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Direct Seeding RevisedJune2008 Agdex519-28 Crop Rotations in Direct Seeding Crop rotations areessential in directseeding The longertheforage cycle, the lowerthecostof systems. An effective crop rotation is required to switchinginto and outofforages in thatrotation. reducediseases, insectpests andweeds. Itcan On the otherhand,when theforages include also helpin managingcropresidue. Manypossible legumes, particularlyalfalfa, the marginal benefit crop rotationsexist, soto makethe mostofthe tosucceedingcrops decreasesafterthealfalfa possible benefits, be flexiblewhenselectingacrop stand isthreeyears old. Thus,sixyearsofalfalfa rotationsystem. followed bysixyears ofannual crops maynotbe as beneficial to annual crop production asthree Notonlydocrop rotations make directseeding years ofalfalfafollowed bythreeyears ofannual work better, directseedingalso makessome crop crops,which isthenrepeated, as longas thereis rotationswork betterbyconservingmoisture or nosoil erosionwhen convertingfromalfalfato byprovidingvaryingcropresidueenvironments annual crops. for nextyear’s crops. Therefore, croprotations and directseedingarecomplementary. Short-term Rotations Short-termrotations usuallyinvolve onlyannual Long-term Rotations crops, such as cereals, oilseeds, pulses,vegetables The benefits oflongertermrotations caninclude and specialtycropslikeborageorcaraway. thefollowing: Sometimes annualforages, such ascereal silage or • fewerherbicide-resistantweed species greenfeed crops, maybe partofashort-term • morebreaks indisease cycles rotation. Annualforages areusedtocontrolweeds • bettersoilstructure orreducenutrientlevels infieldswith excessive nutrients. • less erosion. Foragesinlong-termrotations canbevery Rotatingcerealgrainswith broad-leaved crops, effective inreducingdisease, insectandweed such as oilseeds orpulses, allowsweeds tobe problems. Severalyearsofforages canprovide a controlledwithherbicidesfromdifferentherbicide breakinsome disease andinsectcycles, and help groups,reducingtherisk ofdevelopingherbicide to control perennial and annualweeds as longas resistance. Thistype ofrotationcanalsobreakthe theforagestand ishealthyandvigorous. Weed cycles ofmostdiseases, exceptforthose diseases control isimprovediftheforage cropisharvested thatremain dormantinthe soil orpersiston crop as hayorsilagesincetheweedseeds are often not residuesforlongperiods. yetviable athayingorsilagingtime. Short-termrotationshave beenshowntohave beneficial effects onall cropsintherotation. For /llberta Direct Seeding Page 2 example,wheatorbarleygrownafterpeas or thenclopyralid (Lontrel) canbe used. Peas should canolausuallyperformsbetterby 10to20per notbeseeded afteralfalfa. cent(rangingfrom0to 50percent)thanacereal grownafterasimilarcereal crop. Otherstudies Agrassforagestand canusuallyberemovedby have shownan 11 to34percentyield advantage applyingglyphosateinthefall orspring. Spraying whengrowingcanolaafteracereal compared to inthelate summerorearlyfallwill helpreduce canolaaftercanola. moistureloss inthenextspring. However,the grasswill regrow. Itmaynotstartregrowinguntil Alternatinglong-seasoncropswith short-season afterthenextcropis seeded, makingapre- crops canimproveweed controlbecause pre- seedingherbicide applicationineffectivein seedingand in-cropherbicides canbe applied controllingthe grass regrowth. Seedinga earlierorlaterinthespring. Also, ashort-season glyphosate-tolerantcropallowsfollow-up cropmaybeharvested earlyenoughtoallowthe applicationsto control thegrass asitregrowsin seedingofwinterwheatorfallrye,which cantake thecrop. advantageofearlyspringmoisture. Fall dormant- A seeded canolausuallymatures earlierthe next broad-leaved cropshouldbeseeded afterthe year,which mayalso allowseedingoffall or grassto allowtheuse ofsomegrassyherbicides wintercereals. thatwill hindergrass regrowth. Ifagrassyweed herbicideisnotused, thenoats isrecommended With annual croprotations, itis importantto asitisthemostcompetitivewithanyregrowth. monitorherbicideuse, sincesomeherbicideshave Growingoatsworksbestifthegrassis sprayedin residualsthatcanaffectthe nextyear’s crop. thespringratherthanlateintheprevious fall. Withthisapproach,the oatshave moretimeto out-competethegrass because regrowth of spring-sprayed grass occurs laterintheseason. Forages in Rotations Removingamixedforage stand is moredifficult Forages canbeincludedinrotations inseveral becausein-cropcontrol oftheregrowthrequires ways. Hay, pasture, grass seed crops and timothy herbicidesthatcontrol bothgrassyand broad- oralfalfaforcompactioncanbegrowninrotations leaved perennials. Some ofthegrassyweed forvaryinglengthsoftime.Allthese crops canbe herbicides suppress perennial grasses, butapre- directseeded intostubblefromannual crops,with harvestorpre-seedingapplicationofglyphosateis orwithoutannual covercrops. The moisturein neededformoreeffectivelong-termcontrol. directseededfieldswill allowthesesmall-seeded crops tobeseeded nearthe soil surfaceforbetter Annualcrops seeded directlyintoforagestubble germinationand emergence. oftenproduceloweryields, particularlyifthe forageis killedjustbefore seeding. Killingthe Removingforagesin adirectseedingrotationis foragejustbeforeseedingreducesseed bed soil more difficultthanseedingforages intoannual moisture, resultinginpoorgermination. In cropstubble. Optionsforremovingforages addition, the soil microbestemporarilytieup depend onthetypeofforagestand. nitrogenas theydecomposetheforage roots and A straw. Eventually, the nitrogenis releasedfor broad-leaved foragecropcanusuallybetreated subsequentcropgrowth, butthis maynothappen with glyphosateand some broad-leaved herbicides significantlyuntil thesecondyearofannual crop beforeseedingthenextcrop. Theycanthenbe growth. Forthisreason, directseedingan annual treatedwithanin-cropbroad-leaved herbicide. nitrogen-fhdngpulse cropintograss stubble/;an Growingacereal cropafterabroad-leavedforage producegoodyields provided thegrassregrowth allowstheuseofseveral herbicides to control iswell controlled and soil moistureisadequate. regrowth. Ifcanolaisgrownaftertheforage crop, Page 3 Hired Seeding Directseedingan annual cropintoa legume Effects of Crop Rotations foragestand is less problematicfromafertility perspective because legumesfix nitrogen, and Disease control mostofthis nitrogenwill becomeavailable later in Stubbleorsoil-borne diseases, such assclerotinia thegrowingseason. However, in the early partof andvirulentblackleg, are reducedwhentwo or thegrowingseason, nitrogenwill still need to be threeyears ofnon-hostcrops are planted and host added forthe newcrop. weeds arecontrolled. Leafand stem diseases of cereals arealso reduced byrotatinghostcrops. Directseedinginto aforagestand usuallyresults Rotations do notaffectair-bornediseases as in fewerannualweeds than doestillingthestand much. andseedinginto it. For more information on forages in rotation, seeRemovingForagesfrom Some diseases, such as rootrot, maydecrease theRotationinaDirectSeedingSystem underdirectseedingdue to improved soil , Agdex519-17. structureand soil health. Otherdiseases may increase underthe moisterand coolerconditions in directseededfields. However, cropyield increasesduetotheextrasoil moisturecan Annual Legumes and Pulse Crops in sometimes offsetlossesduetothesediseases, and rotations can helptocontrolthe diseases. Rotation Weed control Annual legumesor pulses cangive significant Weeds such as Canadathistle canbe reduced in benefits tosucceedingcrops. Theyprovide a perennialforage crops cutforhayorsilage. nitrogen benefitthatcanreplace 10to 15 kgof Dandelions mayincreaseinforagestands ifthe nitrogen per hectare. Theyalso provide an stand is thin.Wild oats are oftenreduced after a additional benefit,which is usuallylargerthanthe forage stand has existedforseveralyearsand are nitrogen benefit, byreducingweed and disease reduced evenmorewhen anannual cropis direct problems and improvingsoil tilth. seededintoforagestubble, sincethesoil has not been disturbed muchforseeding. Croprotations allowherbicidesfromdifferent Summerfallow in Rotations herbicidegroupstobe usedforweed control, Manystudies haveshownthatsummerfallow reducingtherisk ofherbicideresistance and allowingproblemweeds tobecontrolled. decreases soil organicmattercontentand soil qualityin mostsituations. In directseedingand Insect pestcontrol reduced tillage systems, the moisture conserving Manyinsectsare mobile and caninvadefields aspectsofsummerfalloware notassignificant, fromtheedges. Rotations reducetheimpactof becausedirectseedingconserves moistureby insectpests thatareless mobile. Rotations may reducingevaporation, increasinginfiltration and also reduceinsecticide costsifyou canspraythe reducingrunoff. Thus, directseedingallows field edges tocontrol invadinginsectpests. summerfallowto beused less often. 'M Direct SBftdiny Page 4 Soil fertility Environmental implications Bothlegumeforage and pulsecropscanincrease Croprotationsthatinclude pulsecrops and theamountofnitrogenavailableforsubsequent legumeswill reduce energyconsumptionin a crops. Inthe case offoragelegumes, the majorwaysincetheydo notrequirenitrogen additional nitrogencanlastformore thanone fertilizerswhile theyare growingand often add year.Whengrassforage stubbleis seededto an nitrogentothe soilforsucceedingcrops. Withthe annualcrop, nitrogenapplicationsmaybe increasedcosts ofenergyand offertilizers ofall requireduntiltheforageresidue decomposes types, reducingfertilizerrequirementsis avery enoughtoreleasenutrientsforplantgrowth. significantaspectofcroprotations. Crop residue Growingperennial cropsinrotations alsoreduces Residueimpactsfrom differentcrops are not energyconsumption duetofewerseeding greatlydifferent, butsome effectsshould be requirementsforperennials comparedtoannual noted. crops. Bothpulse crops and legumeswithin rotationswill improve and reduce the carbon Low residue crops, like annual silage crops, footprintand the energyfootprintofvarious canolaorflax, inarotationmaybebeneficial in crops. wetter, coolerconditions. The lowerresiduelevels mayallowthesoiltowarmupsoonernextspring, Croprotationsalsoimprovethebiodiversityofa permittingearlierseedingofalongerseasoncrop. farmbyprovidingdiverse habitatsforvarious birds and otherspeciesthatlive onthefarm. Higherresidue levelsincreasemoisture Revenue conservation,which canbeveryusefulforshallow seeded crops. Togetuniformgermination,the Rotatingcrops allowsvaryingsources ofrevenue cropresidue mustbespread evenlybehindthe to even outthe price highs and lows. Forexample, combine. whengrainprices arelow,forage seed prices mightbe high. Whencanolais low, hayprices may Soil quality behigh. In awetyearwhenpeas and canolaget The effectofdifferentannual croprotations on rootrot, silage mayperformquitewell. When soil qualityis notwell known. Forages inrotation legumegrassseed productionislowdueto do improve soil quality. excessive moisture,wheat, hayand grazingyields maybeverygood. Crops such as alfalfa, peas and Inageneral sense, improved cropyields dueto chickpeas do notrequire nitrogeninputcosts, and good croprotations also enhance soil quality forages canreduceherbicide costs. because additional residueas strawand rootswill be addedto thesoil. Improvedyieldsalsomean Time management bettererosionprotectionofthesoilsurfaceby Adiverse rotationthatincludes cropslikewinter growingplants. wheat,fall rye, dormant-seeded canola, silageand haycanhelpspread outtheworkload. These Includingpulses orlegumes in arotationis likely differentcrops spread outseedingdates, to increasecropyieldswithfewershortagesof herbicide applicationwindows and harvesting nitrogenatcriticaltimes oftheyear. Deep-rooted legumes such as alfalfaalsobringup dates. micronutrientsfrom deeperinthesoil, eventually Growingagreatervarietyofcrops requires makingthemavailableto cropsinfutureyears increased managementskillsin production, through decomposition.Alfalfacan oftencontinue harvestingand marketing. However, more crops to growwell in dryyears since itcanaccess inthe rotation can provide manyrewardsforthat moisturefromdeeperin the soil. management. Direct Seeding Page 5 Flexibility Itis importanttobeflexible inyourcrop rotations. Flexibilitymeans adaptingyour rotation to theweed, disease and insectsituations onyourfarm. As thesesituations change, your rotation should change toachieve the maximum benefit. Itis also useful to respond to marketforcesand prices byadjustingyour rotations slightly. If marketpricesarefavorable forcereals,you may have apredominantlycereal rotation, such as wheat, barleyand canola. Ifpricesfor pulses are good, you mayswitch to barley, peas,wheatand canola. The peas can helpwheat protein inthe followingyear. Ifforageseed prices are good, you mightextend yourforageseed cropforoneyear. However, the price difference mustbe large enough tooffsetthe disadvantages ofrotations thatdon’tgiveyou all thesoil and cropbenefits youwant. Itis alsoimportantto rememberthat prices canchange bythetimeyou have productto sell, unlessyou have hedged themin. Summary Crop rotations are avital partofdirectseeding systems. Rotations maximizethebenefits of moistureconservationandreduce theimpacts of diseases,weeds and insectpests. PreparedbyJohnZylstra, AlbertaAgricultureand RuralDevelopment FactsheetsintheDirectSeedingSeriesarealso availablethroughAlbertaAgriculture’swebsite www.agriculture.alberta.ca 06/08/300