A Comparison of Seed- and Seedling-Focused Ecologically Based Weed Management Strategies

Transcription

1 The University of Maine Electronic Theses and Dissertations Fogler Library Spring A Comparison of Seed- and Seedling-Focused Ecologically Based Weed Management Strategies Bryan Brown University of Maine, bryan.brown@maine.edu Follow this and additional works at: Part of the Agriculture Commons Recommended Citation Brown, Bryan, "A Comparison of Seed- and Seedling-Focused Ecologically Based Weed Management Strategies" (2017). Electronic Theses and Dissertations This Open-Access Dissertation is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine.

2 A"COMPARISON"OF"SEED."AND"SEEDLING.FOCUSED"ECOLOGICALLY"BASED"WEED"MANAGEMENT" STRATEGIES" By BryanBrown B.A.ColbyCollege,2009 ADISSERTATION SubmittedinPartialFulfillmentofthe RequirementsfortheDegreeof DoctorofPhilosophy inecologyandenvironmentalsciences TheGraduateSchool TheUniversityofMaine May2017 AdvisoryCommittee: EricGallandt,ProfessorofWeedEcologyandManagement,Advisor GregoryPorter,ProfessorofCropEcologyandManagement MarkHutton,AssociateProfessorofVegetableCropsandExtensionVegetableSpecialist AndreiAlyokhin,ProfessorofAppliedEntomology JianjunHao,AssistantProfessorofPlantPathology ii

3 A"COMPARISON"OF"SEED."AND"SEEDLING.FOCUSED"ECOLOGICALLY"BASED"WEED"MANAGEMENT" STRATEGIES" By BryanBrown DissertationAdvisor:Dr.EricGallandt AnAbstractoftheDissertationPresented inpartialfulfillmentoftherequirementsforthe DegreeofDoctorofPhilosophy inecologyandenvironmentalsciences May2017 Manyfarmerstargetweedsattheseedlingstage,aimingtocontrolweedswiththeminimum amountoflabornecessarytoavoidcropyieldloss.otherfarmerswithamorelongwterm,seedwfocused approachaimtopreventweedsfromsettingseedsothatemergencewillbedecreasedinsubsequent crops.thesestrategieslikelyvaryinshortwandlongwtermeffectsonfarmecologicalandeconomic health.in ,Icomparedthesestrategiesinatestcropofonion.Unexpectedly,duetohigh yields,themorelaborintensive,seedwfocusedstrategywasthemostprofitable.casewstudyinterviews offarmerswhohaveadoptedeachapproachindicatedseedwfocusedmanagementimprovesovertime, whereasseedlingwfocusedmanagementbecomesmorechallenging.akeyobstacleforbothseedwand seedlingwfocusedmanagementwasthecontrolofweedsdirectlyinthecroprow,wheremechanical cultivationtoolsareonlymarginallyeffectiveduetotheneedtoavoidcropdamage.in ,I iii

4 testedthehypothesisthatratherthanusingjustonetool, stacking onasecondorthirdtypeoftool wouldincreaseefficacy.indeed,formosttoolcombinationstested,efficacyincreasedinanadditive mannerwhenmoretoolswereused.oneparticularcombinationofthreetoolsexhibitedasynergistic increaseinefficacy,evenoverarangeofconditions,suggestingthatfarmerscouldimproveintrawrow weedcontrolbyadoptingthistechnology.weedseedlingcontrolcouldbefurtherimprovedby decreasingtheburdenoncultivationthroughamorediversesetofecologicallybasedweed managementpractices.suchtacticscouldbebenefitedbyimprovedknowledgeofthetimingofweed seedgerminationandemergence.in2014,irecordedthetimingofemergenceofweedspeciesat RogersFarminOldTown,MEandfoundthatmanyweedspecieshadpeakemergenceperiodsthat couldbetargetedbyecologicallybasedmanagementtactics.overall,myresearchresultsprovide farmersseveralwaystoenhanceeffectivenessofecologicallybasedweedmanagementbyencouraging morethoughtfulselectionofpreventative,suppressive,andreactivetactics,increasedefficacyofweed seedlingcontrol,andimprovedtimingofmanagementactivities. iv

5 ACKNOWLEDGEMENTS" IamgratefultoUniversityofMaineRogersFarmmanger,JosephCannon;myfieldtechnicians ThomasMacy,AnthonyCodega,AudreyCross,andIsaacMazzeo;andinternsLydiaFox,Diego Grossman,LuciaHelder,andGraceSmith.IalsothankDr.JianjunHaoforplantpathologyassistanceas wellasdr.balunkeswarnayakandkatherinedaviswdenticiforassistancewithonionqualityanalysis. ThefourfarmersthatparticipatedinmycaseWstudies MarkGuzzi,TomRoberts,DaveColson,andTom Honigford wereinstrumentalinfurtheringmyunderstandingofdifferentweedmanagement philosophies.iamgratefultotheexpertadvisingofdr.ericgallandtaswellastherestofmy committee,dr.gregoryporter,dr.markhutton,dr.andreialyokhin,anddr.jianjunhao. ThisworkwassupportedbyaGraduateStudentGrantfromtheUSDANortheastSustainable AgricultureResearchandEducationProgram,entitledBalancing(economy(and(ecology:(A(systems( comparison(of(leading(organic(weed(management(strategies,projectgne14w072w27806,withprinciple Investigators,B.BrownandE.Gallandt;theUSDANationalInstituteofFoodandAgriculture,Organic AgricultureResearchandExtensionInitiativeCompetitiveGrant,(Farmer(designed(systems(to(reduce( tillage(in(organic(vegetablesaccessionnumber ;a.rangarajan,projectdirector;ajoint researchandextensionprojectfundedbythecornelluniversityagriculturalexperimentstation(hatch funds)andcornellcooperativeextension(smithleverfunds)receivedfromthenationalinstitutefor FoodandAgriculture(NIFA)U.S.DepartmentofAgriculture(Project:2013W14W425);theMaine AgricultureandForestryExperimentStation;FrenchANRCOSAC(ANRW14WCE18W0007),andtheBurgundy RegionofFrance(FABERprojectCouv Herbi). ii

6 TABLE"OF"CONTENTS" ACKNOWLEDGEMENTS...ii LISTOFTABLES...vii LISTOFFIGURES...x LISTOFEQUATIONS...xi CHAPTER1.ASYSTEMSCOMPARISONOFCONTRASTINGORGANICWEEDMANAGEMENTSTRATEGIES...1 ChapterAbstract...1 Introduction...2 MaterialsandMethods...3 CriticalPeriodWeedControl...5 ZeroSeedRain...7 Polyethylene(PE)Mulch...7 PEMulchwithStrawMulchedPaths...7 StrawMulch...7 HayMulch...7 ExperimentalDesign...7 DataCollection...9 LegacyEffectsofTreatment...11 StatisticalAnalyses...12 iii

7 ResultsandDiscussion...13 InWseasonEffectsofWeedManagementSystem...13 LegacyEffects...21 ManagementImplications...23 CHAPTER2.ANECONOMICCOMPARISONOFWEEDMANAGEMENTSYSTEMSUSEDINSMALLWSCALE ORGANICVEGETABLEPRODUCTION...25 ChapterAbstract...25 Introduction...26 MaterialsandMethods...28 CriticalPeriodWeedControl...29 ZeroSeedRain...29 Polyethylene(PE)Mulch...29 HayMulch...30 FieldManagement...30 EconomicAnalysis...31 ResultsandDiscussion...34 Labor...34 Economicanalysis...35 OverallPerformanceofEachSystem...39 CHAPTER3.TOEACHTHEIROWN:CASESTUDIESOFFOURSUCCESSFUL,SMALLWSCALEORGANIC VEGETABLEFARMERSWITHDISTINCTWEEDMANAGEMENTSTRATEGIES...45 ChapterAbstract...45 Introduction...46 MaterialsandMethods...48 iv

8 ResultsandDiscussion...49 MarkGuzzi CriticalPeriodWeedManagement...51 TomHonigford ZeroSeedRain...52 DaveColson Polyethylene(PE)Mulch...53 TomRoberts NaturalMulch...53 AdditionalBenefitsofEachStrategy...54 DrawbacksofEachStrategy...55 RequiredEquipment...56 CropRotationandCoverCropping...57 EffectsofWetWeatheronOperations...58 WeedSpecies...59 WeedSeedbankData...59 SoilOrganicMatter...60 ImportanceofCriteriaRelatedtoManagement...61 LikelihoodofAdheringtoCurrentStrategyUnderDifferentCircumstances...63 CHAPTER4.EVIDENCEOFSYNERGYWITH STACKED INTRAWROWCULTIVATIONTOOLS...66 ChapterAbstract...66 Introduction...66 MaterialsandMethods...68 ExperimentalSetup...68 Treatments...72 Calculations...73 v

9 ResultsandDiscussion...75 ScreeningofToolCombinations...75 EffectsofConditions...77 Selectivity...81 ComparisonofResultstoPreviousResearch...83 CHAPTER5.EMERGENCEPERIODICITYOFPROBLEMWEEDSINNORTHEASTERNUSAANDIMPLICATIONS FORECOLOGICALLYBASEDMANAGEMENT...86 ChapterAbstract...86 Introduction...87 MaterialsandMethods...88 ResultsandDiscussion...91 EmergencePeriodicity...91 ManagementRecommendations...98 REFERENCES APPENDIXA.Supplementarymaterials BIOGRAPHYOFTHEAUTHOR vi

10 LIST"OF"TABLES" Table1.1. Scheduleoffieldoperationsforsixorganicweedmanagementstrategies testedinoldtown,me,in2014and Table1.2. EffectsofweedmanagementsystemonendWofWseasonabovegroundweed biomassandweedseedproduction...14 Table1.3. Effectsofweedmanagementsystemonearlyoniongrowthandyieldin 2014and Table1.4. Effectsofweedmanagementsystemononionbulbfirmnessandsoluble solidsafteraperiodofcoldstorage...17 Table1.5. Effectsofweedmanagementsystemonbeneficialinvertebratesin2014 and Table1.6. Effectsofweedmanagementsystemonfourmeasuresofsoilqualityin 2014and Table1.7. ThesignificanceofsoilWrelatedparametersontheonionyieldofmainplots in Table2.1. Weeding,mulching,andharvestinglaborrequiredtogrowonionsusingfour weedmanagementsystems...34 Table2.2. Table3.1. Summaryofenterprisebudgetsforfourweedmanagementsystems...37 Summaryofsoiltexture,farmsize,andlanduseforcasestudyparticipants representingeachweedmanagementstrategy...50 Table4.1. Fieldconditionsforexperimentsconductedin2016comparingefficacyof intrawrowcultivationtools...71 Table4.2. Screeningofefficacy(±SE)ofdifferentsequencesofintraWrowcultivation toolsforpotentialsynergy...76 vii

11 Table4.3. Evaluationofsynergyinefficacy(±SE)ofatorsionWfingerWrowharrow combinationofintrawrowcultivationtoolsinexperimentsvaryingforward speed,soilmoisture,andweedsize...77 Table4.4. ANOVAofcultivationefficacyforseveralintraWrowtoolsasforwardspeed varied...79 Table4.5. ANOVAofcultivationefficacyofseveralintraWrowtoolsassoilmoisture varied...80 Table4.6. ANOVAofcultivationefficacyintwofieldtrialsforseveralintraWrowtoolsas abovegrounddrymassperplant(mass)varied...81 Table4.7. Comparisonofcropmortality(±SE)andweedcontrolefficacy(±SE)of severalintrawrowcultivationtools...82 Table4.8. ANOVAofcropmortalityforseveralintraWrowcultivationtoolsin experimentsinwhichforwardspeedandsoilmoisturewerevaried...83 Table5.1. Comparisonoftillagedatesresultinginmaximumweedemergenceto previousworkonpeakemergence...94 Table5.2. Weedmanagementoptionsbasedonpeakemergenceoftargetedweedsin temperateclimates...99 TableA.1. Assumptionsandsourcesofassumptionsusedinenterprisebudgetsof organiconion(allium(cepa)andsweetcorn(zea(mays)productioninseveral weedmanagementsystems TableA.2. Enterprisebudgetsummaryfororganiconion(Allium(cepa)production usingfourdifferentweedmanagementsystems TableA.3. Enterprisebudgetsummaryfororganicsweetcorn(Zea(mays)production usingfourdifferentweedmanagementsystems viii

12 TableA.4. TableA.5. Interviewquestionsaskedtoeachcasestudyfarmer Scheduleoffieldoperationsforexperimentsconductedin2016comparing efficacyofintrawrowcultivationtoolsusingwhitemustardandwhiteproso milletassurrogateweeds ix

13 LIST"OF"FIGURES" Figure1.1. Averagedailytemperature(line)andtotaldailyprecipitation(bars)inOld Town,MEforthestudyperiodsin2014and Figure1.2. Afternoonsoiltemperaturemeasuredatadepthof5cmforeachweed managementsystemin2014and Figure2.1. Temporalspreadoflaborrequiredtogrowonionsusingeachweed managementsystem...36 Figure2.2. CumulativedistributionfunctionsofnetfarmincomebasedonMonteCarlo simulationwith1,000iterationsofeachweedmanagementsystem...38 Figure2.3. Tornadographsdisplayingthesensitivityofnetfarmincometovariationin selectedinputvariablesforeachweedmanagementsystem...40 Figure3.1. Weedspeciescompositiondeterminedfromgerminableseedbankassaysof soilsamplesfromeachparticipatingfarmer...61 Figure3.2. Radarplotoftheimportanceoffourcriteriarelatedtomanagementtocase studyfarmersrepresentingeachweedmanagementstrategy...62 Figure4.1. CultivationefficacyofintraWrowtoolsinthreeseparateexperimentsin which(a)forwardspeed,(b)soilmoisture,and(c)weedsizewere manipulated,respectively...78 Figure5.1. Figure5.2. Airtemperature(line)andprecipitation(bars)forthestudyperiod...90 Violinplotsofemergenceofthefivemostabundantweedsresultingfroma rangeoftillagedates...92 FigureA.1. ApprovalfromtheInstitutionalReviewBoard(IRB)toworkwithhuman subjects " x

14 LIST"OF"EQUATIONS" Equation Equation Equation Equation Equation Equation Equation Equation xi

15 CHAPTER"1" A"SYSTEMS"COMPARISON"OF"CONTRASTING"ORGANIC"WEED"MANAGEMENT"STRATEGIES" BryanBrownandEricR.Gallandt* *Firstandsecondauthors:SchoolofFoodandAgriculture,UniversityofMaine,Orono,ME04469,USA. Chapter"Abstract" Manyfarmersmanageweedseedlingsonlyduringtheearly,weedWsensitive criticalperiod of theircrops.however,thisapproachoftenpromoteslatewseasonweedgrowthandabundantweedseed rain.alternatively,somefarmersperformfrequentweedcontroleventstoensure zeroseedrain, so thatweedemergencewilllesseninsubsequentyears.anotherapproachistousemulchtosuppress weeds.polyethylene(pe)mulchmaybeusedtocoverbedswhilepathsareleftbareorcoveredwith naturalmulches.naturalmulches,suchasstraworhay,mayalsobeusedinthebedsandpaths.eachof theseweedmanagementstrategiesmayvaryintheirabilitytomanageweeds,andlikelyhaveunique agroecologicalimplications.toevaluatepotentialtradeoffs,weimplementedeachstrategyin organicallymanagedyellowonion.asexpected,endwofwseasonweedbiomassandweedseed productionweregreatestinthecriticalperiodsystemandnearlyzeroforthezeroseedrainsystem. WeedswerealsowellWcontrolledinnaturalmulchsystems.Averageonionyieldpertreatmentwas50.7 Mgha W1.Inoneyearoftwo,theCriticalPeriodsystemandthePEmulchsystemdemonstratedyieldloss, likelyduetoweedcompetitionandexcessivesoiltemperature,respectively.carabidbeetles, earthworms,soilcompaction,soilnitrate(no 3 WN),andactivecarbonwereaffectedbyweed managementsystem,withnaturalwmulchedsystemsgenerallyperformingmostfavorably.however, thesebenefitswerenotsubstantialenoughtoaffectyieldofasubsequentcropgrowninweedwfree 1

16 conditions.contrastingly,asubsequentcropinwhichweedsweremanagedwithonlyseveral cultivations,demonstratedyieldlossinplotswherethecriticalperiodsystemwasimplementedthe prioryear,indicatingthatweedcompetitionresultingfromabundantweedseedproductioninthat systemwasthemostinfluentiallegacyeffectoftheweedmanagementstrategies. Introduction" ManyfarmersfocusonearlyWseasoncontrolofweedseedlings(Jabbouretal.2014b).However, thisweedmanagementstrategymayworsenweedproblemsovertimeifweedsareallowedtosetseed. Conversely,farmerswithalongerterm,weedWseedbankWfocus,attempttopreventweedsfromsetting seed(jabbouretal.2014b).athirdsetoffarmersavoidtheneedfordirectweedcontrolthroughuseof mulch.whilethereareexamplesofsuccessfulfarmersthatemphasizeeachoftheseapproaches(brown andgallandt,inreview),eachstrategylikelyhasdistinctagroecologicalimplications. Growersfocusingonmanagementofweedseedlingsoftenprioritizecontroleventsduringthe crop s criticalperiod, whencropsaremostsensitivetocompetitionandweedwfreeconditionsshould bemaintainedtoavoidyieldlosses(nietoetal.1968).suchanapproachhasbeenusedtomaximize efficiencyofinwseasonweedmanagement(knezevicetal.2002),whichcanreduceweedinglaborcosts onorganicfarms.however,ifweedsareonlycontrolledintheearlywseason,lateremergingweedsoften setseedpriortoautumntillage.consideringthatseedraincanincreasetheweedseedbankfifteenwfold inasingleyear(bondetal.1998),criticalperiodweedcontrolmayperpetuatetheweedproblem,often necessitatinganincreasedcontroleffortovertime. AnalternativetoseedlingWfocusedweedweedmanagementinvolvesalongerWterm,seedbankW focusedperspective.sincemanyweedspecieshaveseedlongevity halfwlives oflessthanoneyear (RobertsandFeast1972),preventingseedraincausesarapiddecreaseintheweedseedbank,and therefore,subsequentweedemergence,providingalaborsavingsinsucceedingyears(norris1999).a 2

17 zeroseedrainapproachoftenutilizesfrequentsoildisturbancetominimizecreditstotheweed seedbankwhilemaximizingdebits(forcella2003;gallandt2014). Othergrowerssubstitutedirectphysicalweedcontrolforweedpreventionorsuppressionby mulch.blackpemulchismostcommon,duetoitsabilitytowarmthesoilandpromoteearlyyieldof cropsliketomatoes(schonbeckandevanylo1998a).pemulchcanreducetheamountofrequired irrigation(abuwawwad1999)andconservesoilnitrate(schonbeckandevanylo1998b).ontheother hand,naturalmulches,suchasstraworhay,mayalsobeusedtosuppressweedgrowth(teasdaleand Mohler2000)andimprovewaterinfiltration(Shocketal.1999;Tindalletal.1991),increaseearthworm populations,andreplaceseasonalcarbonandnitrogenlosses(schonbeckandevanylo1998b).mulches mayalsoreduceinsectpestpopulations(larentzakietal.2008;vantooretal.2004)anddisease incidence(hilletal.1982). Whileeachofthesealternativeweedmanagementstrategiesmayprovideadequatecropyields, theyincludetradeoffsineffectsonfarmecology.growerdecisionofwhichstrategytoimplement shouldincludeconsiderationofweedmanagementandcropyield,butalsotheeffectsontheweed seedbank,edaphicarthropodsandmicrobes,andtherelativemixofsoilaggradingvs.degrading practicesemployed.ouraimwiththisprojectwastocharacterizethemultipledimensionsofthese fundamentallydifferentweedmanagementstrategiesinordertoprovidegrowerswithimproved understandingofwhichstrategybestmatchestheirfarmmanagementgoals.economicperformanceof thesystems(bbrown,unpublisheddata)aswellasarelatedcasestudynarrative(brownandgallandt, inreview)arepresentedelsewhere. Materials"and"Methods" Fieldexperimentscomparingseveralcontrastingweedmanagementstrategieswereconducted attheuniversityofmainerogersfarminoldtown,me(44.93 N,68.70 W)in2014and2015on separatefields,bothnicholvilleveryfinesandyloam.yellowstorageonions(cv. Cortland )wereusedas 3

18 thetestcropsincetheyarecommonlygrownusingeachstrategy.weatherconditionsduringthestudy weretypicalfortheregion(datafromwww.ncdc.noaa.gov).averagetemperaturewas16.9and17.2c andtotalprecipitationwas380and473mm,forthegrowingperiodsof2014and2015,respectively (Figure1). Figure1.1.Averagedailytemperature(line)andtotaldailyprecipitation(bars)inOldTown,MEforthe studyperiodsin2014and

19 OurbroadaimwastocompareseedlingW,seedW,andmulchWbasedweedmanagement approaches.ultimately,wechosesixsystems,describedindetailbelow.literaturereviewandextensive interviewswithfarmersthathavespecializedineachweedmanagementstrategy(brownandgallandt, inreview)wereusedtoensurethateachsystemwasimplementedinarealisticmanner. Critical"Period"Weed"Control"" Weedingeventswereperformedaboutevery2wkforthedurationofthecriticalperiod(Table 1.1.).ThecriticalperiodfordirectWseededonionsisthefirst8to12wkfollowingemergence(Brewster 2008;MengesandTamez1981;Wicksetal.1973).Sincetheonionsweretransplanted,weusedan8wk criticalperiodin2014.however,yieldlossin2014indicatedtheperiodwasnotlongenough.in2015, thecriticalperioddurationwasadjustedasdescribedbyknezevicetal.(2002),whichextendeditfrom 56din2014to78din

20 Table1.1.ScheduleoffieldoperationsforsixorganicweedmanagementstrategiestestedinOldTown,ME,in2014and2015. Weedmanagement Date Year system Planting Mulching Weeding Harvest Onioncuring 2014 CriticalPeriod May13 May29,Jun9,Jun19,Jun27,Jul3 Sep18 Aug24ROct20 May29,Jun9,Jun19,Jun27,Jul3,Jul10,Jul ZeroSeedRain May13 30,Aug12,Aug26 Sep10 Sep13RSep27 Beds(Jun9,Jun19,Jul10),Paths(May29, PolyethyleneMulch May13 May12 Jun9,Jun19,Jun27,Jul10) Aug27 Aug29RSep12 PolyethyleneMulch, StrawPaths May13 May12 Jun9,Jun19,Jul10 Aug27 Aug29RSep12 StrawMulch May13 Jun24RJul1 May29,Jun9,Jun19,Jun24,Jul30 Sep18 Aug24ROct20 HayMulch May13 Jun24RJul1 May29,Jun9,Jun19,Jun24,Jul30 Sep18 Aug24ROct CriticalPeriod May18 Jun4,Jun17,Jun30,Jul14,Jul30 Sep28 Sep29ROct26 Jun4,Jun17,Jun30,Jul14,Jul30,Aug11, ZeroSeedRain May18 Aug20,Sep10 Sep28 Sep29ROct26 Beds(Jun22,Jul14,Aug11),Paths(Jun17, PolyethyleneMulch May18 May14 Jun30,Jul14,Jul30,Aug14) Sep10 Sep12RSep29 PolyethyleneMulch, StrawPaths May18 May14 Jun17,Jul14,Aug11 Sep10 Sep12RSep29 StrawMulch May18 Jul2 Jun4,Jun17,Jun30,Aug11 Sep28 Sep29ROct26 HayMulch May18 Jul2 Jun4,Jun17,Jun30,Aug12 Sep28 Sep29ROct26 6 6

21 Zero%Seed%Rain% Forthissystem,bedsandpathswereweededaboutevery2wkthroughoutthegrowingperiod (Table1.1.)withagoalofcompletelypreventingweedseedinputstotheseedbank. Polyethylene%(PE)%Mulch% EmbossedblackPEmulch1.2mwide,0.025mmthick(FedCoSeeds,Waterwille,ME)was appliedwithamechanicalapplicator(model385pl,bartvilleweldingshop,christiana,pa)priorto transplanting.transplantingholesweremadewitha5cmwidetrowel.weedsinplantingholeswere handnpulledseveraltimes,whilepathswerecultivatedmorefrequently(table1.1.). PE%Mulch%with%Straw%Mulched%Paths% Mulchwasappliedandbedswereweededinthesamemannerasabove.Beforeplanting,oat (Avena&sativaL.)strawwasappliedtothepathsatarateof20Mgha N1 (Schonbeck1998).Weedsand volunteeroatemergingthroughthestrawrequiredhandnpulling(table1.1.). Straw%Mulch% Oatstrawwasappliedmorethanonemonthaftertransplanting(Table1.1.)toallowtimefor thesoiltowarmandforonionstogrowlargeenoughtowithstandthedisturbanceofmulching.straw wasappliedbyhandatarateof20mgha N1 (Schonbeck1998).Strawwasspreadquicklyinthepaths, butinthebedsitwascarefullylaidinbundlesaroundtheonions.onehandnpullingeventwasnecessary tocontrolweedsandvolunteeroatafterthemulchwasapplied. Hay%Mulch%% Decayingtimothy(Phleum&pratenseL.)hay,notsuitableforhorses,wasobtainedlocally.Hay wasappliedandmanagedinthesamemannerasthestrawmulch(table1.1.). Experimental%Design%% Eachofthesixweedmanagementsystemswasimplementedasatreatmentinarandomized completeblockdesignwithfourreplicates.eachplotwas6.1mlongby1.7mwide.toensure 7

22 consistentcompetitionandedgeeffects,abufferbedofonionswastransplantedoneithersideofeach plotandblockswereseparatedbyanunplantedareaof2.4m. Primaryandsecondarytillagewereconductedusingarototillerandfieldcultivator,respectively. PreNplantingfertilitywasappliedbasedonsoiltestrecommendationspriortosecondarytillage.In2014, 1,483kgha N1 soybeanmeal(7.0n0.5n2.3,fedcoseeds,waterville,me),908kgha N1 compostedpoultry litter(3n2n3,microstart60,perdueagribusinessllc,salisbury,md),454kgha N1 bonechar(0n16n0, FedCoSeeds,Waterville,ME)provided131N98N61kgha N1 (NNPNK).In2015,1,337kgha N1 soybeanmeal, 1,110kgha N1 dehydratedpoultrylitter,and441kgha N1 bonecharprovided127n100n64kgha N1 (NNPNK). Allmaterialsweremeasuredandappliedbyhand. OnionswerestartedinlateFebruaryinaheatedgreenhouse.Flatscontaininganorganicpotting mix(lightmix,livingacres,inc.,newsharon,me)wereplantedwith500seedsperflat.intheperiod priortotransplanting,seedlingswerefertilizedthreetimeswithfishhydrolysate(2.9n3.5n0.3,fedco Seeds,Waterville,ME)dilutedto1%concentration.TransplantingwasdonebyhandinMay(Table1.1.), followingtillageandpemulchapplication.toreducetransplantshock,oniontopsweretrimmedto13 cmthedaypriortoplanting.onionswerebarenroottransplantedwithrootstrimmedto3cm. Transplantingwasdonebyblock.Eachplotcontainedonebedofthreeonionrows,withrowsspaced30 cmapart,plantingholes15cmapart,andtwoonionsperhole.anadditional408kgha N1 fishhydrolysate wasappliedimmediatelyfollowingtransplanting. Pathswereweededwithwheelhoes,longNhandledhoeswereusedclosertocroprows,shortN handledhoeswereusedinthecroprow,andhandnpullingwasonlynecessaryformulchedplots.buffer bedswereunmulchedandweededevery2wkthroughouttheseason.weednfreesubplots2.0mlong by1.7mwidewereestablishedwithineachmainplotandwereweededatleastweeklytoensurethat weedcompetitiondidnotaffectyield. 8

23 Optimalsoilmoisturewasmaintainedforeachsystemusingdripirrigation(TripleKIrrigation, Morenci,MI)with16mmdiameteremittersspacedevery30cmthateachoutput19ccmin N1.Irrigation wassetuppriortotransplanting,withonelineperbed.soilwaterholdingcapacitywasdeterminedby examiningsoilmoistureovertimeafteraheavyrain.capacitywasestimatedtobe17and20% volumetricsoilmoisturefor2014and2015fields,respectively.volumetricsoilmoisturewasmeasured weeklywithadeltanthh2soilmoisturemeterwitha5.1cmthetaprobe(deltantdevices,burwell,uk) atfourlocationsineachplottodeterminetheamountofirrigationneededtorechargethewaterdeficit toadepthof32cm. Data%Collection% EndNofNseasonabovegroundweedbiomasswasmeasuredwithin1dofharvestusinga0.25m 2 quadratplacedrandomlyinthebedandrandomlyinthepathsofeachplot.withinthequadrat,all weedswereclippedatthesoilsurface,andseparatedbyspecies.sampleswereplacedindryingovens for1wkat46c,anddriedsampleswereweighed.weedseedswerethreshedfromthedriedweed samplesandweighed.thetotalnumberofweedseedswasfoundbydividingthetotalseedmassof eachspeciesbytheaveragemassofasingleseed.toevaluatetheamountofweedseedintheorganic mulches,injulyofeachyear,four100gsamplesofeachmulchwerelaidonflatsofsterilepottingmix (ProMixAllPurposeMix,PremierTech,Quebec,Canada)andcoveredwitha1cmlayerofpottingmix. Flatswerewateredregularlyforonemonthtoencouragegermination.Emergedseedlingswere identified,recorded,andremoved. Earlyseasononionleaflengthwasdeterminedbasedontheaveragelengthofthelongestleaf offourrandomlychosenonionsperplotonjune27,2014andjuly9,2015. Onionswereharvestedat70% topsndown onapertreatmentbasis.harvestoccurredina1m by1mquadratcenteredonthebedinarandomlocationwithineachmainplotandeachweednfree subplot.harvestedonionswerelaidinasinglelayeronwiretablesinaventilatedgreenhousetocure. 9

24 Treatmentsharvestedlaterintheseasonrequiredalongercuringduration(Table1.1.),likelydueto decreasedtemperatureanddecreasedlightintensity.oncealloniontopshaddriedtoabrownpapery state,rootsandloosescaleswereremoved,topswerecut1ncmabovethefoldingpointintheneck,and onionbulbswereweighed.visiblydiseasedonionswerenotincludedinyielddata.diseaseswere diagnosedbyplantpathologistdr.jianjunhao. InDecemberofeachyear,followinganautumncoolingperiodinanunheatedbarn,four marketableonionsfromeachplotwererandomlyselectedtobestoredinawalknincoolerat1.7cand 75%relativehumidity.The2014and2015onionswereremovedfromcoldstorageMay19,2015and July15,2016,respectively.FirmnesswastestedusingaBrookfieldLFRATextureAnalyzer(Brookfield Ametek,Inc.,Middleboro,MA)runningat4mmsec N1 witha5cmdiameteracryliccompressionhead. Whentheheadconfrontedan8gtriggeritmeasuredpeakpressurerequiredtocontinuefor1.5mm. OnionpHandsolublesolidsweremeasuredusinganOrionStarA211pHMeter(ThermoFisher Scientific,Waltham,MA)andanAtagorxN5000iRefractometer(AtagoU.S.A.,Inc.,Bellevue,WA), respectively,usingblendedsamplesfromeachplot. Throughoutthefieldexperiments,soiltemperaturewasmeasuredatadepthof5cm,onceper weekinthemidnafternoonusinganomegamodelhh21microprocessorthermometerwithahanna TypeKThermocouple(OmegaEngineering,Inc.,Stamford,CT). ActivityNdensityofgranivorouscarabidbeetlesincludinggeneraAmara,Bembidion,Clivinia, Harpalus,Poecilus,andPterostichus,wasmeasuredinearlyAugustbyinstallingonepitfalltrapina randomlocationinthebedofeachplotusingmethodsadaptedfrombirthiseletal.(2014).a30cmslit wascutinthepemulchtreatmentstofacilitateinstallation.trapswereexaminedfourtimesin2014 andtwicein2015,with24hto48hcatchtimeforeachevent.earthwormabundancewasmeasuredby excavatinga15cmby42cmby20cmvolumebetweenonionrowsineachplotinlateaugust,and siftingsamplesfollowingedwardsandlofty(1977). 10

25 Onionthrips(Thrips&tabaciLind.)populationsweremeasuredweeklyin2014usingahandlens tocountthethripsoneightrandomonionplantsperplot.in2015,thedestructivesamplingmethodof Larentzakietal.(2008)wasadopted.TherevisedmethodwasimplementedonceinJune,July,and August.Anactionthresholdof3thripsperleafwasnotattainedineitheryear.Additionally,in2015, plotswereexaminedforotherarthropodanddiseasedamagebyfourfieldscoutingeventsinaugust. InlateAugustofeachyear,severalsoilqualitymeasurementswereconducted.Soilsamples collectedtoadepthof15cmfromtenrandomlocationswithinthebedofeachplotwereanalyzedfor nitrate(no 3 NN),ammonium(NH 4 NN),andactivecarbon,whichincludesanestimateofmicrobial biomass.inaddition,soilwaterinfiltrationratewasmeasuredbyrecordingthetimerequiredfor1l watertosoakintoprenwetsoilinsidea20cmdiameteraluminumcylinderthathadbeeninserted8cm intothesoil(andersonandingram1989).compactionwasmeasuredatfourlocationsperplotusinga penetrometerwith1cmtipthatwasinsertedtoaresistanceof2.1mpa enoughcompactionto severelyimpairrootgrowth(bengoughandyoung1993). Legacy%Effects%of%Treatment% InSeptember2014and2015,immediatelyfollowingonioncropharvest,fieldswererototilled andoats(cv. Aroostook )wereplantedwitha3mgraindrill(masseyferguson,duluth,ga)with15cm rowspacingatarateof224kgha N1.InMay2015and2016,priortoincorporatingtheoats,soilorganic matterwastestedfromahomogenizedsampleoftensoilcoresperplot,toadepthof15cm.in2015, analyseswereconductedwitha2mm,butin2016,a5mmsievewasusedsothatmoreoftheresidue wouldbeincludedinthetest.sinceorganicmattermayhaveexceeded2mm,thistestincludedraw residue.sampleswerealsocombustedusing20to25gratherthan4to5gamounts.immediately followingsoilsampling,oatswereincorporatedbyrototillingandfieldcultivating. In2015only,sweetcorn(cv.XtraNTender3473)wasplantedonJune4withrowsspaced81cm apartandplants20cmapartwithinrows.inthisspacing,tworowswerecenteredwithintheboundsof 11

26 thepreviousyear splots.mostfertility(1,318kgha N1 soybeanmeal,412kgha N1 compostedpoultrylitter, and165kgha N1 bonechar)wasappliedpriortosecondarytillageandadditionalfertility(659kgha N1 compostedpoultrylitterand329kgha N1 fishhydrolysate)wassidedressedonjuly10,providingatotal of134n66n63kgha N1 (NNPNK).Toprotectthecornfromcrows,plotswerecoveredwithspunNbonded polypropylene(agribon,sanluispotosi,mexico)untilthecornwasinthethreenleafstage.thecornwas manageduniformlyacrossallprevioustreatments.weedcontrolconsistedofaspringtineharrowing (LelyIndustriesNV,Series982,Type3,Maasland,Holland)onJune15;interNrowcultivationswitha4N rowcaseinternationalmodel183(caseih,racine,wi)withdanishsntinesand10cmsweepsandgage wheelsonjune15,june25,andjuly7;anddischillings(weedmaster,elomestarioy,ltd.,kukkola, Finland)onJune25andJuly10.InadditiontothefieldNwidecultivations,weedNfreesubplotswere maintainedbyhandnweedingonjune19,july6,july20,july31,andaugust12.harvestoffirstears occurredonaugust24andsecondearsonseptember2.entireplotswereharvestedforyielddata.yield wasdefinedasthefreshmassofearsfrombothharvests.cornearworm(helicoverpa&zeaboddie) damagewasevaluatedintenearsperplotonthesecondharvestdate. Statistical%Analyses% AllanalyseswerecompletedusingJMP10(SASInstituteInc.,Cary,NC).Analysisofvariance (ANOVA)wasusedtodetermineeffectsofweedmanagementsystemondependentvariables.Dueto severalimportantyear*treatmentinteractions,yearswereanalyzedseparately.fisher sprotectedlsd wasusedformeanscomparisonsunlessotherwisestated.analphalevelof0.05wasusedthroughout. DatafailingtomeetassumptionsforANOVAweresubjectedtolog,squareroot,orBoxNCox(Boxand Cox1964)transformationsasnecessary.Dataunabletopassassumptionsaftertransformationswere analyzedwiththenonparametrickruskalwallistest(kruskalandwallis1952).pairwisewilcoxon signednranktests(wilcoxon1945)wereusedformeanscomparisonsasappropriate.ifaneffectofweed managementsystemwaspresentinonionyieldofweednfreesubplots,edaphicvariablesthatwere 12

27 affectedbysystemwereevaluatedasmaineffectsinalinearregressionmodelofonionyield.stepwise backwardselectionwasusedtoeliminatenonnsignificantvariables,followedbyevaluationwith adjustedr 2 andakaikeinformationcriterionwithcorrectionforfinitesamplesizes(akaike1974).to evaluatetheeffectsofeachsystemonsubsequentcrops,anorthogonalcontrastwasusedtodistinguish betweensweetcornyieldofthecriticalperiodsystemversusallothers. Results%and%Discussion% InEseason%Effects%of%Weed%Management%System% Thesix%weedmanagementstrategiesinthisexperimentvariedintheireffectsonweedbiomass andseedproduction,onionyieldandstorability,soilhealth,andedaphicinvertebrates.% Themostabundantweedspeciesincludedwerecommonlambsquarters(Chenopodium&album L.),smoothcrabgrass(Digitaria&ischaemumSchreb.),andlowcudweed(Gnaphalium&uliginosumL.).As expected,inbothyears,thecriticalperiodsystemhadthegreatestweedbiomass(table1.2.),reflecting uncontrolledweedgrowthinlatejuly,august,andearlyseptember.thereductioninweedbiomassin 2015comparedto2014wasexpectedbecauseweextendedthecriticalperiodinthatyear.Weed biomasswasleastinzeroseedrain,strawmulch,andhaymulchtreatments,commensuratewiththe increasedlaborrequiredforthosesystems(bbrown,unpublisheddata).comparatively,pemulched plotshadgreaterweedbiomass,likelyduetotheinfrequentweedingeventsthatwereadvisedby farmers,aswellasthedifficultycontrollingweedsemergingfromtheplantingholesandthemarginsof thepemulch. Asexpected,weedseedproductionwasgreatestfortheCriticalPeriodtreatmentandcloseto zerointhezeroseedrainsystem(table1.2.).weedseedproductioninpemulchedtreatmentswas greaterthanthatofzeroseedrain,butproductioninnaturalnmulchedtreatmentswasnot(table1.2.). AverageweedseedproductionoftheCriticalPeriodsystemswas25,359seedsm N2,whichissurprising 13

28 giventhatpreviousworkwithmaineorganicvegetablefarmsfoundthatmosthadgerminableweed seedbanksoflessthan15,000seedsm N2 (Jabbouretal.2014b). Table1.2.EffectsofweedmanagementsystemonendNofNseasonabovegroundweedbiomassandweed seedproduction.datawascollectedimmediatelyafteronionharvestin2014and2015.withineach column,meansfollowedbythesameletterarenotsignificantlydifferent. Weedmanagement system EndNofNseasonaboveground weedbiomass a Weedseedproduction b gm N2 no.m N2 CriticalPeriod 619a 367a 29,042a 21,675a ZeroSeedRain 7c 8c 0c 57d PolyethyleneMulch 97b 117b 787b 5,277b PolyethyleneMulch,Straw 110b 161ab Paths 1,267b 4,515b StrawMulch 10c 20c 27c 285cd HayMulch 15c 16c 19c 599c ANOVA P System <0.001<0.001 <0.001 <0.001 a MeansseparatedusingFisher sprotectedlsdtestatp b BoxNCoxtransformedforANOVAandFisher sprotectedlsdtestatp 0.05.Reportedvalues untransformed. Anunexpectedresultwasthattheoatstrawmulchcontainedalargeamountofoatseed (contributing711totalseedsm N2,mostlyoats)eventhoughitwasbaledafteroatharvest.Oatseedwas abletogerminateandemergefromwithinthemulch,whichlikelyaffectedyield,andrequiredextra weedmanagement.incontrast,haymulchadded991weedseedsm N2,buthadmuchlessweed emergencethroughthemulch(datanotshown).% Onionyieldvariedbysystemin2014,withZeroSeedRainandnaturalNmulchedsystemsyielding greatest(table1.3.).comparedtothehaymulchsystem,pemulchingandcriticalperiodtreatments demonstratedayieldloss.onionyieldinweednfreesubplotsalsovariedbysystemin2014,withpe mulchedtreatmentsyieldingleast,possiblyduetohighersoiltemperatures,whichacceleratedearlyn 14

29 seasonleafgrowth(table3)(in&sensuanisuzzamanetal.2009),andlikelycontributedtotheonionsin thepemulchedsystemssenescingandrequiringharvest22dearlierthanmostothers(table1.1.). However,in2015,onionyieldsweresimilaracrossstrategiesinmainplotsandweedNfreesubplots (Table1.3.).Thisresultreflectsthelengthenedweedcontrolperiod(Table1.1.)fortheCriticalPeriod treatmentandreducedsoiltemperatures(figure1.2.)thatslowedmaturationoftheonionsinthepe mulchedsystems,allowingmorebulbingtimebeforesenescenceandharvest(table1.1.).similarly,in Maine,lightercoloredPEmulchesarebeginningtobeusedtoavoidcausingprematureonion senescence(jkafka,personalcommunication). Table1.3.Effectsofweedmanagementsystemonearlyoniongrowthandyieldin2014and2015. Withineachcolumn,meansfollowedbythesameletterarenotsignificantlydifferent. Earlyseasonleaf Yield a WeedNfreeyield Weedmanagement length a system b 2015 a cm Mgha N1 Mgha N1 CriticalPeriod 29b 34bc 34.6c c 55.2 ZeroSeedRain 27bc 33c 52.5ab abcd 55.3 PolyethyleneMulch 35a 43a 42.5bc bcd 56.5 PolyethyleneMulch, 35a 44a 47.4b d 58.4 StrawPaths StrawMulch 29b 38b 51.9ab a 63.2 HayMulch 24c 35bc 60.5a ab 52.0 ANOVA P System <0.001 < a MeansseparatedusingFisher sprotectedlsdtestatp b MaineffectstestsperformedwithKruskalWallistestsandmeanscomparisonsperformedwith Wilcoxonpairedtests,bothatP

30 Figure1.2.Afternoonsoiltemperaturemeasuredatadepthof5cmforeachweedmanagementsystem in2014and2015.eachlinerepresentsweeklyafternoonsoiltemperaturereadingssmoothedbyacubic spline(lambda=0.05).readingswerediscontinuedafterharvestofeachtreatment. Afterharvest,onionswithapparentdefectswereevaluatedfordisease.Diseasesincludedblack mold(aspergillus&niger),bacterialsoftrot(dickeya&chrysanthemorpectobacterium&carotovorumsubsp. carotovorum),andbluemold(penicilliumspp),howeverdiseaseincidencewasverylowandnot affectedbyweedmanagementsystem. Followingcoldstorage,solublesolidslevels,indicativeofonionsugarsandstorability(McCallum etal.2006),weregreatestinthehighestnyieldingtreatmentsof2014(table1.4.).onionfirmness,a desirablepostnharvesttrait(larsenetal.2009),wasgreatestinunmulchedsystemsin2014(table1.4.). 16

31 However,thesequalityparameterswerenotaffectedbytreatmentin2015.OnionpH,sprouting,mold, androtwerealsoexaminedbutwereunaffectedbyweedmanagementsystem(datanotshown). Table1.4.Effectsofweedmanagementsystemononionbulbfirmnessandsolublesolidsafteraperiod ofcoldstorage.withineachcolumn,meansfollowedbythesameletterarenotsignificantlydifferent. Weedmanagement Bulbfirmness SolubleSolids system 2014 a 2015 c 2014 a 2015 b kg brix CriticalPeriod 3.3ab c 7.3 ZeroSeedRain 3.5a a 7.2 PolyethyleneMulch 2.6c c 7.4 PolyethyleneMulch, StrawPaths 2.7c bc 7.1 StrawMulch 2.9bc ab 6.8 HayMulch 2.7c a 7.1 ANOVA P System a MeansseparatedusingFisher sprotectedlsdtestatp b LogtransformedforANOVAatP 0.05.Reportedvaluesuntransformed. c MaineffectstestsperformedwithKruskalWallistestsatP SoiltemperaturewasgreatestunderblackPEmulch(Figure2),asexpectedandconsistentwith Hilletal.(1982).Lateintheseason,soiltemperaturesinZeroSeedRainsystemapproachedthoseofPE mulchedsystems,likelyduetothesoilremainingunshadedbyweeds.conversely,soiltemperaturein thecriticalperiodsystemdroppedaslatenseasonweedsemerged.soiltemperatureinnaturalnmulched plotscooledaftermulchwasapplied,asreportedelsewhere(teasdaleandmohler1993). Soilmoisturewasmaintainedoptimallyforeachsystembydripirrigation.In2014,Critical PeriodandZeroSeedRaintreatmentsreceived5,600ccwaterm N2 andpeandnaturalnmulchedplots required13%lessirrigation.in2015,thezeroseedrainsystemrequiredthemostirrigation(11,000cc m N2 )whilethecriticalperiod,strawmulch,haymulch,pemulch,andpemulchwithstrawpaths treatmentsrequired11,20,22,45,and47%lesswater,respectively. 17

32 ActivityNdensityofcarabidbeetles,includingHarpalus&rufipesDeg.,awellNknownseedpredator (Gallandtetal.2005),wasgreatestintheCriticalPeriodsystem(Table1.5.),possiblyduetothehabitat providedbyweeds.similarly,withincropfields,carabidactivityndensity(shearinetal.2008)andweed seedpredation(birthiseletal.2015)havebeenpositivelycorrelatedwithvegetativecover.earthworms weremoreabundantinnaturalnmulchedsystems(table1.5.),asfoundbyschonbeckandevanylo (1998b).Earthwormsaregenerallybeneficialforincreasingsoilhumusandaeration(EdwardsandLofty 1977;HoppandHopkins1946). Table1.5.Effectsofweedmanagementsystemonbeneficialinvertebratesin2014and2015. MeasurementswereconductedinAugustofeachyear.Withineachcolumn,meansfollowedbythe sameletterarenotsignificantlydifferent. Weedmanagement CarabidactivityNdensity a Earthworms a system no.trap N1 no.m N2 CriticalPeriod 21a 42a 24b 112bc ZeroSeedRain 3cd 9c 20b 60c PolyethyleneMulch 8b 25b 8b 64c PolyethyleneMulch, 5bc 17b StrawPaths 24b 52c StrawMulch 2d 4c 104a 164ab HayMulch 1d 7c 108a 184a ANOVA P System <0.001 <0.001 < a MeansseparatedusingFisher sprotectedlsdtestatp Invertebratepestsandoniondiseasesincludedonionthrips(Thrips&tabaciLindeman),onion maggot(delia&antiquameigen),cutwormspecies(familynoctuidae),saltmarshcaterpillar(estigmene& acreadrury),andpurpleblotch(alternaria&porriellis),butoccurrencewashighlyvariableandnot affectedbyweedmanagementsystem(datanotshown). 18

33 EndNofNseasonsoilqualitywasgenerallymostfavorableforthemulchedtreatments(Table1.6.). Penetrometertestsmeasuringsoilcompactionvariedbysystemin2014,withmulchedplots demonstratinglesscompaction,possiblyduetodecreasedsoilcrusting(schonbeck2012)or managementnrelatedtraffic.waterinfiltrationrate,ameasureexpectedtobeinverselyrelatedto compaction,wasnotaffectedbysystemin2014(f 5,15 =1.66,P=0.206)or2015(F 5,15 =0.77,P=0.584). Soilnitrate(NO 3 NN)wasgreatestinPEmulchedsystemsinbothyears,aresultobservedelsewherein theliterature(schonbeckandevanylo1998b),possiblyduetoincreasedmineralizationordecreased leachinginheavyrains.ammonium(nh 4 NN)wasalsotestedbutdidnotdifferbysystemin2014(F 5,15 = 0.46,P=0.802)or2015(F 5,15 =0.77,P=0.624).Activecarbon,anindicatorofsoilhealth,wasgreatestin CriticalPeriodandnaturalNmulchedtreatmentsin2014,likelyduethereducedlateNseasonsoil disturbancetothesetreatments(islamandweil2000).itisunclearwhythepemulchedsystemsdidnot alsodisplayincreasedactivecarbon.onepossibleexplanationistheeffectofincreasedsoiltemperature onmicrobialbiomass(scopaanddumontet2007). 19

34 Table1.6.Effectsofweedmanagementsystemonfourmeasuresofsoilqualityin2014and2015.Withineachcolumn,meansfollowedbythe sameletterarenotsignificantlydifferent. Weedmanagement Depthtocompaction a Nitrate(NO 3 GN) c Activecarbon (microbialbiomass) a Soilorganicmatter a system d cm mgkg G1 mgkg G1 % CriticalPeriod 29bc 24 4d 8c 56a c ZeroSeedRain 27c 31 9c 25bc 49b c PolyethyleneMulch 41a 31 63a 110ab 47b c PolyethyleneMulch, StrawPaths 39a a 114a 48b c StrawMulch 37ab 27 9c 13c 58a a HayMulch 35ab 34 17b 6c 55a b ANOVA P System < <0.001 a MeansseparatedusingFisher sprotectedlsdtestatp b LogtransformedforANOVAatP 0.05.Reportedvaluesuntransformed. c BoxGCoxtransformedforANOVAandFisher sprotectedlsdtestatp 0.05.Reportedvaluesuntransformed. d SoilorganicmattertestingmodifiedtoincludelargerGsizedresidue

35 In2014,onionyieldinweed0freeconditionswasaffectedbyweedmanagementsystem(Table 1.3.).Toinvestigatewhichfactors,otherthanweeds,affectedyield,alinearregressionmodelofonion yieldwascreatedwithselectsoil0relatedmaineffects(table1.7.).themodelwasreducedto earthwormabundanceandmeansoiltemperature.earthwormsmayhavepositivelyaffectedyielddue totheirpreviouslydiscussedeffectsonsoilquality.soiltemperaturewaslikelyrelatedtotheearly senescenceofonionsintheblackpemulchedsystems. Table1.7.Thesignificanceofsoil0relatedparametersontheonionyieldofmainplotsin2014. Soil0relatedparameter Fullmodel Reduced model a P Meansoiltemperature Earthworms Compaction Soilnitrate(NO 3 0N) Activecarbon(microbial biomass) Modelperformance P AdjustedR AICc a Stepwisebackwardeliminationofleastsignificantparameterswasusedtoreducethemodelbasedon theadjustedr 2 andakaikeinformationcriterionwithcorrectionforfinitesamplesizes(akaike1974). Legacy'Effects' Animportantfactorinweedmanagementrelatestohowcurrentactionswillaffectfuture management,especiallyforfarmerswithalong0termfocus.thus,effectsonsoilorganicmatterand cropyieldwereevaluatedintheyearaftertheweedmanagementsystemswereimplemented. InMay,followingtheinitialonioncrop,residuefromthenaturalmulcheswasstillevident despiterototillingandwintercovercropping.however,traditionalsoilorganicmatteranalysesdidnot 21

36 differbetweenweedmanagementstrategies(table1.6.).inmayfollowingthesecondonioncrop,a revisedmethodshowedthatthestrawmulchtreatmenthadthegreatestcombinedsoilorganicmatter andresidue,followedbyhaymulch,whileothertreatmentsremainedatbaselinelevels.thedifference betweenstrawandhaymulchesmayrelatetothehighercarbon:nitrogenratioofstraw(schonbeck 2012),sinceequalmasseswereapplied. Despitevisibledifferencesinresidueandaccompanyingdifferencesinothersoilproperties, yieldofsweetcorninweed0freesubplotsdidnotdifferbysystemintheyearfollowingonions,nordid earwormdamage(datanotshown).thisindicatesthatasingleyearofeachweedmanagementsystem didnotaffectsoilqualityenoughtoaffectyieldofthefollowingcrop.however,growersimplementing naturalmulchesformanyyearshaveincreasedsoilorganicmattertotheextentthatitmaysupplymost oftheirfertility(brownandgallandt,inreview).inmainplots,whereweedcontrolwasachievedwith tractorcultivationbutnohand0weeding,criticalperiodplotsfromtheprioryeardemonstrateda22% lossofsweetcornyield(f 1,15 =10.8,P=0.004)comparedtotheothertreatments,whichyielded16.6 Mgha 01 onaverage.theyieldlossreflectstheincreasedweedemergenceduetoseedrainfromthe previousyear(table1.2.)thatcontributedtoend0of0seasonweedbiomassof685gm 02,whiletheother plotshadlowerweedbiomass(f 1,15 =27.14,P<0.001),withameanof117gm 02.Itisalsopossiblethat thereducedend0of0seasonsoilnitratelevelinthecriticalperiodsystem(table1.6.)contributedtothe sweetcornyieldloss.enterprisebudgetsforthesweetcornoperationsshowedthattheyieldlossinthe plotswherethecriticalperiodsystemwasimplementedtheprioryearresultedinalossofover2,500 USDha 01 comparedtotheothersystems(brownetal.inreview),anditislikelythatthislosswouldhave beengreaterinhighervaluecrops. 22

37 Management'Implications' TheweedseedproductionoftheCriticalPeriodsystemhadthegreatestmeasuredeffectonthe subsequentsweetcorncrop;however,thissystemmaybefeasibleifweedseedadditionscanbe reducedbyenhancedseedpredationorsubsequentcovercroppingandstaleseedbedperiods. Conversely,weedcontrolwasgreatestintheZeroSeedRainsystem(Table1.2.),whichwouldlikely reducefutureweedingcosts.unfortunately,suchpreventative,long0termmanagementislesscommon thanseedling focusedmanagementsincegrowersoftenbelievethatweedsareinevitable(dedeckeret al.2014;wilsonetal.2015)perhapsduetoanoverestimationofseedlongevity(jabbouretal.2014a). PEmulchresultedinhigherend0ofseasonnitratelevels(Table1.6.)andwarmedthesoil(Figure1.2.), whichacceleratedonionmaturation(table1.3.).however,foronion,thisincreasedsoiltemperature likelycontributedtoayieldlossinoneyearoftwo(table1.7.),thus,perhapslightercolorsshouldbe used.itislikelythatuseofstrawmulchinthepathsbetweenpemulchcouldhavebeenaneffective meansofweedcontrolhadthestrawnotcontainedoatseed.similarly,thestrawmulchtreatmentdid notperformtoitspotential,giventhevolunteeroats.perhapsfarmerscouldgrowtheirownstrawto ensureseed0freemulchorstorebalesoutdoorsfortheseasonpriortoapplicationtoencouragefatal germinationofseedsinthemulch.generally,strawmulchandhaymulchtreatmentshadhighyields (Table1.3.)andperformedwellinsoilhealthparameters(Table1.6.).Perhapsnaturalmulchescould provideanalternativetocovercroppingforgrowersreluctanttoforegocashcropsbutinterestedin improvingsoilhealth.furthermore,wehavepresentedeachsystemseparately,butapproachescould becombinedtoprovidemultiplebenefits.forexample,azeroseedrainapproachcouldbeused simultaneouslywithnaturalmulchingtoachieveaseedbankreductionwhilebenefitingfromthesoil aggradingpropertiesofmulch. 23

38 Weconcludethatwhileeachweedmanagementsystemyieldedequallyinoneyearoutoftwo (Table1.3.),theypresenttradeoffsineffectsonagroecology(Table1.2.;Table1.5.;Table1.6.)andfarm economics(bbrown,unpublisheddata).ourcasestudiesoffarmerswhohaveadoptedeachweed managementapproachshowedthatthe best systemdependsongrowermanagementgoals(brown andgallandt,inreview).therefore,itisouraimthatthispaperclarifiestheecologicaltradeoffsinvolved witheachsystemsothatgrowersmayidentifywhichapproachbestsuitstheirmanagementgoals. ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 24

39 CHAPTER'2' AN'ECONOMIC'COMPARISON'OF'WEED'MANAGEMENT'SYSTEMS'USED'IN'SMALLDSCALE'ORGANIC' VEGETABLE'PRODUCTION' BryanBrown,AaronK.Hoshide,EricR.Gallandt* *Firstandthirdauthors:SchoolofFoodandAgriculture,UniversityofMaine,Orono,ME04469,USA; secondauthor:schoolofeconomics,universityofmaine,206winslowhall,orono,me04469,usa. Chapter'Abstract' Organicfarmersoftenhavedistinctweedmanagementapproaches.Farmersmaycultivate duringthe CriticalPeriod ofthecropandignoresubsequentweeds;alternatively,theirmanagement mayconsiderthelongterm,withagoalof ZeroSeedRain. Acontrastingstrategyistosuppressweed emergencewithmulch,suchaspolyethylene(pe)filmorhay.weusedasystemscomparisontoprovide farmerswithabetterunderstandingofthelaborrequirementsandeconomicimplicationsofeach approach.inatestcropofyellowonion(allium&cepa&l),weedinglaborrequirementsweregenerally greatestforthezeroseedrainsystemandleastforthehaymulchsystem.however,totallaborcosts weregreatestforthehaymulchsystemandleastforthecriticalperiodsystem.zeroseedrainrequired themostevenlyspreadworkload,whilethehaymulchwasthemostuneven.unexpectedly,despite highweedinglaborcosts,enterprisebudgetsshowedthatthezeroseedrainsystemhadthegreatest netfarmincome(nfi).thehaymulchsystemalsohadhighnfi,despitehavingthegreatestlaborand materialscosts.thepemulchandcriticalperiodsystemshadcomparablylowernfi,reflecting decreasedonionyield,whichwasthemostinfluentialinputvariable.mulchedsystemswereslightlyless 25

40 riskythancultivatedsystems.subplotsmaintainedinseason0longweed0freeconditionswereless profitablethantherespectivemainplotsofeachsystem.inasubsequentcrop,nfiwasdecreasedin plotswherethecriticalperiodsystemhadbeenimplementedthepreviousyear,likelyduetoweedseed rainandresultingweedcompetition.weconcludethatwhiletheremaynotbeasingle best system forallcrops,foronion,thezeroseedrainandhaymulchsystemsperformedfavorably,andwilllikely providecontinuedbenefitsintermsofweedseedbankreductionandincreasedsoilorganicmatter, respectively. Introduction'' Weedmanagementapproachesoforganicfarmersmaybecategorizedintodistinctoverarching philosophies (DeDeckeretal.2014).Manyorganicfarmersaimtocontrolweedseedlings,while othershaveamorelong0termweedseedbankperspective(jabbouretal.2014a).farmersmayalso investinmulchtosuppressweeds(bakerandmohler2014).thereareexamplesofsuccessfulfarmers thatemphasizeeachoftheseweedmanagementapproaches(brownandgallandt,inreview).however, eachapproachlikelyhascontrastingeconomicbenefitsandrisks.small0scalefarmersmaybeunsure whichapproachisbestfortheirsituation,andcorrespondingly,wheretoinvesttheiroften0limited capitaltoimproveweedmanagement. Mostcommonly,organicfarmersaimtocontrolweedseedlings(DeDeckeretal.2014).To minimizelabor,thesefarmersmayconfineweedingeventstothe criticalperiod ofthecrop,when weed0freeconditionsarerequiredtoavoidayieldloss(knezevicetal.2002;nietoetal.1968). However,ifweedsareonlycontrolledduringthecriticalperiod,weedseedproductionislikely (BagavathiannanandNorsworthy2012;BrownandGallandt,inreview).Resultingseedraincangreatly increasetheweedseedbank(bondetal.1998),contributingtoincreasedweedemergencein subsequentcrops(norris1999). 26

41 Azeroseedrainapproachhasamorelong0term,weedseedfocus(Norris1999;Gallandt2014). Thisapproachrecognizesthatseedsofmanyweedspeciesareshort0lived(RobertsandFeast1972), therefore,preventingweedseedrainshouldcausearapiddecreaseintheweedseedbank,andlabor savingsinsubsequentyears(norris1999).indeed,somelarge0scaleconventionalvegetablefarmsin Californiahaveadoptedthissystemtoreducetheirweedseedbanks,andultimately,herbicideusage (Norris1999).NordellandNordell(2009)popularizedthisapproachfororganicmixed0vegetable growers.afterseveralyearsofweedseedpreventionalongwithpracticesthatdepletetheweed seedbank,theyobservedadramaticreductioninweedemergence,whichallowedforreducedweeding labor. Athirddistinctweedmanagementapproachinvolvesuseofmulchtosuppressweed emergence.mulchingrequiresanearly0seasoninvestmentinlaborandmaterialsbutresultsinreduced weedinglaborlaterintheseason.polyethylene(pe)filmmulchiscommonlyusedtowarmthesoiland promoteearlyyieldofsolanaceous(cirujedaetal.2012;schonbeckandevanylo1998b)and cucurbitaceouscrops(farias0lariosandorozco0santos1997;kayaetal.2005;sandersetal.1999). Additionally,theweedsuppressiveandmoistureretainingpropertiesofPEfilmhavealloweditto increasemarketableyieldsinothercrops,suchasonion(vavrinaandroka2000),cabbage(trdanetal. 2008),andheadlettuce(Braultetal.2002).Naturalmulches,suchashay,mayalsobeusedtosuppress weeds.inorganicbellpepper,profitabilityofproductionwithpeandnaturalmulcheswascomparable tolocalconventionalproductionusingherbicides(lawetal.2006).inorganictomatoes,ahaymulch systemreducedweedbiomass,andinsomesite0yearsresultedinanetlaborsavings(schonbeck1998), orgreateryieldscomparedtocultivatedorpemulchsystems(schonbeckandevanylo1998a). Wehypothesizedthatcriticalperiodweedcontrol,zeroseedrainmanagement,andmulching withpeorhaywouldvaryinlaborrequirementsandprofitability,representingcontrastingeconomic 27

42 benefitsandrisks.totestthishypothesis,weimplementedeachsysteminareplicatedfieldexperiment overtwoyears.unlikecontrolledexperimentsthatvaryalimitednumberoffactors,systems comparisonsaimtocontrastwhole0systemeffects.suchcomparisonshavebeenusedtoevaluate alternativeproductionsystemsinvegetables(chanetal.2011;halloranetal.2005),smallgrains(kolb etal.2010,2012),andcorn0soybeanrotations(caldwelletal.2014;coxetal.1999;davisetal.2012). Thesestudiesoftenutilizeenterprisebudgetstocompareprofitability.Additionally,riskanalysismaybe usedtoidentifysystemswithlessvariableprofitability,andthereforelessrisk(ottandhargrove1989; Luetal.1999),andsensitivityanalysiscandeterminethesensitivityofprofitabilitytovariationininput variablessuchasfertilizerprices(ottandhargrove1989),seedprices(luetal.1999),andcropyield (Chanetal.2011).Ouraimwastocharacterizetheeconomicsofseveralweedmanagementsystems usedonsmall0scaleorganicfarmstodemonstratetheprofitability,risk,andsensitivityofeachsystemso thatfarmersmayadjusttheirmanagementappropriately.relatedstudiesoftheecologicaldifferences betweenthesystemsaswellascasestudiesoffarmerswhohaveimplementedeachsystemwere presentedelsewhere(brownandgallandt,inreview). Materials'and'Methods' Weselectedfourweedmanagementsystems(detailedbelow)basedonpreviousliterature (BakerandMohler2014;DeDeckeretal.2014;Jabbouretal.2014a)andprevalenceofuseinMaine, USA.Systemswerecomparedinfieldexperimentsconductedin2014and2015attheUniversityof MaineRogersFarminOldTown,ME(44.93 N,68.70 W).Aseparatefieldwasusedforeachyear.Both fieldswerenicholvilleveryfinesandyloam.weatherwastypicalfortheregionthroughoutthestudy period,withaveragetemperaturesof16.9and17.2candprecipitationof380and473mmfor2014and 2015,respectively( Cortland )wereusedasthetest croptorepresentalong0season,weedsensitivecrop,forwhichweedmanagementisoftenchallenging. 28

43 Additionally,onionsarecommonlygrownusingeachweedmanagementsystem.Eachsystemwas implementedinarandomizedcompleteblockdesignwithfourreplicates.plotswere6.1mlongby1.7 mwide.bufferplotsofthesamedimensionswerelocatedoneithersideanda2.4mbufferwaslocated oneitherend. Usingacombinationofpreviousliteratureandinterviewswithfarmersthathavespecializedin eachweedmanagementsystem(brownandgallandt,inreview),weensuredthateachsystemwould beimplementedinarealisticmanner(table1.1.). Critical'Period'Weed'Control' Indirect0seededonions,thecriticalweed0freeperiodisthefirst56to84dafteremergence (HewsonandRoberts1971;MengesandTamez1981;Wicksetal.1973).Sinceouronionswere transplanted,weuseda56dcriticalperiodin2014(m.guzzi,personalcommunication).duringthis period,hoeingwasperformedaboutevery14d.duetoyieldlossin2014,the2015criticalperiodwas adjustedusinggrowingdegree0days,asdescribedbyknezevicetal.(2002),whichextendeditfrom56d in2014to78din2015(table1.1.). Zero'Seed'Rain' Withagoalofpreventingallseedrain,theseplotswerehoedaboutevery14dfrom transplantinguntilharvesting. Polyethylene'(PE)'Mulch' Priortotransplanting,weappliedembossed,blackPEmulch(1.2mwide,0.025mmthick, FedCoSeeds,Waterville,ME)withamechanicalapplicator(Model385PL,BartvilleWeldingShop, Christiana,PA).A50cmwidetrowelwasusedtomaketransplantingholes.Hoeingwasusedtocontrol weedsinpaths,whilehand0pullingwasusedtocontrolweedsemergingthroughplantingholes. 29

44 Hay'Mulch'' Timothy(Phleum&pratenseL.)mulchhaywasappliedmorethanonemonthaftertransplanting (Table1.1.)toallowtimeforthesoiltowarm.Haywasappliedbyhandatarateof20Mgha 01 (Schonbeck1998).Haywasspreadquicklyinthepaths,butinthebedsitwascarefullylaidaroundthe onions.hand0pullingwasusedoncetocontrolweedsafterthemulchwasapplied. AdditionaltreatmentsincludedaPEmulchsystemwithoat(Avena&sativaL.)strawmulchinthe pathsaswellasanentirelyoatstrawmulchsystem.unfortunately,thestraw,whichaspurchasedfor thisexperiment,containedviableoatseed,whichwasabletoemergethroughthemulch(brownand Gallandt,inreview),requiredconsiderabletimetohand0pull.Thus,thesetreatmentswerenotincluded inthiseconomicanalysis. Field'Management' InearlyMayofeachyear,primarytillagewasperformedwithonepassofarototiller,and secondarytillagewithonepassofafieldcultivator.organicsourcesoffertilitywereappliedpriorto secondarytillageinquantitiesbasedonsoiltestrecommendations(previouslydescribedonpage9).all fertilitysourcesweremeasuredandappliedbyhand. Onionsweresowninflatsoforganicpottingmix(LightMix,LivingAcres,Inc.,NewSharon,ME) inlatefebruaryinaheatedgreenhouse.immediatelyaftertillageandapplicationofpemulch,onions werebare0roottransplantedbyhandataspacingoftwoonionsperplantinghole,withholes15cm apart,androws30cmapart.dilutedfishhydrolysatewasapplieddirectlyaftertransplanting. Un0mulchedpathsbetweenonionbedswereweededwithwheelhoes,whilelong0handledhoes wereusedclosertocroprows,andshort0handledhoeswereusedinthecroprow.weedsinmulched areaswerepulledbyhand.sinceplotsweresmall,alllaborerswereinstructedtoworkatasustainable 30

45 pace,commensuratewiththepaceofworkinalargerfield.bufferareaswerehoedfollowingthezero SeedRainsystem. Dripirrigationwasusedtomaintainoptimalsoilmoistureforeachsystem.Irrigationlines(Triple KIrrigation,Morenci,MI)contained16mmdiameteremitters,spacedevery30cm,eachwithanoutput of19ccmin 01.Irrigationwasappliedweeklyintheamountnecessarytorechargethewaterdeficittoa depthof32cm.thewaterdeficitwasdeterminedweeklyusingadelta0thh2soilmoisturemeterwith a5.1cmthetaprobe(delta0tdevices,burwell,uk)atfourlocationsineachplot. In2015only,sweetcorn(Zea&maysL.cv.Xtra0Tender3473)wasplantedonJune4withrows spaced81cmapartandplants20cmapartwithinrows.inthisspacing,tworowswerecenteredwithin thepreviousyear splots.fertilitywasappliedwithpre0plantandsidedressingapplications(asdiscussed onpage13).weedcontrolwasprovidedbyspringtineharrowing(series982,type3,lelyindustriesnv, Maasland,Holland)onJune15;inter0rowcultivations(Model183,CaseIH,Racine,WI)onJune15,June 25,andJuly7;anddischillings(Weedmaster,ElomestariOy,Ltd.,Kukkola,Finland)onJune25andJuly 10.Weed0freesubplotswereadditionallyhand0weededonJune19,July6,July20,July31,andAugust 12.Yieldwasdefinedasthefreshmassofearsfrombothfirstandsecondharvests,occurringAugust24 andseptember2,respectively. Economic'Analysis' &Economicmodelingwasprimarilybasedonannualrevenue,laborexpenses,andmaterials expensesobtainedfromourfieldexperiments.additionally,assumptionsofonionprice,fuelusage, laborcosts,andfixedcostswereestimated(tablea.1.).thebuildingsandequipmentwereestimated baseontheaveragesizeofanorganicvegetablefarminmaine,usa,whichis1.42ha(usdanass 2014).Annualrevenuewasdeterminedbymultiplyingthewholesaleonionpricebythemarketable onionyield.marketableonionyieldwasmeasuredbyharvestinga1by1mquadrat,centeredonthe 31

46 bedofeachmainplotandsubplot.harvestoccurredonapertreatmentbasiswhen70%oftheonion leaveshadfolded.harvestedonionscuredonmeshtablesinaventilatedgreenhouseforseveralweeks (Table1.1.).Onionswereweighedaftertopsandrootshadbeenpruned,aftercuring.Visiblydiseased onionswerenotincludedinyielddata. Theamountoflaborrequiredforplanting,weeding,mulching,andharvestingwasrecordedto thenearestsecondwithstopwatches.evennessoflaborovertheseasonwasevaluatedwithpielou s evennessindex&(j')(pielou1975),whichwascalculatedbyseparatinglaborforeachsysteminto2wk binsandusingtheequation: = p % lnp %& /ln(s)&(equation&2.1. ) where4 5 istheproportionoflaborineachbinandsisthenumberofbins(10). Expensesofallpurchasedmaterialswerelogged.Returnovervariablecosts(ROVC)was calculatedastheannualrevenueminusrelatedoperatingcosts.netfarmincome(nfi)wascalculatedas theannualrevenueminusboththerelatedoperating(variable)costssuchaslabor,fuel,seedlingsand fertilizeraswellastheownership(fixed)costssuchasdepreciationonequipment,fixedcostoflandand taxesandinsuranceonfixedcapital. Economicriskandsensitivityanalyseswereperformedusing@RISK(PalisadeCorporation, Ithica,NY)followingÖzkanetal.(2015).The@Risksoftwarewasusedtodefinethedistributionsof severalkeyinputvariables(tablea.1.)withinourexcel(microsoftcorporation,redmond,wa)budget modelforeachweedmanagementsystem.using@risk,1,000montecarloiterationswererun,in whichvaluesofinputvariableswererandomlyselectedfrompre0defineddistributions.theinput variablesincludedfuelprice,wagerate,hayprice,onionyield,onionprice,andlaborrequiredfor planting,weeding,mulching,andharvesting.economicriskwasevaluatedusingtheresultingcumulative distributionfunction(cdf)curves,whichdisplaytheprobabilityofachievingannfilessthanorequalto 32

47 x.evaluationofthedifferencesbetweencdfcurveswereusedtodetermineriskinessandstochastic dominanceamongthedifferentsystems(hardakeretal.2004),wheresystemaisfirst0order stochasticallydominanttoweedingsystembifthecdfforaisentirelytotherightofthecdfforb. However,iftwoCDFcurvescross,second0orderstochasticdominanceisdeterminedby: : < : < 6> 8 98&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&(Equation&2.2. ) whereiftheareaunderthecdfforweedingsystemaislessthantheareaunderthecdffor weedingsystemb,thensystemaispreferredtosystembfromaneconomicriskperspective.bothfirst0 andsecond0orderstochasticdominanceassumefarmersarerisk0averse.eventhoughsystembmay haveaslightlyhighernfithansystema,thelowervariabilityofsystemamaybepreferred.stochastic dominancewithrespecttoafunctionanalysesrelaxtheassumptionofriskaversionbyrankingcdf curvesdependingonrisk0seekingorrisk0avoidingoutlooks(hardakeretal.2004). Foreachweedmanagementsystem,sensitivityanalysesarepresentedastornadographs,in whichthehighandlowvaluesofinputvariablesfromthemontecarlosimulationwereusedtograph highandlownfiasothervariableswereheldconstant. StatisticalanalyseswerecompletedinJMP10(SASInstituteInc.,Cary,NC).Acontrastwasused tocompareplantinglaborbetweensystemswithbaresoilandthepemulchsystem.effectsofweed managementsystemsonlaborrequirementswereevaluatedwithanova.yearswereanalyzed separatelyduetomultipleyearbytreatmentinteractions.meanscomparisonswereconductedusing Fisher sprotectedlsd.asignificancelevelof0.05wasusedthroughoutthestudy.datafailingtomeet assumptionsweretransformedasnecessaryoranalyzedwiththenonparametrickruskalwallistest (KruskalandWallis1952)andpairwiseWilcoxonsigned0ranktest(Wilcoxon1945). ' ' 33

48 Results'and'Discussion' Labor' Laborrequiredtohand0transplantonionsdifferedbetweenplotswithbaresoilatthetimeof transplanting CriticalPeriod,ZeroSeedRain,andHayMulchsystems andthosewithpefilm(f 1,42 = 14.01,P<0.001),withlaborrequirementsof366hha 01 and577hha 01,respectively.Weeding,mulching, andharvestinglabordifferedbyweedmanagementsystem(table2.1.).weedinglaborwasgreatestfor thezeroseedrainsystem.inthehaymulchsystem,applicationofmulcharoundtheonionswasvery laborintensive.conversely,inthepemulchsystem,mulchapplicationwithatractor0drawnmechanical applicatorwasrapidandmanualremovalafterharvestrepresentedmostofthemulchinglabor.as expected,harvestinglaborwashighforthecriticalperiodplots.unexpectedly,pemulchalsorequireda highamountofharvestinglabor. Table2.1.Weeding,mulching,andharvestinglaborrequiredtogrowonionsusingfourweed managementsystems.withineachcolumn,meansfollowedbythesameletterarenotsignificantly different. Weed(management( system Critical(Period 8.8 b 12.4 b 0.0 c 0.0 c 2.0 a 0.9 b 0.69 b Zero(Seed(Rain 13.7 a 17.7 a 0.0 c 0.0 c 1.0 b 0.5 c 0.86 a Polyethylene(Mulch 9.9 b 10.8 b 0.5 b 0.3 b 2.0 a 1.2 a 0.66 b Hay(Mulch 7.5 b 7.7 c 9.4 a 6.9 a 1.0 b 0.8 bc 0.59 c ANOVA Weeding a Mulching b Harvesting a (h(ha K1 P <0.001 <0.001 < a MeansseparatedusingFisher sprotectedlsdatp b MaineffectstestsperformedwithKruskalWallistests(KruskalandWallis1952)andmeans comparisonsperformedwithwilcoxonpairedtests(wilcoxon1945),bothatp Workload( evenness a J' <

49 EvennessoftheworkloadovertheseasonwasevaluatedusingPielou sevennessindex&(j'). YearswerecombinedduetoabsenceofaYearbyTreatmentinteraction(F 1,3 =1.48,P=0.245).TheZero SeedRainsystemhadthemostevenworkload(Table2.1.)reflectingtherelativelyconstantweeding requirement(figure2.1.).duetoearly0seasonweedingandmulchingactivities(figure2.1.),thecritical PeriodandPEMulchsystemsrequiredalessevenspreadoflabor,andtheHayMulchsystemrequired themostunevenworkload(table2.1.).harvestofthepemulchsystemoccurredaroundonemonth earlierthantheothersystems(figure2.1.). Economic'analysis' Annualrevenuewasadirectreflectionofonionyield(TableA.1.).Inmainplotsandweed0free subplots,annualrevenueofzeroseedrainandhaymulchsystemswasthegreatest(table2.2.). Comparatively,annualrevenueofthePEMulchsystemwasless,andtheCriticalPeriodsystemhadthe leastannualrevenue. LaborexpenseswereleastfortheCriticalPeriodsystemandgreatestfortheZeroSeedRainand HayMulchsystems(Table2.2.).Materialexpenseswereprimarilyfertilityandseedstartingsupplies (TableA.3.).Themajordifferenceinmaterialexpensesbetweensystemswasmulchcosts,whichwere 509USDha 01 forthepemulchsystemand3,850usdha 01 forthehaymulchsystem.ownership expensesweredominatedbydepreciationofequipmentandfacilities(tablea.3.).theonlydifferencein ownershipexpensesbetweensystemswasthepemulchapplicatorrequiredforthatsystemfor85usd ha 01 peryear. 35

50 Figure2.1.Temporalspreadoflaborrequiredtogrowonionsusingeachweedmanagementsystem: CriticalPeriod(AandB),ZeroSeedRain(CandD),PolyethyleneMulch(EandF),andHayMulch(Gand H).Patternswithinbarsrepresentplanting(gridlines),mulching(solidfill),weeding(dotted),and harvesting(diagonallines). Labor"(h"ha /1 )" 500" " " 1,000" 400" " 300" 750" " 200" 500" " 100" 250" " 500" 0" 1,000" 400" " 300" 750" " 200" 500" " 100" 250" " 0" 0" " 1,000" " " 750" " " 500" " " 250" " " 0" 0" 500" " 1,000" 400" " 300" 750" " 200" 500" " 100" 250" " 0" 0" May"1"to"15" a" A PlanEng" Mulching" b" B Weeding" HarvesEng" c" C d" D Ee" f" F g" G h" H May"16"to"31" Jun"1"to"15" Jun"16"to"30" Jul"1"to"15" Jul"16"to"31" 1" 2" 3" 4" 5" 6" 7" 8" 9" 10" 2014" Aug"1"to"15" Aug"16"to"31" Sep"1"to"15" Sep"15"to"30" 1" 2" 3" 4" 5" 6" 7" 8" 9" 10" May"1"to"15" Date""" May"16"to"31" Jun"1"to"15" Jun"16"to"30" Jul"1"to"15" Jul"16"to"31" Aug"1"to"15" Aug"16"to"31" Sep"1"to"15" Sep"15"to"30" 1" 2" 3" 4" 5" 6" 7" 8" 9" 10" 2015" 36

51 Table2.2.Summaryofenterprisebudgetsforfourweedmanagementsystems.Annualrevenueisa directreflectionofonionyield.laborandmaterialexpensesweresubtractedfromannualrevenueto calculatethereturnovervariablecosts(rovc).netfarmincome(nfi)wascalculatedbysubtracting annualownershipexpensesfromrovc. Weed$ management$ system Annual$ revenue Labor$ costs Materials$ and$other$ operating$ costs Annual$ ownership$ costs Return$over$ variable$costs$ (ROVC) Net$farm$ income$(nfi) 100$USD$ha T1 Critical$Period Zero$Seed$Rain Polyethylene$Mulch Hay$Mulch NetfarmincomewasgreatestfortheZeroSeedRainsystemfollowedbyHayMulch,PEMulch, andcriticalperiodsystems,respectively(table2.2.).nfireflectedrovcsinceitmerelyinvolvedthe extrasubtractionofannualownershipcosts,whichwerenearlyuniformforallsystems. RiskAnalysiswasconductedwithoverlaidcumulativedistributionfunctions(CDF)ofNFIforthefour weedmanagementsystems(figure2.2.).thezeroseedrainsystemdemonstratedfirst0orderstochastic dominancecomparedtothepemulchandcriticalperiodsystems.thehaymulchsystemdemonstrated first0orderstochasticdominanceoverthepemulchsystem.theminimumpossiblenfiforthecritical Period,ZeroSeedRain,PEMulch,andHayMulchsystemswerelossesof46,806,20,633,23,024,and 20,168USDha 01,respectively,whereasthemaximumpossibleNFIwas73,538,102,393,60,271,and 62,237USDha 01,respectively.Thewiderrangesoftheun0mulchedsystemscausedtheirCDFcurvesto crossnearestmulchedsystems.theareaunderthecdfcurveofthecriticalperiodsystemwasgreater thanthepemulchsystem,indicatingsecond0orderstochasticdominanceofthepemulchsystem. 37

52 Likewise,theHayMulchsystemexhibitedsecond0orderstochasticdominanceovertheZeroSeedRain system. Figure2.2.CumulativedistributionfunctionsofnetfarmincomebasedonMonteCarlosimulationwith 1,000iterationsofeachweedmanagementsystem. ThesensitivityofNFItochangesininputvariablesisdisplayedbytornadographs(Figure2.3.). Formostsystems,NFIwasmostsensitivetoonionyield,followedbyonionprice,andwagerate.The exceptionwasthehaymulchsystem,inwhichonionpricewasthemostinfluentialdeterminantofnfi sinceonionyieldwaslessvariableinthissystem(tablea.1.).netfarmincomewasmoresensitiveto 38

53 weedingandtransplantinglaborthanharvestinglaborinallsystems.mulchinglaborwasasignificant inputvariableforthemulchedsystems.haypricewasalsoaninfluentialvariableforthehaymulch system.fuelpricewasminimallysensitivetofuelpriceformostsystems. In2015,theyieldofsweetcorngrowninrotationaftertheonionswasunaffectedbysystem whenweed0freeconditionsweremaintained(brownandgallandt,inreview).however,insweetcorn plotswhereweedsweremanagedwithonlyearly0seasoncultivation,criticalperiodplotsdemonstrated asweetcornyieldloss,whichresultedinannfilossof2,187usdha 01 intheenterprisebudgetfor sweetcornproduction,whereasthemeannfioftheothersystemswaspositiveat337usdha 01 (Table A.3.). Overall'Performance'of'Each'System' Oursystemscomparisonshowedthatforonions,theZeroSeedRainandHayMulchsystems weremostprofitabledespiteincurringthegreatestcosts.thesesystemsareconsideredlong0term investmentsinreducingtheweedseedbank(norris1999)andimprovingsoilorganicmatter(brownand Gallandt,inreview),respectively.Therefore,itwasunexpectedthattheywouldbethemostprofitable systemsinthefirstseasonofimplementation.perhapsthesesystemswouldbecomeevenmore profitableinsubsequentyears.dependingonthetillagesystem(anderson2005),severalyearsof intensivezeroseedrainmanagementcanreduceweedemergence(nordellandnordell2009)tothe extentthatonefarmerwithazeroseedrainapproachisnowabletomanagea40hamixed0vegetable farmwithonlytwoadditionalworkers(brownandgallandt,inreview).alternatively,haymulchingmay improveseveralmeasuresofsoilhealth(brownandgallandt,inreview;schonbeckandevanylo1998b). Increasedsoilorganicmatterfrommanyyearsofhaymulchingmayevenprovidesufficientcropfertility (BrownandGallandt,inreview). ' 39

54 Figure2.3.Tornadographsdisplayingthesensitivityofnetfarmincometovariationinselectedinput variablesforeachweedmanagementsystem;criticalperiod(a),zeroseedrain(b),polyethylenemulch (C),andHayMulch(D).Plottednetfarmincomewascalculatedbyusingtheextremevaluesof1,000 MonteCarlosamplingiterationsfromeachinputvariable,whileallothervariablesremainedatbaseline levels. 40

55 TheprofitabilityoftheZeroSeedRainandHayMulchsystemslikelyrelatestothesesystems providingthebestweedcontrol(brownandgallandt,inreview)andonionsbeingaweedsensitivecrop (BondandBurston1996;WareandMcCollum1975).Indeed,theonionsyieldedhighestinthese systemsandnfiwasmostsensitivetoonionyieldandprice(figure2.3.).similarly,inorganicmixed0 vegetableproduction,chanetal.(2011)observedthatyieldandcroppriceweremoreimportant determinantsofprofitabilitythaninputcosts. SensitivityofNFItowagerates(Figure2.3.)reflectsthehighlaborcostsinvolvedwiththese systems.thezeroseedrainsystemrequiredthemostweedinglabor(table2.1.),whereasthehay Mulchsystemhadthegreatesttotallaborexpenses(Table2.2.),consistentwiththeexperienceof farmersthathaveimplementedthesesystems(brownandgallandt,inreview).theevennessofthe workloadinthezeroseedrainsystem(table2.1.)wouldperhapsbedesirableforafarmwithasteady butlimitedlaborpool.apotentialconflictofmanagementprioritiesmayariseinlate0summer,whenthe shortphotoperiodencouragesmanysummerannualweedstosetseedquickly(giffordandstewart 1965;WeaverandMcWilliams1980),whileharvestoperationsalsoneedtobeconducted.Conversely, theunevenspreadoflaborinthehaymulchsystemwouldperhapsbebestsuitedtofarmerswith ampleaccesstoseasonallabor,whocouldhireashort0termcrewtocompletetheearly0season mulching.alternatively,farmersmaybeabletoaccomplishmulchingbystaggeringplantingdatesso thatitcouldtakeplaceoveramoreprotractedperiod.mulchinglaborcouldpossiblybereducedin warmergrowingregions,wherewarmsoiltemperaturewouldallowformulchapplicationpriorto transplanting.however,naturalmulchesappliedpriortotransplantingmaynotprovideseason0long control(lawetal.2006),thus,increasedapplicationratesmaybenecessary. IntheHayMulchsystem,NFIwassensitivetohayprice(Figure2.3.),reflectingthevariabilityof thisinput.haymaybeprocuredforfreeinthecaseofspoiled,mulchhay,orboughtforashighas

56 USDkg 01 (TableA.1.).Lawetal.(2006)foundsimilarsensitivitytopriceofnaturalmulchesinbellpepper production;whenmulchwasobtainedforfree,profitabilitywassimilartoconventionalproduction,but profitabilitywasgreatlydecreasedwhenmulcheswerepurchased.haymulchcostscouldperhapsbe decreasediffarmersgrewtheirown,whichwouldalsoallowthemtoensureminimalweedseed contamination.alternatively,innewengland,usa,municipalleafcollectionsmaybeinexpensively deliveredtofarmsandusedinasimilarmannerashaymulch(t.roberts,personalcommunication). ThePEMulchsystemdidnotperformasfavorablyasexpected.Itwasunexpectedthatonion yielddidnotincreaseinpemulch,sincemanycrops(kayaetal.2005;trdanetal.2008;zhangetal. 2007;)includingonions(VavrinaandRoka2000),haveshownapositiveyieldresponse.Yieldlossin 2014waslikelyduetowarmersoilcausingearlysenescence(BrownandGallandt,inreview).Insome crops,liketomatoes,earlyyieldwouldlikelyallowforpremiumprices.however,forstorageonions, earlyyieldisunlikelytoincreaseprofitabilitysincethistypeofcropcanbestoredalmostallyear. TheincreasedtransplantinglaborinthePEMulchsystemandtheaddedtaskofPEfilmremoval werealsonotedbyschonbeck(1998)tonegateanylaborsavingscomparedtoahaymulchsystem. However,somesmall0scalegrowershaveinvestedinwater0wheeltransplanters(Rain0FloIrrigation,East Earl,PA),whichhaveincreasedspeedoftransplantinginPEfilm(J.Kafka,personalcommunication). MechanicalPEfilmremovalequipmentisalsoavailable(CropCare,Lititz,PA). ThePEMulchsystemrequiredmoreweedinglaborthanexpected(Table2.1.),duetoweeds emergingthroughtheplantingholes,whichnecessitatedhand0pulling.smallerplantingholesmayhave decreasedthenecessityofhand0pullingbutwouldlikelyhaveincreasedtransplantinglabor.our recommendationisthatblackpefilmbeusedforheat0lovingcrops,whicharetypicallymorewidely spacedthanonions,therebyprovidinglessopportunityforweedstoemergethroughplantingholes. 42

57 TheCriticalPeriodsystemincurredayieldlossin2014,butin2015theperiodwasadjusted usinggrowingdegree0days,followingknezevicetal.(2002),andtherewasnotayieldloss(brownand Gallandt,inreview).Theoretically,criticalperiodweedmanagementshouldnotexhibitayieldloss (Nietoetal.1968).However,thetwoyearswerecombinedintheeconomicanalysisbecausethelength ofthecriticalperiodmaychangebasedonweatherorotherfactors(knezevicetal.2002),whichmay notbeaccountedforbysmall0scalegrowers(m.guzzi,personalcommunication). InadditiontohavingthelowestmeanNFI(Table2.2.),theCriticalPeriodsystemhadawide rangeofpossiblenfi(figure2.3.),indicatinghigherrisk.despitetheunfavorableperformanceofthe CriticalPeriodsystem,itiscommonlyusedbyfarmers(Jabbouretal.2014a),highlightingtheirkeen interestinreducinglaborcosts.indeed,theweedinglaborreductionprovidedbyacriticalperiod approachoffersa huge,practicalbenefit accordingtoonefarmer(m.guzzi,personalcommunication). Additionally,inmoreweedcompetitivevegetables,suchascabbageorcucumber,thecriticalweed0free periodisashorterduration(weaver1984),therebyofferingmorelaborsavingsthaninonions. Furthermore,theeffectofincreasedharvesttimeduetoweedinterferencewouldlikelybelessenedin larger,ormoreprostratecrops. PerhapsthemostimportanteffectoftheCriticalPeriodsystemwastheabundantweedseed rain,whichincreasedweedcompetitioninthesubsequentsweetcorncrop(brownandgallandt,in review),andreducedprofitability(tablea.3.).therefore,thresholdsfordeterminingthelevelof necessaryweedcontrolbasedsolelyonyieldmaynotbeadvantageous(norris1999).however,with sufficientfarmland,farmersmayusefrequentcovercropsintheirrotationtobringtheweedseedbank backdowntoamanageablelevel(brownandgallandt,inreview). Overall,asinglemanagementsystemisunlikelytobepreferableforallcrops(Chanetal.2011). Therefore,itisnotouraimthatfarmersadoptasingle best approach,butforfarmerstounderstand 43

58 thebenefitsandrisksofeachweedingsystemsothateachmaybeusedappropriately.ourresearch withonion,representativeofalong0season,weed0sensitivecropthatgrowswellintemperateclimates, hasdemonstratedthatthemoreintensivesystems ZeroSeedRainandHayMulch performed favorably.however,inthecontextofamixed0vegetablefarm,themostsuccessfulapproachmaybeto useallsystemsconcurrently,witheachsystembeingimplementedaccordingtothecrop,laborand inputavailability,andfarmermanagementgoals. 44

59 CHAPTER'3' TO'EACH'THEIR'OWN:'CASE'STUDIES'OF'FOUR'SUCCESSFUL,'SMALLDSCALE'ORGANIC'VEGETABLE' FARMERS'WITH'DISTINCT'WEED'MANAGEMENT'STRATEGIES' BryanBrown,EricR.Gallandt* *Firstandsecondauthors:SchoolofFoodandAgriculture,UniversityofMaine,Orono,ME04469,USA. Chapter'Abstract' Farmersoftenhavedistinctiveweedmanagementstrategiesthathavedevelopedasaresultof theiruniqueperceptionsandpriorexperiences.tocharacterizethemotivationsandrisksofdifferent weedmanagementstrategies,weconductedcasestudiesofsmall0scale,diversifiedorganicvegetable farmersrepresentingstrategiesfocusedon(i)weedseedlingmanagement,(ii)seedbankmanagement, or(iii)weedpreventionwithpolyethylene(pe)ornaturalmulches.markguzzitendstomanageweed seedlingsinthesocalled criticalweed0freeperiod, whichminimizescropyieldlossbutoftenallows weedstosetseed,contributingtoanabundantweedseedbank.incontrast,tomhonigfordaimsfor zeroseedrain,astrategythatrequiredalargeearly0careerlaborinvestmenttopreventweedsfrom settingseed,buthaspaidoffwithgreatlyreducedweedpressureinsubsequentyears.davecolson utilizespemulchonmanycropstoreduceweedinglabor,whichisespeciallybeneficialintheearly0 seasonwhentheneedtoplantothercropsformerlypreventedhimfromweeding.tomrobertsuses naturalmulchestosuppressweeds,conservesoilmoisture,andbuildsoilhealth.regardingdrawbacks totheirstrategies,guzzispokeofthehighweedinglaborrequiredforweedsensitivecrops,honigford wassomewhatconcernedwithdecreasedsoilqualityduetofrequentcultivation,colsonmentionedthe 45

60 environmentalcostofusingapetroleum0basedproduct,androbertsemphasizedthehighamountof laborrequiredtocollectandapplynaturalmulch.thougheachfarmerutilizedknowledgeoftheweed seedbankintheirmanagement,weedseedbankdensitiesrangedfrom3,065seedsm 02 (Honigford)to 38,482seedsm 02 (Guzzi).SoilorganicmatterwasveryhighforRoberts,reflectinghisregularadditionof naturalmulches.pairwisecomparisonsofselectmanagement0relatedcriteriashowedthatguzziplaced mostimportanceonreducingweedinglabor,honigfordvaluedtheweedseedbank,colsonplaced nearlyequalimportanceonallcriteria,androbertsmostvaluedsoilquality.thesesuccessful,highly0 regardedfarmersdemonstratethatthereisnotaclear,single best weedmanagementstrategyfor small0scaleorganicvegetablegrowers,butbeginningandexperiencedfarmersalikemaybenefitfroma thoughtfulanalysisoftheirweedmanagementphilosophiesandthemotivationsandrisksoftheir foundationalstrategies. Introduction' Organicfarmersoftenhavedistinctattitudesrelatedtoweedmanagement(Dedeckeretal. 2014).Theymayfocusonshort0termcontrolofweedseedlings,longer0termweedseedbank management(jabbouretal.2014a,b),orweedsuppressionwithmulch(bakerandmohler2014). Motivationsdrivingeachofthesefundamentallydifferentweedmanagementstrategiesvarywidely.For example,farmersfocusedonmanagementofweedseedlingsoftenprioritizeweedcontrolduringthe criticalweed0freeperiod(jabbouretal.2014a,b),theperiodwhenweed0freeconditionsneedtobe maintainedtoavoidcropyieldloss(knezevicetal.2002;nietoetal.1968).however,thisstrategyoften allowslate0seasonweedstosetseed,resultinginabundantseedrainandahighweedseedbank(norris, 1999). Conversely,farmerswithaseedbankmanagementphilosophyemphasizetherisksofweedsand employmorepreventativetechniques(jabbouretal.2014a,b).forexample,controllingweedsbefore 46

61 theysetseedwouldlessenweedemergenceinsubsequentyearsandreduceweedcontrolcosts(norris, 1999).Suchazeroseedrainstrategyhasbeenusedtoeffectivelyreducetheweedseedbank(Gallandt, 2014;Riemensetal.2007). Athirddistinctgroupoffarmersaimtofront0loadtheirweedmanagementeffortsusingmulch tosuppressweeds(bakerandmohler2014),astrategygenerallyemployedinhigh0valuevegetable crops.innortherntemperateregions,blackpemulchisoftenusedforitssoilwarmingproperties; however,itisalsovaluedforweedsuppressionandsoilmoistureretention(lament1993),andcan increaseyieldsinavarietyofvegetablecrops(kayaetal.2005;vavrinaandroka2000;zhangetal. 2007).InOhio,USA,farmersdiscussedthepotentialforblackPEmulchtosavelaborandweedcontrol costs,butalsotheriskofhavingtocontrolweedsinthepathwaysandplantingholes(zwickle2011). Naturalmulches,suchashayortreeleaves,mayalsobeusedtosuppressweedgrowth.Naturalmulch applicationrequiresalargeearlyseasoninvestmentinmaterialsandhandlabor,butthereisa psychologicalboosttofarmworkersinknowingthatlittlesubsequentweedingisrequired(p.arnold, personalcommunication).oneconcernaboutnaturalmulchesamongfarmersistheriskofbringingin weedseed(zwickle2011),whichfarmersaddressbyknowingthemulchsourceorharvestingit themselves. Eachofthesefundamentalapproachestoweedmanagementhasuniquebenefitsand drawbacks.sincefarmersarestronglyinfluencedbytheexperienceofotherfarmers(rogers1988),itis theintentofthispapertoshowcasefarmermotivationsforeachstrategy,therebyinformingbeliefsand influencingweedmanagementdecisions(wilsonetal.2009;zwickle2011)byaffectingperceptionsof riskandhowtomitigatethatrisk(slovic1987).todoso,wepresentcasestudiesofsuccessfulfarmers thathavespecializedineachapproachinordertocharacterizethemotivationsandrisksofeach managementstrategy. 47

62 Materials'and'Methods' AfarmerrepresentativeofeachofthefourweedmanagementstrategieswasselectedinJuly 2014basedontheirinterestandwilingnesstoparticipate,involvementwithpreviousstudies(i.e., Jabbouretal.2014a,b),andtheauthors familiaritywiththefarmers practices.farmerswereallsmall0 scale,organic,mixedvegetablegrowerslocatedinnorthernnewengland.inseptember2014,tensoil corestoadepthof18cmwerecollectedfromarepresentativefieldateachfarm.homogenized samplesweresenttotheuniversityofmainesoiltestingserviceforsoilorganicmatter(som)testing. Anadditional,tensoilcoreswereobtainedusingabulbplanter(YardButlerIBPL06BulbandGarden Planter,LewisTools,Poway,CA),8cmdiameter,insertedtoadepthof10cm,toperformgerminable weedseedbankassays(gallandtetal.1998).followingryanetal.(2010),soilwasplacedin4l resealableplasticbagsandtransportedinaninsulatedcoolertostorageindarkconditionsat012c.bags wereremovedfromstorageonmay1,2015andallowedtothawfor48hbeforecontentswerespread on51by51cmflatsovera2.50cmlayerofvermiculite.flatswerewateredregularlytoencourage germination.commonseedlingswereidentifiedtospeciesorgenus,whilelesscommonseedlingswere recordedas otherbroadleaf or othermonocot. Seedlingswereremovedafterbeingidentified. Whengerminationslowed,flatswereallowedtocompletelydrysothatthehardenedsoilcouldbelifted fromthevermiculite,placedinabucket,mixed,returnedtotheflat,andwateredtoencourageanew flushofgermination.fivesuchcyclesoccurredduringtheassayperiodofmay1toseptember30,2015. FarmerswereinterviewedinMarch2015afterobtainingapprovalfromtheInstitutionalReview BoardfortheProtectionofHumanSubjects(IRB)(FigureA.1.).Followingtheinterviews,permission fromthefarmersandirbwasgrantedtodiscloseidentities.thefourparticipantswereeach compensated250usdfortheirtime.interviewquestionsweredevelopedtohighlightkeydifferences betweenfarmerweedmanagementstrategies.thisresearchaimedtocaptureindividualnarrativesof 48

63 thepracticesandmotivationsrelatedtoeachweedmanagementstrategy.thesamequestions(table A.4.)wereaskedinallinterviewsinasemi0structuredformat(Bernard2011)thatallowedforoccasional follow0upquestions. FollowingtheAnalyticHierarchyProcess(Saaty1982),theinterviewsalsoincludedaseriesof pairwisecomparisonquestionstodetermineimportanceoffourmanagement0relatedcriteriatothe farmers.thefourcriteriawere:weedinglabor,theweedseedbank,environmentalsustainability,and soilquality.eachpossiblepairofcriteriawerepresentedtofarmerswiththeinstructiontorankthepair onascaleofzerototenwithzeromeaningthefirsttermisextremelyimportantandthesecondterm hasnoimportance,andvisaversa,andwitharankoffivemeaningthatthetwotermsareequally important.theweightsoftheindividualcriteriawerecalculatedbycreatinganormalizedcomparison matrix,thendividingeachvaluebythesumofitscolumn,andtakingthemeanofeachcriteriarow. Interviewswereconductedbytelephone,werearoundonehourinduration,andwererecorded usingadigitalvoicerecorder.interviewsweretranscribedmanuallyandcheckedforaccuracyand consistencybytheauthors.priortopublication,allinterviewedfarmersapprovedthefinaldraft. Results'and'Discussion' Participatingfarmersallownedandmanagedsmall0scale,diversifiedorganicvegetable operations.alongwithfarmers differentweedmanagementphilosophiesandstrategies,farmsvaried intheirsoiltype,numbersofworkers,landareaincultivation,covercropusage,andseasonalworkload (Table3.1.).Eachofthecasestudyfarmersiswell0established,havingaminimumof17yearsof experience,andishighlyregardedintheorganicfarmingcommunity.eachmanagesweedsinadistinct mannerand,aswillbediscussed,thefactorsthatinfluencedtheformationoftheirweedmanagement philosophyrangedwidely. 49

64 Table3.1.Summaryofsoiltexture,farmsize,andlanduseforcasestudyparticipantsrepresentingeachweedmanagementstrategy. Farmer Weedmanagement strategy Soiltexture Landin Landin cultivation summer covercrop no. ha % % Seasonal workers Landin winter covercrop Busiesttime ofyearfor farm operations MarkGuzzi Criticalperiod Siltloam Allseason TomHonigford Zeroseedrain Sandyloam AugQSep DaveColson Polyethylenemulch Loam 5Q MayandSep TomRoberts Naturalmulch Clayloam 3Q Aug Sep 50 50

65 Mark%Guzzi% %Critical%Period%Weed%Management%%% Guzziusesamixofmechanicalcultivationandhandhoeing,oftenfocusedontheearlygrowth periodofhiscrops.guzzisometimesconfinesweedingeventstotheearlyseasontosavelabor(in#sensu Knezevicetal.2002).Hesays, crops#can#tolerate#some#weed#pressure,#especially#later#on#in#the#season#and#so#it# becomes#an#issue#of#whether#those#weeds#are#going#to#interfere#with#harvest#or#not.# There#is#a#window#when#the#competition#is#the#most#and#it#tends#to#be#when#the#crop# is#small.#you#get#the#crop#passed#a#certain#stage#and#then#the#weed#pressure#is#going# to#make#less#of#a#difference#on#the#ability#of#that#crop#to#grow.#that#doesn t# necessarily#mean#that#those#weeds#aren t#going#to#be#a#problem#later#on#[due#to#seed# rain]. ## RegardinghowGuzziestablishedhiscurrentweedmanagementstrategy,herecalled, It s#very#short#term#thinking #the#[previous#owner]#had#allowed#the#weed#seedbank# to#grow#and#become#a#very#significant#problem.#so#when#we#got#here #we#got#used# to#growing#in#very#weedy#fields.#our#level#of#tolerance#is#no#doubt#higher#than#it# should#be #We#created#this#farm#business#with#all#of#these#markets#and#expectations# despite#the#fact#that#we#were#totally#contaminated#with#weeds.#i#recognized the# smart#thing#to#do#would#be#to#have#done#a#nordellitype#approach#where#we#would# have#taken#that#ground#and#exhausted#the#weed#seedbank#before#expanding# production #[Now]#there#is#a#psychological#barrier#that#I#feel#to#scaling#the#whole# thing#back#and#going#to#the#nordell#approach. # 51

66 GuzziisreferringtoEricandAnneNordell,whohelpedpopularizedweedseedbank managementapproaches(gallandt2014;nordellandnordell2009).guzzi sexplanationmentions shortmtermthinking,whichhasbeenfoundtobecorrelatedwithhighweedseedbanks(jabbouretal. 2014b). Tom%Honigford% %Zero%Seed%Rain%% Honigfordhasaverylowtoleranceforweeds.Heusesmechanicalcultivationevery10 14days untilcropsgrowtoolargetobecultivated.shortlyaftereachmechanicalcultivation,scufflehoeing(also calledstirruphoeing)isusedtocontrolweedsthattractorcultivationmissed.inthisprocess,weedsin closeproximitytothecroparepulledbyhand,andanycropplantsthatwereburiedbycultivationare uncovered.aftercropsaretoolargefortractorcultivation,hecontinuestocultivatewithhandtools untillateintheseasonwhenweedsnolongerhavetimetoproduceseedbeforethecropisharvested andtilled.earlycareerweedcontroleffortshaveledtoadramaticreductioninthesizeofhisweed seedbank(in#sensunorris1999),whichmeansthatweedseedlingdensitiesarerelativelylow,and followingevenmoderatelyeffectivecultivation,handmweedingisminimal.whenaskedwhatmotivated himtodevelopsuchalowweedthresholdhejoked, probably#because#i m#german# #There#will#be#order##I#just#like#the#look#of#a#clean# field.#[weeds]#never#get#that#big#in#my#operation.#i#nail#those#little#[expletive]#as#soon# as#they#come#out#of#the#ground#...#after#a#while#i#said# Hey,#wait#a#minute,#this#is# actually#working# #I ve#front#loaded#the#process,#i#worked#my#ass#off#over#those#first# few#years,#killing#all#those#weeds #Every#year#I#find#that#I#weed#less#than#I#did#the# year#before#because#i#don t#have#any#weed#seed#rain#anymore. # 52

67 Dave%Colson% %Polyethylene%(PE)%Mulch%% Colsonusesadiversearrayofecologicallybasedweedmanagementpractices.Wefocuson Colson suseofblackpemulchformanyofhiscrops.hiscropsgrownwithpemulchgenerallydonot needtobeweededinthebeds.exceptionsincludesomelongmseasoncrops,whichmayrequirehand pullingtocontroltheweedsemergingthroughtheplantingholes,butthiscanoftenbedoneduring harvestingoperations.hemostlyusesmechanicalcultivationforthepathswiththeadditionofhand hoeingtocontroledgesofpemulchedbeds.forcropsinthecucurbitaceaefamilyheusesnatural mulchforthepathsinbetweenthepetosuppressweedsandtokeepthefruitcleanerandeasierto find.colsonrecountedthefactorsinvolvedwithhisincreaseduseofpe: We#started#using#black#[polyethylene]#because#we#wanted#to#get#more#heat#units#on# heatiloving#crops.#the#problem#is#in#the#spring,#you re#so#busy#getting#so#much# planted#that#by#the#time#you#hit#june#you re#ready#to#go#back#and#start#doing# maintenance#on#the#stuff#you ve#put#in.#often#a#lot#of#stuff#we#wouldn t#have#thought# about#putting#[polyethylene]#on#are#filled#with#weeds,#like#those#early#brassicas #the# reason#for#putting#them#in#[polyethylene]#was#so#we#could#put#the#hand#weeding# time#into#things#like#[planting#or#weeding#the#direct#seeded#crops]. # Tom%Roberts% %Natural%Mulch%% Robertsapplieshayortreeleafmulchestomostcropsbyhandaftertheyhavegrownlarge enoughtoavoidbeingsmothered.hemowshaybeforeitsetsseedwithaflailmowertoproducefinely choppedmulchthatisappliedbyhandarounddelicateorcloselyspacedcrops,likeonion.heusesa stringmtrimmertoharvestirregularareasinaccessibletotheflailmower,andusesthismulch,which includeslongerpieces,oncropslesspronetobeingsmothered.healsoacceptshistown smunicipal treeleavestouseasmulch.wholeleavesareusedinpathsbutleavesneedtobeshreddedforusein 53

68 bedstoavoidmattingandnotlettingoxygentoroots.manyofhiscropsaremulchedimmediatelyafter transplantingbutsome,likeonions,aretoosmalltobemulchedinitiallyandrequireweedingbefore theycanbemulched.somehandpullingmayalsobenecessarytocontrolanyweedsthatemerge throughthemulch.robertsexplainedthefactorsthatledhimtoincludenaturalmulchasanintegral partofhisfarmingsystem: Several#things,#one#is#we#have#mulch#available#and#if#something#is#available#to#boost# our#organic#matter#we#ought#to#be#using#it.#it#also#retains#water #We#don t#have#a# lot#of#water#available#to#us #So#that#water#retention#is#really#important#to#us.#The# fact#that#it#suppresses#weeds#is#a#real#bonus #It s#not#just#for#weed#suppression,#if# that s#all#it#did,#the#cost#of#the#hand#labor#would#be#hard#to#justify. # Aswillbediscussedinthefollowingsections,farmersrangedwidelywhenspeakingabout benefitsanddrawbacksoftheirstrategies,requiredequipment,croprotation,responsetowetweather, andproblemweeds.farmersalsohaddifferingweedseedbanks,soilorganicmatter,andranked importanceofcriteriarelatedtomanagement. Additional%Benefits%of%Each%Strategy% Whenaskediftherewereanyadditionalbenefitstotheirweedmanagementstrategies,Guzzi repliedthatthegreatestbenefitofprioritizingweedingduringthecriticalperiodwasthelaborsavings buthealsomentionedtheadditionoftheweedbiomassthatisincorporatedintothesoileveryyear, theweedsactingasanindicatorofsoilhealth,andthefoodandhabitatthatweedsprovidetobirds, mice,andbeetles.whileweedsactingasanindicatorofsoilhealthiscontroversial(kopittkeand Menzies2007;Tillmanetal.1999),theecosystemservicesprovidedbyweedsiswellMdocumented (Marshalletal.2003;Petitetal.2010).Honigfordreportedthatcustomersraveaboutthetasteofhis produce,whichheattributestothelackofweedcompetition.additionally,heneverappliesmidmseason 54

69 fertilizer,whichhebelieveshecanomitbecauseofthelackofweedcompetition.asabenefittousing PEmulchotherthanlaborsavingsandsoilwarming,Colsonmentionedthatweedslikelygerminatein thewarm,moistenvironmentunderthemulchbutsincemostareunsuccessfulatemergingthroughthe mulch,itmayhelptoreducetheweedseedbank.healsoindicatedthatsincethemulchhelpsthesoil retainmoisture,itlessenstheneedtoirrigate.likewise,robertsnotedthatincreasedwater conservationduetothenaturalmulchisoneofthemainbenefits.healsovaluestheincreasedsom duetothemulchapplications.robertsbelieveshishighsombufferstheph,decreasesnutrient leaching,andimprovesthesoilstructure.robertsisgraduallyreducingtheamountofcomposthe applieswiththeexpectationthatthehighsomwillbesufficienttoprovidemostofhisfertility.indeed, forevery1%ofsom,22to34kgnha M1 canbecomeavailableduringthegrowingseason(grubinger 2005).Robertsmentionedthatnutrientsmaywashdownfromthemulchtotheplantrootsduringrains. Thismaybepossibleforsomenutrients,butFerreiraetal.(2015)foundthatnitrogeninrotarymowed legumemulchislosttovolatilizationifnotincorporatedintothesoil.however,naturalmulchcanresult innitrogensavings(singhetal.2015),attributedtodecreasedwaterevaporationandmoderationofsoil temperature,whichmayreducenitrogenmineralization. Drawbacks%of%Each%Strategy% Guzzinotedthattheincreasedweedemergencethatresultsfromhislettingweedsgotoseedis detrimentalinseveralways.heexplained, in#some#crops#that#have#less#tolerance#to#weed#pressure# #and#a#lot#of#those#are# valuable#crops#that#we#want#to#keep#in#the#mix# #we#would#make#more#money#off# them#if#we#didn t#have#to#spend#the#time#we#did#weeding#them.#fall#carrots#being#an# example,#onions#being#an#example,#salad#mix#being#an#example.#the#weeds# themselves#create#competition#but#they#also#do#other#things,#they#can#reduce#airflow# 55

70 in#the#crop#resulting#in#disease#problems,#they#can#host#insects,#they#can#provide# habitat#for#rodents.#the#weeds#can#be#more#of#an#issue#besides#just#being#direct# competition. # RegardingdrawbackstoHonigford sfrequentcultivation,hementionedthepossiblenegative effectsofsoildisturbancebutwasoptimisticthatsinceitwasmerelyshallowdisturbanceitisnotas detrimentalastillage.thisisconsistentwithpreviousworkshowingthatorganicfarmersusing extensivecultivationrarelyconsideredriskstotheirsoil(jabbouretal.2014b;riemensetal.2010).he alsocitedhisprofitabilityasevidencethatwhatheisdoingisworking.hejoked,"i'vereadarticlesabout thestarvingfarmer andi mnotoneofthem.i mnottakingthreetripstobermudaeveryyear,buti m notcryinginmysoupeither. Colsonspokeoftheenvironmentalcostsofplasticulture,saying, [Polyethylene]isoneofthosetradeoffs.IfIdidn thavetouseit,iwouldn t.idon tlikeusinga petroleumproductandhavingallofthattothrowawayeveryyear."healsotalkedabouttheextra managementstepofapplyingthepeandkeepingtrackofwhereitisreadyforplanting.roberts acknowledgedthatsoilcoolingisadrawbackofthemulch,butforcropsthatthriveinheat,like tomatoes,hewaitsuntilearlyjulytoapplythemulchandatthattimethesoilissufficientlywarmand themulchbeginstobecriticalformoistureretention.buthesaysthat,"thebiggestdrawbackof [natural]mulchingisallthelaborinvolved.growingit,harvesting,movingittothefieldandthen actuallyapplyingit. Healsoestimatesthatgrowingthemulchrequiresfivetotentimesasmuchlandas themulchedarea.forthesereasons,perhapsnaturalmulchingisbestusedonasmallscale. Required%Equipment%% Whenspeakingabouttheequipmentcriticaltohisweedmanagementstrategy,Guzzicitedhis springtinecultivator,hiscollectionofsweepsandknives,andhisreggieweeder(univerco,quebec, Canada),whichisapowered,rotatingsetoftinesthatarearoperatorcanmoveinandoutofthecrop 56

71 rows.honigfordhassixdifferentcultivators,eachbestsuitedtodifferentconditions(bowman2002).he explained,"noneofthemarehighend,buteachdoessomethingalittledifferent theyworkunder differentconditionsanddifferenttypesofweeds [which]givesmetheabilitytobemoreflexible." Colson smainpieceofnecessaryequipmentwasasinglebedpemulchapplicator.healsohasatoolbar withgangsofsweepssettocultivatethepathways.robertsinitiallyusedarotarymowertomakehis haymulchbutitcutthepiecestoolong.hewantedfinermulchthat"youdon thavetoputitonasthick becauseitfitsaroundtheplantbetter,biggerpiecesjustdon tpackaswellsotheydon tstayaswell.so fouryearsagoweboughtaflailmower.itworksreallywell.we vereplaced[therotarymower]." Crop%Rotation%and%Cover%Cropping%% Guzzi scroprotationisadjustedtoavoidplantingweedsensitivecropsinareasofheavyseed rainfromtheyearbefore.inyearsofextremelyheavyseedrain,hesometimesusesamoldboardplow toburyweedseedsdeeply.atgreatersoildepth,germinationmaybeinhibited(holm1972;stollerand Wax1973)andweedsthatdogerminatearelesslikelytosuccessfullyestablish,butseeddecaymaybe slowed(reviewedbymohler1993),meaningthattheburiedweedseedswouldlikelyremain problematicifreturnedtothesurface.honigfordmakesfrequentuseofcovercropsbutwarnedthat I willneverletacovercropgoformorethanamonthortwo becausethenweedseedsform Nothing everstaysuntilledformorethanacoupleofmonths,otherwisetheweedswill[gotoseed]. Colson s croprotationisdependentonthegoalforthatground.ifthegoalistoreducetheweedseedbankhe canincreasethenumberofbarefallowperiods,whereasiftheweedseedbankissufficientlylowhe usesmorelegumembasedrotationstoincreasefertility.henotes, the#critical#part#is#not#what#you re#doing#for#weeds#in#the#year#that#you re#growing# the#crop,#it s#the#management#that#leads#up#to#growing#the#crop#that#has#the# greatest#effect#on#the#weed#seedbank#and#thus#the#type#of#control#we#decide#to#do.# 57

72 Often#we ll#anticipate#going#into#a#less#weed#tolerant#crop#and#so#we ll#try#and#reduce# that#weed#seedbank#a#year#or#two#ahead. # Robertsusessummercovercropseveryfouryears,whicharemixedwithbarefallowperiodsto promoteflushesofweedgerminationthatarecontrolledpriortoplantingthesubsequentcovercrop. Robertsrarelyplantswintercovercropsbecauseofthesufficientcoverprovidedbythemulch,even afterithasbeendisked. Effects%of%Wet%Weather%on%Operations%% Mostfarmersstressedthatcultivationistypicallynoteffectiveinwetweather,whichisawellM documentedeffectintheliterature(cirujedaandtaberner2004;evansetal.2012;terpestraand Kouwenhoven1981).Guzzinotedthatwetweathercancausehimtomisstheopportunitytocultivate whileweedsaresmall.thiswasalsothemainperceivedriskofcultivationdescribedbypreviously interviewedorganicfarmersinthisregion(jabbouretal.2014a).guzzialsonotedthatifthereisa stretchofwetweathertowardtheendofthespringplantingseason,itismoreimportantforhimto finishplantingthantocatchuponweeding,sothoseunweededcropsmayneedtobeignored. Honigfordwatchestheweatherforecastclosely.DuetohishighpostMharvestrefrigerationcapacity,he hastheflexibilitytoweedduringthedrypartoftheweekwhenweedingismosteffectiveandharvest duringthecoolorwetpartoftheweek.colsonrecalledthat itusedtoalwaysbethat...we dprepthe beds,havethemallreadyforthe[polyethylene],waitforagoodsoakingrain,thenwewouldcoverthe bedstosealsomemoisturein.thelastfewyearsitseemslikewe retryingtofindadryperiodin coveringthebedssotheyaren tgettingwaterlogged. Robertsmentionedthatinthewettestrecent yearhewasworriedaboutmulchedcropsbeingtoowet,butitwasnotaproblem. 58

73 Weed%Species%% Mostofthefarmershighlightedcrabgrass(Digitariaspp)andhairygalinsoga(Galinsoga#ciliata) astheirmostproblematicspecies,consistentwithpreviousinterviewsofnorthernnewenglandorganic growersperformedbyjabbouretal.(2014b).honigfordhasa mostwantedposter displayedforhairy galinsogaathisfarmtoeducateemployees.althoughhedoesnothavemuchhairygalinsoga,hewants topreventitfromestablishing.healsoinstructsemployeestohandpullcommonpurslane(portulaca# oleracea)andwalkitoutofthefieldduetohispreviousexperienceinwhichhewouldpullitupbutit wouldproduceviableseedpriortodesiccation.indeed,sincecommonpurslanecanselfmfertilize (Zimmerman1969),senescentplantscanproduceviableseediffloweringhasoccurredpriortofrost (MiyanishiandCavers1980).Itcanalsospreadvegetativelyfromstemcuttings(Proctoretal.2011). Colsonstruggleswithsummerannualgrassesthatgrowandsetseedquickly.Theyalsoformthick clumpsinthepathsthataredifficultforhimtocontrolwithcultivation.robertsalsostruggleswith summerannualgrasses.possiblycontributingtotheproblemsofcolsonandrobertswithgrasses, BrownandGallandt(inreview)noticedthatmonocotmorphologymayallowittoemergethroughthe mulch.robertsnotedthatsummerannualbroadleafweedssuchashairygalinsogaareeasily suppressedbyhismulch.herecognizesthathairygalinsogaseedshaveashorthalfmlife,thusathorough mulchingintheyearfollowingseedrainwillcausemanyoftheseedstoperish. Weed%Seedbank%Data% Guzzihadthelargestweedseedbank(38,482seedsm M2 )(Figure3.1.),whichisasexpectedsince criticalperiodweedcontroloftenallowsweedstosetseed(norris1999).twocompetitiveandfecund broadleafweeds,hairygalinsogaandredrootpigweed(amaranthus#retroflexus)dominatedhisweed seedbank.givenhonigford szeroseedrainstrategy,itfollowsthathehadthelowestweedseedbank (3,065seedsm M2 ),themajorityofwhichwascommonpurslane,aspeciesthatwasgoingtoseedafterit 59

74 waspulled.subtractingcommonpurslane,honigford sseedbankwasextremelylow,736seedsm M2, whichissimilartothe550seedsm M2 atericandannenordell sbeechgrovefarm(gallandt unpublished).colson sweedseedbank(18,945seedsm M2 )reflectstheeffectofthemulchsuppressing mostweedsinthebeds,butoftenallowingweedsinthepathstogotoseed.roberts seedbankwas surprisinglylow(7,164seedm M2 ),perhapsdemonstratingtheeffectivenessofhismulchingandhis timingofhaymulchharvesttopreventweedseedcontamination.overall,despiteeachfarmer demonstratinginmdepthknowledgeoftheweedseedbank,seedbankdensitiesvariedwidely.similarly, farmerknowledgewasnotthelimitingfactorinpredictingsuccessfulweedmanagementinthemidwest (Zwickle2011),butemphasisonlongMtermmanagementwasinverselyrelatedtoabundanceof particularlyperniciousweedsspeciesonfarmsinnorthernnewengland(jabbouretal.2014b). Soil%Organic%Matter%% SOMatGuzzi sfarmwas6.0%,whichisonthehighendoftypicalnorthernnewenglandorganic vegetablefarms.honigfordhadthelowestsomat3.8%,possiblyrelatedtohismorecoarselytextured soil,frequentcultivation,andtwicemannualtillage.colson ssomwas4.8%.robertshadthehighest SOM,at21.0%,reflectinghisregularapplicationofnaturalmulch.AsampletakenfromthenoMtill perennialcropsofrobertshadsoilorganicmatterof30.5%. 60

75 Figure3.1.Weedspeciescompositiondeterminedfromgerminableseedbankassaysofsoilsamples fromeachparticipatingfarmer.listedbeloweachfarmer snameistheweedmanagementstrategythat theyrepresentandtheirtotalweedseedbankdensity. Mark%Guzzi Critical%period% weed%control 38,482%seeds%m ;2 Tom%Honigford Zero%seed%rain 3,065%seeds%m ;2 Hairy%galinsoga% Common%lambsquarters% Redroot%pigweed% Dave%Colson% Polyethylene%mulch% 18,945%seeds%m ;2 Tom%Roberts Natural%mulch 7,164%seeds%m ;2 Common%chickweed% Shepherd s%purse% Common%purslane Other%broadleaf Crabgrass%spp Other%monocot Importance%of%Criteria%Related%to%Management% Basedonrankingofpairwisecomparisonsofcriteriarelatedtomanagement,Guzziplacedmost emphasisontheamountofweedinglaborofhisoperation(figure3.2.) thisalignswiththeabilityof criticalperiodweedcontroltomaximizeyieldwhileminimizinginmseasoncontrolefforts(knezevicetal. 2002).TheweedseedbankwasalsovaluedhighlybyGuzzi,althoughthismayrepresentamorerecent changeinhispriorities.honigfordplacedthemostimportanceontheweedseedbank,whichprovides insightintohisrationaleforfrequentcultivation.colsonwashighlybalancedinhisvaluations,which 61