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