Why recycle irrigation water

Greenhouse nutrient feedwater (GNF) is waterthatisgenerallyrichinnutrientsandhasvalueforcropproduction, but has inherent risks for re-usewithinthegreenhouse.Whilewaterandnutrientsare valuable commodities to greenhouse farmers,GNF may require treatment to manage nutrientimbalancesorpathogenrisktomakeitsuitableforuse on certain crops. In the absence of effectivetreatment, transport offsite using an approvedwaste hauler or pre-approved discharge to amunicipalsewerareacceptableoptions.

AnalternativetotreatmentorapprovedremovalistocollectGNFinholdingtanksanduseittoirrigateless sensitive alternative crops such as orchards,fruit, vegetable, field, or biomass crops. Landapplication under the Nutrient Management Act(NMA) encourages best management practices,and provides valuable water to local farmers. Ifnearby crops are available to the operation, landapplicationmaybea simple, cost-effectiveoptionfor GNF management, and has the advantage ofusingwhatwould otherwise be consideredwaste(waterandnutrients).The following legislative details should beconsidered:• The Greenhouse Nutrient Feedwater regulation(Ontario Regulation 300/14) under the NMA isdesigned to regulate and permit the landapplicationofGNFtoagriculturalcrops.

• To be considered GNF under the NMA, thenutrient solution must come from a closedcirculationsysteminyourgreenhouse,andmustnotbemixedwithanyothermaterial (GNFmaybe mixed with liquid Agricultural SourceMaterials(manure)incertaincircumstances.)

• Inorderto landapplyGNFundertheNMA,youmustregisteryouoperationwithOMAFRA.

• LandapplicationrequiresaGNFStrategy(coversthe generation and storage) and a GNF Plan(covers land application) if the farm generatesmore than 5 nutrient units (NU) in any onecalendaryear(1NUhasafertilizerreplacementvalue of the lower of either 43kg N or 55kgP2O5). If the farm generates 5 NU or less, asimplified version of a GNF Strategy, called aGNFDocument,isrequired,andtheGNFPlanisnotrequired.

• GNFStrategiesandPlansneedtobepreparedbya certified nutrient management planner or bysomeone from the operation who hascompletedtheappropriatetraining.

• Both theGNF Strategy andPlanmust include acontingencyplan.

• GNF Plans account for nutrient levels in thereceivingsoilandtheappliedGNFusingupdatedNMANsoftware

• Maximumapplicationratesneedtobefollowed.There are requirements for maximumapplication of a range of nutrients, regulatedmetals, and other ions, as well as maximumapplication rates based on volumes applied(based on runoff potential rather than nutrientloadings)

• ApplicationtimingisgenerallyrestrictedtoApril1toNovember30(cropgrowingseason),andisprohibited on snow-covered or frozen ground.Having enough GNF storage for the wintermonthsisnecessary.

Otherconsiderations:• Thereisalimitedpracticaldistancefortransport

ofGNFbetweenstorageandthereceivingcrop• Thedailymaximumamountofwaterthatcanbe

irrigated onto a crop is regulated and dependsonsoiltype,slopeandthecropbeingirrigated

LandApplicationofGreenhouseNutrientFeedwater

Why land apply greenhouse nutrient feedwater to alternative crops?

• Irrigation should be applied based on properirrigationschedulingtoavoidsecondaryrunoff

• Standard irrigation equipment is sufficient ifavailable, or portable irrigation systemsmaybeused

Land application is a low cost, closedmanagementoption fordealingwithGNF so itcloses the environmental loop. Nutrients arebeneficially used for crop production, so itclosesthenutrient loop.Ifthealternativecropcanbeharvestedasbiomassandfacilitiesexistfor producing energy from it, it may also helpclosetheenergyloop.

Figure 1: Irrigation of feedwater onto a youngMiscanthusbiofuelcropTo demonstrate how the environmental,nutrient and energy loops on an operationcouldbeclosed, irrigationof containernurseryfeedwater onto a biofuel crop wasdemonstrated(Figure1,2).Theyieldsfromtheexperimentalcropdescribedaboveapproached14tonnesperhectareforthesecondyearcrop.Literaturesuggestsyieldsofupto20drytonnesare feasible for fully mature crops. One drytonne yields an estimated energy value of 17-18.5GJ.

Figure2:Maturebiofuelcrop

• Greenhouseoperationsthathaveaccessto

suitablelandandcrops• Operations that need to get rid of a

proportionofGNFduetoissuesofbuildupoflimiterssuchassalts

• Operations with concerns over pathogenissues

• Operational waters that meet the GNFcriteria as set out in the regulations butcannotberecirculated

• Operations that need to empty and cleanfertilizertanksattheendofacropcycle

• Operations that normally recirculate butrequireacontingencyplan

OMAFRA:Applyinggreenhousenutrientfeedwateronagriculturallandhttp://www.omafra.gov.on.ca/english/nm/regs/gnfpro/gnfland.htmhttps://www.nutrientmanagement.ca/directories/nutrient-management-consultants/Formoreinfo:ag.info.omafra@ontario.ca

Application of nursery irrigation runoff water to a biofuel crop

Who can use this management option?

Further Reading

ONTARIO

FundingforthisprojecthasbeenprovidedbyAgricultureandAgri-FoodCanadathroughtheCanadianAgriculturalAdaptationProgram(2014-2019).

TheresearchteamacknowledgesthesupportofOMAFRA.TheviewsexpressedinthisfactsheetaretheviewsoftheresearchteamanddonotnecessarilyreflectthoseofOMAFRA.