Cover Crop-Based, Organic Rotational No-Till Corn and Soybean Production Systems in the Mid

21 Pages·2017·1.49 MB·English

agriculture
Article
Cover Crop-Based, Organic Rotational No-Till Corn
and Soybean Production Systems in the
Mid-Atlantic United States
JohnM.Wallace1,AlwynWilliams2,JeffreyA.Liebert3,VictoriaJ.Ackroyd2,4,
RachelA.Vann5,WilliamS.Curran1,ClairL.Keene6,MarkJ.VanGessel7,MatthewR.Ryan3
andStevenB.Mirsky4,*
1 DepartmentofPlantScience,ThePennsylvaniaStateUniversity,UniversityPark,PA16802,USA;
[email protected](J.M.W.);[email protected](W.S.C.)
2 DepartmentofPlantScienceandLandscapeArchitecture,UniversityofMaryland,CollegePark,
MD20742,USA;[email protected](A.W.);[email protected](V.J.A.)
3 SectionofSoilandCropSciences,CornellUniversity,Ithaca,NY14853,USA;[email protected](J.A.L.);
[email protected](M.R.R.)
4 SustainableAgriculturalSystemsLaboratory,USDA-ARS,Beltsville,MD20705,USA
5 DepartmentofCropandSoilSciences,NorthCarolinaStateUniversity,NC27695,USA;[email protected]
6 WillistonResearchExtensionCenter,NorthDakotaStateUniversity,Williston,ND58801,USA;
[email protected]
7 DepartmentofPlantandSoilSciences,UniversityofDelaware,Georgetown,DE19947,USA;[email protected]
* Correspondence:[email protected];Tel.:[phone]
AcademicEditor:PatrickCarr
Received:11February2017;Accepted:31March2017;Published:6April2017
Abstract: Covercrop-based,organicrotationalno-till(CCORNT)cornandsoybeanproductionis
becomingaviablestrategyforreducingtillageinorganicannualgrainsystemsinthemid-Atlantic,
UnitedStates. Thisstrategyreliesonmechanicalterminationofcovercropswitharoller-crimperand
no-tillplantingcornandsoybeanintocovercropmulches. Here,wereportonrecentresearchthat
focusesonintegratedapproachesforcrop,nutrientandpestmanagementinCCORNTsystemsthat
considersystemandregionalconstraintsforadoptioninthemid-Atlantic. Ourresearchsuggests
thatno-tillplantingsoybeanintoroller-crimpedcerealryecanproduceconsistentyields. However,
constraintstofertilitymanagementhaveproducedlessconsistentno-tillcornyields. Ourresearch
showsthatgrass-legumemixturescanimproveN-releasesynchronywithcorndemandandalso
improveweedsuppression. Integrationofhigh-residueinter-rowcultivationimprovesweedcontrol
consistency and may reduce reliance on optimizing cover crop biomass accumulation for weed
suppression. System-specificstrategiesareneededtoaddressvolunteercovercropsinlaterrotational
phases,whichresultfromincompletecovercropterminationwiththerollercrimper. Thepaucityof
adequatemachineryforoptimizingestablishmentofcashcropsintothickresiduemulchremainsa
majorconstraintonCCORNTadoption. Similarly,breedingeffortsareneededtoimprovecovercrop
germplasmanddevelopregionally-adaptedvarieties.
Keywords: cerealrye;conservationtillage;covercrop;hairyvetch;high-residuecultivation;manure;
nitrogen;poultrylitter;sustainableagriculture;weedsuppression
1. Introduction
Demand for organic grains continues to increase in the United States in response to growing
consumer preference for organic feed (required for meat and milk production) and food-grade
agricultural products (e.g., soymilk and tofu) [1]. Increasing societal demand for sustainable
Agriculture2017,7,34;doi:10.3390/agriculture7040034 www.mdpi.com/journal/agriculture
Agriculture2017,7,34 2of21
agricultural production practices likely contributes to observed increases in consumer preference
for organic food [2]. Recent analysis suggests that with current premium prices, organic crop
productioncanbehighlyprofitable[3]eventhoughcropyieldsaretypicallylowerthaninconventional
systems[4]. However,productionoforganicgrainhasnotkeptupwithdemand. Thishasresulted
in a national shortage of organic grain for direct human consumption and for livestock feed, thus
requiringhighlevels(>60%)ofimportedorganicgrain[5]. Whilethereareinfrastructurelimitations
to expanding organic grain production, the inability of organic grain producers to scale up their
operations due to time committed to weed and soil fertility management, as well as aversion to
tillagebymanyconventionalfarmershasalsocontributedtothelimitedadoptionoforganicgrain
production. There ispotential for increaseddomestic production of organicgrains in regions that
supportintegratedcropandlivestocksystemswithinoramongfarms,asorganicgrainproduction
reliesheavilyoninexpensivesuppliesoforganicnutrientamendmentsforcropproduction[6].Organic
productioninthemid-AtlanticU.S.(encompassingtheregionbetweenNewYorkandNorthCarolina)
has potential for expansion due to a prevalence of agricultural production systems that include
small integrated crop and livestock (dairy, poultry, swine) farms, large cash-crop farms without
animals,consolidatedlivestockoperationsthatpurchasefeedgrainoff-farmandreadyaccesstomajor
metropolitanmarkets[7]. AnnualgrainproductionprimarilyoccursintheAtlanticCoastalPlain,
Piedmont,andRidgeandValleyregionsofthemid-Atlantic,whichrangefromsandytohighclay
contentsoils. Annualprecipitationisrelativelyhigh(760–1012mm)andevenlydistributed,allowing
fortheuseofcovercropsinthespringorfallgrowingseasons.
Developmentofsustainablecroppingsystemsiscriticalforimprovingsoilandwaterconservation.
Inthemid-Atlantic,agricultureiscurrentlythelargestcontributorofnutrientandsedimentpollutants
intheChesapeakeBaywatershed[8].Inresponse,conservationtillage(e.g.,no-till)iswidelypromoted
andincentivizedinconventionalgrainproductionsystemstoreducenutrientandsedimentloading
intotheChesapeakeBayfromagriculturallands. Adoptionofno-tillcornandsoybeanproduction
variesacrossthemid-Atlantic,butisestimatedtorangefrom28%–64%ofthetotalproductionarea[9].
Incomparison,organiccornandsoybeanproductioninthemid-Atlantictypicallyreliesonfrequent
use of full-inversion tillage to incorporate nutrient amendments and crop residues, as well as to
control weeds. Additional soil disturbance occurs with the use of secondary tillage for seedbed
preparationandblind-orinter-rowcultivationtocontrolweedsinthecashcrop. Frequenttillageand
cultivationdegradessoilhealth,increasesthepotentialforsoilerosionandisbothlaborandenergy
intensive[10,11]. Consequently,successfulorganiccroppingsystemsinthemid-Atlanticrelyonsoil
buildingpractices,suchastheintegrationofcovercrops,thereturnofcropresidues,useofcarbon
(C)-rich amendments and diversified crop rotations to mitigate the effects of frequent tillage [12].
Organicgrainproducersareinterestedinintegratingconservationtillagepracticeswiththesesoil
buildingpracticestoincreasesoilqualityintheirproductionsystems.
Cover crop-based, organic rotational no-till (CCORNT) corn and soybean production is one
approachtointegratingthesoilconservationpracticesofno-tillwiththesoilbuildingpracticesof
organicsystems. CCORNTsystemsofferaviablealternativetotillage-basedproductionandarebeing
adoptedbyanincreasingnumberoforganicfarmers[13,14]. Inthesesystems,winterannualcover
cropsaremechanicallyterminatedinthespringusingaroller-crimper,andthecashcropisthenno-till
planted into the cover crop mulch. Labor and fuel savings are maximized when a front-mounted
roller-crimperisusedtoterminatethecovercrops,andcashcropsareno-tillplantedinthesamepass.
Soybeanistypicallyno-tillplantedintofall-plantedcerealrye(SecalecerealeL.)orasimilarwinter
cereal,andcornisno-tillplantedintohairyvetch(ViciavillosaRoth)oragrass-hairyvetchmixture.
Similarrolledcovercropstrategieshavealsobeendevelopedforgrainandvegetablecropsystems
inthesoutheastern[15]andtheMidwesternU.S.[16]. Centralfeaturescommontorolledcovercrop
strategiesincluderelianceonroll-crimpedcovercropmulches(grassesandlegumes)astheprimary
mechanismofwithin-seasonweedsuppressionandthecontributionofnitrogen(N)-fixinglegume
covercropstomeetthehighN-demandofthesubsequentcashcrop(e.g.,corn). Optimizingcovercrop
Agriculture2017,7,34 3of21
biomassaccumulationtoenhancephysicalsuppressionofweedsiscriticaltothesuccessofno-tillcash
cropproduction. Consequently,practicesthatimprovecovercropperformance(e.g.,tillageforcover
cropseedbedpreparation,earlyseedingandhighseedingrates)aretypicallyemployed. Simulation
modelsindicatethatarotationalno-tillapproachhasthepotentialtoincreaseCsequestration,reduce
greenhousegasemissionsandincreaseenergyefficiencyviareduceddieselfuelandlaborneedsin
comparisontocurrenttillage-basedorganicannualgrainsystemsthatrelyonprimarytillagebefore
bothcoverandcashcrops[13].
Improvedcrop,nutrientandpestmanagementstrategiesareneededtodevelopCCORNTgrain
productionsystemsinthemid-Atlanticthatsuccessfullymeetproductionandconservationgoals. Soil
andclimateinfluencethefeasibilityandperformanceofvariousintegrated,multi-tacticapproaches.
In the mid-Atlantic, CCORNT corn and soybean research has primarily focused on developing
general principles for optimizing cover crop performance and management, devising multi-tactic
weed management strategies and improving cash crop planter configurations [13,14]. The aim of
thispaperistoupdatepastreviews[13,14]bycollatingrecentandongoingresearchthataddresses
theconstraintsthatlimitproduceradoptionandthepracticesthatimprovetheperformanceofboth
coverandcashcrops. First,wepresentanoverviewoftheproductionviabilityofCCORNTinthe
mid-Atlantic,bycomparingtheyieldoutputandyieldstabilityofthesesystemsagainstcounty-level
averagesandtillage-basedorganicproductionsystems. Wethenevaluatecovercroppracticesand
integrated,multi-tacticpestmanagementstrategies,focusingourdiscussiononthetwodominant
regionalgraincrops: cornandsoybean. Lastly,weidentifymajorconstraintsandresearchpriorities
neededtofurtherimprovethepotentialofCCORNTinthemid-AtlanticU.S.
2. CornandSoybeanYieldPerformanceinCCORNT
TheviabilityofCCORNTproductionsystemshingesonthedevelopmentofintegratedcover
crop, nutrient and pest management strategies that result in consistent high yielding cash crops
acrossarangeofsoilandenvironmentalconditions. Recentresearchhasevaluatedasuiteofcover
cropandweedmanagementapproachesduringtheorganictransitionperiodwithinawinterwheat
(Triticumaestivum)-hairyvetch/triticale(xTriticosecaleWittm.)-no-tillcorn-cerealrye-no-tillsoybean
rotation. Theresearchproject,knownastheReduced-tillageOrganicSystemsExperiment(ROSE),was
aninter-disciplinary,multi-institutionaleffortbetween2010and2013atPennsylvaniaStateUniversity,
the USDA Agricultural Research Service (ARS), Sustainable Agricultural Systems Laboratory at
Beltsville, Maryland, and the University of Delaware (Supplemental Table S1). The ROSE tested
the role of cover crop termination date (early, intermediate and late) and high-residue cultivation
(+/−) in the no-till corn and soybean phases of the rotation. These treatments were imposed in a
full-entrycroppingsystemexperimentaldesign. Thisenabledtheevaluationofhowcovercropand
pest management approaches influenced cash crop performance and pest management objectives
within-seasonandacrossthethree-yearrotation. Delayedcovercropterminationhasthepotentialto
improvecashcropmanagementviahigherlevelsofweedsuppressionandNprovisioningservices
thatresultfromhigherlevelsofcovercropbiomassaccumulation.However,thisstrategycanconstrain
cashcropgrowingseasonlength. IntheROSE,shorterseasoncropvarietieswereusedwhencover
cropterminationwasdelayedforbothcornandsoybeansystems(Table1).
Agriculture2017,7,34 4of21
Table 1. Cereal rye biomass and soybean yields in an organic cover crop-based rotational no-till
experiment(2011–2013)conductedbyPennStateUniversity,theUSDAAgriculturalResearchService
(ARS)SustainableAgriculturalSystemsLaboratoryinBeltsville, MDandUniversityofDelaware.
Cerealryebiomassandsoybeanyieldsareaveragedacrosshigh-residuecultivationtreatments(n=2),
blocks(n=4)andyears(n=3;2011–2013)forthethreeplantingdatetreatments(early,middle,late)
evaluatedintheexperiment. Thecoefficientofvariation(CV)isreportedtodescribeinter-annual
yield variability (2011–2013) among alternative planting date strategies and county-level average
conventionalyields.
Site(Soybean PlantingDate PlantingDate CerealRyeBiomass SoybeanYield
Production) (MaturityGroup)† Range(2011–2013) Mean(CV%) Mean(CV%)
———————-Mgha−1———————-
PennStateUniversity Early(2.9) 26–31May 5.3 (21) 3.2 (5)
RockSprings,PA Middle(2.7) 3–6June 5.8 (16) 3.3 (5)
Late(1.1) 11–17June 7.0 (20) 2.7 (11)
CountyAverageYield —– 3.2 (6)
USDA-Beltsville Early(3.8/4.3) 3–28May 6.4 (29) 3.3 (27)
Beltsville,MD Middle(3.4) 11May–5June 7.4 (31) 3.8 (22)
Late(2.7) 18May–17June 8.2 (33) 3.4 (39)
CountyAverageYield —– 2.7 (10)
UniversityofDelaware Early(3.8/4.3) 3–21May 7.7 (15) 1.7 (16)
Georgetown,DE Middle(3.4) 8–28May 8.6 (6) 2.6 (1)
Late(2.7) 15May–5June 9.9 (11) 1.9 (16)
CountyAverageYield —– 2.7 (7)
†Maturitygroupsarebasedon~150kmlatitudinalgradientsfromsouth(4s)tonorth(1s)inthemid-Atlanticregion.
Delayed cover crop termination in CCORNT soybean systems resulted in greater cereal rye
biomass across mid-Atlantic locations, with step-wise increases in biomass levels observed across
plantingdatesatmoresouthern(MarylandandDelaware)locations(Table1). However,cerealrye
biomassisonlyoneofseveralinteractingfactorsthatcaninfluencesoybeanyieldsinCCORNTsystems.
Forexample,lowersoybeanyieldswereobservedwhenplantingdatesweredelayeduntilmid-Juneat
thePennsylvanialocation,whichcanbeattributedinparttotheshortergrowingseasoninthenorthern
mid-Atlantic. Incomparison,laterplantingdatesatthesouthernlocationsproducedsoybeanyields
comparabletoearlyplantingdates. Ateachmid-Atlanticlocation,thehighestyieldingplantingdates
werecomparabletocounty-levelaveragesforconventionalsoybeanproduction(Table1). Moreover,
inter-annualyieldvariabilitywasalsocomparabletocountyaverages.
Delayed cover crop termination in no-till corn systems produced similar regional trends to
soybean (Table 2). In general, hairy vetch/triticale biomass increased as cover crop termination
wasdelayed,butobservedtrendssuggestthatcornyieldswerenotpositivelycorrelatedwithcover
cropperformance. Inmorenorthernareasofthemid-Atlantic(Pennsylvania), therelativelyshort
growingseasonrequiredcorntobeharvestedforsilagetoenableprimarytillage,seedbedpreparation
andcerealryeestablishmentpriortono-tillsoybeanproduction. Earlierplantingdatesresultedin
highercornsilageyieldsatthePennsylvanialocation,butyieldswereconsistentlybelow(16%–34%)
county-level averages for conventional corn silage production over the same period. Longer fall
growingseasonsinsouthernareasofthemid-Atlantic(MarylandandDelaware)enabledcerealrye
establishmentfollowingcorngrainproduction. IntheROSE,corngrainyieldswerewellbelowcounty
averagesinDelaware,butexceededcountyaveragesinMaryland. Despitevariationsinyield,organic
rotationalno-tillproductionofbothcornandsoybeanwasprofitablewithouttheneedtofactorin
organicpricepremiumsatthePennsylvaniaandMarylandlocationseachyearandinoneyearat
Delaware[17].
Agriculture2017,7,34 5of21
Table2. Covercrop(hairyvetch/triticale)biomassandcornyieldsinanorganiccovercrop-based
rotationalno-tillexperiment(2011–2013)conductedbyPennsylvaniaStateUniversity(RockSprings,
PA),USDAAgriculturalResearchService(ARS;Beltsville,MD,USA)andUniversityofDelaware
(Georgetown,DE,USA).Covercropbiomassandcornyieldsareaveragedacrosstreatments(n=2;
+/−high-residuecultivation),blocks(n=4)andyears(n=3;2011–2013)forthethreeplantingdate
treatments(early,middle,late)evaluatedintheexperiment.Thecoefficientofvariation(CV)isreported
todescribeinter-annualyieldvariability(2011–2013)amongalternativeplantingdatestrategiesand
county-levelaverageconventionalyields.
Site(Corn PlantingDate PlantingDate CoverCropBiomass CornYieldMean
Grain/Silage) (HybridMaturity) Range(2011–2013) Mean(CV%) (CV%)
——————–Mgha−1———————
PennStateUniversity Early(99day) 31May–1June 5.9 (8) 35.8 (10)
RockSprings,PA Middle(95day) 7–12June 6.4 (2) 31.2 (2)
(silage) Late(85day) 15–18June 6.4 (1) 28.0 (14)
CountyAverageYield —– 42.2 (26)
USDA-ARS Early(104day) 13May–4June 5.6 (17) 7.5 (8)
Beltsville,MD Middle(99day) 24May–12June 5.8 (3) 7.0 (31)
(grain) Late(88day) 31May–18June 6.0 (15) 7.6 (13)
CountyAverageYield —– 6.0 (48)
UniversityofDelaware Early(104day) 4–30May 5.5 (27) 3.8 (35)
Georgetown,DE Middle(99day) 11May–6June 6.4 (12) 5.2 (9)
(grain) Late(88day) 16May–17June 7.2 (6) 3.6 (14)
CountyAverageYield —– 9.3 (11)
Comparedwithmid-Atlanticcounty-levelaverages,soybeanyieldsintheROSEweregenerally
moreconsistentthancornyields. Thisdifferenceinyieldstabilitybetweencornandsoybeanhasbeen
observedinpreviousstudiesofCCORNTsystems[13]. Inconsistentorganicno-tillcornperformance
inthemid-Atlanticcouldbedue,inpart,toregionalconstraintsonfertilitymanagement. Southern
areasofthemid-Atlantichaveaccesstopoultrylitterforcorncropproduction. Pelletizedpoultrylitter
wasbroadcastatplantinginDelawareandsubsurface-bandedatside-dressusingcustom-fabricated
bandingequipmentattheMarylandlocation. Incomparison,thePennsylvanialocationutilizedliquid
dairymanureandapplieditduringthelate-summerhairyvetchestablishmentphasetheprevious
summer,approximatelyninemonthspriortocornestablishment. Theeffectofthesedifferentfertility
practices likely influences N availability to corn during corn peak N demand. Further research is
neededtodetermineifasynchronybetweencornpeakNdemandandNsupplyfromfall-applied
liquiddairymanureisasignificantconstraintthatmaylimitadoptionofCCORNTcornproductionin
dairy-basedregionsofthemid-Atlantic.
Beyondcomparisonswithcounty-levelaverages,whicharepredominantlybasedonyielddata
forconventionally-managedfarms,itiscriticaltocomparetheyieldperformanceoforganicrotational
no-tillagainsttillage-basedorganicsystems,inorderfortraditionaltillage-basedorganicgrainfarmers
todeterminethevalueofCCORNT.ExperimentscomparingCCORNTagainsttillage-basedorganic
systemshavebeenconductedattheAgriculturalResearchCenterinBeltsville,Marylandsince2008
(SupplementalTableS1). Datacollectionhasprimarilyfocusedoncorn(2008–2016growingseasons),
but new data are now emerging for soybean (2015–2016 growing seasons). These data show no
difference in soybean grain yields between CCORNT and tillage-based systems, while corn grain
yieldsinCCORNTincreasedcomparedwithtillage-basedsystems(Figure1). Theseresultssuggest
that,despitethegreateroperationalchallengesassociatedwithCCORNT,thereisanopportunityto
increaseyieldoutputintheseorganicsystems. However,maintainingconsistentcornyieldsacross
yearsinCCORNTsystemsremainsamajorchallenge. Plantingthroughthickmulchcaninterferewith
achievingsatisfactoryseed-soilcontact,whichcanresultininconsistentestablishmentoftargetedcorn
populationsandlowyields. Soybeancanrecoverfrominconsistentgerminationandestablishment
duetohavingacomparativelyhigherseedingrate[18]. Inaddition,thelaterplantingdatesrequired
inmorenorthernpartsofthemid-Atlantic(duetoclimateconditions)canfurthernegativelyimpact
CCORNTcornyields.
Agriculture2017,7,34 6of21
Agriculture 2017, 7, 34  6 of 21 

Figure1.Cornandsoybeangrainyieldsinorganicrotationalno-tillsystems(No-till)andtillage-based
Figure  1.  Corn  and  soybean  grain  yields  in  organic  rotational  no‐till  systems  (No‐till)  and  
organtiilclasgye‐sbtaesmeds (oTrgilal)niact styhseteAmgs r(iTciulll)t uatr athleR AesgeraicruclhtuCraeln Rteers,eaBreclht sCveilnltee,rM, Baerltyslvainlled,. MCaorrynladndat. aCsoprna nthe
2008–d2a0ta1 6spgaronw thineg 2s0e0a8s–o2n01s6( 2g0r0o8w–i2n0g1 0sewasiothnsm (o2n00o8c–u2l0t1u0r ewhiathir ymvoentocchucltouvree rhcarioryp ;v2e0t1c1h– c2o0v1e6r wcritohp;c  ereal
rye/h20a1i1ry–2v01e6tc whictho vceerrecarlo rpyem/hiaxitruy rveest)c;hs ocyovbeera ncrodpa tmaiaxrtuerferso);m sotyhbeea2n0 1d5a–t2a 0a1r6e gfrroomw itnheg 2s0e1a5s–o2n0s1.6 Corn
yieldgsrwowerinegs isgenaisfiocnasn. tClyorgnr eyaietledrsi nwneroe- tsiilglncoifmicapnatrlye dgrweaitther tiilnl (nFo1‐,t5i0ll =co6m.4p5a,rped= 0w.0it1h) ;tislol y(Fb1e,5a0 n= y6i.e4l5d, s  did
notdpi f=fe 0r.0b1e)t; wsoeyebneasny sytieemldss .dBido xnoptl odtifsferre pbreetwseenetn tshyestmemeds.i aBnox( hpolortisz orenptraelsleinnte t)h,ein mteerdqiuana r(thiolerirzaonngtael (box)
andtlhineem), ianxteimrquumartialen dramngien (ibmoux)m anvda ltuhee sm(aexnidmuomfe aancdh mveinrtimicaulmli vnael)u.es (end of each vertical line). 
3. Cover and Cash Crop Management in CCORNT 
3. CoverandCashCropManagementinCCORNT
Management strategies that produce high cover crop biomass and optimal cash crop yields are 
cMriatincaalg teom theen tsustcrcaetsesg oief sCtChOatRpNrTo dcourcne ahnidg hsocyobveearnc proropdbuicotimona.s Csraintidcalo pchtiamlleanlgceass hof cCroCpOyRiNelTd sare
criticsaylstteomtsh einsculuccdees: s(o1)f CpCooOr RcNovTerc ocrrnopa nedstasbolyisbhemanenpt, rowdhuicchti ocna.n Cnreitgiactaivleclhy alilmenpgacets  boifoCmCasOs RNT
systeamccsuimncululadtieo:n( 1a)npdo sourbcsoevqeurencrt owpeeesdta sbulipsphrmesesniotn,;w (h2)i cphocoarn ensteagbalitsivhemlyenitm opfa lcetgbuimome acsosvearc ccurompus,l ation
and swuhbicshe qreudeunctesw Ne‐efdixastuiopnp; r(3e)s fsaiiolunr;e( t2o) apdoeoquraetsetlya btelirsmhimnaeten tthoef colevgeur mcroepc, owvheicrhc nroegpast,ivwelhyi acfhfercetsd uces
N-fixcaatsiho nc;ro(3p)s faviilau rlieghtot, awdaetqeru aatnedly ntuetrrmieinnt actoemthpeetcitoiovne;r acnrodp (,4w) phliacnhtenre gcoantifvigeulryataioffnesc ttshcaat schancnroopt svia
sufficiently cut through or remove cover crop biomass, which can lower cash crop populations and 
light,waterandnutrientcompetition;and(4)planterconfigurationsthatcannotsufficientlycutthrough
yields. Consequently, understanding the potential agronomic tradeoffs related to cover and cash crop 
or remove cover crop biomass, which can lower cash crop populations and yields. Consequently,
management strategies is critical for improving the consistency of CCORNT soybean and corn systems.  
understandingthepotentialagronomictradeoffsrelatedtocoverandcashcropmanagementstrategies
iscrit3i.c1a. lSofoybreiamn provingtheconsistencyofCCORNTsoybeanandcornsystems.
3.1. SoybeAangronomic factors influencing the success of no‐till planting soybean into roller‐crimped cereal 
rye in the mid‐Atlantic have been well documented [19,20]. In our experience, CCORNT soybean 
sAygstreomnso hmaivce fparcotdoursceidn flcoumenpceitnitgiveth yeiesludsc cmeossreo cfonnosi-sttielnltplyla tnhtainn gcosrony. Tbheiasn cainn tboe raottlrleibru-cteridm inp pedartc ereal
ryeinto tthhee mfacitd t-hAattl saonytbiceahnasv heavbee elenssw meallnadgoecmuemnte ncotemdpl[e1x9i,t2y0 t]h.aInn coorunr. eTxhpe ecreireenalc ery,eC mCoOnRocNuTltusroesy bean
systeumsesdh apvrieorp troo dsouycbeedanco amrep teytpitiicvaellyy ieealsdiesrm too rmeacnoangsei sttheannt llyegtuhmane‐cgorranss. Tmhixistucraens ubteilaiztetrdi bpurtioerd tion  part
tothefactthatsoybeanshavelessmanagementcomplexitythancorn. Thecerealryemonocultures

used prior to soybean are typically easier to manage than legume-grass mixtures utilized prior to
corn. Here,wediscussbestmanagementpracticesforoptimizingcerealryebiomassaccumulation
Agriculture2017,7,34 7of21
andsubsequentterminationwitharollercrimper,alternativewintergrainsforno-tillsoybeansystems
andmulti-tacticstrategiesthatimproveweedmanagement.
3.1.1. CoverCropEstablishmentPriortoSoybean
Previousresearchhasidentifiedagronomicpracticesthatimprovecerealryeestablishmentand
performance in no-till soybean systems [14]. These practices include manipulating establishment
timing, seeding rates and soil fertility to maximize cereal rye biomass production and ground
cover[21,22]. Soybean typically follows corn in rotation in the mid-Atlantic. In the northern
mid-Atlantic (e.g., Pennsylvania and New York), late-fall corn grain harvest limits the agronomic
windowforcerealryeestablishment,butalongerfallgrowingseasoninsouthernmid-Atlanticstates
(e.g.,MarylandandNorthCarolina)allowsforconsistentcerealryeestablishment. Inourexperience,
adequateseedbedpreparationiscriticaltomaximizingcerealryeperformance. Prioritizingearlier
cornharvesttoensuresufficienttimeforcornstovermanagementandprimaryandsecondarytillage
isoftennecessary. Basedonthewindowoftimeaffordedbythepreviouscrop,producerscaneither
prepareaseedbedwithtillagepriortodrillingorno-tilldrillcovercrops. Processingpreviouscorn
stoverresidueswithaturbo-tilloftensufficestoensureoptimalcovercropestablishment. Historically,
wehaveadvocatedtillagepriorseedingfallcovercrops,asperennialweedsandpestcyclesaremost
effectivelycontrolledwithprimarytillageusingachisel-ormoldboard-plow. However,duringwet
falls,itmaybebesttoavoidtillageandno-tillplantcovercrops,asseedingintotilledgroundcanbe
greatlystalledbyawetfall. However,researchandexperiencehaverepeatedlydemonstratedthat
covercropestablishmentandgrowtharegreaterwithapreparedseedbed.
Basedonourbodyofresearch,bestmanagementpracticesforcerealryeestablishmentinclude
seedingathighrates(approximately134kgha−1)withagraindrill. Increasingcerealryeseedingrates
hasbeenshowntoincreaseweedsuppressionduetogreatergroundcoverinearlyspring[22]. Theuse
ofagraindrillimprovesestablishmentandprovidesamoreuniformplantpopulationincomparison
tobroadcastmethods. Alternativepracticesthathavebeenemployedincludeadualseedingmethod
inwhichseedisbothdrilledandbroadcasttoencourageincreasedgroundcoverininter-rowspaces.
Finally,whilecerealryeisanefficientscavengerofresidualinorganicsoilN,itmayalsobenecessary
tofertilizecerealryetomaximizebiomassandgroundcoverwhensoilmineralizableNlevelsarelow.
3.1.2. CoverCropTerminationPriortoSoybean
Optimizations of cover crop termination efficacy and biomass accumulation are the primary
factorsthatinfluencecovercropterminationtimingdecision-making. Mechanicalcontrolofcerealrye
usingaroller-crimperismosteffectivewhenterminatingafteranthesis,with>85%controlofcerealrye
occurringoncetheZadoksgrowthStages60–65arereached[21]. Covercropmulchessuppressweed
germinationandgrowthofsummerannualweedsviaphysicalobstructionandbyloweringlightand
temperatureatthesoilsurface[14]. Thelevelofcovercropbiomasstypicallyneededtoprovidehigh
levelsofweedsuppression(>8000kgha−1)requiresdelayedcashcropplantingandgoodbasesoil
fertility[23,24]. Delayingcovercropterminationbyonly7–14dayscanresultinsignificantgainsto
covercropbiomassaccumulation. Inthemid-Atlanticregion,cerealryebiomassaccumulationcan
increase200kgha−1day−1afterstemelongation[21]. Consequently,delayedcerealryeterminationis
aviablestrategyforincreasingtheweedsuppressionpotentialofsurfacemulchresidue.Othercultural
strategiesthatcanbeintegratedwithdelayedcerealryeterminationtomaximizeweedsuppression
includeearlierfallplanting[21]andincreasedseedingratestoenhancecerealryegroundcoverin
earlyspring[22].
Cover crop termination timing can also shift the composition of weed species in CCORNT
systemsbyalteringbothcovercropbiomassaccumulation(increasingwithdelayedtermination)and
thetimingofmechanicalcontrolinrelationshiptoweedemergence. Forexample,inaPennsylvania
experiment,insufficientcanopycoverfromcerealryeresultedintheemergenceofcommonragweed
(AmbrosiaartemisiifoliaL.)priortocovercropterminationwiththerollercrimper,whichdidnotcontrol
Agriculture2017,7,34 8of21
Agriculture 2017, 7, 34  8 of 21 
emerged common ragweed seedlings [19]. In comparison, later emerging summer annual species
sucha(sAgmiabnrotsifao xarttaeimli(sSiiefotalirai aL.f)a bperriiorH teor rcmov.e)ra cnrdops mteromotinhaptiiognw weietdh (thAem raorlalenrt hcruismhpyebr,r iwduhsicLh. )dwide nreotl ess
abundaconnt.trTohl eemseelregcetdio cnomofmdoonm riangawnetewd eseededfllionrgas w[1a9s].a Isns occoimatpeadriwsointh, lgateerrm eimneartgioinngp sruiomrmtoerr oalnlninugala nd
survivasplefocilelso swuicnhg asth geiarnotl floinxtgaiol p(Seertaartiiao fna.beri Herrm.) and smooth pigweed (Amaranthus hybridus L.) were 
ThleessR aObuSnEddanetm. Tohnes sterlaetcetdionth oaf tdvomoliunnantet ewreceodv felorrcar wopass ahssaovceiatthede wpoitthe gnetriamlintoatliiomn iptrtiohre tov iraoblliilnigty  of
and survival following the rolling operation. 
CCORNT practices in annual grain rotations [25]. Although previous studies have identified the
The ROSE demonstrated that volunteer cover crops have the potential to limit the viability of 
optimalterminationtimingforlimitingregrowthofroller-crimpedcovercrops,mostresearchhas
CCORNT practices in annual grain rotations [25]. Although previous studies have identified the 
been conducted using annual experiments that did not track management legacy. Consequently,
optimal termination timing for limiting regrowth of roller‐crimped cover crops, most research has 
the agronomic impacts of volunteer cover crop recruitment that may result from cover crop seed
been conducted using annual experiments that did not track management legacy. Consequently, the 
producatgioronnfoomlloicw iimnpgaecvtse nofl ovwolluenvteelesr ocforveegrr ocwrotph raerceruniotmtwenetl ltuhnatd emrastyo oreds.uIlnt tfrhoemR OcoSvEe,r wcirtohpi ns-eseeda son
controplroofdcuecrteioanl rfyoellowwiitnhg theeverno llleorw-c rliemveplse roifm  rpegrorovwedth asartee rnmoitn  wateiolln  uwndaesrsdteoloady. edIn, bthuet cReOreSaEl, r ye
continuweitdhitno‐smeasaotun rceonotnrolt hofe cgerreoaul nryde wwihthe nthete rromlleirn‐acrtiimonpeor cimcuprrroevdeda fatse trertmheinoatniosne twoafs tdheelaymedil,k bustt age
(>Zadocekrsea7l0 r)y.e cRoengtianrudelde stso omfatcuorvee ornc trhoep grtoeurmndi nwahtieonn tetrimmininagti,onv oolcucunrtreeedr acfeterre tahler oynesewt oafs thdee tmeciltka ble
acrosssltoacgaet i(o>nZsadinokws i7n0t)e. Rrewgharedaltes(Fs iogfu croeve2r) ;cirnops otemrmeicnaasteiosn, gtirmaiinngc, ovnotlaumntienear tcieornealle rvyeel swaaps pdreoteaccthabelde the
across locations in winter wheat (Figure 2); in some cases, grain contamination levels approached the 
5%maximumthresholdallowedforforeignmaterialsinfood-gradewheat. Consequently,thereis
5% maximum threshold allowed for foreign materials in food‐grade wheat. Consequently, there is 
likelyanarrowagronomicwindowfrom50%anthesis(Zadoks65)tothemilkstage(Zadoks70–79)
likely a narrow agronomic window from 50% anthesis (Zadoks 65) to the milk stage (Zadoks 70–79) 
foroptimizingcerealryecontrolandminimizingtheeffectofvolunteercovercropsinsubsequent
for optimizing cereal rye control and minimizing the effect of volunteer cover crops in subsequent 
years. System-specificstrategiesareneededtomanagevolunteercovercropsinCCORNTsystems.
years. System‐specific strategies are needed to manage volunteer cover crops in CCORNT systems. 
For exFaomr epxlaem, tphlee, tRheO RSOESEre rveevaealeledd tthhaatt a acocmopmarpaatirvaetliyv leolnygelor nfaglle grrofawlilngg rsoewasionng ins Deaelsaownarien alDloewlaewd are
allowefdorf ofralfsael sseeseede‐bde-dbdeidndg inbgefboreef orweinwteirn tewrhweaht,e awt,hwichh icmhinmiminizimedi zveodluvnotleuenr teceerrecale reryael riysesuiesss.u  es.
AlternAatlitverenlya,tivfoellylo, wfoilnlogwtihnge tshoey bsoeyabneapnh pahseasoe fotfh teher orotatatitoionn wwiitthh aa sspprriningg‐ -oro rsusmummemr‐esro-wsonw crnopc rop
providpersovaindeos papno orptuponrittuynittoy mto amnaangaegev ovolulunntteeeerr wwiinntteerr cocvoevre crrocpros pwsitwh tiitlhlagtiel lpargioer ptor ipolrantotinpgl athnet ing
the nexntexctr corpopi ninr roottaattiioonn.. OOththere rstrsattreagtieegsi mesaym ianycluindcel umdueltimplue lrtoiplleler proasllseers opra mssoerse oarggmreosrseivae groglrleers‐sive
crimper technology.  
roller-crimpertechnology.

FigureF2ig.uEreff e2c. tEofffeccte oref aclerreyael rteyrem teirnmaitnioantiotnim tiimnigngin in2 0210111o onn vvoolluunntteeeerr cceerereala lryrey eabaubnudnadncaen cine tihne the
followifnolglowwiinngte wrwintheer awthceaasth ccarsoh pcr(o2p0 1(220)1a2t) taht ethPee Pnennsnyslyvlvaanniaia aanndd MMaarryyllaanndd lolocactaiotinosn (sda(dtaa ftraomfro tmhe the
ReduceRde-dtiullcaegde‐tiOllraggae nOicrgSaynsitce SmyssteEmxps eErxipmeerinmte(RntO (RSEO)S)E.C)).e Creearlearly reytee tremrmininataitoionnr raannggeedd ffrroomm tthhee oonnsseet tof
anthesiosf (aZnathdeoskiss (5Z9a)dtookst h5e9)s toof tthdeo suogfth dsotuagghe s(tZagaed (oZkasd8o5k)s. 85). 
Although cereal rye is the most commonly‐used cover crop species in CCORNT soybean 
Although cereal rye is the most commonly-used cover crop species in CCORNT soybean
production, other winter cereal species might provide advantages over cereal rye. As the timing of 
producctoiovner, ocrtohper tewrminitneartcioenre ias lbsapseecdi eosnm coigvhert cprroopv pidheenaodlvoagnyt, augseinsgo avne recaerlrieear‐lmryaetu.rAinsgt hspeetcimiesi nsgucohf acso ver
croptebramrlienya (tHioonrdiesumba vsueldgaoren Lc.)o mveigrhctr eonpabplhe eeanrolileorg tye,rmusininagtioann aenadr slioeyrb-meaant pulrainntginsgp aencdie, tshsuusc, ah laosngbearr ley
(Hordeusomybveualgna greroLw.)inmgi gsehatseonna abnlde egarrelaiteerr tyeiremldi npaottieonntiaanl. dIns oayn beexapnerpimlaenntti ncgonadnudc,tethdu isn, Malaornylgaenrds oanydb ean
growinNgeswe aYsoornk afrnodmg 2r0e1a3t–e2r0y1i4e l(dSuppoptleenmteianlt.alI nTaabnlee xSp1)e, rdimelaeynitngco tnerdmuicntaetdioinn bMy aornyel awnedeka rnedsuNlteedw inY ork
greater biomass for both cereal rye and six‐row barley (Figure 3A). For each species at each site, 
from2013–2014(SupplementalTableS1),delayingterminationbyoneweekresultedingreaterbiomass
forbot hcerealryeandsix-rowbarley(Figure3A).Foreachspeciesateachsite,terminatingthecover
croplaterreducedbothweedbiomass(Figure3B)andthepercentageofuncontrolledcovercropplants,
Agriculture2017,7,34 9of21
Agriculture 2017, 7, 34  9 of 21 
terminating the cover crop later reduced both weed biomass (Figure 3B) and the percentage of 
or“bounce-back”(i.e.,plantsthatsurvivedrolling-crimpingandreturnedtotheiruprightgrowthhabit).
uncontrolled cover crop plants, or “bounce‐back” (i.e., plants that survived rolling‐crimping and 
InMaryland,covercropbounce-backdecreasedfrom5%downto0%forbarleyand3%downto0%
returned to their upright growth habit). In Maryland, cover crop bounce‐back decreased from 5% 
forcerealryeasterminationtimingwasdelayedbyoneweek. InNewYork,thelaterterminationtime
down to 0% for barley and 3% down to 0% for cereal rye as termination timing was delayed by one 
reducwedeecko. vIne rNcerwop Yboorku,n thcee- lbaatecrk tferrommin1a7ti%on dtiomwen retdou1c1e%d cfoovrebr acrrloepy baonudnc9e%‐bdacokw frnomto 167%%f doorwcenr etoa lrye.
Altho1u1g%h tfoerr mbianraletyio nanedf fi9c%ac ydotwennd stot o6%be fporro pceorretailo nryael.t oAcltohvoeurgchr otpermgrionwattiohns teafgfiec,awcye tdeniddsn otot obbes erve
lessbporuonpocert-iboancakl tow ciothvebr acrrloepy gcroomwtpha srteadget, owcee drieda lnoryt oeb,sdeervspe ilteessb baorulenycem‐baatcuk rwinitgh ebaarrllieeyr cionmtphaeresdp ring.
Interetsot icnegrelayl, wryee,a dlseospditied bnaorlteoyb mseartvueriningc erearalsieerd inw teheed sspuripnpgr. eIsnstieornestiinngcelyr,e waler yalesod edsidp inteotg orebasteervrec over
cropbiniocrmeaassesdp wroededu csutipopnrtehssainonb ianr lceeyr.eaSlo ryybee daenspyiiteel dgrweaatesrs ciomvielra rcraocpr obsiosmalalscs opmrobdiuncattiioonn tshoanf sbpaerlceiye.s and
Soybean yield was similar across all combinations of species and termination times at each site 
terminationtimesateachsite(Figure3C),suggestingthatcompetitionbetweenuncontrolledcover
(Figure 3C), suggesting that competition between uncontrolled cover crops and soybean was 
cropsandsoybeanwasnegligible. Resultsfromthisexperimentindicatethatlowerlevelsofcovercrop
negligible. Results from this experiment indicate that lower levels of cover crop biomass (5000–6000 
biomass(5000–6000kgha−1)canprovideadequateweedsuppressioninthenorthernmid-Atlantic,
kg ha−1) can provide adequate weed suppression in the northern mid‐Atlantic, which might help 
whichmighthelpalleviatesomeofthechallengesassociatedwithsoybeanseedplacementthrough
alleviate some of the challenges associated with soybean seed placement through thick layers of 
thickmlauylechrs. oOfumr urelscuhl.ts Oaulsro resusuggltessta ltshoats ubgargleeyst mthiagthtb abrel eayblme itgoh tcobmepaebnlseatteo fcoorm lopweners abteiofmoarslso wer
biomapsrsodpuroctdiounc taionnd aancdhiaevche ireevleatrivelealyti vheiglyh hliegvhellse vofe lwsoeefdw seuepdpsruespspiorne sdsiuoen tdou ae mtooarem roapreidr acpaindopcayn opy
closurceloasunrde wanidd ewrildeearf lbealaf dbelasdceos mcopmapreadretdo toce creeraelalr yryee[ [2266]].. 

FigurFeig3u.rTeh 3e. Timhep iamcptaocft coof vceorvecrr ocrpopte tremrmininaatitoionn ttiimmiinngg oonn ccoovvere rcrcorpo pbiobmioamssa (sAs)(, Aw)e,ewd ebeiodmbaisosm (Ba)s s(B)
andsaonydb esoaynbgeraani gnryaiine lydie(lCd )(Cu)s iunsginsgi xsi-xr‐orwoww winintteerr bbaarrlleeyy aanndd cecreeraela rlyrey ceocvoerv cerrocprso ipns MinarMylaanrydl (aMnDd)( MD)
andNaenwd NYeowrk Y(oNrkY ()NinY)2 i0n1 240.1L4a. Lteattee rtemrminiantaitoionnt itmimiinngg ooccccuurrrreedd oonne ewweeeke kaftaefrt ethret heaerelya rdlayted. aBtoex. pBlooxtsp  lots
represent the mean (open diamond symbol), median (horizontal line), interquartile range (box) and 
representthemean(opendiamondsymbol),median(horizontalline),interquartilerange(box)andthe
the maximum and minimum values (end of each vertical line). For each response, species and 
maximumandminimumvalues(endofeachverticalline).Foreachresponse,speciesandtermination
termination timing were included as fixed effects: cover crop biomass (F1,25 = 12.68, p = 0.0015 for 
timingwereincludedasfixedeffects: covercropbiomass(F =12.68,p=0.0015forspeciesand
1,25
F =12.33,p=0.0017forterminationtiming);weedbiomass(F =0.032,p=0.86forspeciesand
 1,25 1,25
F =11.65,p=0.0022forterminationtiming);andsoybeanyield(F =0.0041,p=0.95forspecies
1,25 1,20
andF =0.90,p=0.35forterminationtiming).
1,20
Agriculture2017,7,34 10of21
3.1.3. SoybeanPlantingandManagement
Incontrasttoconventionalandtillage-basedorganicsoybeanproduction,farmersthatmanage
soybeaninCCORNTsystemsmustovercometheuniquechallengesassociatedwithplantingthrough
thick cover crop mulch. In particular, achieving adequate soybean seed-to-soil contact can be
difficult [27]. Soil moisture can be depleted through cover crop transpiration, thereby inhibiting
soybeangermination[27–29],andsoybeanlodgingcanbeproblematicashypocotylelongationmay
weakenstemstrength[30].
Itisrecommendedtoplantsoybeaninthesamedirectionasroller-crimping(ideallyinasingle
pass)sothatthecoultersonano-tillplantercanparttheresidueratherthanbeforcedtocutthrough
covercropsrolledperpendicularlytothedirectionofplanting. However,covercropresiduecanstill
be pushed into the seed furrow (i.e., hair-pinning), which can impede seed-to-soil contact [31,32].
Insuchinstances,itiscommontoobservedesiccated,non-germinatedsoybeanseedontopofthe
hair-pinnedresidue,especiallywhenthesoilisdryandtheclosingwheelsareunabletocoverthe
furrow. Rowcleaners(trashwheels)canreducehair-pinningbymovingcovercropmulchawayfrom
thesoybeanrow[29]. Thereareseveralcommercially-availabletrashwheels, butunitsmusthave
anarrowbladeangleandideallyoverlapinordertoadequatelybothcutandmovetrash. Wehave
customizedplanterstoincludeanextratoolbarinfrontofthedouble-diskopenerandunitmounted
coulter. Thisextratoolbarhasresidueslicersputinlinewiththeunitmountedcoulters. Theresidue
slicershavedepthwheelsoneachsideofthecoulter,whichhelppressresiduedownandimprove
thecuttingaction. Theframemountedresidueslicersprovideadditionalcuttingaction. Trashwheels
havealsobeenmountedtotheframeandtherebyprovidetwosetsofcoulterandtrashwheelsto
adequatelymoveresidueandcuttheremainingmaterialpriortoplanting. Thiscanimprovesoybean
seedplacementandgermination,butinsomecases,theresiduecanbecomewrappedaroundtherow
cleaners,impairingtheirfunction[13]. Moreover,mulchcoveringthecroprowisimportantforin-row
weedsuppression. Ifrowcleanersmovetoomuchresidue,emergingcropseedlingscansufferfrom
increasedweedcompetition. ManyofthesemachineryconsiderationsalsoapplytoCCORNTcorn.
Usinghighersoybeanplantingratesisaneffectiveculturalweedmanagementpractice[20,33–35].
Higher soybean planting rates enhance weed-crop competition primarily through earlier crop
canopy closure and greater shading [33,36,37]. High planting rates can also help maintain
maximumyields[34,38].Thepricepremiumfororganicsoybean(five-yearaverageforfeed-grade
soybean=$0.92kg−1[39]) helps ensure that high planting rates are profitable for organic farmers
despitetheincreaseinseedcost. Narrowerrowspacing(<76cm)canalsobeusedtohastencanopy
closure,butthisprecludestheoptionofhigh-residue,inter-rowcultivationtomanageinter-rowweeds.
Multi-tacticapproachesthatcombineculturalstrategiesformaximizingcovercropbiomasswith
supplemental high-residue, inter-row cultivation have been investigated [26,40,41]. High-residue
cultivators for no-till soybean and corn systems typically have two depth-gauge wheels with a
residue-slicingcoulterbetweenthewheels,whicharefollowedbyasinglewideflatsweep. Thesweep
cutsthroughthesoilata2.5–5-cmdepth,slicingtherootsystemsofweedswhileleavingthesurface
residuemostlyintact.Unlikemostinter-rowcultivatorsthataremosteffectiveonsmallweedseedlings
beforetheirrootsystemsbecomeestablished,high-residuecultivatorsaremoreeffectiveonweedsafter
theyhavebecomeestablished. Standardcultivatorsrelyondislodgingthesesmallseedlings,while
thehigh-residuecultivator’ssweepsseparatetherootsfromtheabove-groundportionoftheplant.
Nordetal.[41]foundthatcerealryebiomassaloneprovidedhighlevelsofweedsuppressionwhen
weedinfestationswerelow,buthigh-residuecultivationwasneededtoachieveacceptablelevelsof
weedsuppressionwhenweedinfestationswerehigh(i.e.,supplementedweedseedbank),regardless
ofcerealryebiomassaccumulation. High-residuecultivationcaneffectivelycontrolsummerannual
weedsthatemergepriortocovercroptermination, suchascommonragweed[26,41]. TheRodale
Institute(PA)testedtheeffectsofhigh-residuecultivatortimingonweedsinrotationalno-tillsoybeans
at3–4,5–6and7–8weeksaftersoybeanplanting[42].Averagedacrosstimings,high-residuecultivation