the criticalphosphorussoil test value. The critical soil test value is the phosphorussoil test value above which the soil is normally capable osupplying phosphorus to crops in amounts suicient toachieve about 9 to 95 percent o maximum yield orsingle year optimum economic growth. Figure 8 illustrates

the concepts o both suiciency and build-maintenanceapproaches to phosphorus nutrient management.

Suiciency programs minimize phosphorus inputs inthe early years o adopting this approach, but recommendedapplication rates eventually stabilize at phosphorus ratesthat maintain soil test values in the crop responsive range.Generally, ertilizer phosphorus application rates equal to cropremoval are needed to maintain soil test phosphorus levels.Since phosphorus soil test values are eventually maintained inthe crop responsive range, ertilizer phosphorus applicationsare required each year in order to take care o crop needs. Iertilizer phosphorus application is skipped in a particular

year, overall crop production proitability would be expectedto suer. For suiciency programs, no ertilizer phosphorusis recommended at soil test values much above the criticalphosphorus soil test value.

Build-maintenance programs require somewhat higherphosphorus rates in the early build phase o the program (orsoils initially testing in the crop responsive range), but applica-tion rates eventually stabilize at phosphorus rates that main-

tain soil test values at a desired targeted level. The targeted soiltest value will be just above the critical phosphorus soil testvalues. By building or maintaining soil phosphorus test valuesin the targeted range, the soil will be capable o supplyingcrop phosphorus nutritional needs or or 2 years without theapplication o ertilizer phosphorus.

Suiciency programs it best or short land tenure situa-tions (generally 2 to years or ewer) and in situations o cashlow shortages. Adoption o a suiciency phosphorus ertilityprogram requires the application o ertilizer phosphorus andpotassium every year i soil test levels are not above the criticalphosphorus soil test value. This lack o lexibility is due to the

act that soil test values are maintained in the crop responsiverange over the long term. Build-maintenance programs gener-ally it best or longer land tenure situations ( to 4 years andlonger), when lexibility in application rate in a given year isdesired (ater soil tests built to targeted non-responsive range)

when the producer desires to maintain soil tests at a givenvalue over the long-term or other armer speciic reasons.


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As a result, both sufficiency and build-maintenanceprograms are appropriate phosphorus nutrient managementstrategies depending on the individual producer situations,goals and objectives or speciic ields. Producers may adoptdierent phosphorus management approaches or individualields within their operation.

Suiciency phosphorus and potassium recommendationsor corn are presented in Table 2. Included is the equationused to generate these guidelines. These recommendations areintended to, on the average, provide or optimum economicreturn in the year o application. I more phosphorus isremoved in the corn grain than is supplied rom variousnutrient sources, soil tests values would be expected to declineover time. The inormation in Table 2 also provides an esti-mate o the amount o P

2O

5and K

2O equivalent removed in

corn grain at various yield levels.The estimated amount o P

2O

5required to build

phosphorus soil test values are presented in Table . As ageneral rule-o-thumb, about 8 pounds P

2O

5in excess o

crop removal is required to increase the Bray P- or Mehlich

soil test one part-per-million or the surace inches osoil. Sandy soils and shallower tillage will typically requireless and ine-textured soils containing larger amounts o clayand deeper tillage operations may require more. In addition

to the amount o phosphorus required to build up soil testphosphorus, enough P

2O

5needs to be applied to replace the

amount removed in the crop in order to maintain phosphorussoil tests. Crop removal is about . pounds P

2O

5per bushel

o corn grain removed.Phosphorus can be applied either preplant broadcast,

preplant banded with nitrogen (dual placement), placed ina starter band near the seed or placed directly with the seed.Banded applications are recognized as being most eicient,particularly when small amounts are applied on very acid orcalcareous soils low in soil test phosphorus. Savings in timeat seeding achieved by broadcasting rather than banding mayoset lower eiciency or the broadcast application.

Starter applications can be placed in direct contact withthe seed or placed to the side and below the seed (preerred).I placed in contact with the seed, the starter material shouldcontain no more than 8 to pounds per acre o nitrogenplus potash. The nitrogen and potash can cause germina-tion damage. Recently, research has shown that applyingstarter phosphorus mixed with to 4 pounds o additional

nitrogen in a surace band an or 2 inches to the side o theseed slot to be an eective method o starter application orhigh surace residue corn production systems.

Table 12. Phosphorus and Potassium Sufficiency Recommendations for Corn Production.

Phosphorus Sufciency Recommendations or Corn1 Potassium Sufciency Recommendations or Corn1

Mehlich 3Bray P1Soil Test

Yield Goal (Bu/A) Yield Goal (Bu/A)

60 100 140 180 220 Exch. K 60 100 140 180 220

(ppm) - - Lb P2O

5/A (ppm) - Lb K

2O/A

-5 55 7 75 8 -4 7 8 85 95

5- 4

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