June 3, 2011 - Issue 9Purdue Cooperative Extension Service

http://extension.entm.purdue.edu/pestcrop/index.html

I n T h i s I s s u e

Insects, Mites, and Nematodes • CutwormsChewingThroughTechnology • BlackLightTrapCatchReport

Weeds • CoverCropsandtheCornandSoybeanHerbicide

RotationRestrictions

Plant Diseases • EarlyFungicideApplicationsinCorn • AreLate-PlantedSoybeansatRiskforSoybean

Rust?

Agronomy Tips• EffectsofFloodingorPondingonYoungCorn

• ThoughtsonLatePlantingofSoybean • AssessingAvailableNitrogenfromFall-andSpring-

AppliedNitrogenApplications

Weather Update • TemperatureAccumulations

I n s e c t s , M i t e s , A n d N e m a t o d e s

Cutworms Chewing Through Technology–(Christian Krupke and John Obermeyer)

•Cutwormsareabundant,especiallywhereweedswereplentifulbeforeplanting.

•Aspredicted,seedinsecticidesand/orBtcornareNOTcontrollingsevereinfestations.

Numerous reports have been received of emergingcornbeingdamagedbycutworms.Asmentioned inprevi-ousPest&Crop issues (#4, 5, 6, 8 <http://extension.entm.purdue.edu/pestcrop/2011/index.html>), the seed-appliedinsecticidesand/orBttraitedcornwillonlyprovidesuppres-sionofcutworms.Withtheseveredamagesomefieldsarereportedlyreceiving,itisobviousthatproducerswereneg-ligent in scouting fields after emergence to determine theneedforrescuefoliarinsecticides.

Blackcutwormisnottheonlyspeciesofcutwormpres-entanddamagingfields.Many reportsof claybackedcut-wormhavebeenreceivedaswell.Thisspeciesoverwintersasapartiallygrown larva, so it is largerwhen thecorn isemerging,comparedwithblackcutworms,whichbegintheir

annual Indianacycleaseggs in thespring.What’s impor-tant is that larger larvae,≥0.5 inch,arenot controlledbyBtproteinsexpressedinHerculexandSmartStax.Produc-ersareunhappilyfindingoutthatblackcutwormistheonlyspecies labeled for control with these traited-seeds, and

CutplantsandpulledunderleavesbyBCWlarvae

Pest&Crop No. 9 June 3, 2011 • Page 2

rescuetreatmentsareontheirtab.Aswe’velearnedinthepastandhearingagainthisspring,theseed-appliedinsec-ticides (e.g.,Cruiser,Poncho)provideonlysuppressionofcutworms.They likelydoafine jobofsuppressing light tomoderateinfestations,butsevereinfestationsareNOTcon-trolled,evenbythehigherrate.

TwowiltingplantsfromundergroundBCWfeeding

Controlmaybeneeded if3-5%of theseedlingshaveobvious foliar feeding and/or plant cutting and live larvaecanbefoundwhilediggingarounddamagedplants.Higherlabel ratesof insecticides shouldbe considered if the soilsurfaceiscrustyandmostcutwormactivityisbelowground.Foralistingoffoliarinsecticidesforrescuecontrol,referto“CornInsectControlRecommendations–2011,”whichcanbe viewed by clicking <http://extension.entm.purdue.edu/publications/E-219.pdf>.

BCWlarvanexttocutplant

Black Light Trap Catch Report - (John Obermeyer)

County/Cooperator

5/17/11 - 5/23/11 5/24/11 - 5/30/11

VC BCW ECB SWCB CEW FAW AW VC BCW ECB SWCB CEW FAW AW

Dubois/SIPACAgCenter 0 0 0 0 0 0 0 0 0 3 0 0 0 0

Jennings/SEPACAgCenter 0 0 2 0 0 0 0 0 0 4 0 0 0 0

Knox/SWPACAgCenter 0 0 0 0 0 0 0 0 0 0 0 0 0 8

LaPorte/PinneyAgCenter 0 0 0 0 0 0 2 0 0 0 0 0 0 10

Lawrence/FeldunAgCenter 0 0 0 0 0 0 3 0 0 0 0 0 0 4

Randolph/DavisAgCenter 0 0 0 0 0 0 1 0 0 0 0 0 0 4

Tippecanoe/TPACAgCenter 0 0 0 0 0 0 0 0 0 0 0 0 0 3

Whitley/NEPACAgCenter 0 0 0 0 0 0 1 0 0 0 0 0 0 3

VC=VariegatedCutworm,BCW=BlackCutworm,ECB=EuropeanCornBorer,SWCB=SouthwesternCornBorer,CEW=CornEarworm,FAW=FallArmyworm,AW=Armyworm

Pest&Crop No. 9 June 3, 2011 • Page 3

W e e d sCover Crops and the Corn and Soybean Herbicide

Rotation Restrictions–(Bill Johnson and Glenn Nice)

Therehasbeenanincreasedinterestintheuseofcovercrops.Thebenefitsofusingcovercropsarewellreported.TheMidwest CoverCropsCouncil lists them as reducingsoil erosion and increase nutrient recycling on farmlands[Midwest Cover Crop Council].Theyalsostatethatsomeoftheotherbenefitsareimprovingsoilquality,fertilitymanage-ment, landscape diversification, and wildlife habitat. How-ever,therearesomechallengestogrowingacovercropinfieldswherecornandsoybeanaregrown.

Oneof thechallengesofcovercropsthat if theydon’twinterkilland theyhave tobechemicallyormechanicallycontrolledinthespringbeforeplantingcornorsoybean.Insomecases theyarecontrolledwellenoughwitha typicalburndownherbicideprogramthatwouldbeusedtocontrolawinterannualweeds.Occasionallyduetocoolwetenviron-mentalconditions,lateapplicationtiming,orcontaminationofseed theburndowndoesnotgetcompletelycontrol thecovercropinthespring.

Onequestionthathasbeenbroughtupinrecentcovercropsituationsisreplanttimingwhencovercropsareplantedaftertheuseofresidualherbicidesusedincornorsoybean.Thereareseveralplantspeciesbeingpromotedfortheuseofcovercrops.Someoftheplantsincludeannualryegrass,wheat,buckwheat,clovers,radish,cowpeaandvetch.Infor-mationregardingeffectsorcornandsoybeanherbicidesonthesespeciesissomewhatlacking.Herbicidelabelrotationrestrictionsoftenrequiresubstantialwaitingperiodsbeforethe cover crop canbeplanted.Thesewaitingperiodsaretoassurethatresidualeffectsfromtheherbicidedonotim-pactthefollowingcropnegatively.Inmanycasesrotationalworkhasbeendonetoattainthesewaitingperioddurations.However,insomecasesplantsusedascovercropsfallun-derthe‘other’or‘notlisted’categoryrequiringthemaximumdurationbeforeplanting.This isoftennotbasedonactualworktoascertainthisinformation,butbecausetheworkhasnotbeendoneanditisalwaysbettertobesafethansorryandthelabelsarewrittentoprotecttheuserfromdamagingthecovercrop.

InrecentcommunicationswiththeOfficeoftheIndianaStateChemistthequestionwasbroughtup.Theinterpreta-tionofthelabelis,ifthecovercropisnotharvested,usedas feed for livestockorsold inanywayand that thecovercropisterminatedintheappropriatemanner,thattherota-tionrestrictiondoesnotapply.However,becausethecom-panysellingtheherbicidedoesnotrecommendorapprovearotationotherthantheoneslistedonthelabel,thecompanysellingtheherbicideisnotliableforanyinjuryorgerminationproblemsseeninthecovercrop.

Purdueispresentlyworkingonastudythatwilllookatsomecovercropspeciesresponsetosomeofthecommoncornandsoybeanherbicides.Lookforafuturearticlewiththatdata.

Thetableonthenextpagelistsseveralherbicidesusedincornandsoybeanandtheirrotationrestrictionstoafewoftheplantsusedascovercrops.Remember,failuretofollowlabelscanleadtopossibleinjuryofdesiredplants.

Pest&Crop No. 9 June 3, 2011 • Page 4

Examples of rotation restrictions of several corn and soybean herbicides and a few of the plants used as cover crops in months. See footnote for cover crops.

Herbicide Crop 1 2 3 4 5 6 7 8 Comments

atrazine NY NY NY NY NY NY NY NY IfnotappliedafterJune10,donotplantthefollowingyear.TakenfromtheAatrexlabel.Injurymayoccur.

Authority First -Soybeansulfentrazone+cloransulam

12 4 30 30 30 12 12 30 Cropsnotlisedare30months.

Autority MTZ-Soybeansulfen-trazone+metribuzin

18 4 18 18 18 18 18 18 Cropsnotlistedare18months.

Balance Flexx -Cornisoxiflu-tole

12 4 30 30 30 12 12 30 Cropsnotlistedare30months.

Capreno-Cornthiencarbazone+tembotrione

18 4 18 18 18 18 18 18 Springoatscanbeplanted10monthsafterapplication.Rotationrestrictionsof18monthsrequire30inchesofprecipation.

Callisto-Cornmesotrione 18 4 18 18 18 18 18 18 Cropsnotlistedare18months.Grassesgrownforseedcanbeplantedimmedi-ately,butannualryegrassisnotdirectlyaddressed.

Canopy DF -Soybeanchlo-rimuron+metribuzin

18 4 18 18 18 18 18 18 Barleycanbeplanted4monthsafterapplication.Cropsnotlistedare30months.

Canopy EX -Soybeanchlo-rimuron+tribenuron

30 3 12 30 30 3 9 30 Cropsnotlistedare30months.

Dual II Magnum-CornSoy-beanS-metolachlor

4.5 4.5 9 N/A N/A 4.5 N/A Spr Clovermaybeseededin9months.Toavoidinjurytoclover,donotapplymorethan1.9lb.ai/A(2pts./A).Donotmakeanypostapplications.

FirstRate-Soybeancloran-sulam

18 4 18 18 18 9 9 18 Barleycanbeplantedin12months.Cropsnotlistedare18months.

Flexstar -Soybeanformesafen 18 4 18 18 18 4 10 18 Cerealryecanbeplantedin4months.

Prefix -SoybenS-metolachlor+formesafen

4.5 4.5 18 18 18 4.5 18 18 Cropsnotlistedare18months.

Valor XLT-Cornflumioxazin+chlorimuron

4 4 18 30 30 30 30 30 Cropsnotlistedare30months.

1=Annualryegrass;2=Wheat;3=Clover;4=Vetch;5=Radish;6=Oats;7=Cowpea;8=Buckwheat;NY=NextYear;Spr=Spring

Pest&Crop No. 9 June 3, 2011 • Page 5

P l a n t D i s e a s e s

Early Fungicide Applications in Corn – (Kiersten Wise)

Earlyfungicideapplicationsareanewtrendinfieldcornproduction,andarereportedtoincreaseyieldevenintheab-senceofsignificantdiseaseoradiseasethreat.Thetimingofanearly fungicidespraycoincideswithpost-emergenceherbicide applications, making them easier and possiblycheapertoapplythanlaterfungicideapplicationsthattargetthetasseling(VT)growthstage. However, there isnotanextensiveamountofreplicatedresearchthatshowsacon-sistentyieldbenefitfromearlyfungicideapplicationstocorn.

In2010,weestablishedseveraltrialsattheAgronomyCenterforResearchandEducation(ACRE),andtheThrock-morton PurdueAgricultural Center (TPAC) in TippecanoeCounty, IN. Wecomparedtheyieldbenefitsofearly, late,anddoubleapplicationsoffungicidestonon-treatedcontrols(Figure1).Inthesetrials,wedidnotseeaneconomicben-efitfromanearlyfungicideapplication.

Figure1.2010responseofearlyfungicideapplicationsincorninTippecanoeCounty,IN.Valueswereaveragedacrossallfungicidestestedateachapplicationtimingineachofthreeexperimentsconductedatthislocation.Dis-easeseverityintheuntreatedcontroldidexceed1%onthe

earleaf(atR4)inanyexperiment.LSD(0.05)=NS.

ItisimportanttorememberthataV4-V6applicationoffungicidetocornwillnotprotecttheearleaforabovefromdiseasethatdevelopsaroundtasseling.Producersmaybeconcernedaboutfoliardiseaseslikeanthracnoseleafblight(caused by the fungusColletotrichum graminicola), whichcanbepresent in youngcorn.Typically, symptomsof thisdiseaseareconfinedto lower leavesthroughoutthegrow-ingseason,anddonottypicallyrequiremanagement.Pro-ducerswhohavefieldsoffloodedorpondedcornmayalsobeconcernedaboutthediseasecrazytop,whichiscausedbythefungusSclerophthora macrospora.Thisdiseasecan

Figure2.Deformed,proliferatingtasselsareacommonsymptomofcrazytopincorn.Thediseaseisrarelyyield-

limiting.(Picture courtesy G. Shaner)

deform tassels and leaf tissue (Figure 2), but symptomsmaynotbenoticeableuntil later in the season. Althoughthisdiseasecancausestrikingsymptoms, itrarelycausessignificantyieldlosses,andfoliarfungicidesarenotlabeledforcontrolof thisdisease.Producers thinking about ap-plying foliar fungicides at early growth stages of corn to improve the health of stressed or damaged corn should consider that past research indicates that the most con-sistent yield advantage from a fungicide application oc-curs when fungicides are applied in response to a high risk of disease development at VT-R1.Hybridsusceptibil-ity,previouscrop,andweatherconditionspriortotasselingstrongly influencediseasedevelopment,and these factorsshouldbeconsideredbeforedecidingtoapplyafungicide.

Pest&Crop No. 9 June 3, 2011 • Page 6

Are Late-Planted Soybeans at Risk for Soybean Rust?–(Kiersten Wise)

The 2011 planting season has not gone smoothly formany Indiana producers, with only 25% of the intendedsoybeanacreageinthegroundasofFriday(USDANASS).ThisputstheIndianasoybeancropabout2-3weeksbehindtheaveragedevelopmentschedule,andtherearequestionsabout if thisyear’ssoybeancrop isatgreaterriskforsoy-beanrustduetothelateplanting.Juneplantedsoybeanswill be at a younger growth stageandpossibly at risk foryield loss from soybean rust should spores of the fungusthatcausessoybeanrust(Phakopsora pachyrhizi)reachIn-dianainAugustorSeptember.However,thelikelihoodthatdiseasewillestablishandcauseyieldlossinIndianain2011dependsonmany factors, includingweather patterns andthelevelofdiseasethatdevelopsthroughouttheyearinthesouthernU.S.

Soybean rusthasbeenslow todevelop in theU.S. in

2011duetodroughtconditionsinmostsouthernstates(Fig-ure1).Thismeans that there iscurrentlya lowamountofdiseasedkudzuthatcanserveassourceofsporesforsoy-beaninfectionandthenorthwardmovementofthedisease.Weather conditions will dictate how quickly the diseaseprogressesinsouthernstates,andsentinelplotsareestab-lished in theseareas tomonitor themovementof thedis-ease.Indianaalsohassoybeanplotsthatcanbeobservedforsoybeanrustshouldthediseasemovenorthatacriticalpointinthegrowingseason.

Sincesoybean rustwasfirstdiscovered in theU.S. in2004,IndianaandmuchoftheMidwesthavebeensparedfromsoybeanrustoutbreaks thatcouldresult inyield lossdue to the late northwardmovement and development ofthedisease.However,producersthatareconcernedaboutsoybean rusthaveseveraloptions tostay informedof theriskofsoybeanrustinIndiana:

1.Soybeanrustdevelopmentcanbe trackedusingtheipmPIPEwebsite<http://www.sbrusa.net>.Observa-tionsofsoybeandiseasesandfungicidesprayadvisoriesspecifictoIndianacanbeaccessedbyselectingtheout-lineofthestateofIndianaonthenationalmap.

2.IndianasoybeanproducerscansubscribetotheIn-dianasoybeandiseaseupdatelistserve,at<https://lists.purdue.edu/mailman/listinfo/indiana-soybean-update>.ThisemailalertservicewillprovideconvenientandtimelyupdatesonsoybeandiseasemonitoringinIndiana,andalsoprovideinformationonfungicidesprayapplicationsifsoybeanrustreachesIndianaatacriticaltimeduringthegrowingseason.

3.PurdueUniversitywillcontinuetomaintainatoll-free soybeandiseasehotline,which is updatedweeklybeginning in late June.Thephonenumber is866-458-RUST(7878).

4.UpdatedcommentaryontheriskofsoybeanrustandothersoybeandiseaseswillbereleasedinthePestandCropnewsletterastheseasondevelops.

Figure1.CurrentstatusofsoybeanrustinNorthAmeri-ca.(ipmPIPEwebsite;<http://www.sbrusa.net>)

Pest&Crop No. 9 June 3, 2011 • Page 7

A g r o n o m y T i p sEffects of Flooding or Ponding on Young Corn –

(Bob Nielsen)

Recent intense rainfall events (technically referred toas “toad stranglers” or “goose drownders”) have causedfloodingoflow-lyingcornfieldsorpondinginpoorlydrainedswaleswithinfields.Otherareaswithinfields,whilenottech-nicallyfloodedorponded,mayremainsaturatedforlengthyperiods of time.What are the prospects for recently sub-mergedcornfields?

Thesarcasticanswer is thatfloodedcropswillsurviveuntiltheydie.WhatImeantosayisthatnoonecantellyouwithcertaintythedayafterthestormwhetherapondedareaofacornfieldwillsurviveorwhethertherewillbelong-termyieldconsequencesuntilenoughtimehasgonebysuchthatyoucanassesstheactualrecoveryofthedamagedplants.Wecan,however,talkaboutthefactorsthatincreaseorde-creasetherisksofseveredamageordeathtofloodedsoils.

• Plants thatarecompletelysubmerged isathigherriskthanthosethatarepartiallysubmerged.

oPlants that are only partially submergedmaycontinuetophotosynthesize,albeitatlim-itedrates.

• Thelongeranarearemainsponded,thehighertheriskofplantdeath.

oMost agronomists believe that young corncansurviveuptoabout4daysofoutrightpond-ingiftemperaturesarerelativelycool(mid-60’sF or cooler); fewer days if temperatures arewarm(mid-70’s°Forwarmer).

oSoil oxygen is depleted within about 48hours of soil saturation.Without oxygen, theplants cannot perform critical life sustaining

functions;e.g.nutrientandwateruptakeisim-pairedandrootgrowthisinhibited.

• Even if surface water subsides quickly, the likeli-hoodofdensesurfacecrustsformingasthesoildriesincreases the risk of emergence failure for recentlyplantedcrops.

oBepreparedwitharotaryhoetobreakupthecrustandaidemergence.

• Thegreaterthedepositionofmudoroldcropresi-duesonplantsasthewatersubsides,thegreaterthestressontheplantsduetoreducedphotosynthesis.

o Ironically,suchsituationswouldbenefitfromanotherrainfalleventtowashthemuddepos-itsfromtheleaves.

• CornyoungerthanaboutV6(sixfullyexposedleafcollars)ismoresusceptibletopondingdamagethaniscornolderthanV6.

Pest&Crop No. 9 June 3, 2011 • Page 8

oThis is partly because young plants aremoreeasilysubmergedthanoldertallerplantsand partly because the corn plant’s growingpointremainsbelowgrounduntilaboutV6.Thehealth of the growing point can be assessedinitially by splitting stalks and visually exam-ining the lower portion of the stem (Nielsen,2008a).Within3 to5daysafterwaterdrainsfromthepondedarea,lookfortheappearanceoffreshleavesfromthewhorlsoftheplants.

• ExtendedperiodsofsaturatedsoilsAFTERthesur-facewater subsideswill take their toll on the overallvigorofthecrop.

• Somerootdeathwilloccurandnewrootgrowthwillbe stunteduntil the soil dries to acceptablemoisturecontents.Asaresult,plantsmaybesubjecttogreaterinjuryduringasubsequentlydrysummerdue to theirrestrictedrootsystems.

• Concomitant(Ifoundanewwordinthedictionary!)withthedirectstressofsaturatedsoilsonacorncrop,flooding and ponding can cause significant losses ofsoil nitrogendue todenitrificationand leachingof ni-trateN.

oSignificantlossofsoilNwillcausenitrogendeficienciesandpossibleadditionalyieldloss.

oOn the other hand, if the corn dies in thepondedareasitprobablydoesnotmatterhowmuchnitrogenyou’velost.

• Lengthyperiodsofwetsoilconditionsfavorthede-velopmentofseedlingblightdiseases,especiallythosecausedbyPythiumfungi(Sweets,2008).

oPoorly drainedareasof fieldsaremost atriskforthedevelopmentofthesediseasesandsowillalsoberiskyforpotentialreplantopera-tions.

• Certaindiseases,suchascommonsmutandcrazytop, may also become greater risks due to floodingandcooltemperatures(PatakyandSnetselaar,2006;Sweets,2011).

oThefungusthatcausescrazytopdependsonsaturatedsoilconditionstoinfectcornseed-lings.

oThecommonsmutfungalorganismisubiq-uitousinsoilsandcaninfectyoungcornplantsthroughtissuedamagedbyfloodwaters.Thereis limited hybrid resistance to either of thesetwodiseasesandpredictingdamageisdifficultuntillaterinthegrowingseason.

Related References

Butzen,Steve.Flooding ImpactonCrops.PioneerHi-Bred Int’l. [On-line].Available at <http://www.pioneer.com/home/site/us/template.CONTENT/agronomy/crop-man-agement/adverse-weather-disease/flood-damage/guid.DE1A9B1D-CAC0-4A04-B9CC-E0820B29080A> [URL ac-cessedMay2011].

Elmore,RogerandLoriAbendroth.2008.FloodedCornandSaturatedSoils.IntegratedCropManagementNewslet-ter,IowaStateUnivExtension.[On-line].Availableat<http://www.extension.iastate.edu/CropNews/2008/0530RogerElmoreLori+Abendroth.htm>[URLaccessedMay2011].

Farnham,Dale.1999.Cornsurvival inwetconditions.Iowa State Univ. Integrated Crop Management Newslet-ter. [On-line] Available at <http://www.ent.iastate.edu/ipm/icm/1999/5-24-1999/wetcorn.html> [URL accessed May2011].

Hager,Aaron. 2011.ReplantingCorn:How toControlPlantsfromtheInitialPlanting.theBulletin,Univ.ofIllinoisExtension.[On-line].Availableat<http://bulletin.ipm.illinois.edu/article.php?id=1480>[URLaccessedMay2011].

Nielsen,RL (Bob). 2008a.GrowingPoints of Interest.CornyNewsNetwork,PurdueUniv. [On-Line].Availableat<http://www.kingcorn.org/news/timeless/GrowingPoints.html>[URLaccessedMay2011].

Nielsen,RL(Bob).2008b.TipsforStagingCornwithSe-vereLeafDamage.CornyNewsNetwork,PurdueUniv.[On-Line].Available at <http://www.kingcorn.org/news/timeless/VStagingTips.html>[URLaccessedMay2011].

Nielsen,RL(Bob).2008c.UseThermalTimetoPredictLeaf Stage Development in Corn. Corny News Network,PurdueUniv. [On-Line].Available at <http://www.kingcorn.org/news/timeless/VStagePrediction.html> [URL accessedMay2011].

Nielsen,RL(Bob).2010.DeterminingCornLeafStages.CornyNewsNetwork,PurdueUniv. [On-Line].Availableat<http://www.kingcorn.org/news/timeless/VStageMethods.html>[URLaccessedMay2011].

Owen, Mike. 2008a. Replant Options in Corn Fields.IntegratedCropManagementNewsletter, IowaStateUnivExtension. [On-line].Available at <http://www.extension.ia-state.edu/CropNews/2008/0531MikeOwen2.htm> [URL ac-cessedMay2011].

Owen, Mike. 2008b. Replanting Corn – How Do YouGet Rid of the Existing Stand? Integrated Crop Man-agement Newsletter, Iowa State Univ Extension. [On-line]. Available at <http://www.extension.iastate.edu/CropNews/2008/0531MikeOwen.htm>[URLaccessedMay2011].

Pest&Crop No. 9 June 3, 2011 • Page 9

Pataky, J. K., and K. M. Snetselaar. 2006. Commonsmutofcorn.ThePlantHealthInstructor.DOI:10.1094/PHI-I-2006-0927-01 [On-line] Available at <http://www.apsnet.org/edcenter/intropp/lessons/fungi/Basidiomycetes/Pages/CornSmut.aspx>[URLaccessedMay2011].

Sweets,Laura.2008.SeedDecayandSeedlingBlightsofCorn. IntegratedPest&CropManagementNewsletter,Univ of Missouri Extension. [On-line].Available at <http://ppp.missouri.edu/newsletters/ipcm/archives/fullissue/v18n9.pdf>[URLaccessedMay2011].

Sweets,Laura.2011.CrazyTopofCorn.IntegratedPest& Crop Management Newsletter, Univ of Missouri Exten-sion. [On-line].Available at <http://ppp.missouri.edu/news-letters/ipcm/archives/fullissue/v21n9.pdf> [URL accessedMay2011].

Thomison, Peter. 2010. Injury to Corn from PondingandSaturatedSoils.C.O.R.N.Newsletter,OhioStateEx-tension.[On-line].Availableat<http://corn.osu.edu/newslet-ters/2010/2010-11/injury-to-corn-from-ponding-and-saturat-ed-soils/?searchterm=ponding>[URLaccessedMay2011].

Thoughts on Late Planting of Soybean –(Shaun N. Casteel)

Thisplantingseasonisgoingdownintherecordbooksas one of the wettest and one of the slowest for Indianaandtheeasterncornbelt.AsofMay22nd,only17%oftheintendedsoybeanacreswereplantedacrossIndianawiththemajorityinthenorthwesternandwest-centralareas(USDA-NASS,2011).Weareapproximatelytwoweeksbehindthefive-yearaverageandnearlyfourweeksbehindlastyear’s

Late Planting of Soybean

Figure1.Indianasoybeanplantingprogressin2011(USDA-NASS,2011).

furious pace (Figure 1). Soybean planting progress nearthiscalendardaywas25%in2009,38%in2008,and19%in 2002. The current planting progress is mirroring 2009growingseasonuptothispoint(Figure2).

Figure2.LatesoybeanplantingsinIndianafrom1997to2010(USDA-NASS,2011).

Late Planting Effects. Icertainlypreachtheimportanceof timely plantings to maximize yields, which is normallywithinthefirstthreeweeksofMayforIndiana.Twobenefitsoftheseplantingsincludegreaternodedevelopmentpriortofloweringandquickercanopytocapturesunlightandshadeoutweeds.Theyieldpotentialcanbereducedasplantingisdelayed,butitisnotaguaranteethatyieldswillbelower.Delayedplantingprobablycontributedtothelowstateyieldsin 2002 (41.5 bu/acre) and in 2008 (45.0 bu/acre), whichwere nearly 7% and 4% BELOW the annual yield trend.However Indiana averaged 49.0 bu/acre in 2009, whichwas3%ABOVEtheannualyieldtrend.Favorableseedfillperiod in 2009 allowed many soybeans to increase seedsize to compensate for fewer nodes and thus, yield well.Approximately33%ofsoybeanyielddepartureswererelatedtothedateatwhichhalfofthesoybeanacreswereplantedin Indiana (Figure3)which isslightlyhigher than isnotedfor corn (Nielsen, 2011). Soybeans trip their reproductive

Figure3.Departurefromsoybeanyieldtrendbasedon50%plantingdatesinIndiana(USDA-NASS,2011).

Pest&Crop No. 9 June 3, 2011 • Page 10

trigger(flowering)asthedaylengthshortens,whichoccursmuchquickerwithdelayedplantings(Figure4)andpartiallyexplainsthegreatereffecttosoybeanovercorn.

Figure4.NumberofdaysfromplantingtoreachR1(FirstBloom)inWestLafayette.

Tips When Planting Soybeans Late. We need setthe stage for the best possible return on late plantings ofsoybean. Planting in the first weeks of June require 10to 20% increase in seeding rates to facilitate quicker rowclosureandhigherpodheightwithfewerdaystoflowering.Increasedseedingrateswillalsobeneededinthosefieldsthat have heavy corn residue and weed biomass (seeCasteel,2011formyseedingratediscussion).Late-plantedsoybeansshouldalsobeplantedinnarrowrowstohastenthe time to rowclosure.Wide rows (30-in) takenearly 25days longer and 40 days longer to canopy compared to15-inand7.5-inrows,respectively.Thisdelaywillcertainlydecreasetheyieldpotentialascanopyclosurewouldoccurwell after reproductive initiation. Full-season varieties foryourrespectiveregionsshouldbeplanteduntilJune15forthenorthernquarter,June20forthecentralhalf,andJune25for thesouthernquarterof Indiana.Varietiesshouldbedroppedahalfmaturitygroupafterthesedatesandplantedforanothertwoweeksbeforeweconsiderotheralternatives.

References:

Casteel, S.N. 2011. Fine-tune soybean seedingrates during chilly and wet spring. [On-line]. Availableat <http://www.agry.purdue.edu/ext/soybean/Arrivals/2011_0421SOYSeedRate.pdf>[URLaccessedMay2011].

Nielsen, R.L. 2011. Corn planting date is important,but…[On-line].Availableat<http://www.kingcorn.org/news/timeless/PltDateCornYld.html>[URLaccessedMay2011].

USDA-NASS. 2011. Crop Progress and Condition.USDA, National Agricultural Statistics Service. [On-line].Available at <http://usda.mannlib.cornell.edu/MannUsda/viewDocumentInfo.do?documentID=1048> [URL accessedApr2011].

Assessing Available Nitrogen from Fall- and Spring-Applied Nitrogen Applications - (Jim Camberato, Bob Nielsen, and Brad Joern)

Excessiverainfallandfloodinginearlytolatespringcanresult in the lossofsome fall-andspring-appliednitrogen(N).BothoftheseNformsaresubjecttoleachingthroughthesoilintotiledrainsorgroundwater.Inaddition,thenitrateformofNcanconvertedtoseveralgaseousformsandlostto theatmosphere fromdeepwithin thesoilbyabacterialprocesscalleddenitrification.Unfortunately,nomatterwhatformofNwasaddedtothesoilitwilleventuallybecomeni-trate.CalendartimesinceNapplicationandspringtempera-turesinfluencetheextenttowhichbothfall-andspring-ap-pliedNconverttothenitrateform.ManyfactorsaffecthowmuchNislostfromsoil,thereforeitisdifficulttoaccuratelyestimate theamountofN loss thatmayhaveoccurredbyanypointintime.OneoftheviableoptionstoestimatetheamountofremainingsoilNistoconsidersoilsamplingandanalysisforthenitrateandammoniumformsofN.

Soil sampling strategies

Collect soil cores for soilN analyses to a depth of atleast1foot.Whereearlier-appliedfertilizerNwasbroadcastratherthanbanded,collect20to30soilcorespersample.Where earlier-applied fertilizerNwas banded (e.g., anhy-drousammonia),collect15to20soilcoresusingthesam-pling scheme illustrated inFigure1.Consider collectingaseparate deeper soil sample from between 1- and 2-footdeepforamorecompleteassessmentofplantavailableN,especiallyinsandysoilswhereleachingthroughthesoilpro-fileisthepredominantformofNloss.

TIP: One sample should represent no more than 10 acres.

Sample handling

DryorrefrigeratethesoilsamplesassoonaspossibletostopthesoilmicrobesfromalteringtheNlevels.Spreadthesoilthinlyonplastictoairdryandhastendryingwithafanifpossible.Ifyouchoosetouseanoventodrythesoil,keep the temperaturebelow250F.Alternatively refrigeratethe samples and keep them cold through shipping to thelaboratory.Alistofcertifiedsoiltestinglaboratoriesisavail-able at <http://www.ag.purdue.edu/agry/extension/Pages/soil-testing-labs.aspx>.MostshouldoffersoilNtestanalysisservices,butcontactthemfirsttoconfirm.

Soil-test laboratory analyses

AmmoniumN(NH4-N)isjustasavailabletoplantsasis

nitrateN(NO3-N),buttypicallylittleaccumulatesinthesoil

becauseitisreadilyconvertedtonitrateundermostcondi-tions.However,ifNfertilizerwasrecentlyapplied,theremaywellyetbesomeammoniumNavailableinthesoilforplantuse.

TIP: When you submit the soil samples to the soil-testing laboratory, request analyses for exchangeable

Pest&Crop No. 9 June 3, 2011 • Page 11

Figure1.RecommendedsoilsamplingpatterninrelationtotwocornrowswhenNfertilizerhasbeenbandedwiththerow.Alwayssampleperpendiculartothedirectionfertilizerwasapplied.(Source of image: Brouder & Mengel, 2003).

ammonium as well as for nitrate, particularly if anhy-drous ammonia was applied relatively recently or a nitri-fication inhibitor was used with the N fertilizer.

Significantlevelsofsoilammoniumaremostlikelyifan-hydrousammoniawastheNsource,anitrificationinhibitorsuchasnitrapyrinordicyandiamide(DCD)wasused,and/orsoilpHwaslow(below5.5).Inthesesituations,lowlevelsofsoilnitratemayindicatelittleconversionofammoniumtonitrate,ratherthansimplylossofnitrate.

Ifsoiltestvaluesforammoniumandnitratearereportedas ppm ormg/L nitrogen (NH

4-N or NO

3-N), then pounds

peracreofavailableNarecalculatedbymultiplyingthetestresultsby4when thesampledepthwas1 foot.Forothersampledepths,dividethesampledepth(ininches)by3andthenmultiplybythetestresults.

Example:SoilNO3-N ina1-footsamplewas30ppm.

Conversionfromppmtopoundsperacreis(12inches/3)x30ppm=120poundsperacre.

Ifsoil testvaluesare reporteddirectlyasNH4orNO

3,

then these valuesmust be converted toan ‘N’ basis first.Thecalculationsare:NH

4-N=NH

4/1.2andNO

3-N=NO

3

/4.5.

Example: Soil NO3 was reported to be 90 ppm.

Conversion fromNO3 toNO

3-N is90ppmNO

3 /4.5=20

ppmNO3-N.

Interpreting soil nitrate and ammonium levels

Inouropinion,soilnitrateandammoniumlevelscanbeusedtoguideadditionalNapplicationstofieldssubjectedtosaturation and flooding.However, there are admittedly nohardandfastresearch-basedrecommendationsforthispar-ticularsituation.

TheprimarytoolforsoilNsamplingintheEasternCornBelt has been the pre-sidedress soil nitrate test (PSNT)whichismostapplicableasanindicatorofNavailabilityinsoilswheremanurehadbeenappliedoralegumesuchasclover or alfalfa had been plowed down (Brouder &Men-gel,2003).Forthesefieldsituations,thelevelofsoilnitratefoundisconsideredanindexofNavailability,i.e.,anindica-torofhowmuchNiscurrentlyavailableANDhowmuchNmaybecomeavailable fromthemanureororganicmatter.Whenused in this context, soilNO

3-N levels greater than

25ppmarethoughttobeadequateforoptimumcornyieldwithouttheadditionofmorefertilizerN.Duringtheresearchthatdevelopedthissoiltest,samplingdeeperthan1footoranalyzingforexchangeableNH

4-Ndidnotincreasethepre-

dictiveabilityofthePSNTenoughtowarranttheextraeffort.

However,whentheintentistoassessthelossofNduetorainfall,wesuggestthatdeepersamplingplusanalysisforNH

4-Ncontentcanprovideusefulinformationtohelpgrow-

ersdecidewhetheradditionalfertilizerNismerited.Itisim-portant to recognize that in thiscontext,measurementsofsoilnitrateandammoniumfollowingfertilizerNapplicationsindicatecurrentNavailabilityonly,becausethereisnoma-nure-or legume-derivedNtobereleased later in thesea-son.Consideringthisfact,thecommonlyaccepted25ppmNO

3-Ncriticallevelformanure-orlegume-Nfertilizedsoils

maybetoolowforsoilsthathaveonlyreceivedfertilizerN.

Leachingofsoilnitrateisexpectedwithponding,flood-ing,orsoilsaturation,butnotallofthenitratewillhavebeenmovedbelowtherootzone.Ashortcomingofthe1-footsam-plingdepthisthatitdoesnotalwaysreflectplantavailableNdeeperintheprofile,particularlywhenabnormalleachingoccurs.Thisiswhywesuggestalsosamplingfromthe1-to2-footdepthforassessmentofsoilNavailability,particularlyinsandysoils.

Inouron-goingNrate trialsconducted throughout thestate, the “normal” background levels of soil N in the up-per1footofmineralsoilstypicallyrangefrom5to10ppmNO

3-Nand4to8ppmNH

4-Nforcorngrowninrotationwith

soybeanorcornwithoutmanure-orlegume-derivedN.Typi-callythedeeper1-to2-footsoilsampleswouldhaveslightlylowerNlevels.

Making a decision

Wesuggestthatthe25ppmNO3-Ncriticallevelforma-

nure-or legume-N fertilizedsoilsmaybe too low for soilsthathaveonlyreceivedfertilizerNandwhereNlosscondi-tionshavebeensevere.WhereenoughrainfallhasoccurredtocausesubstantialNloss,wesuggestthislevelofrainhasdepleted the lowersoilprofileaswellas theupper footofsoil.

Theaccompanyingtablecontainsestimatesofexpect-edsoilNO

3-Nlevelswithdifferent fertilizerratesassuming

“normal”backgroundlevelsofnitrateandammoniumatthetimeoffertilizationanda“normal”amountofmovementbe-low theone footsamplingdepth (approximately1/3of thefertilizer N ismoved below the 1-foot sampling depth but

Pest&Crop No. 9 June 3, 2011 • Page 12

retainedwithintherootzonewithnormalrainfall).Ifthecornishealthyandthegrowingseasontypicalfromhereonout,wewouldsuggestapplyingnomorethan10poundsofNforevery2ppmreductioninsoilsampleNbelowtheexpectedlevelslistedinthetable.

TheexpectedNO3-Nlevelfromthetablebelowfora160-lb

Napplication is35ppm.Laboratory results indicatedonly20ppmNO

3-N.ThesuggestedNapplicationratewouldbe:

((35ppm–20ppm)/2)x10=(15ppm/2)x10=7.5x10=75poundsperacre.

Example calculation when both NO

3-N and NH

4-N are determined:

Anhydrous ammonia with nitrapyrin was applied at 160poundsofNperacreinlateAprilinnorthernIndiana.Sincethe N application was relatively recent and a nitrificationinhibitorwasused,bothNO

3-NandNH

4-Nanalysisofsoil

sampleswererequested.TheexpectedNO3-NplusNH

4-N

levelslistedinthetablefora160-lbNapplicationis41ppm.Laboratoryresultsindicated15ppmNO

3-Nand20ppmNH

4-

NforatotalmeasuredNlevelof35ppm.ThesuggestedNapplicationratewouldbe:((41ppm–35ppm)/2)x10=(6ppm/2)x10=3x10=30poundsperacre.

Sidedress N application rates

Ifnofertilizer-NhasbeenappliedthisseasonorsoilNmeasurementssuggestlittleNremainsfromfall-andspring-applied N, consider using our recent research findings todeterminetheproperapplicationrate.Resultsfromfieldtri-alsconductedsince2006throughoutthestatewithefficientmethodsandtimingsofNfertilizerapplicationsuggestthatthe averageN rate needed tomaximize yield [AgronomicOptimumNRate(AONR)]forcornfollowingsoybean(corn/soy)variesbyregionorsoiltype.TheestimatedAONRforfine textured soils inwestcentral andnorthwest Indiana is173lbsN/ac.TheAONRforfinetexturedsoilsinnortheast,eastcentral, and central Indiana is approximately 221 lbsN/ac.TheAONRfortheremainderofthestate(NC,SW,SC,andSE)isapproximately183lbsN/ac.FormoredetailsontheserecommendationsseeourcurrentpublicationNitrogenManagement Guidelines for Indiana at: <http://www.agry.purdue.edu/ext/corn/news/timeless/NitrogenMgmt.pdf>.

AtthefivePurduelocationswhereweconductedpairedtrialsofcorn/soyandcornfollowingcorn(corn/corn)in2007-2010, theaverageAONRforcorn/cornwas44 lbsgreaterthan for corn/soy while average corn/corn yields were 18bu/aclessthanthecorn/soyyields.Basedon$0.50-$0.70/lbNand$7.00/bucorn,theaverageEconomicOptimumNRate(EONR)forcornfollowingsoybeanwasapproximately164, 203, and 172 lbsN/ac forWC+NW,NE+EC+C, andtheremainderofthestate,respectively.TheEONRvaluesforothercombinationsofNcostandgrainpricearelistedintheNitrogenManagementGuidelines for Indianaor in theon-lineNcalculatorforIndianaatthiswebsite:<http://exten-sion.agron.iastate.edu/soilfertility/nrate.aspx>.

Related References

Blackmer,A.M.,D.Pottker,M.E.Cerrato,andJ.Webb.1989. Correlations between soil nitrate concentrations inlatespringandcornyieldsinIowa.J.Prod.Agric.2:103-109.

Brouder, Sylvie andDavidMengel. 2003.ThePresid-edress Soil Nitrate Test for Improving N Management in

Table 1. Expected levels of nitrate and nitrate plus am-moniumintheupper1footofsoilfordifferentratesofap-pliedNfertilizer.NOTE:UsetheNO

3-Ncolumnifthisisthe

onlyformofNmeasuredinyoursoilsample.AddNO3-N

andNH4-NlevelstogetherifbothformsofNaremeasured

in thesoil sampleanduse the last column toassessNsupply.

Fertilizer N applied prior

to rains

Nitrogen Analysis

Expected N levels, ppm or mg/L N

NO3-N NO

3-N + NH

4-N

lb/acre * **

130 30 36

140 31 37

150 33 39

160 35 41

170 36 42

180 38 44

190 40 46

200 41 47

210 43 49

220 45 51

NO3-N=Nitratenitrogen

NH4-N=Ammoniumnitrogen

*Assumesbackgroundlevelofammoniumat67ppmand“normal”levelsofsoilNbelowthe1-footsamplingdepth.**Assumes“normal”levelsofsoilNbelowthe1-footsam-plingdepth.

Recognize that as a healthy crop moves through therapidgrowthphasepriortopollination,soilNlevelswillnatu-rallydecreaseinresponsetorapidNuptakebytheplants.However, by the time a healthy crop reaches the V9 leafstage(about30inchestall),only19lbs/acN(equivalentto5ppmsoilNO

3-Nina1-footdeepsample)havetypicallybeen

takenuptheplants(Mengel,1995).However,bythetimeahealthycropreachesshoulder-high(~V15or60inchestall),approximately116lbs/acN(equivalentto29ppmsoilNO

3-N

ina1-footdeepsample)havebeentakenupbytheplants.

Thefollowingexamplesgiveyouanideaofhowthetab-ularinformationmaybeusedtomakethisdecision.

Example calculation when only NO3-N is determined:

FertilizerNwasappliedat160poundsofNperacreinearlyAprilas28%UANinsouthernIndiana.OnlysoilNO

3-Nanal-

ysiswasrequestedbecauseitwasassumedthatmostoftheurea-andammonium-Nhadbeenconvertedtonitratesincetemperatureswerewarmprior to theApril andMay rains.

Pest&Crop No. 9 June 3, 2011 • Page 13

Corn(AY-314-W).PurdueExtension.[On-line].Availableat<http://www.agry.purdue.edu/ext/pubs/AY-314-W.pdf>.[URLaccessedMay2011].

Camberato,Jim,RL(Bob)Nielsen,EricMiller,andBradJoern.2011.NitrogenManagementGuidelinesforIndiana.Applied Crop Research Update, Purdue Univ. AgronomyDept. <http://www.agry.purdue.edu/ext/corn/news/timeless/NitrogenMgmt.pdf>.[URLaccessedMay2011].

CertifiedSoilTestingLaboratories.2010.PurdueAgron-omyExtension[On-line].Availableat<http://www.ag.purdue.edu/agry/extension/Pages/soil-testing-labs.aspx>.[URLac-cessedMay2011].

W e a t h e r U p d a t e

Corn Nitrogen Rate Calculator. 2011. A regional NratecalculatorhostedonaWebserveratIowaStateUniv.<http://extension.agron.iastate.edu/soilfertility/nrate.aspx>[URLaccessedMay2011].

Ferrer, Francesc, J.M. Villar, C.O. Stockle, P. Villar,andM.Aran.2003.Useofapre-sidedresssoilnitratetest(PSNT) todeterminenitrogen fertilizer requirements for ir-rigatedcorn.Agronomie23:561-570.

Mengel,David.1995.Roots,Growth,andNutrientUp-take.PurdueAgronomyExtensionPaperAGRY-95-08.[On-line]. Available at <http://www.agry.purdue.edu/ext/pubs/AGRY-95-08.pdf>.[URLaccessedMay2011].

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