optimizing molybdenum levels in subirrigation floriculture ......rates based on the composition of...
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OptimizingMolybdenumLevelsinSub-IrrigationFloricultureSystems
WaterAdaptationManagementandQualityInitiativeProject#11
FinalReport–March2015
Preparedby:
Dr.JeanineWestWaterSpecialist
FlowersCanada(Ontario)Inc.
and
WayneBrownOMAFRA
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ExecutiveSummaryOriginalrecommendationsforfertiliserratesinfloriculturegreenhouseswerebasedontopfeeding
(irrigation) systems that were inherently open: leachate was captured by a strategically placed
subsurface drainage system systematically installed beneath the production area discharging to the
environment. Since the 1990’s,many greenhouse flowering potted plant producers have switched to
sub-irrigation,wherethenutrientsolutionissuppliedfrombelowinatrough-styleorflood-floorsystem.
Nutrientfeedwaternotabsorbedthroughcapillaryactionisreturnedtoaholdingtankwhereitisstored
for reused (closed systems) during the next irrigation cycle. If this water no longer has value to the
indoorcrop, itcanbe landappliedunder theNutrientManagementAct;however,molybdenum(Mo)
levelsmay trigger a flag in theNMAN system (program that determines appropriate land application
ratesbasedonthecompositionofthewastewatertobeapplied).ThisprojectstudiedMorequirements
for aMo-sensitive crop to determine if the fertiliser rates can be decreased given thatmuch of the
potted flowering plants are produced using sub-
irrigationwhereno leachingof nutrients occurs from
the media in the container. Preliminary results
comparing Mo levels of 0-100% of the typical
fertiliser rate revealed no difference in the quality
of the plant material by the time of harvest (early
December), indicating that substantially decreasing the Mo
concentration in the feed water after establishmentmay have negligible effect in the production of
saleableplantswhileallowinglandapplicationofnutrientfeedwaterwithfewerrestrictions.
IntroductionAt certain points in greenhouse production, it may be desirable to refresh the nutrient feed
solution and dispose of the re-circulated water (in open systems, nutrient solution is discharged
continuously).Theexpansionof theOntarioWaterResourcesAct toallow landapplicationofnutrient
feedwater(excessorwastenutrientsolutionfromgreenhouses)followingtheguidelinesoftheNutrient
ManagementActprovidesasustainablesolution fordisposingof thisexcesswater.However,aTOGA
study (SRG, 2012) revealed that levels ofmolybdenum (Mo) andboron (B) in floriculture greenhouse
nutrientfeedwaterexceededtheallowableratesintheNMANprogram,indicatingthatfullapplication
of this solution on landwould be limited under the NMAN program. Excess B andMo released into
surface water can affect aquatic life, as well as plant growth (CCME 2009, Gupta 1993, Kaiser et al.
2005).Molybdenuminparticularcancausetoxicityinruminantanimalsifitbuildsupinthesoiltolevels
Poinsettiassub-irrigated
(afterspacing)without
molybdenumafterpottingshowed
noevidenceofModeficiency
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exceeding5ppm(CCME1999).
Molybdenum,theleastabundantessentialmicronutrient(Kaiseretal.2005), isrequiredforplant
growth,metabolismofnitrogenandreproduction(OMAFRA2010).Thistraceelementisconsideredto
beofintermediatemobility,meaningthatitcanmovewithinthexylemandphloem,andthatlowlevels
within theplantdonot immediately lead todeficiency symptoms.Sink regions, suchas flowers, fruit,
and new foliage can obtain this nutrient, at least in part, from older parts of the plant as required.
HoweverthemovementofMoinplantsisnotalwaysclear(Kaiseretal.2005).Atsomepoint,however,
theamountofavailablenutrientcanbelimitingandModeficiencyappearsfirstintherecentlymatured
leavesasinterveinalchlorosisandmottling,cupping,curlinganddeformation,andnecroticspotsontips
andmarginsofleaves(Arreolaetal.2008,Gupta1993).Ratesoffertilisationincommercialgreenhouse
floriculture operations that have adopted sub-irrigation systems, have significantly decreased in
practice, since experience has shown that previously
recommended rates based on top-irrigated open
systems are much higher than crops require for
optimal growth, often leading high soluble salts in
themedia, root rot issuesand increaseduseofplant
growth retardants to control plant height. Despite this
decrease,Molevelsarestillatrateshigherthandesiredfor landapplicationfromanoutdoorgrowing
perspective.
This project tested a range of concentrations of Mo in the nutrient feed solution (from the
maximum commercially available rate to zero) to determine the lowest, yet optimal level for plant
growth,bloomyield,andoverallplantquality.TheexperimentwasperformedattheVinelandResearch
and InnovationCentre researchgreenhousecomplexusingMo-sensitivepottedpoinsettiaplantsover
thecourseofonegrowingcycle(AugustthroughDecember2014).Usingsensitiveplantsensuredthat
theresultscouldbetransferredtootherflowerspecies.
Whiletherearetechnologiesdevelopedtoremovenitrogenandphosphorus,salts,andotherkey
compounds ingreenhouseeffluents (e.g.denitrifyingwoodchipbiofilters,constructedwetlands, radial
deionization,andnanofiltration),therearecurrentlynoreadilyavailableandcost-effectivetechnologies
for removingessentialmicroelements suchasMo fromsolution. In top irrigated recirculatingsystems
using rockwool or coir, undesirable salts (Na, Cl and sulphates) can become limiting for these crop
production systems. Greenhouse vegetable and cut gerbera flower production are typical examples
Fertiliserrecommendations
forfloriculturegreenhouse
cropsareover40yearsold
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wherecropshavelongcropcyclesandwhenarecirculationsystemisusedthenthesaltscanbuildup
over timeasotherelementscritical forplantgrowthareselectively takenupby theplants.However,
most other elements (such asMo) do not accumulate sufficiently to influence plant growth. In open
systems,thecompositionofthedischargewateriscritical,andrequiresremovalofmacro-andmicro-
elements todecrease the impacton theenvironment.Ultimately, it isbest forproducers tominimize
theuseofnutrients, ifpossible,providingtherearenonegative impactsontheircropyieldandpost-
harvestquality.
Objectives:
• Researchgreenhouse(i.e.laboratory)studyofasensitivefloriculturecrop(Poinsettia)grownusingasub-irrigationsystemtodetermineminimalMoapplicationrateswithoutnegativelyimpactingbloomyieldandplantquality
• CorrelatetissuelevelsofMowiththepresence/absenceofdeficiencysymptoms• Communicateresultstothesectorandfertilisermanufacturers/suppliers
Materials&MethodsThree hundred rooted Poinsettia “Christmas Day” cuttings were generously supplied by Linwell
Gardens,a localcommercialgreenhouserootingstation, inproductionweek31forplanting. Cuttings
hadbeenrootedinpeat-basedEllegaardstyleplugs.Rootedcuttingswereplantedinto16.5cmplastic
azaleapotsfilledwithSunshine#1soillessmediacourtesyofSunGroHorticulture,onJuly31,2014and
placedonanexpandedmetalbenchinaglassgreenhousecompartmentattheVinelandResearchand
InnovationCentreresearchgreenhousecomplexandwateredwithclearwateruntilmoist.Duringthe
establishmentphasethefollowingsetpointswereestablished:D/Nheat22oC,ventingat24oC;shading
wastriggeredbasedonlightand/ortemperature(600W/m2from10:00-17:00hor26oC).Cuttingswere
pinchedto7/8nodes2weeksafterplanting.Thecuttingswerefertilisedoverheadbyhandbeginning
oneweekaftertransplantingusingPlantProd20-8-20at100ppmNwitheachirrigationevent(roughly
2xperweek).RefertoTable1formoredetailedcroppingschedule.
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Table1–2014VinelandCroppingSchedulefortheReducedMolybdenumTrial
Activity Week Date CommentsChristmas)Day)–)Selecta)varietyAll)rooted)in)ellegaard7type)plug
Growing5Media Sunshine)#1)in)6.5)ITML)plastic)azalea)pots.)All)were)grown)pot7to7pot)until)spacing.
31735 July)30)–)Aug)30Shade)closed)at)600)W/m2)(10717:00)h))or)26oC
36/37 Aug)31)–)Sept)15Shade)closed)at)700)W/m2)(11715:00)h))or)26oC
31736 Aug)77)Sept)5 2078720)@)1.0)EC)–)100)ppm)N)–)1)wk)after)plant)until)spacing)out)onto)troughs150$ppm$N$–$4$levels$fo$Mo$–$100%,$50%,$25%,$0%
37750 Sept)7)–Dec)1 Agral$90)added)monthly)to)improve)H2O)uptake
Lights5on/off5(photoperiod) No No)night)break)lighting)used
Use5of5Blackout Yes Beginning)Sept)29To)prevent)stray)HPS)light)B/O)open/closed)30)minutes)after/before)sunrise/sunset
36 Sept)5&6 Initial)12”x12”40 Oct)4 Respaced44 Oct)30 Spaced)as)required
PGR5Applications 3371 Aug)10 B7Nine/)CCC)spray)(1000/1000)ppm)B"Nine/Cycocel-Extra 3571 Aug)24 All)PGR)applied)with)HV)sprayer
3576 Sept)5PGR5Applications 3575 Aug)29 Spray)at)1000)ppm)(2.2)mL/L)Cycocel-Extra 3773 Sept)10 Spray)@)1000)ppm))(sprayed)to)glisten)
3874 Sept)18 Spray)@)1000)ppm3976 Sept)27 Spray)@)1000)ppm)4076 Oct)4 Spray)@)1000)ppm4175 Oct)10 Spray)@)1000)ppm4276 Oct)18 Spray)@)1000)ppm)
38 Sept)15 Subdue$Maxx)+)wetting)agent)sub7irrigated)@)0.4g/L
40 Oct)3 Subdue$Maxx)+)wetting)agent)sub7irrigated)@)0.4g/L
Temperature5(heat/vent) 31 Jul)31 D/N)Heat)22oC)))))))))))))D/N)Vent)24oC
Set5Points 36 Sept)2 D/N)Heat)21oC)))))))))))))D/N)Vent)22.5oC38 Sept)16 D/N)Heat)20oC)))))))))))))D/N)Vent)22oC40 Oct)1 D/N)Heat)20oC)))))))))))))D/N)Vent)21oC42 Oct)16 D/N)Heat)19oC)))))))))))))D/N)Vent)21oC46 Nov)3 D/N)Heat)18oC)))))))))))))D/N)Vent)20oC48 Nov)16 D/N)Heat)18oC)))))))))))))D/N)Vent)19oC50 Dec)1 D/N)Heat)17oC)))))))))))))D/N)Vent)18oC51 Dec)8 D/N)Heat)15oC)))))))))))))D/N)Vent)16oC
Soft)pinch)to)778)nodes)+)top)leaf)removal
Spacing
Fungicide5Application(s)5for5Pythium5Root5Rot5Control
Planting5of5cuttings 31 July)30731
Shading
Nutrition
Pinching 33 Aug)13
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Table2–2014AverageWeeklyGreenhouseClimateandTotalSolarRadiationforeachCompartmentduringtheReducedMolybdenumTrial
Hse10(pottopot)
Week# Avg24hTempoC Avg24hRH%
HeatSetpointsD/NoC
VentSetPointsoCD/N
TotalSolarRadiationJ/cm2
31 25.1 73 22/22 24/24 14,15832 25.5 71 14,63533 24.4 69 13,10634 25.3 75 12,74335 26.5 70 13,65136 25.1 74 21/21 22.5/22.5 11,558 Hse20
(spacedonsub-irrigation)
37 21.7 70 7,04138 22.1 69 20/20 21/21 10,56239 22.8 77 12,42440 20.8 62 18/18 21/21 5,85141 20.8 66 9,87442 21.8 73 4,40843 20.2 66 5,14944 19.4 64 18/18 20/20 3,41145 18 67 17/17 20/20 3,935
46 18.5 61 4,00347 18.2 58 15/15 16/16 3,77548 18.3 64 3,21149 18.2 59 3,21150 18.1 66 1,77151 15.3 75 1,972
InWeek38(September10,2014)youngplantswerespacedintoanotherglassgreenhouseforthe
remainderof thetrial,maintainedwithoutsupplemental lightingand initiallyat21oC,and lateras the
plantsmaturedat19oC.Theplantswereplacedin12rows(troughs)of24plantseach,and3ofthe4
treatments(0%,50%,100%Mo)wererandomlyassignedtoeachtroughwiththeexceptionofthe25%
Mo treatment. Each trough had its own nutrient solution tank and pump to supply the randomly
selectedtreatment.The25%Motreatmentwasassignedtothe2outsiderows,andthethirdrowwas
insertedintothecentreofthetenrows.Becausetheoutsiderowscouldpotentiallyexperienceanedge
effect, the decision was made to use the 25% Mo fertiliser solution on these plants and if there
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appearedtobenosignificantedgeeffect,thenthistreatmentcouldbeusedintheresults.Ifaneffect
wasnoted,thetreatmentwouldberemovedfromthefinalresults.Replicationforthefourtreatments
wereasfollows:23biologicalreps,3blocks(1genus*1element*4rates*23plants*1lightregime*
1pHlevels*3blocks)=276plantsperexperiment(anadditionalrowofbufferplantswasplacedatthe
beginningandendofeachgreenhousetroughasguardsandtheseplantswerediscardednotincludedin
thefinalharvestmeasurements(December9th).Onceplantsweresetoutonthetroughstreatmentat
the4levelsofMowasinitiated(September11,2014).Forthisphaseofthestudy,thenutrientsolutions
weremadeusinganA/Bstocktanksystembasedonmmol/Lforsupplyingthemacronutrientsandthe
standardratesofmicronutrientsbasedonmicromole/L.Allthemacroandmicronutrientsremainedthe
sameforalltreatmentsexceptMo.Table3belowoutlinesthenutrientlevelssupplied.
Table3–FertiliserlevelsforReducedMolybdenumTrial2014
Macronutrients Mmol/L PPMnutrientHCO3-1 1.0 61H2PO4-1–P 1.0 31SO4-2–S 1.0 32NO3-1–N 9.5 133Ca+2 3 120Mg+2 1.25 30NH4+1-N 2 14K+1 3 117Micronutrient Micromol/L Fe(13%EDTA) 25 Mn(manganesesulphate-25%) 5 Zn(zincsulphate35%) 3.5 B(borax-15%) 2.0 Cu(coppersulphate-25%) 0.8 Mo(sodiummolybdate–39%) 0.5(100%),0.25(50%),0.125(25%)
ThefourtreatmentswerecontinueduntilDecember1,2014.Thefertilisersolutionwasappliedvia
sub-irrigation to all plantswith the same volumes (i.e. each trough received the same volume of it’s
particular feed solution), with the recirculating feed solution passing by the pots for a period of 20
minutes.Therewere4separateBconcentratetankssetup,containing0%,25%,50%,and100%ofthe
recommendedMorateandoneAconcentratetank.Weekly,therequiredamountofconcentratefrom
eachofthefourBconcentratetanksandfromtheAtankwereblendedwithfreshwaterandaddedto
replenishtheindividualrecirculatingtanksconnectedtoeachofthethreetroughsassignedtothatMo
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rateoffertilisation.Attheendofeachtrough,abarrelcollectedthefeedsolutionthatwasrecirculated
withinthatsametrough,withthebarrelsrequiringweeklytop-upfromtheconcentratetank.Typically
20Lofnutrientsolutionwasaddedweekly.Onoccasionthetwoperimeter25%Motreatmentplants
requiredadditionalfreshwaterirrigationbecausetheyweredrierthantheoutsideplants.Thisoccurred
approximatelyonceeverytwoweeks.Thegreenhousetechnician(CathyGray,UniversityofGuelph)and
theOMAFRA floriculture specialist (WayneBrown)maintained humidity and temperature throughout
theresearchtrialthroughattentivecareandventingasrequired.TheSilverleafWhiteflypopulationwas
controlled using biweekly introductions of Amblyseius cucumeris, Amblyseius swirski and Encarsia to
prevent the possibility that foliar applied pesticides might have an influence on the levels of Mo
measuredintheassociatedplanttissueattheconclusionofthetrial.
Figure1–DesignoftroughsystemingreenhouseH20,withtroughsslopedtoemptyintobarrelsattheendofeachrowforrecirculating.
Measurements/SamplingPlan:
• Initialsamplingofthegrowingmedium(SGSAgri-foodLaboratories,Guelph)onSeptember10th,2014,aswellasatissuesample(UniversityofGuelphLaboratoryServices,Guelph)of50newlymatureleavestakenrandomlyfromthetrialplants.
• Tissue/Medium/FertiliseranalysesincludedMo,andnutrientssuchasN,BandCa,whichserveasmarkersforphloemmobileandimmobileelements
• Biweeklytissuesamplingofrecentlymatureleaves(onefromeachofthe23plantsinaspecificrow/trough,soatotalof12samplesrepresentingeachrow)betweenSeptember30andDecember9,2014fortissueanalysis.
9|F C O
• MonthlywatersamplingoftheconcentratetankstoverifyfeedsolutionscontainedtheappropriateamountofMo(senttoALSEnvironmental,Waterloo).
• Yield/Sizemeasurements,including:finaltotalheights(fromsoilleveltotip)ofall276plants,plustotalfreshanddryweightsforleaves,inflorescence(bractsandcyathia)andstems.Notethatsincetheflowerportionofthepoinsettiaissosmall,theentirebractportion(theinflorescence)plusflowerswasincludedinthebractsample.Onlybracts(whicharemodifiedleaves)thatwerefullycolouredwereincludedinthe‘bract’sample,whileanyleavesthatwerepartiallyred(transitional)wereincludedinthe‘leaf’sample.
• Finalsamplingofthreetissuepartsfornutrientanalysis:leaves,bractsandstemsforthe276plants.
• Visualobservationsofplantgrowth,bloomyieldandoverallplantqualityweremadethroughoutandattheendofthetrial.
• Plantqualitywasofparticularimportance(appearanceofvisualsymptomsofnutrientdeficiencyorimbalance,leafandinflorescencedevelopment).
Statistical analysisof thedatawas limited to calculationofmeansand standarddeviationwhere
appropriate.Analysisofvariance(ANOVA)isplannedforthefulltissueanalysisdataset.
Results&Discussion
Initialresults(September10,2014):
Molybdenum level in theaggregategrowingmedia sample fromearly Septemberwas0.01ppm,
yetinthetissue,theMowasdeterminedtobe0.59ppmdryweight.Nitrogenandcalciumlevelsinthe
mature leaveswere found tobe4.07%and0.979%dryweight, respectively. At this time, theplants
werespacedinthegreenhouseinarandommanner,andappearedhealthy,withafreshgreencolour
(Figure2).ThelevelofMointheplantsaftertheinitialestablishmentperiodisparticularlyimportant,as
tissueandphysicalappearanceoftheplantsbytheendofthestudysuggestmovementoftheinternal
Molevelstosinkregionstomaintainoverallplantquality.
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Figure2–Initiallayoutofthepoinsettiacrop(September10,2014)ingreenhouseA20,andacloseupofoneoftheplantstoillustratecolour/appearance.
Biweeklyresults(September30throughDecember9):
Table4detailsthelevelsofMoinmatureleavesoverthetreatmentperiodforeachrowofplants
(three replicates of the four fertiliser rates). Nearly every row of plants (composite leaf samples)
experienced a reduction in Mo levels over the 13.5-week period, suggesting that Mo was being
mobilizedfromoldermatureleavesafterthebractsbegantodevelop(lateOctober,seeFigure3)and
evenmoresoafterthefertilisersourcewasdiscontinued(December1).Onaverage(averageofthe3
rowsofthesametreatment),overthecropcyclethe0%Mo-treatedplantshadareductioninleafMo
levelsof35%(ifRow4dataisremoved,thedecreaseaverages57%),the25%Mo-treatedplantsa52%
reduction,andthe50and100%treatmentshadreductionsof26%and21%,respectively.ByDecember
9th,Mo levels in themature leaves for the0and25%treatmentswereslightly lowerthanthe50and
100% treatments (0.20ppmcompared to0.26ppm, respectively).Averaging thedataover theentire
treatment period showed no difference among treatments or replicate blocks (troughs) of the same
treatment.AnanalysisofMolevelsthroughouttheplantonamonthlybasisthroughoutthetrialwould
haveprovidedmoreinformationregardingthemobilityofMoandallowedamassbalance,butthiswas
notwithinthescopeofthestudy.Notably,alltheMolevelsmeasuredinmatureleavesthroughoutthis
studyaregenerallyconsideredtobewithinthesufficiencyrangeforMo(0.1-2ppm).
Nitrogen(N)levelsincreasedinmatureleavesbyapproximately25%overthetrialperiod,whereas
calcium (Ca) and boron (B) levels increased by approximately 100%. Note that the fertiliser levels of
theseessentialelementsweresuppliedatthefull(recommended)ratesuptoDecember1,2014.
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Table4–Mo(ppmdryweight)levelsinmatureleavesfromSeptember10,2014throughthe
growingcycle,followedbyresultsofnitrogen,calciumandboron.
Summary'results'for'Molybdenum'(ppm)'in'mature'leaves'of'Poinsettia
1st$dayRow$1+25%
Row$2+$50%
Row$3+$100%
Row$4+$0%
Row$5+$0%
Row$6+$100%
Row$7+$50%
Row$8+$25%
Row$9+$100%
Row$10+$0%
Row$11+$50%
Row$12+$25%
10+Sep 0.5930+Sep 0.34 0.31 0.28 0.31 0.32 0.34 0.38 0.35 0.38 0.35 0.42 0.4614+Oct 0.46 0.55 0.40 0.61 0.48 0.58 0.53 0.41 0.49 0.42 0.45 0.3928+Oct 0.32 0.35 0.29 0.38 0.25 0.38 0.31 0.24 0.32 0.20 0.32 0.2511+Nov 0.48 0.41 0.25 0.37 0.37 0.25 0.30 0.22 0.34 0.17 0.54 0.5425+Nov 0.31 0.46 0.31 0.44 0.25 0.46 0.31 0.22 0.36 0.19 0.34 0.2409+Dec 0.21 0.31 0.22 0.34 0.15 0.34 0.25 0.16 0.22 0.14 0.24 0.17
Summary'results'for'Nitrogen'(%'dry'weight)'in'mature'leaves'of'Poinsettia
1st$dayRow$1+25%
Row$2+$50%
Row$3+$100%
Row$4+$0%
Row$5+$0%
Row$6+$100%
Row$7+$50%
Row$8+$25%
Row$9+$100%
Row$10+$0%
Row$11+$50%
Row$12+$25%
10+Sep 4.0730+Sep 4.48 4.50 4.55 4.30 4.69 4.48 4.30 4.15 4.24 3.98 4.62 4.3714+Oct 4.74 4.71 5.22 5.31 5.03 5.31 4.98 5.14 4.90 4.49 5.08 5.1128+Oct 4.57 4.69 4.79 5.28 4.93 5.31 4.82 4.62 5.24 4.90 4.93 4.8711+Nov 5.03 4.74 5.23 5.05 5.06 5.07 5.39 5.04 5.32 5.23 4.98 4.7225+Nov 5.17 5.40 5.36 5.2 5.46 5.26 5.38 5.28 4.74 5.51 4.86 5.1809+Dec 4.48 4.90 4.86 4.83 4.94 4.97 4.91 4.86 4.89 5.05 5.00 4.62
Summary'results'for'Calcium'(%'dry'weight)'in'mature'leaves'of'Poinsettia
1st$dayRow$1+25%
Row$2+$50%
Row$3+$100%
Row$4+$0%
Row$5+$0%
Row$6+$100%
Row$7+$50%
Row$8+$25%
Row$9+$100%
Row$10+$0%
Row$11+$50%
Row$12+$25%
10+Sep 0.9830+Sep 1.29 1.09 1.24 1.21 1.35 1.14 1.12 1.15 1.37 1.18 1.16 1.1814+Oct 0.92 1.11 1.39 0.97 1.09 1.10 1.05 1.18 1.11 1.27 1.13 1.1928+Oct 1.01 1.10 1.07 1.06 1.16 1.06 1.07 1.09 1.11 1.06 1.10 1.1811+Nov 1.23 1.19 1.26 1.18 1.19 1.17 1.16 1.17 1.21 1.26 1.12 1.2025+Nov 1.46 1.51 1.44 1.43 1.48 1.41 1.48 1.46 1.43 1.48 1.56 1.4709+Dec 1.77 1.76 1.67 1.57 1.75 1.72 1.64 1.69 1.74 1.69 1.71 1.75
Summary'results'for'Boron'(mg/kg'dry'weight)'in'mature'leaves'of'Poinsettia
1st$dayRow$1+25%
Row$2+$50%
Row$3+$100%
Row$4+$0%
Row$5+$0%
Row$6+$100%
Row$7+$50%
Row$8+$25%
Row$9+$100%
Row$10+$0%
Row$11+$50%
Row$12+$25%
10+Sep 2130+Sep 20 21 20 19 19 19 21 22 19 20 21 1814+Oct 24 25 23 25 27 24 25 26 26 27 25 2528+Oct 25 23 23 23 24 22 22 23 23 23 25 2611+Nov 29 28 26 26 25 26 25 26 27 26 27 2925+Nov 36 35 33 33 35 32 33 34 37 35 38 3809+Dec 40 42 42 37 39 39 38 41 42 38 40 42
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Figure3–Poinsettiacrop(November3,2014)ingreenhouse#20,toillustratecolour/appearanceasthebractsstarttoformandplantsenterthefloweringstage.
Bylookingattheaveragetissuedataforeachtreatmentonamonthlybasis(Table5),itisevident
that theMo levels in mature leaves decrease through the various developmental stages (vegetative
state, bract development, and atmaturity) at the lower level treatments of 0% and 25% but remain
abovethepublishedacceptablerangeforMoinpoinsettialeaftissue.Figure4illustratesthevariation
inMo levels over time. Nitrogen (N) levels increased steadily in all treatments (no difference among
treatmentsasexpectedasallfourtreatmentsreceivedthesameamount),whiletheimmobileCalevels
actually declined across all treatments duringbract development before increasing again atmaturity.
This result is most interesting, and warrants further investigation. Boron, also partially mobile,
demonstrated increased levels in the recently matured leaves at the mature plant stage in late
November,comparedwiththeothertwodevelopmentalgrowthstages.
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Table5–Keynutrientlevels(ppm)incompositesamplesofrecentlymatureleaves(rawdatatakenfromTable4),andaveragedbytreatmentonamonthlybasis.
Figure4–LevelsofkeynutrientsduringPoinsettiaplantdevelopmentfromSeptemberthroughlateNovember(datafromTable5).
veg$state bract$devpt maturityTREATMENT 2014;09;30 2014;10;28 2014;11;25
0% 0.33 0.28 0.2925% 0.38 0.27 0.2650% 0.37 0.33 0.37100% 0.33 0.33 0.380% 4.32 5.04 5.3925% 4.33 4.69 5.2150% 4.47 4.81 5.21100% 4.42 5.11 5.120% 1.25 1.09 1.4625% 1.21 1.09 1.4650% 1.12 1.09 1.52100% 1.25 1.08 1.430% 19 23 3425% 20 25 3650% 21 23 35100% 19 23 34
Mo
Ca
B
N
0"
0.1"
0.2"
0.3"
0.4"
30(Sep" 28(Oct" 25(Nov"
ppm"
Molybdenum+Levels+in+Matured+Poinse4a+Leaves+at+Varying+Molybdenum+Fer8liser+Rates+2014+
0%" 25%" 50%" 100%"
0"
10"
20"
30"
40"
30'Sep" 28'Oct" 25'Nov"
ppm"
Boron%Levels%in%Matured%Poinse2a%Leaves%at%Varying%Molybdenum%Fer9liser%Rates%2014%
0%" 25%" 50%" 100%"
0"
2"
4"
6"
8"
30(Sep" 28(Oct" 25(Nov"
%"dry"weight"
Nitrogen)Levels)in)Matured)Poinse3a)Leaves)at)Varying)Molybdenum)Fer9liser)Rates)2014)
0%" 25%" 50%" 100%"
0"
0.5"
1"
1.5"
2"
30(Sep" 28(Oct" 25(Nov"
%"dry"weight"
Calcium(Levels(in(Matured(Poinse4a(Leaves(at(Varying(Molybdenum(Fer:liser(Rates(2014(
0%" 25%" 50%" 100%"
14|F C O
Solutionresults:
Accordingtotraditionalfertiliserrequirements,thefertilisersolution(at100%Mo)shouldinclude
0.5µmol/L. ThemolecularweightofMo=95.94, soafter converting tomg/L itwasdetermined that
0.04797mg/L(orppm)isrequiredforthe100%solution.Theconcentrationintheothertreatmentswas
determinedbasedonthiscalculation,with0,25,and50%oftheratedeterminedabove.Initialanalysis
at A&L Laboratories (London, Ontario) used the ICP process, with a detection limit of 0.02 ppm,
insufficient for testing of the individual trough solutions from the recirculation barrels. ALS
Environmental (Waterloo, Ontario) tested (with a detection limit of 0.0005 ppm) the stock tank
solutions(i.e.,theconcentrate)onthreeseparatedates(Table6).Notethattheconcentrationinthese
tankswasconcentratedby100-fold,anddilutedwithfreshtoachievethecorrectfertiliserrateduring
application.Notethattheconcentratetanksdidexperiencesomesettling,andthedifferencebetween
theexpectedrateandactualcalculatedratemaybeduetoimpropersamplingtechnique.
Table6–Molevelsintheconcentratestocktanks(ppm).
Endoftrialresults(December15-16,2014):
Attheendofthetrial,therewerenovisibledifferencesamongtherowsandtreatments,ineither
colourofleavesorflowers,overallheight,apparentbloomyield,andnovisibleinterveinalchlorosiswas
observed(Figure5).
Treatment( Oct(29/14 Nov(11/14 Nov(25/14 Target(ppmActual(average(ppm(
inTreatmentActual(Average(%(of(full(rate(in(Treatment
0% 0.12 0.0005 0.0005 0 0.04 0.8%25% 1.16 1.73 1.69 1.2 1.53 31.8%50% 3.02 3.9 3.08 2.4 3.33 69.5%100% 3.41 4.48 4.71 4.797 4.20 87.6%
15|F C O
Figure5–Poinsettiacrop(December9,2014)ingreenhouseA20,toillustratecolour/appearanceoneweekbeforethecropcyclewascompleted.Markersattheendofeachrowidentifiedthetreatments;
nodifferenceincolourorheightwasapparentamongrowsortreatments.
By comparingoverall plantheight, and freshweightsof the threeplantparts (bracts, leaves and
stems,seeFigure6),thereappearedtobenodifferencebetweenthe25%Motreatedplantsinrow8
(embedded in the treatmentarea) and the twooutside rows.While theremightbe slightdifferences
apparentinthetissueanalysisthroughthegrowingcycle(Tables4&5),therewasnotenoughevidence
toshowanedgeeffect.Therefore,the25%treatmentwasincludedinthefollowingdataanalysis.
Figure6:HarvestingtheplantsonDecember15,2014,separatingplantshootparts,andweighingleafandstemportions.
16|F C O
BasedondatacollectedattheDecemberharvest,therewerenosignificantdifferencesamongthe
fourtreatments(Figure7).Overallheightoftheplants(shownasreddiamonds),aswellasbract, leaf
andstemfreshweights(bars)wereaveragedforalltheplantsinatreatmentrow,andacrossthethree
replicaterows.Thestandarddeviationwascalculatedbasedonthedatafromthose69plants(23plants
perrow,3rows).
Figure7:Averagefreshweightsandheightsofthebracts,leavesandstemsineachofthefourtreatments.Notethateachbarandpointrepresentstheaverageof72plants.Errorbarsrepresentthe
standarddeviations.
ThedistributionofMo,N,CaandB invarioustissuesatmaturitywasdependentontheelement
under consideration: however, this distribution was unaffected by the Mo treatments (Table 7 and
Figures8-11).While this resultwasexpected forCa,NandB (sinceallplants in theexperimentwere
provided with consistent levels of these elements throughout the study), the Mo levels would be
expectedtovaryiftheelementbecomeslimiting(especiallyatthelowerapplicationrates).
Table7–MeanLevelsofNandCa(%dryweight)andBandMo(mg/kgdryweight)inBract,LeafandStemTissuesofPoinsettiaafterPlantsReachedMaturity(December15,2014)
0"
5"
10"
15"
20"
25"
30"
0"
50"
100"
150"
200"
250"
300"
0%" 25%" 50%" 100%"
Height'(cm)'
Mass'o
f'Plant'Parts'(g)'
Treatments'
Average'Weight'and'Height'of'Poinse:as'in'Each'Treatment,'December'2014'
Bracts" Leaves" Stems" Total"Shoot" Height"
Trt/Tissue N Ca B Mo Dry Wt N Ca B Mo Dry Wt0% Bract 3.35 0.555 23 0.22 15.37 0.16 0.064 1 0.05 1.200% Leaf 4.42 1.697 44 0.39 21.33 0.19 0.136 3 0.08 2.20
0% Stem 1.84 1.517 13 0.14 13.78 0.16 0.171 1 0.04 1.2525% Bract 3.23 0.592 23 0.20 17.10 0.17 0.061 1 0.07 1.7025% Leaf 4.42 1.804 46 0.39 22.17 0.19 0.151 5 0.23 2.17
25% Stem 1.79 1.534 13 0.11 14.20 0.12 0.192 1 0.05 1.5750% Bract 3.36 0.579 23 0.28 15.77 0.15 0.065 1 0.04 1.1550% Leaf 4.48 1.724 45 0.42 22.15 0.16 0.134 4 0.08 1.67
50% Stem 1.80 1.554 13 0.17 14.17 0.11 0.194 1 0.06 1.21100% Bract 3.33 0.593 23 0.24 15.76 0.16 0.141 3 0.07 0.89100% Leaf 4.47 1.697 43 0.41 21.35 0.16 0.129 5 0.11 1.62
100% Stem 1.82 1.535 13 0.12 13.84 0.19 0.156 1 0.04 1.13
Average within treatment Std Deviation within treatment
17|F C O
Figure8:MeanMolevelsinthebracts,leavesandstemsineachofthefourtreatments.Notethateachbarandpointrepresentstheaverageof69plants.Errorbarsrepresentthestandarddeviations.
Figure9:MeanBlevelsinthebracts,leavesandstemsineachofthefourtreatments.Notethateachbarandpointrepresentstheaverageof69plants.Errorbarsrepresentthestandarddeviations.
0.00.10.20.30.40.50.60.7
0% 25% 50% 100%
mg/kgDryWeight
Treatment
MeanMolybdenumLevelsinTissueDecember152014
Bracts Leaves Stems
0
10
20
30
40
50
60
0% 25% 50% 100%
mg/kgDryWeight
Treatment
MeanBoronLevelsinTissueDecember152014
Bracts Leaves Stems
18|F C O
Figure10:MeanNlevelsinthebracts,leavesandstemsineachofthefourtreatments.Notethateachbarandpointrepresentstheaverageof69plants.Errorbarsrepresentthestandarddeviations.
Figure11:MeanCalevelsinthebracts,leavesandstemsineachofthefourtreatments.Notethateachbarandpointrepresentstheaverageof69plants.Errorbarsrepresentthestandarddeviations.
WhenmeanMoandB levelsarecomparedamongthefourtreatments,andalsotothoseofCa
(immobile)andN(mobile),itispossibletoexplorethelevelofmobilityoftheseelementsbetweenplant
partsandtestourpredictionthattheseelementshaveintermediatemobility.Table8liststheratiosof
thefourelementsofinterest,comparinglevelsoftheseelementsinthebracttoboththeleafandstem
tissues (Bract:Leaf, Bract:Stem). Larger numbers suggest greater mobility in the plant. As predicted,
calcium has the lowest ratios (0.327-0.386), and nitrogen has the highest ratios (0.731-0.759) for
0
1
2
3
4
5
0% 25% 50% 100%
mg/kgDryWeight
Treatment
MeanNitrogenLevelsinTissueDecember152014
Bracts Leaves Stems
0.0
0.5
1.0
1.5
2.0
2.5
0% 25% 50% 100%
mg/kgDryWeight
Treatment
MeanCalciumLevelsinTissueDecember152014
Bracts Leaves Stems
19|F C O
Bract:Leaf,and1.804-1.836forBract:Stem.BoronandMoratiosareintermediateandfairlysimilarfor
Bract:Leaf indicating some mobility. The Bract:Stem ratios for B andMo are similar to N, indicating
similar mobility. While it is possible that Mo mobility may be decreased by the 0% treatment (less
availableMo),itisnotlikelysignificant,andthereisstrongindicationthatMoisnotinshortsupply.
Table8–RatiosofBractnutrientlevelstoLeafandStemnutrientlevelsforMo,B,NandCainPoinsettiaPlantsatMaturity(December15,2014)
Outcomes/Recommendations• SignificantdecreasesinthelevelsofMoinfertiliserapplicationratesappear,basedonthis
initialstudy,tohavenoimpactontheproductionofsaleablePoinsettiacrops(knowntobesensitivetoModeficiency)whengrownusingsub-irrigationtechnology.
• DecreasingtheMofertilisationby50%overthecurrentrecommendedratesbasedonthisonestudywillnothaveanegativeeffectonMolevelsinplanttissues(aftertheestablishmentstage)whenplantsaregrowninaclosed,sub-irrigationsystemwherenoleachingoccursfromthesubstrateinwhichtheplantsaregrown.
• OthercultivarsofpoinsettiamayhavedifferentresponsestoMorates,soitwouldbevaluabletotrialvariousModoseratesbeforechangingproductionpractices
• DecreasedlevelsofMoindischargewatercouldresultinlevelsmeetingtheProvincialWaterQualityObjectivesandnotberedflaggedunderlandapplicationproposedrulesofNMA.
• Post-harvestimpactswerebeyondthescopeofthisstudy.• DecreasingthelevelofMoinfertilisermixesmaydecreasethecosttothefarmer,although
sincetheamountofMoinfertiliserissosmall(amicronutrienttypicallysuppliedat0.04797mg/L),theimpactonfarmercostswillbenegligible.TheenvironmentalimpactofdecreasingMoinopensystemsisthelargergainresultingfromthisstudy.
• Both0%and25%MotreatmentsdecreasedtheMolevelsinmatureleaftissueovertime;however,thedecreaseinmatureleafMolevelswasinsufficienttoresultindeficiencysymptomsduringthecropcycle.ThelevelofMo(andCa,N,andB)inthebracts,aswellasthe
Bract : LeafParameter: 0% 25% 50% 100%
Mo/Mo 0.573 0.528 0.667 0.599B/B 0.525 0.493 0.521 0.537N/N 0.759 0.731 0.750 0.745Ca/Ca 0.327 0.328 0.336 0.349
Bract : StemParameter: 0% 25% 50% 100%
Mo/Mo 1.567 1.824 1.689 2.089B/B 1.824 1.805 1.810 1.795N/N 1.821 1.804 1.868 1.836Ca/Ca 0.366 0.386 0.373 0.386
Treatment
Treatment
20|F C O
maturetissuesfromtheDecemberharvest,mightprovidecluesastothedegreeofmobilityandabilityoftheplanttosustainitselfbeyondthetrialperiod.
• Moappliedthroughtheestablishmentperiod(August)mayprovidesufficientMototheplantfortheremainderofthegrowingcycle(SeptemberthroughDecember),sinceplantspossesssomeabilitytomobilizeMo.
• Inopensystems,‘waste’nutrientfeedwatercanbereusedonothercrops(e.g.outdoorcontainers)orcanbelandappliedasabeneficialsolutionundertheNutrientManagementAct.Lowlevelsoftraceelementsareimportantforplantgrowth,butcannotexceedtherequirementsofthereceivingcroporland,orresultintoxiclevelsforlivestockgrazingonreceivingcrops.
• Thisresearch,whilenotdirectlyapplicabletovegetablegreenhouseproduction,willsetaprecedentfortestingsimilartheoriesforvegetableMorequirements.Originalrecommendationsfortomato,pepperandcucumbercropswerenotbasedonsub-irrigation/hydroponicsystems.However,itmaybemorecomplicatedtosatisfytheModemandsoffruitingcrops.
• Basedonthisinitialstudy,evaluatingtheoptimallevelofmicronutrientsinstandardgreenhousebasedwater-solublefertiliserswhenusingrecirculatingsub-irrigationtechnologyisrecommended.
AcknowledgementsTheresearchteamwould liketoextendtheirappreciationforthefundingofthisprojectthrough
theWaterAdaptationManagementandQualityInitiative,administeredbyFarmandFoodCareOntario.
Theproject’ssuccessisduetothesupportoftheOntarioMinistryofAgriculture,Food&RuralAffairs,
theVinelandResearch&InnovationCentre,andthesignificantcontributionsofWayneBrownandCathy
Grayincaringfortheplants.WayneBrownisprobablythebestgrowerofpoinsettiasinallofOntario,
andCathykeepsplantsaliveandkeepsgreatrecords!Special thanksareextendedtoLinwellGardens
for the donation of plantmaterial, and othermembers of the research team: ShannonGauthier, Dr.
BarryShelp (UniversityofGuelph), JamieAalbers (FCO),andElizabethHuber-Kidbywere invaluable in
supportingtheexperimentaldesign,datacollectionandanalysis,andpreparationofthereport.
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