optimizing molybdenum levels in subirrigation floriculture ... · optimizing molybdenum levels in...

OptimizingMolybdenumLevelsinSub-IrrigationFloricultureSystems

WaterAdaptationManagementandQualityInitiativeProject#11

FinalReport–March2015

Preparedby:

Dr.JeanineWestWaterSpecialist

FlowersCanada(Ontario)Inc.

and

WayneBrownOMAFRA

2|F C O

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

3|F C O

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

4|F C O

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.

5|F C O

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

6|F C O

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

7|F C O

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

8|F C O

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.

10|F C O

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.

11|F C O

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%


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%


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

12|F C O

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.

13|F C O

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.

ReferencesArreola,J.A.,Gonzalez,C.A.,Aguilar,L.A.,Leon,M,T.,Pineda,J.P.,andGarcia,E.A.2008.Calcium,Boron

and Molybdenum on Plant Growth and Bract Pigmentation in Poinsettia. Revista FitotecniaMexicana,31(2),165-172.

CanadianCouncilofMinistersoftheEnvironment.1999.CanadianWaterQualityGuidelinesfortheProtectionofAquaticLife:Molybdenum.In:Canadianenvironmentalqualityguidelines,1999,

21|F C O

CanadianCouncilofMinistersoftheEnvironment,Winnipeg.Gupta,U.(1993).Boronanditsroleincropproduction.BocaRaton,Fla.:CRCPress.Kaiser,B.N.,Gridley,K.L.,Brady,J.N.,Phillips,T.,andTyerman,S.D.2005.TheRoleofMolybdenumin

AgriculturalPlantProduction.Botany96,745-754.OntarioMinistry of Agriculture and Rural Affairs. 2010. Production recommendations for greenhouse

floriculture.Publication370.Queen’sPrinterforOntario.Toronto.SoilResourceGroup.2012.GreenhouseProcessWaterQualityandQuantityCharacterizationAnalysis.

FinalreportsubmittedtoTheOntarioGreenhouseAlliance(TOGA).Whipker,B.E.,andHammer,P.A.(1997).NutrientUptakeinPoinsettiaduringDifferentStagesof

PhysiologicalDevelopment.JournaloftheAmericanSocietyforHorticulturalScience,122(4),565-573.

optimizing molybdenum levels in subirrigation floriculture ... · optimizing molybdenum levels in...

Documents