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The Suitability of Worm Castings & Compost Tea in Organic Hydroponic Lettuce Propagation
AsherHaug‐Baltzell
FacultyAdvisor:Dr.TanyaQuistUniversityofArizona,PLS330H(PlantPropagation)
November30,2011
Abstract ThepurposeofthisexperimentwastodeterminethesuitabilityofusingamediacomposedofcoconutcoirandwormcastingsandacompostteafertilizerforthepropagationoflettucedestinedforaNFThydroponicsystem.Lettuceseedsweregerminatedindifferentmediascomposedofvaryingproportionsofcoconutcoirandwormcastingsandfertilizeddailywithawormcastingbasedcomposttea.Itwasdeterminedthatamediacomposedof70%coconutcoirand30%castingsfertilizeddailywith10mLofcompostteaproducedthehighestqualityseedlings.
I. Introduction Hydroponiccropproductionsystemsareknownfortheirefficiencyand
sustainability,butduetomanyofthechemicalsutilized(i.e.fertilizers,pHadjusters)aretraditionally“inorganic”innature.Withrisingdemandfor“organic”produceandwithsuchproductsfetchingpricesupwardsof50%higherinthemarketthereismuchinterestinconvertingthesetraditionalsystemstoonesthatmeetthecriteriatobeclassifiedas“CertifiedOrganic”.Differentapproachestoaccomplishthisgoalarecurrentlybeinginvestigated,butforthemostpartthisresearchisbeingconductedbycommercialoperationsandthusresultsareproprietary.Oneapproachthathasshowngreatpotentialisusinga“composttea”asthefertilizersolutionandusingacompost‐basedmedia.
Thepracticeofbrewingcompostintoa“tea”andutilizingitasasupplementalfertilizerforagriculturehasbeenaroundforamanyyears.Recentresearchhassuggestedthattherearesignificantbenefitstousingcomposttearangingfromincreasedplantvigor,increasedpestanddiseaseresistance,curingofnutrientdeficiencies,andeventhepossibilityforitsuseasaprimaryfertilizer.Unfortunatelythisresearchhasfocusedontheuseofcompostteainfieldagriculture,andfewstudieshavebeenconductedonitsuseinhydroponic,controlledenvironmentcropproductionsettings.Becauseofthepositiveresultsfoundinfieldstudies,thisexperimentwillinvestigateapotentialuseforcompostteainahydroponiclettuceproductionsystem.
Themostcriticalingredientinanycompostteaisthecompost.Thereareanumberofdifferenttypesofcomposts,eachcategorizedbasedonitsmethodofproduction.Thesimplestformsofcompostareknownas“staticpile”and“aeratedpile”compost,whereorganicwasteisformedintoamoundandallowedtodecomposewithtime,withorwithoutaeration.Thismethodtakesalongperiodoftime,andresultsinonlysemi‐completedecomposition.Amuchmoreeffectivemethodofproducingcompostisusingworms.Thesewormsconsumeanddecomposetheorganicwastecompletelyintocompostknownas“wormcastings”or“vermicompost”.Sincewormcastingshaveahighernutrientcontentthanotherformsofcomposttheywillbeusedasthecompostinthisexperiment Thisexperimentwillfocusontheuseofbothawormcastingbasedmediaandwormcastingcompostteainalettucepropagationsystem.Intheexperimentaltreatments,lettuceseedswillbegerminatedinavarietyofmediacomposedofdifferentratiosofcoconutcoirtowormcastings.Theseedlingswillbefertilizedwith10mL/dayofCompostTea.Theseexperimentaltreatmentswillbecomparedagainsttwocontrolmedia,RockwoolandCoconutCoir,bothfertilizedwith10mL/dayoftraditionalhalf‐strengthmodifiedHoagland’ssolution.Theexperimentwilllast12days(Day0‐Day11),thetimefromseedtotransplantincommercialhydroponiclettuceproductionsystems.II. Hypothesis
Itispredictedthatseedlingqualitywillincreaseastheconcentrationofwormcastingsinthestartingmediaincreasesuptoa“criticalconcentration”,afterwhichgermination/seedlingqualitywillrapidlydecrease.ItisalsopredictedthattheseedlingstreatedwithCompostTeawillbeofhigherqualitythanthosetreatedwiththeInorganicHoagland’sSolution.
III. Materials & Methods a) Materials
1) 130,“Rex”LettuceSeeds‐Pelleted(Johnny’sSelectSeeds)2) 5,1020PropagationFlatsw/HumidityDomes3) 130,2”NetPots4) 2,5mLPlasticPipets5) 1,“BigDaddy”OMRICertifiedCococoirGrowBag6) 1,30lbBagofWormCastings(“WiggleWormSoilBuilder”Brand,1‐0‐0
GuaranteedAnalysis)7) 10,1”RockwoolCubes8) ModifiedHoagland’sSolution(SeeSupportingAppendices“Document#1”)9) CompostTea(SeeSupportingAppendicies“Document#2”)
b) Methods1) Eachseedlingwasgrownina2”netpot.Theseedswereplantedon11/3/11
(Day0)andgrownuntil11/14/11(Day11).Netpotswerekeptin1020propagationflatscoveredwithstandardHumidityDomestopreventdryingofmedia.
2) Beforeseeding,the2”netpotswerefilledwithdifferentmediaaccordingtothetreatment.TheCococoirandwormcastingsweremeasuredvolumetricallytoproducethecombinations.
Treatment#1:Control‐RockwoolTreatment#2:Control–CoconutCoirTreatment#3:100%CocoCoirTreatment#4:90%CocoCoir,10%WormCastingsTreatment#5:80%CocoCoir,20%WormCastingsTreatment#6:70%CocoCoir,30%WormCastingsTreatment#7:60%CocoCoir,40%WormCastingsTreatment#8:50%CocoCoir,50%WormCastingsTreatment#9:40%CocoCoir,60%WormCastingsTreatment#10:30%CocoCoir,70%WormCastingsTreatment#11:20%CocoCoir,80%WormCastingsTreatment#12:10%CocoCoir,90%WormCastingsTreatment#13:100%WormCastings
3) Seedsweresowed1/8”deepinmedia,1seedpernetpot.4) OnDay0,alltreatmentswerewateredwithanoverheadmistfor35seconds.5) FertilizationbeganonDay1.Eachseedlingreceived10mL/dayoffertilizer
appliedbyhandwitha5mLpipet.Treatments#1‐2(Controls):Half‐strengthmodifiedHoagland’ssolution(seeSupportingAppendiciesDocument#1)Treatments#3‐13(Experimental):WormcastingbasedCompostTea(seeSupportingAppendicesDocument#2)
6) Photographsweretakendailytomonitorgrowth.7) GerminationpercentagewasmonitoredthroughDay4.8) FinalDatawascollectedonDay11.
i. PercentRootProtrusion–Visuallyidentifiedandcountedii. TrueLeaf#‐Visuallyidentifiedandcounted
iii. LeafArea–measuredwithLI‐CORBiosciencesLI‐3100cLeafAreaMeter
IV.Results&DataTable1:GerminationPercentagebyDay
Treatment Day 1 (11/4/11) Day 2 (11/5/11) Day 3 (11/6/11) Day 4 (11/7/11)Rockwool Control 0% 40% 100% 100%Cococoir Control 0% 30% 100% 100%100% Coir 0% 70% 100% 100%90% Coir 0% 20% 100% 100%80% Coir 0% 20% 100% 100%70% Coir 0% 50% 100% 100%60% Coir 0% 20% 100% 100%50% Coir 0% 30% 100% 100%40% Coir 0% 20% 90% 100%30% Coir 0% 30% 100% 100%20% Coir 0% 20% 100% 100%10% Coir 0% 10% 90% 100%0% Coir 0% 30% 100% 100%Table1showspercentgerminationbydayforalltreatments.ItshouldbenotedthatgerminationwasfirstobservedonDay2,andbyDay4allseedshadgerminated.GerminationpercentagehadthemostvariationonDay2,rangingfrom10‐70%,butthevariationfollowednospecifictrendcorrelatingtotreatment.ByDay3allbut2seedshadgerminated,andbyDay4allseedshadgerminated(100%germinationwasachieved).Table2:RootProtrusionPercentagebyTreatment
Treatment % Root Protrusion
Rockwool Control 70%Cococoir Control 0%100% Coir 70%90% Coir 100%80% Coir 100%70% Coir 100%60% Coir 100%50% Coir 100%40% Coir 100%30% Coir 100%20% Coir 100%10% Coir 100%0% Coir 100%
Figure1:RootProtrusionPercentagebyTreatmentTable2andFigure1showthepercentofnetpots(bytreatment)thathadrootsprotrudingatDay11.Therewassignificantvariationinthecontroltreatments;rockwoolshowed70%withprotrudingrootswhilethecoconutcoirshowed0%rootprotrusion.Additionofcompostteato100%coconutcoirincreasedrootprotrusionto70%.Allmediascontainingwormcastingsandtreatedwithcompostteahad100%rootprotrusion.Table3:AverageTrueLeafNumberatDay11
Treatment Avg. True Leaf #Rockwool Control 1.9Cococoir Control 1.9100% Coir 1.790% Coir 1.880% Coir 1.970% Coir 260% Coir 1.850% Coir 1.440% Coir 1.630% Coir 1.620% Coir 110% Coir 10% Coir 1
0%10%20%30%40%50%60%70%80%90%100%
%RootProtrusion
Figure2:AverageTrueLeafNumberatDay11Table3andFigure2showtheaveragenumberoftrueleavesperseedlingatDay11(bytreatment).Treatment#6hadthemosttrueleaves,withanaverageof2perseedling.Treatments1,2,3,4,5,and7closelyfollowedTreatment#6(>1.7leaves/seedling).Aswormcastingpercentageincreasedto50%andgreateradecreaseintrueleafnumberwasobserved,with80%castings,90%castings,and100%castingsproducingonly1trueleafperseedling.Table4:CumulativeLeafAreabyTreatment
Treatment Cum. Leaf Area (cm2)
Rockwool Control 11.24Cococoir Control 15.12100% Coir 14.8390% Coir 17.5980% Coir 19.9270% Coir 19.7460% Coir 15.350% Coir 11.3740% Coir 14.3430% Coir 11.4520% Coir 7.6110% Coir 7.030% Coir 7.2
00.20.40.60.81
1.21.41.61.82
Avg.TrueLeaf#
Figure3:CumulativeLeafAreabyTreatmentTable4andFigure3showCumulativeLeafAreabyTreatment(cumulativeforall10seedlings).Adistincttrendcanbenotedwithintheexperimentaltreatments(#3‐13),asleafareaincreaseswithincreasingcastingpercentageupto20%,andafter30%adeclineinleafareaisnoted.Treatments4,5,and6producedsignificantlymoreleafareathanthecontrols.Table5:AverageLeafAreaperSeedling
Treatment Avg. Leaf Area (cm2)
Rockwool Control 1.124Cococoir Control 1.512100% Coir 1.48390% Coir 1.75980% Coir 1.99270% Coir 1.97460% Coir 1.5350% Coir 1.13740% Coir 1.43430% Coir 1.14520% Coir 0.76110% Coir 0.7030% Coir 0.72
0
5
10
15
20
25
Cum.LeafArea(cm2)
Figure4:AverageLeafAreaperSeedlingTable5andFigure4showaverageleafareaperseedlingbytreatment(incm2).Thesametrendaswithcumulativeleafareacanbenoted,withTreatment#5producingthemostleafareaat1.992cm2perseedling.
Day4(11/7/11)
Day5(11/8/11)
00.20.40.60.81
1.21.41.61.82
Avg.LeafAreaperSeedling(cm2)
Day6(11/9/11)
Day7(11/10/11)
Day8(11/11/11)
Day9(11/12/11)
Day10(11/13/11)
Day11(11/14/11)
Figure5:Growth‐ProgressionPhotos(LefttoRight,Treatments1‐13)Figure5showsphotographsofalltreatmentsfromDay4(when100%germinationwasnoted)throughDay11(endofexperiment).Treatmentsarearrangedinverticalrows.TreatmentnumberincreasesfromlefttorightwithTreatment#1beingtheleftmostrowandtreatment#13beingtherightmostrow.V. Conclusions
Theresultsfromthisexperimentappeartosupportthehypothesis.Tobegin,itwaspredictedthatseedlingqualitywouldincreaseastheconcentrationofwormcastingsinthestartingmediaincreaseduptoa“criticalconcentration”,afterwhichseedlingqualitywasexpectedtorapidlydecrease.AlthoughallseedlingsgerminatedanddevelopedthroughDay11,theleafarearesultsshowanobvioustrendofincreasingleafareaascastingpercentageincreasedto20%‐30%,afterwhichacleardecreasecanbeseen(SeeTables3and4andFigures4and5).Inadditiontoleafarea,trueleafnumberwashighest(2trueleaves/seedling)at30%castings,althoughthecontrolswereonlyslightlylowerat1.9trueleavesperseedling.However,ascastingpercentageincreasedbeyond30%asignificantdecreaseintrueleafnumberwasobserved,withtreatmentscontaining80%,90%and100%castingsproducingonly1leafperseedling(SeeTable3andFigure2).Theseresultssuggestthatthe“criticalconcentration”ofwormcastingsinthemediaisbetween20‐30%.
ItwasalsopredictedthattheseedlingstreatedwithcompostteawouldbeofhigherqualitythanthosetreatedwiththeinorganicHoagland’ssolution.Whilenodirectbenefitcanbeobservedintheleafnumberorarearesults,treatmentwithcompostteaeffectivelyincreasedthenumberofseedlingswithrootsprotrudingfromthenetpot,especiallywhen
combinedwithamediacontainingwormcastings.Thecoconutcoircontroltreatment(100%coconutcoirfertilizedwithHoagland’ssolution)producednoseedlingswithrootsprotruding,butwhen100%coconutcoirwastreatedwithcomposttea70%oftheseedlingshadrootsprotruding.Alltreatmentscontainingwormcastingsandtreatedwithcompostteaproduced100%ofseedlingswithprotrudingroots(SeeTable2andFigure1).Theseresultssuggestthatfertilizationwithcompostteaassistsinrootdevelopmentforlettuceseedlings.VI. Supporting Appendicies (Attached)
1. Document#1:InorganicModifiedHoagland’sSolution:LettuceRecipe2. Document#2:CompostTeaRecipe