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Irrigation and water use(Best practice guide for potatoes)

2 I R R I G A T I O N A N D W A T E R U S E ( B E S T P R A C T I C E G U I D E F O R P O T A T O E S )

Section 2

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Growers recognise the importance of

water and how valuable a resource

it is. However, as demand for

water increases, it is increasingly

necessary to justify need and provide

evidence of efficient use, both for

environmental protection and to meet

crop protocol requirements.

•Waterrequirementsneedtobedefinedandbasedonlocalclimate,soiltype,soilstructure,cropandintendedmarket.Includewaterneededforcropquality,pestanddiseasecontrol,damageminimisation,etc.

•Assessadequacyofsupply,distributionandapplicationequipmentandidentifyareasforimprovement

•Keepclearrecordsofrainfall(andevapo-transpirationifpossible),waterusage,scheduling,operatortrainingandequipmentmaintenanceacrossallcroppingareas(sixyearshistoryminimum)

•Avoidwindyconditionsandexcessevaporationbyirrigatingatnight,whichalsoensuresmaximumpenetrationoftherootzone

•Setupequipmenttocombathighwindsorprovideshelterbeltstopreventdrift.TheWoodlandTrusthaspublishedadocumentonshelterbeltswhichcanbeaccessedatwww.woodlandtrust.presscentre.com/imagelibrary/downloadMedia.ashx?MediaDetailsID=1877

•Monitoroperatingpressuresandwaterapplicationuniformityduringthegrowingseason

•Checkirrigationapplicationsmatchtheinfiltrationrateofthesoiltoavoidunnecessaryerosion

•Carryafieldbooktorecordeachirrigation‘event’asithappens.See6.1Irrigationessentials–EnvironmentAgencyformoreinformation.

Top tips

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I R R I G A T I O N A N D W A T E R U S E ( B E S T P R A C T I C E G U I D E F O R P O T A T O E S ) 3

Section 6Contents

Contents

2.1 Business planning ................................................................... 7

2.1.1 Externalinfluences 7

2.1.2 Legislationandirrigation 7

2.1.3 WaterFrameworkDirective2000/60/EC 7

2.1.4 Impactonpotatogrowers 8

2.1.5 Legislationthathasadirectimpactonpotatogrowers 12

2.1.5.1 GroundwaterDirective2006/118/EC 12

2.1.5.2 HabitatsDirective92/43/EEC 12

2.1.5.3 NitratesDirective91/676/EEC 12

2.1.5.4 KeyrequirementsoftheNVZrulesinEngland 12

2.1.5.5 CheckingcompliancewiththeNVZrules 13

2.1.5.6 EnvironmentalLiabilityDirective2004/35/EEC 13

2.1.5.7 AgriculturalWastesRegulations 13

2.1.5.8 WaterResourcesAct2003and

Abstractionlicensing 13

2.1.5.9 FloodandWaterManagementAct2010 14

2.2 Business fundamentals ......................................................15

2.2.1 Cost/benefitanalysisofirrigation 16

2.2.2 Costs 16

2.2.3 Benefits 17

2.2.4 Climatechangeanddrought 17

2.3 Irrigation planning .................................................................18

2.3.1 Watercharacteristics 19

2.3.2 Waterrequirementsandreservoirs 19

2.3.3 Theneedforwaterandhowmuchtosupply 20

2.3.4 Evapo-transpiration(ET) 20

2.3.5 Thewaterheldinthesoil 21

2.3.6 TypicalsoilAvailableWaterCapacity(AWC)21

2.3.7 SoilMoistureDeficit(SMD) 22

2.3.8 Irrigationsystemoptions 22

2.3.9 Designofsystem 22

2.3.10 Uniformityofapplicationacrossthe croparea 22

2.3.11 Applyingirrigationwaterefficiently 23

2.3.12 Gettingthebestfromrainguns 23

2.3.13 Problemsthatmayoccurwithrainguns 242.3.13.1 LowPressure 24

2.3.13.2 Pipesizesandlengths 24

2.3.13.3 Pumps 25

2.3.13.4 Lanespacing 25

2.3.14 Checkingwaterdistribution 25

Section 1 Introduction �� 6

Section 2 Key principles �� 7

Top tips ................................................................................................... 2

Contents ................................................................................................ 3

Foreword ............................................................................................... 5

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2.3.15 CalculatingtheCoefficientofUniformity (CU) 26

2.3.16 Mitigatingforwindeffects 26

2.4 Alternatives to rain guns ........................................ 26

2.4.1 Booms 26

2.4.2 Sprinkleranddripirrigation 27

2.5 Irrigation techniques ............................................................27

2.6 Drainage ......................................................................................28

3.1 Water benchmarking .............................................. 29

3.2 When to start irrigating .......................................... 29

3.3 How much water and when? ................................. 29

3.4 Soil moisture monitoring techniques ................... 29

3.4.1 Directmethods 303.4.1.1 Neutronprobes 30

3.4.1.2 Tensiometers 31

3.4.1.3 Capacitanceprobes 31

3.4.1.4 TimeDomainReflectrometry(TDR)andFrequency

DomainReflectrometry(FDR) 31

3.4.2 Indirectmethods 313.4.2.1 ManualWaterBalanceSheet 31

3.4.2.2 ComputerisedWaterBalanceMethods 32

3.4.2.3 Newinnovation 32

3.5 Precision irrigation ................................................. 32

3.6 Fertigation ............................................................... 32

4.1 Plant growth ............................................................ 33

4.2 Nutrition ................................................................... 33

4.3 Soil condition .......................................................... 33

4.4 Infiltration ................................................................ 34

4.5 Slopes ...................................................................... 34

4.6 Reduce run off and soil erosion ............................ 34

5.1 Record-keeping of water use ................................ 35

5.2 Basic farm irrigation planning ............................... 35

5.2.1 Dailyworkplanning 36

5.2.2 Backgroundinformation 365.2.2.1 Dailysoilandwatermanagementinformation 36

5.2.3 Additionalusefulinformation 365.2.3.1 Additionalmanagementinformation 36

6.1 Irrigation essentials – Environment Agency ........ 37

6.2 General farm irrigation template ........................... 38

6.3 Pests and diseases associated with irrigation .... 40

6.4 References .............................................................. 43

Section 4 Crop and soil management �� 33

Section 5 Monitoring �� 35

Section 6 Appendix �� 37

Section 3 Irrigation management �� 29

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Section 2


Section 6

Globally, water resources are subject to extreme pressure, with urban centres competing with growers for the increasingly scarce water supply, as river basins and aquifers dry up and the climate becomes more extreme. The demand for water is expected to double in the coming decades.

Theimportanceofwaternotonlytoagriculturebuttothecountryasawholewasdemonstratedduringtheextremelydryconditionsofearlyspring2012.WatermanagementhasbeenonthepoliticalagendaforsometimeduetothedeadlinessetoutintheEUWaterFrameworkDirective(http://ec.europa.eu/environment/water/water-framework)whichisdrawingevernearer.

ThreeGovernmentpolicyreviewshavealreadytakenplaceandmanyoftheirrecommendationsappearintheFloodandWaterManagementAct2010.ThesewillalsobetakenforwardintherecentNaturalEnvironment

WhitePaperandWaterWhitePaper.ChangesinwaterpolicywillalmostcertainlyhaveamassiveimpactonUKagricultureandespeciallyonthosegrowingpotatoes.

ThemanagementandefficientuseofwaterisahighprioritywithintheUKPotatoindustryandtheactionsofgrowerswillhaveanimpactonfutureresources,especiallyasPotatoCouncildatasuggests55%ofgrowershaveirrigationequipmentand40%ofthetotalpotatocropisgrownonlandwithshorttermtenancies.However,bychangingmanagementpracticesandhavingalongtermstrategyforwateruse(usetheKeyprinciplesonpage7asaguide)therecentproblemsofscarcityfloodingandpoorwaterqualitycouldbealleviated.

Thisguidesuggestswaysofusingwaterefficientlyandhelpsirrigatorsdealwiththechallengesahead.Betterwatermanagementwillenablegrowerstomakethemostoffutureopportunitiesandimproveprofits.

Foreword

Chris Steele – Potato Council


Section 2

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Section 2Section 1

Introduction

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All growers recognise that water use and supply is an essential factor in crop production. A reliable and consistent supply of water is vital to maximise both yield and quality. With the extreme pressure on increasingly scarce water resources, it is expected that global demand for water will be expected to double over the next few decades. Worldwide irrigation uses a total of 2.7 million gigalitres to produce about 40% of the world’s food.

ClimatemodelsindicatethatfreshwaterwhileabundantinplacessuchasCanada,RussiaandBrazil,intherestoftheworlditwillbecomescarceandthecompetitionbetweenurban,environmentalandruraluseswillescalateasthepopulationincreases.

TheMetOfficeHadleyCentre,theUK’sleadingclimatechangeresearchfacility,predictsthat40-50%oftheworldwillbeindroughtby2100anincreaseof10%frompresentday.RegionssuchastheIndiansubcontinent,westernstatesofAmericaandSouthAmericathatrelyonsnowmeltforirrigation,mayfaceacuteshortages.Theseissues,althoughglobal,arealsorelevanttotheUKandwillplayoutatscalesofnational,toriverbasin/catchmenttolocalandfarmlevels.Itisclearthatmoreisneededtobedonetorecycleallwater,renovateinfrastructureienewinvestmentandmoreco-operationwithneighbours,increasewateruseefficiency(onandoffthefarm),restoredamagedriverbasinsandendthewastefuluseofwater.

OverthenextfewyearswaterlegislationintheUKwillalsohaveahugeimpactonthepotatoindustry,eventhoughthereisstillsomeuncertaintyonthe

implementationofthislegislation.However,theseimpactscanbeanticipatedandapro-activeapproachisalmostcertainlythebestwayforward.ThesewillbeinfluencedbythecurrentdesiretosimplifyregulationbyGovernmentandkeydepartments(Defra)andregulators(EnvironmentAgencyandScottishEnvironmentalProtectionAgency),andbytheadoptionofrisk-basedapproachesandself-monitoring.

Itisimportantthatwaterisappliedatthecorrecttimetoachievetherightcropresult.Itisequallyimportantthattheapplicationofwateravoidsthewasteofavaluableresourcewiththeminimumaffectontheenvironment.IrrigationearlyinthegrowingseasonminimisesCommonscab(Streptomyces spp.),maximisestubernumbersandencouragesthegrowthofthecropcanopy.Italsoencouragestuberstogrowatanoptimumrateand,attheendoftheseason,itenablesharvestingwithminimalcropdamage.

Inrecentyears,theintroductionoftheWaterFrameworkDirectiveintoUKlegislationin2003,changestoabstractionlicencingregulationsandplanstoplacetrickleirrigationunderlicensingcontrol,havemeantthatgrowersneedtopayevencloserattentiontothewayinwhichtheyusewater.

Evidencesuggestsgrowersneedtounderstandhowclimatechangecouldaffecttheirwatersupplyandinevitably,profitability.Growersmustplanatleast5to10yearsaheadtoensuretheirbusinessisresilienttodroughtandextremeweather.Carefulandeffectivewatermanagementplanning,alongsideenvironmentalconsiderations,arecriticaltoprofitablecroppinginthefuture.

7I R R I G A T I O N A N D W A T E R U S E ( B E S T P R A C T I C E G U I D E F O R P O T A T O E S )

Section 2Section 2

CHART

Key principles – essential ingredients for effective and effi cient irrigation

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2.1 Business planning

Potatoenterprisesneedasoundbusinessplanbuttheoftenhighcapitalcostsofirrigation,therelianceonwaterprovidersandtheinflexibilityofsomeproductionsystemshighlightitsimportance.Therearealsosomeopportunitiesthatneedtobeconsideredsuchaswatertradingandtheimpactofgovernmentpoliciesontheplanningprocesses.

2.1.1 External infl uencesGrowersneedtounderstandhowexternalissuesaffecttheirbusiness.Governmentpolicies(regulations,incentives,watertrading)climatechange,resources(land,labour,waterandenergy),foodandwaterpolicies,consumerdemands,commoditymarketsandirrigationserviceswillallhaveanimpact.

2.1.2 Legislation and irrigationThemanagementofwaterresourceshasbeenonthepoliticalagendaforsometime,duetothedeadlinessetoutintheEUWaterFrameworkDirective,whichisdrawingevernearer.TheGovernment’swhitepapersontheNaturalEnvironmentandWateraimstopromotemoreefficientandsensitiveuseofwaterforbothfoodproductionandtheenvironment.

2.1.3 Water Framework Directive 2000/60/ECTheWaterFrameworkDirective(WFD)cameintoforceon22December2000.TheDirectivesetsoutatimetableforboththeinitialtranspositionintolawsofMembersstatesandthereaftertheimplementationofrequirements.

IRRIGATION

Irrigation planning

Sitesuitability

Productionsystemsandcropselection

Irrigationanddrainagesystems

CHART

Irrigation management

Waterbudget

Irrigationscheduling

Irrigationstrategies

Crop and soil management

Plantperformance

Soilcondition

Monitoring

Monitoringandevaluation

Continuousimprovement

Business planning

Externalinfluences

Businessfundamentals

I R R I G A T I O N A N D W A T E R U S E ( B E S T P R A C T I C E G U I D E F O R P O T A T O E S )

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ThekeyissuesrelatingtotheWFDare:

• Itappliestoallwaters(domestic,industrialandagricultural)

• Itaimstoreduceand/orminimisediffusesourcepollutionfromagriculturalandurbanrun-offforthefirsttime

• Itintroducesecologicalwaterqualityforthefirsttimeandincludeshydromorphologicalaspects

• Itdemandscosteffectivemeasuresandfullcostrecovery.

The key dates for the implementation of the WFD are given below:

Date Action

2021

2015

2027

Meet environmental objectives [Art. 4] (extended to 2027)

First management cycle ends [Art. 4/13]

Third management cycle ends, final deadline for meeting objectives [Art. 4/13]

Transposition into national legislation [Art. 23]Identification of River Basin Districts and Authorities [Art. 3]

Establishment of the monitoring network [Art. 8]Start public consultation [Art. 14]Completion of inter-calibration exercise

Characterisation of river basin, pressures, impacts and economic analysis [Art. 5]

Establishment of good status standards for different waters

Finalise River Basin Management Plans, including programme of measures

Introduce pricing policies [Art. 9]

Make operational programmes of measures [Art. 11]

Present draft River Basin Management Plan [Art. 13]

2003

2004

2006

2007

2008

2009

2010

2012

Directive came into force [Art. 25]2000

TheimpactoftheWFDoncurrentactivitiesisdependentonthecurrentwaterqualitystatusforeachwaterbody(rivers,lakes,streams,groundwaterandcoastalwaters).Thefirstrequirementistoensurenodeteriorationandthesecondistoachievegoodstatus.

TheWFDclassificationschemeforwaterqualityincludesfivestatusclasses:high,good,moderate,poorandbad.‘Highstatus’isdefinedasthebiological,chemicalandmorphologicalconditionsassociatedwithnoorverylowhumanpressure.Thisisalsocalledthe‘referencecondition’asitisthebeststatusachievable–thebenchmark.Thesereferenceconditionsaretype-specific,sotheyaredifferentfordifferenttypesofrivers,lakesorcoastalwaters,soastotakeintoaccountthebroaddiversityofecologicalregionsinEurope.

Assessmentofqualityisbasedontheextentofdeviationfromthesereferenceconditions,followingthedefinitionsintheDirective.‘Goodstatus’means‘slight’deviation‘moderatestatus’means‘moderate’deviation,andsoon.Thedefinitionofecologicalstatustakesintoaccountspecificaspectsofthebiologicalqualityelements,forexample“compositionandabundanceofaquaticflora”or“composition,abundanceandagestructureoffishfauna”(seeWFDAnnexVSection1.1forthecompletelist).ThesedefinitionsareexpandedinAnnexVtotheWFD.

FurtherdetailsontheDirectivecanbeobtainedfrom:

•www.defra.gov.uk/environment/quality/water/wfd/index.htm

•http://europa.eu/rapid/pressReleasesAction.do?reference=IP/07/388&format=HTML&aged=0&language=EN&guiLanguage=en

2.1.4 Impact on potato growersTheimpactonanyindividualgrowerwillnotbeclearuntilgoodecologicalstatusforeachwaterbodyisdecidedandthenecessaryprogrammesofmeasureshavebeenproposed,implementedandevaluated.

Theinitialcharacterisationindicatedthatmanywaterbodieswouldnotmeet‘good’status.Thisimpliesthatextraeffortswillberequiredtoachieve‘good’status,althoughprioritymustbegiventoensurethatthereisnodeteriorationfromcurrentstatus.

ThemainapproachbeingadoptedbygovernmenttoaddresssomeoftheWFDrequirements,relevanttofarming,istousetheexistingCatchmentSensitiveFarming(seeBox1),SingleFarmPayment(seeBox2)andEnvironmentalStewardship(seeBox3)schemes,soinitialchangesforfarmerswillbeminimal.

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Box 1: England Catchment Sensitive Farming Delivery InitiativeDefra’sCatchmentSensitiveFarming(CSF)programmeaimstotackleDiffuseWaterPollutioninAgriculture(DWPA)inordertomeettheobjectivesoftheWaterFrameworkDirective(WFD).TheCSFisajointventurebetweentheEnvironmentAgencyandNaturalEngland,fundedbyDefraworkingin50prioritycatchments.Thisisdeliveringpracticalsolutionsandtargetedadvicetoenablefarmersandlandmanagerstotakeactiontoprotectwaterbodiesandthewiderenvironment.ThiswillachievereductionsindiffusewaterpollutionfromagriculturebyencouragingCSF.

CatchmentSensitiveFarmingencouragesbestpracticeintheuseof:

•Fertilisers

•Manuresandpesticides

•Promotinggoodsoilstructuretomaximiseinfiltrationofwater

•Minimisingerosionandrun-off

•Protectingwatercoursesfromfaecalcontaminationandsedimentation

•Reducingstockingdensity.

Thisislandmanagementthatkeepsdiffuseemissionsofpollutantstolevelsthatareconsistentwiththeecologicalsensitivityandusesofrivers,groundwatersandotheraquatichabitats,bothintheimmediatecatchmentandfurtherdownstream.

ForfurtherinformationabouttheCSF,pleaseuse:https://www.gov.uk/catchment-sensitive-farming.

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Box 2: Cross compliance: Single Payment SchemeSinceJanuary2005thenewSingleFarmPaymentSchemehasprovidedsubsidiestofarmerswhicharenolongerlinkedtotallytoproduction.UndertheschemefarmersareobligedtomaintainlandinGoodAgriculturalandEnvironmentalCondition(GAEC)aspartofAnnexIVofCouncilRegulationEC/1782/2003.ThisisrelevanttomeetingobligationsundertheWFDandtheproposedSoilFrameworkDirective(SFD).Itincludessoilmanagementtominimisebothonandoff-sitedegradation.AlthoughtherearedifferentGAECdefinitionsforthedifferentUKregions,therequirementsonfarmersaresimilar.

CrosscompliancerequirementsapplytofarmerswhoreceivedirectpaymentsunderCommonAgriculturalPolicy(CAP)supportschemesand/orpaymentsundercertainRuralDevelopmentschemes.

PAYMENTS MAY BE REDUCED IF YOU DO NOT COMPLY WITH THESE REQUIREMENTS.

Thetwomainaspectstocrosscompliancerequirements:

•SpecificEuropeanlegalrequirements,knownasStatutoryManagementRequirements(SMRs)

•DomesticlegalrequirementsrequiringyoutokeepyourlandinGoodAgriculturalandEnvironmentalCondition(GAEC).

CrosscompliancerequirementsapplyinadditiontounderlyingobligationsunderEuropeanandUKlegislation.Remember, you may face penalties if you do not carry out those obligations, as well as reductions to and loss of CAP payments.

All agricultural activities are covered by cross compliance and you must comply with the standards across the whole agricultural area of your holding, regardless of the amount of land you entered into the Single Payment Scheme (SPS).TheonlyexceptionisthatyoudonotneedtoproduceaSoilProtectionReview(SPR)forcommonland(unlessyouarethesoleoccupierofthecommon).FurtherinformationmaybeobtainedfromtheRuralPaymentsAgency(RPA)website:www.rpa.gov.uk/rpa/index.nsf/UIMenu/C63617FF7C4FBE2F8025767E0052995B


Section 2

TheTargetedelementofGlastirisaimedatthoseareasofWaleswhichcandeliverdefinedtargetsrelatingtothefollowingobjectives:

•Carbonmanagement

•Watermanagement

•Biodiversity

•Historicenvironmentprotection

• Improvingaccess.

AsetoftargetedareamapsforeachoftheaboveobjectiveshasbeendrawnupbytheWelshAssemblyGovernment.ThosefarmswhichfallintooneormoreofthesetargetedareaswillbeeligibletojointhetargetedelementprovidingthereisalreadyasignedAll-WalesElementcontract.

Scotland Rural Development Programme (SRDP)TheSRDPisaprogrammeresourcedby€679mofEuropeanfunding(EAFRD),match-fundedbytheScottishGovernment,whichisdesignedtohelpdevelopruralScotland.Theprogrammeisspreadoversixyearsandprovideshelpandsupporttoindividualsandgroups,tohelpcreateawealthierandfairerruralScotland.

Theschemeisdesignedtohelpmeetnationaleconomic,socialandenvironmentaltargetsiewaterquality.

SomeoftheSRDPschemesandinitiativesinclude:

•CroftingCountiesAgriculturalGrantScheme

•FoodProcessing,MarketingandCo-operationGrantScheme

•ForestryCommissionChallengeFunds

•TheLEADERinitiative

•LessFavouredAreaSupportScheme

•RuralDevelopmentContracts

•SkillsDevelopmentScheme.

Box 3: Agri-environment schemes

Entry Level Stewardship (ELS)Withwellover50%ofEngland’sagriculturallandnowinEntryLevelStewardship(ELS),thisisthebasicunderlyingschemeopentoallfarmersandlandmanagersinEngland.ELSrequiresabasiclevelofenvironmentalmanagementandyoucanchoosefromawiderangeofmorethan80managementoptions.Thesecoverallfarmingtypesandincludethingssuchashedgerowmanagement,stonewallmaintenance,lowinputgrassland,bufferstrips,maintenanceoftraditionalfarmbuildingsandarableoptions.Itprovidesastraightforwardapproachtodeliveringsimpleandeffectiveenvironmentalmanagementacrossthewholefarmthatcomplementsexistingfarmingoperationsandallowsthefarmertocreateapracticalenvironmentalmanagementprogramme.ELSagreementsareforfiveyears.

Higher Level Stewardship (HLS)HigherLevelStewardship(HLS)aimstodeliversignificantenvironmentalbenefitsinhighprioritysituationsandareas.Itinvolvesmorecomplexenvironmentalmanagement,soyouwillgetadviceandsupportfromNaturalEngland.HLSisusuallycombinedwithEntryLevelorOrganicEntryLevelSchemeoptions.ThereisawiderangeofmanagementoptionsandthesearedesignedtosupportkeyfeaturesofthedifferentareasoftheEnglishcountryside.HLScancontributetoawiderangeofcapitalworkssuchasrestorationofhedgerowsortraditionalfarmbuildings.HLSagreementslast10years.

Glastir (Wales)GlastiristhenewAll-WalesAgri-environmentSchemeintroducedbytheWelshAssemblyGovernment.ItisafiveyearwholefarmagreementandreplacesTirMynydd,TirCynnal,TirGofalandOrganicFarmingSchemes.Glastirismadeupoftwosections–anAll-WalessectionandaTargetedsection.

TheAll-WalespartofGlastirisavailabletoallfarmersacrossWaleswhoareabletoaccumulatesufficientpointstoenterthescheme.Therearetwoadditionalpackagesavailable,thefirstisspecificallyfordairyfarmersandthesecondisforfarmerswithincertainregionsofWales.

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Campaign for the Farmed Environment (CFE)Sincethelossofset-asidetherehavebeenconcernsaboutthemanagementoflandtoefficientlyproducefoodanditsimpactontheenvironment.SirDonCurry’sHighLevelSet-AsideGroup(HLSAG)commissionedarangeofstudiestoconsiderthebenefitsofformerset-asideandultimatelywhatourfarmedenvironmentstoodtoloseifnoenvironmentalsolutionweretotakeitsplace.

Aschemewasintroducedthataimedforsixpercentofarablelandtakentobeoutofproduction.Thislandwouldfurtherhavetobemanagedtobenefittheenvironment,inadditiontoanyotherworkundertakenthroughagri-environmentalschemes.Inresponse,theCLAandNFU,withthesupportofindustryleadersandenvironmentalorganisations,pulledtogethertocreateavoluntaryalternative–theCampaignfortheFarmedEnvironment.

TheCampaignaimstopulltogetherthehugeamountofworkthatfarmersandlandmanagersalreadydotoencouragewildlife,tobenefitsoilandwaterresourcesandsupportfarmlandbirds.Itpromotesexistingstewardshipschemesandencouragesvoluntarymanagementthatwillbenefittheenvironment,whileensuringefficientandprofitablefoodproduction.

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Section 2

2.1.5 Legislation that has a direct impact on potato growers

2.1.5.1 Groundwater Directive 2006/118/ECIn2013theWaterFrameworkDirective(WFD)willrepealDirective80/68/EEContheprotectionofgroundwateragainstpollutionbycertaindangeroussubstances.TheWFDstatesthatmeasureswouldbeadoptedtopreventandcontrolgroundwaterpollution.ThesemeasuresaresetoutintheGroundwaterDirective.ThisDirectiveisdesignedtoprotectgroundwaterandfillthelegislativegapfollowingtherepealofDirective80/68/EEC.

2.1.5.2 Habitats Directive 92/43/EECTheHabitatsDirectivehascreatedaEuropeannetworkofprotectedwildlifeareasconsistingofSpecialAreasofConservation(SAC)andSpecialProtectionAreas(SPA).TheSPAswereoriginallyestablishedundertheBirdsDirective79/409/EEC.

SinceApril2005thereare634designatedSACsinEngland.Allaffectedlandowners/occupierswere

notifiedandmanagementagreementsestablished.TheagreementsspecifyPotentiallyDamagingOperations(PDOs)whicharenotallowedwithouttheexpressedconsentofNaturalEngland.SpecialNatureConservationOrderscanbeinvokedwhichprovideapermanentbanonPDOs.

AllpermittedactivitiesoccurringpriortodesignationhavetobereviewedtoassessimpactonaSACandifhavinganadverseeffectthenthepermit/consentmustberevisedorrevoked.

AlistofallSACs(UK)isavailableatwww.jncc.gov.uk/protectedsites/sacselection/SAC_list.asp

2.1.5.3 Nitrates Directive 91/676/EECTheNitratesDirective,adoptedbytheEuropeanUnionin1991,aimstoreducewaterpollutioncausedbynitrogenfromagriculturalsourcesandtopreventsuchpollutioninthefuture.TheDirectiverequiresMemberStatesto:

•DesignateasNitrateVulnerableZones(NVZs)alllanddrainingtowatersthatareaffectedbynitratepollution

•Establishavoluntarycodeofgoodagriculturalpracticetobefollowedbyallfarmersthroughoutthecountry

•EstablishamandatoryActionProgrammeofmeasuresforthepurposesoftacklingnitratelossfromagriculture.TheActionProgrammeshouldbeappliedeitherwithinNVZsorthroughoutthewholecountry

•ReviewtheextentoftheirNVZsandtheeffectivenessoftheirActionProgrammesatleasteveryfouryearsandtomakeamendmentsifnecessary.

2.1.5.4 Key requirements of the NVZ rules in EnglandThekeymeasuresincludedinthenewNVZrulesinEnglandinclude:

•Manure N farm limit:Farmersmustensurethatthetotalloadingofnitrogenfromlivestockmanurestothefarmdoesnotexceedaloadinglimitof170kgofnitrogenperhectareperyear

•Closed periods:Thesearetimesduringtheyearwhenthespreadingoforganicmanurewithhighavailablenitrogencontent(egslurry,poultrymanure)isprohibited.Closedperiodsapplyforbothorganicmanuresandmanufacturednitrogenfertilisersandtypicallyrangefrom3-5monthsdependingonthesoiltypeandlanduse

•Crop requirement:Farmersmustplanallapplicationsofnitrogentoacrop(whetherthenitrogenispresentwithinmanufacturednitrogenfertiliser,organicmanure,S

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oranyothernitrogen-containingmaterial)sothattheyarecompliantwithanuppercaponnitrogenapplications(termedanNMaxlimit)

•Spreading locations:Farmersarerequiredtoundertakeawrittenassessmenttoidentifyareasoflandatriskofrunoffandcausingwaterpollution.Applicationsofnitrogenfertiliserandorganicmanurestoareasoflandidentifiedasposingahighriskrunoffareprohibited

•Spreading techniques:Farmersmustspreadorganicmanuresandmanufacturednitrogenfertilisersinasaccurateamanneraspossible.Hightrajectoryspreadingtechniquesforspreadingslurryarestrictlyprohibited,unlesstheequipmentusedcanachieveanaverageslurryapplicationrateofnotmorethan2mmperhourwhenoperatingcontinuously.Additionally,applicationsoforganicmanuretobaresoilorstubblewillrequireincorporationintothesoilincertainsituations

•Record-keeping:Farmersarerequiredtokeeparecordofallnitrateapplicationstheymaketotheirland.Allrecordsmustbemadeavailableforinspectionandkeptforatleastfiveyears.

FulldetailsoftherequirementsonfarmsintheNVZareavailableviathefollowingweblink:https://www.gov.uk/nitrate-vulnerable-zones

2.1.5.5 Checking compliance with the NVZ rulesTheNVZrulesundertheNitratesDirectivearealsoaStatutoryManagementRequirement(SMR)forcrosscomplianceundertheSinglePaymentScheme.ThismeansthatfarmerswillhavetocomplywiththenewNVZrulestobeentitledtotheirfullsubsidypayment;failuretocomplycouldleadtodeductions.

TheEAhastakenarisk-basedapproachtoenforcement,prioritisingfarmsthathavethegreatestpotentialfornitratelossratherthanvisitingallfarms.InWalestheregulationsarethesameasinEngland.Around2.3%ofWalesiscurrentlywithinaNVZ.InScotlandonlyfourareashavebeendesignatedasbeinginNVZ.TheseareLowerNithsdale,Lothianandborders,StrathmoreandFifeandMorayAberdeenshire/BanffandBuchan.

TheEAhaspublishedasetofQ&AwhichprovidepracticaladviceondetailedaspectsoftheNVZrulesandcanbeaccessed:http://www.environment-agency.gov.uk/static/documents/Business/NVZ_QA_Version9_Sept2011.pdf

2.1.5.6 Environmental Liability Directive 2004/35/ EECDirective2004/35/EEC(TheEnvironmentalLiabilityDirective)seekstoachievethepreventionandremedyingofenvironmentaldamage–specifically,damagetohabitatsandspeciesprotectedbyEClaw,damagetospeciesorhabitatsoraSSSIforwhichthesitehasbeennotified,damagetowaterresourcesandlandcontaminationwhichpresentsathreattohumanhealth.Itreinforcesthe‘polluterpays’principle–makingoperatorsfinanciallyliableforthreatsoforactualdamage.

TheEnvironmentalDamageRegulations,whichtransposetherequirementsoftheEnvironmentalLiabilityDirectiveintonationallawinEngland,cameintoforceon1March2009.

Fordamagetowaterorbiodiversity,remediationmayinvolve:

•Primaryremediation(toreturnthesitetobaselinecondition)

•Complementaryremediation(equivalentoff-sitemeasureswhereprimaryremediationdoesnotreturnthesitetobaselinecondition),

•Compensatoryremediation(tocompensateforthe‘interimloss’ofnaturalresourcesandservicespendingrecovery).

2.1.5.7 Agricultural Wastes RegulationsTheserefertotheWasteManagement(EnglandandWales)Regulations200614.TheseRegulationsimplement(inpart)theWasteFrameworkandtheLandfillDirectivesandamendtheEnvironmentalProtectionAct1990(inparticularthes.75(7)(c)exemptionfor“wastefrompremisesusedforagriculture”)andtheEnvironmentAct1995.

ItisimportanttorecognisethattheDirectivedefinitionofwasteisstrict–“Anysubstanceorobjectwhichtheholderdiscardsorintendsorisrequiredtodiscard.”AgriculturalwasteistakenaswastefrompremisesusedforagriculturewithinthemeaningoftheAgriculturalAct1947.SinceMay2006agriculturalwaste,previouslyexemptfromcontrol,nowcomesundertheWasteRegulations,althoughthereareprovisionsforquiteawiderangeofexemptions.

2.1.5.8 Water Resources Act 2003 and Abstraction licensingManyofthecurrentandfuturechangesinwaterresourcemanagementinEnglandandWalesstemfromtheWaterAct2003publishedon28November2003,andtheconsequentmeasuresbeingimplementedbythe


Section 2

EAthroughtheirCatchmentAbstractionManagementStrategies(CAMS).TheimplementationoftheWaterActisongoing,viaaseriesofCommencementOrders,withthedifferentprovisionsoftheActbeingbroughtintoforceatdifferenttimes.

Thekeyissueswithrespecttopotatogrowersare:

•Allsmallabstractions,currentlysetat20m3/day,donotneedalicence.Thisisunlikelytoberelevanttomostpotatogrowersbutdoesofferopportunitiesforgrowersofotherhighvalueproduceonsmallareas(~1ha)toabstractwithouttheneedforalicence

•Theuseofwaterfortrickleirrigationwillneedanabstractionlicenceinthenearfuture.Inthiscontext,potatogrowersusingtrickleirrigationshouldbeawareoftheCAMSprocessandtheimplicationsofusingtrickle.TheCAMSprocessrequirestheEAtodevelopaledgerofallabstractionsineachcatchment.However,becausetrickleirrigationwasnotlicensed,theEAhavelimitedrecordsofabstractionquantitiesandcannotthereforeaccuratelyincorporatethisuncontrolledbutlegitimateuseintotheCAMSledger.TheformulationoftheledgertakesplacebeforeformalpublicconsultationonCAMSandthereforepotatogrowersusingtrickleirrigationareadvisedtobepro-activeinsupplyingthenecessaryinformationontrickleirrigationwaterusetotheirlocalEACAMSofficer

•Administrationformakingapplications,transferringandrenewinglicenceswillbemadesimpler.Thisshouldreducebarrierstothetradingofwaterrightsbetweenirrigators

•Thestatusoflicenceshaschangedsignificantly.Allabstractorsnowhavearesponsibilitynottolettheirabstractioncausedamagetoothers.From2012,theEAwillbeabletoamendorremovesomeone’spermanentlicencewithoutcompensationiftheyaredeemedtobecausingseriousdamagetotheenvironment

•Allnewlicencesaretime-limited.AlllicensesissuedsincetheWaterAct(2003)cameintoforceandmanyissuedpreviously,arenowtime-limited.Governmentpolicyistoencourageallotherlicenceholderstomovetotime-limitedstatus.Normallytheselicenceswillhavetoberenewedat12yearlyintervals,althoughsomelicencesmayhaveshorterorlongerdurationsandtherearetransitionalarrangementstobringallthelicencesineachcatchmenttoaCommonEndDate(CED).Therewillbeapresumptionoflicencerenewalsolongasthreetestsaresatisfied.TheEAconsiderstheseteststobean‘EnvironmentalMOT’.Thethreetestsare:

Test 1: Continued environmental sustainability:Toassesswhetherthecontinuedabstractioncanbesustainedwithoutsignificantimpactonwaterresources,otherwaterusersortheenvironment

Test 2: Continued justification of need:Toassesswhethertheabstractionisstillrequired,basedonthe‘reasonable’requirementsofthelicenceholderandtocheckthatthemaximumlevelsofabstractionarestillreasonable

Test 3: Efficient use of water:Toassesswhethertherightamountofwaterisbeingusedintherightplaceattherighttime.

Test1willbelargelyundertakenbytheEAthroughCAMSandotherwaterregulationprocesses,althoughlicenceapplicantsmayberequiredtoprovideadditionalinformation.Test2willrequirethelicenceholdertosubmitastructuredcaseforlicencerenewal,addressingandquantifyingarangeoffactorsthatimpactontherequirementforirrigation(justifying‘reasonable’need).Themethodologiesarealreadyinplaceforjustifyingreasonableneedforanewabstractionlicence,thoughtheusetheapplicanthasmadeofthelicenceinpreviousyearscanalsoprovideusefulsupportinginformation.Test3requiresthelicenceholdertodemonstratethat‘efficientuse’willbemadeofthewaterinfuturebutlargelybasedonevidenceontheuseofthewaterinpreviousyears.

TheEAhasadutytopromoteefficientuseofwaterbyabstractors,asenshrinedinTest3.Itissuggestedthatthebestwaytoachievethisistohelppotatoirrigatorsusetheirwatermoreefficiently,byforexampleensuringthattherequirementsinassuranceschemesmatchthoseinanywaterauditingprocedure.Non-renewalremainsasanultimatesanction.

2.1.5.9 Flood and Water Management Act 2010TheFloodandWaterManagementActgainedRoyalAssentonthe8April2010.TheActwillimplementseveralkeyrecommendationsofSirMichaelPitt’sReviewoftheSummer2007floods,protectwatersuppliestoconsumersandprotectcommunitygroupsfromexcessivechargesforsurfacewaterdrainage.

TheAct’sprovisionsinclude:

•Newstatutoryresponsibilitiesformanagingfloodrisk:TherewillbenationalstrategiesandguidanceonmanagingfloodriskinEnglandandWales.Unitaryandcountycouncilswillbringtogethertherelevantbodies,

15

Section 2


whichwillhaveadutytocooperatetodeveloplocalstrategiesformanaginglocalfloodrisk

•Protectionofassetswhichhelpmanagefloodrisk:TheEnvironmentAgency,localauthoritiesandinternaldrainageboardswillbeabletoensurethatprivateassetswhichhelpmanagetherisksoffloodscannotbealteredwithoutconsent.Forexample,puttingagateinawallthatishelpingprotectanareacouldincreasetheriskofflooding

•Powerstocarryoutenvironmentalworks:TheEnvironmentAgency,localauthoritiesandinternaldrainageboardswillbeabletomanagewaterlevelstodeliverleisure,habitatandotherenvironmentalbenefits

•Sustainabledrainage:DrainagesystemsforallnewdevelopmentswillneedtobeinlinewithnewNationalStandardstohelpmanageandreducetheflowofsurfacewaterintotheseweragesystem

•Newsewerstandards:Allsewerswillbebuilttoagreedstandardsinfuturesothattheyareadoptedandmaintainedbytherelevantseweragecompany

•Reservoirsafety:Thepublicwillbeprotectedbyanewrisk-basedregimeforreservoirsafety.Itwillreducetheburdenonregulatedreservoirswherepeoplearenotat

risk,butintroduceregulationforsomepotentiallyriskyreservoirscurrentlyoutsideofthesystem

•Protectionofwatersupplies:therewillbewiderpowersforwatercompaniestocontrolnon-essentialdomesticusesofwaterintimesofdrought

•Otherprotectionforwatercompanycustomers:therewillbenewpowerstoreducethelevelofbaddebt,newarrangementsformanagingveryriskyinfrastructureprojectswhichcouldbeathreattotheabilityofthewatercompanytoprovideitsservices,andupdatedarrangementsforadministrationofwatercompaniesshouldtheygetintodifficulties.

2.2 Business fundamentals

Growersneedtobeontopoftheinternalfactorsaffectingtheirbusiness:suchasfinance(equity,capital,successionplans),personaltraitsforexampleattitudetorisk,andembracingnewtechnologies,healthandsafety,farmingsystems(aretheyflexibleenough?),waterdeliveryinfrastructureandbusinessandmarketoptions.

Thelevelofoperatingsurpluses,debtandthecostofservicingitaswellasthevalueofassetswilldictatetheabilityofthefarmenterprisetoaccessfinanceand

Sou

rce:

Gar

y N

aylo

r P

hoto

grap

hy


Section 2

investinanycapitalupgradestoirrigationsystems.Thebusinessstructureanditssuccessionplanswillalsoaffectthegrowers’willingnesstotakerisksandusenewtechnologiesorpractices.Businessimprovement/benchmarkingsoftwareisavailableonthePotatoCouncil’swebsite:www.potato.org.uk/publications/potato-council-guide-business-improvement

Anyexistingirrigationinfrastructureandproductionsystemwillinfluencethecapacityofthebusinesstochange.Bybeingflexible,smallchangescanbeintroducedandtestedbeforeimplementingmoresignificantchangesbutwherecapitalworksaremoreexpensive,therisksarealsohigher.

Howthewaterisaccessedwillfurtherinfluencetherangeofoptionsavailable.Itisessentialthatgrowersmustallowforthereliabilityofsupply,waterpressure(egtodrivesprinklersorfortrickle/dripirrigationsystems)andanyneedforonfarmstorage.

Anotherfactorthatisessentialtoconsiderislabour.Theavailabilityoflabourwillinfluencethedegreeoftechnologythatisintroducedtothesystemanddecisionsonthetypeofcropgrown.Asnewtechnologiesemergeinirrigation,managementoftenbecomesmorecomplex.Increasedautomationwilloftenresultinanincreaseinthelevelofsophisticationrequiredintechnicalunderstandinginordertogetthebestresults.HealthandSafetyissuesmaymeanaworkforcewithdifferentskills,suchascomputing,arerequired.Askillsauditofstaffandtheexpertiseavailabletothegrowerisagoodexercisetoseeifthereareanygaps.

2.2.1 Cost/benefit analysis of irrigationAnimportanttooltothepotatogroweristoweighupthecostsandtheassociatedbenefitsoftheirrigationsystemandseeifwhatisbeingusedisactuallycosteffectiveornot.AmaindriverforirrigationofpotatoesistheneedtomeetqualitystandardsforCommonscab,particularlyforthepre-packedmarket.Evenminorscablesionscandrasticallyreducethevalueofcrops.ThePotatoCouncilreportChanges to water policy and their effect on the potato industry (TompkinsandClayton,2003)summarisestheimpactofincreasingrestrictionsonwaterabstractionandtheeffectonthecostsofirrigationthathasresultedfromchangesinlegislationandpolicyonenvironmentalprotection.

Farmersaregenerallymostinterestedinmaximisingeconomicreturnssowherewaterisscarce(limiting),theseshouldbemaximisedperunitofwaterapplied(£/m3).InastudyconductedbyCranfieldUniversityin2007,anirrigationcost-benefitanalysiswasundertaken.

Acomparisonofirrigationbenefitslesscosts(expressedas£/m3ofirrigationwaterapplied)providesthefarmerwithanindicativevalueofwaterforthatfieldandhencebesteconomicuse.Inordertoassesstheadditionalvaluethatirrigationprovides,itwasnecessarytoestimatecropyieldforanequivalentun-irrigatedpotatocrop.Thiswasderivedbycropmodellingusinglocalsoilsandclimatedata.

2.2.2 CostsThecostsofirrigationwillvaryconsiderablyaccordingtolocalcircumstances.Thisvariationisdueto:

•Thecroprequirementsforirrigation

•Sourceofirrigationwater(surfaceorgroundwater)

•Theneedforwaterstorage

•Typeofapplicationsystemand

•Thesize,configurationandtopographyoftheirrigatedarea,itsdistancefromandheightabovethewatersource.

AstudybyCranfieldUniversityfoundthatmostirrigationinEnglandisappliedthroughhosereel-gunsystems.Foratypicalhosereelsystemwithoutwinterstorage,capitalcostsareapproximately£2800-£3200perhectareirrigated,thetotalannualcostisestimatedat£500-£600perhectareirrigatedandtheaveragecostperunitofwaterappliedisaround£0.40-£0.45perm3appliednetoflosses(£4.00-£4.50perha/mm).

Winterstoragewilltypicallyincreasetheannualcostsperhectareandthecostsperunitofwaterby50%and130%forunlinedandartificiallylinedreservoirsrespectively.Averagecostsforunlinedreservoirsareapproximately£0.63perm3netoflosses.Artificialliningwouldincreasethistoabout£0.92perm3.Forlargerreservoirstheremaybeeconomiesofscale.

Fixedcostsaccountforover60%oftotalcostsevenfordirectabstractiontohosereel-gunsystems,andover70%withstorage.Themoreefficientsystemsincludingboom,centrepivotsandtricklesystems,haveanevenhigherproportionoffixedcoststovariablecosts.Iffixedcostsarealready‘sunk’,waterconservationmeasurescanonlyhopetorecoupsomeoftherunningorvariablecosts.Totalrunningcostsforhosereelsystemsaretypicallyabout£0.15perm3netoflosses,or£0.12perm3includinglosses,andnotallofthesearedirectlyrelatedtothevolumeofwaterapplied.

Irrigatorsusinghosereel-gunsystemswithanamplewatersupplyandsunkcapitalcostsmighttherefore

17

Section 2


typicallyhopetosavearound£0.10perm3ofwaterconservedbyreducinglosses.Savingswouldbelesswithmoreautomatedsystems.

WaterchargesinEAAnglianRegion2012/2013wereonly£0.0252perm3fordirectsummerabstractionand£0.00234perm3forwinterabstractionandhalfthesearefixedcostsunderthepresenttwoparttariffsystem.Measurestoincreasesupply,suchaswaterharvestingorre-use,willsaveonlythevariablepartoftheabstractioncharges,iearound£0.01and£0.001perm3,ofextrawaterproducedinsummerandwinterrespectively.

2.2.3 BenefitsIrrigationservesmainlytoincreasecropyieldandcropqualityoverandabovethatobtainedthroughrainfedcropproduction.Thesizeofthebenefitdependsoncroptypeandvariety,thestagesinthecropcyclewhenwaterisapplied,thestandardofcrophusbandryandenvironmentalfactors,especiallysoilandclimate.

Forpotatoes,thequalityassurancebenefitsofirrigationaresubstantial.Theyrelatetothewholecrop,notjusttotheextrayieldduetoirrigation.Qualitycriteriaareincreasinglyspecifiedasaconditionofcontractandsale.Failuretomeetqualitystandardscanleadtolargepricedeductionsandpossiblytorejection.

2.2.4 Climate change and droughtClimatechangepredictionsincludelikelychangestowaterresourceavailabilityacrossmuchoftheglobe.Inmanyareaswaterresourcesareexpectedtodecrease,particularlyinsemi-aridareas.Increasesinextremeweatherevents,includingflashflooding,arepredicted,eveninareaswhereoverallaveragerainfallispredictedtodecrease.

Potatoesaremuchmoresensitivetosoilwaterdeficitscomparedtoothercropssuchaswheatandneedfrequentirrigation,especiallywhiletubersaregrowing.Reducedrainfallinmanyareasispredictedtoincreasetheneedforirrigationofpotatocrops.ForexampleintheUKtheamountofarablelandsuitableforrainfedpotatoproductionisexpectedtodecreasebyatleast75%.Aswellasreductionsinoverallrainfall,potatocropsalsofacechallengesfromchangingseasonalrainfallpatterns.

Duetothechangingrainfallpatternsoverthelastcoupleofyears,therehasbeenashortageofirrigationwaterinsomeregionsoftheUK.Ifwatersupplyisrestricted,thequestionthenarisesastowhetherirrigationshouldcontinueonpartofthecroportobeappliedtothewholecropusinglimitedamounts.Alotwilldependonwhichmarketthecropisintendedfor.Irrigationincreasescropyieldbutqualityisoftenofgreaterimportance,becauseacropthatdoesnotmeetthenecessaryqualitycriteriawilleitherfetchalowerpriceorbeunsalabletothetargetmarket.

Irrigated Not irrigatedDifference due to

irrigation

Averaged over 20 years

Yieldt/ha 50 40 10

Price(£/t) 90 66.50 28.50

Revenue(£/ha) 4500 2660 2090

Design dry year

Yieldt/ha 50 36 14

Price(£/t) 175 96 79

Revenue(£/ha) 8750 3456 5294

Source: Irrigation Best Practice: Water Management for Potatoes: A Guide for Growers basford et al, 2005

Example of yield and quality benefits associated with irrigation on a potato crop, on a medium AWC soil in the Fens. 2005.


Section 2

Droughtearlyinthegrowingseasonrestrictsthecanopyexpansionwhichthenhasaknockoneffectonlightinterceptionandyield.Duringcanopyexpansionthecrophasn’treacheditsmaximumrootingdepthsotheSoilMoistureDeficit(SMD)atwhichthereisayieldpenaltywillbelower.Itisoftenstatedthatdrysoilsencouragerootactivitytosearchforwater.However,theoppositeisthecaseandinfactmoistsoilsencouragerootgrowth.Thus,itisessentialthatirrigationtakesplaceatlowerSMDsandearlierintheseasontoencouragerootgrowth(indryconditions).

Indryyears,growershavehadtoirrigatethesoiltominimisebruisingandaidliftingduringtheharvest.Tobeabletodothis,thegrowermustapplyforanextensiontotheirabstractionlicence.TheEnvironmentAgency’spositiononthisisto‘varyyourlicencenow’,ieapplyfortheextensionbeforetheseasonstarts.Moreinformationonhowtodothiscanbefoundat:http://publications.environment-agency.gov.uk/pdf/GEHO1111BUIU-E-E.pdf

2.3 Irrigation planning

Investigationandplanningisessentialpriortoestablishment.Therightsitemustbematchedtotheproductionsystem,cropchoiceandirrigationdesign,withsoiltype,landscapeandthesecurityandsupplyofwater.Asdroughtandtheshiftsinthemarketschange,thenthegrowermustrevisitandrevisetheirplansandthevarietiesgrown.

SITE SUITABILITY. Understand the site. Assess, understand and update information about soil type and the variability, topography, climate, water supply, salinity and depth to groundwater and any site preparation needed.

Thebasicsitecharacteristicswilldictatethesuitabilityofthelocationforirrigation.Factorsinclude:

•Soiltype:Asoilsurveyisrecommendedtoaidplantingdecisionsandthedesignoftheirrigationsystem

Sou

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Ahm

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19

Section 2


Constraintssuchassalinityandacidityshouldbenotedforremediation,specialmanagementordesignatedas‘notsuitable’.Thewaterholdingcapacityofthesoilshouldbedeterminedasaguidetoirrigation

•Slope:Surfaceirrigationrequiresgentlyslopingandconsistentgradientswhereastrickle/dripcanbeusedonsteeperground

•UnderlyingGeology:Siteswithpoordrainageandshallowwatertablesaremoresusceptibletosalinityandrisinggroundwater

•Climate:Rainfall,temperatureandwindwillbeaguideonhowmuchirrigationisneeded.Theincidenceoffrosts,hail,heatwavesandstormsshouldalsobeconsidered.

PRODUCTION SYSTEM AND CROP CHOICE. Select crops that are suitable for the location. The history of previous irrigated potato crops should be noted. Decide if you are aiming for high yield, high quality or both.

2.3.1 Water characteristicsThequality,quantityandreliabilityofwatersupplyhastobefactoredintodecisionsaboutthecropchoiceandirrigationsystem.

•Quality:Salinitywilllimittheamountofpotatoesthatcanbegrownifatall.Contaminantssuchassediment(especiallyafterflooding)anddissolvedsaltsmaynecessitatefiltrationorchemicaltreatment

•Quantityandavailability:Theamountofwateravailableatdifferenttimesofyearwillimpactontheareaofcropandvarietygrowntobeirrigated

•Securityandvariability:Thereliabilityofwatersuppliesisessential.Ifthesupplyisvariablethenit’simportanttoplanasystemthatisflexibletocoverthedryerseasons

•Supply:Growersneedtoknowhowquicklythewatercanbedeliveredandtheconsistencyofsupplytoalloweasiermanagement

•Regulations:Growersneedtoapplyfortheappropriateabstractionlicencetofulfilltheirneeds.

Planningforimprovementalsomeanstryingtofindsometimetoassessperformanceandtorecordareaswhereadjustmentsorimprovedpracticecanmakesavingsorleadtomoreefficientperformance.Optimisingwaterusetobenefitcrops,otherwaterusersandtheenvironment

meanthatgrowershavetoincreasinglyjustifytheirneedforwatertodemonstratethatitisbeingusedefficiently.Matchingthepotentialcroprequirementswithasuitablesourceofwaterattherighttimeisatthecoreofanyplanforwateruse.

2.3.2 Water requirements and reservoirsAshasalreadybeenmentioned,waterrequirementwillvarywithsoiltype,climate,cropandthegrowingsystem.Storingwateron-farminreservoirshasbecomeincreasinglyimportantforbusinessesthatdependonirrigationtosupplyhighqualityproduce.Recentdroughtsuchastherecent2011-2012growingseasonandthelongtermthreatofclimatechangehaveonlyincreasedconcernsaboutthereliabilityoffuturesuppliesforirrigation.

Thebenefitsofareservoirinclude:

•Securityandadegreeofflexibility,bybalancingsupplyanddemandandtakingadvantageofgroundwaterandhighriverflowswhenwaterisplentiful

•Reducedenvironmentalimpactofdirectabstractionduringlowflows

•Reducedriskassociatedwithpotentialwaterconflictsinthecatchment

•Takingadvantageofgroundwaterandhighriverflowswhenwaterismoreplentifulandreliableandstoringitforsummeruse.HoweverHandsoffflowie.abstractionprohibitedorSection57restrictionswhenabstractingcanstillapplyifwaterisextremelyscarce.Undersection57oftheWaterResourcesAct1991,theEnvironmentAgencycanreduceorstopsprayirrigationtoprotecttheenvironment.Thisisalastresortrestriction.Moreinformationcanbefoundat:http://publications.environment-agency.gov.uk/pdf/GEHO0412BUNH-E-E.pdf

•Chargesforabstractionduringthewintermonths(NovembertoMarch)areatenthofthecostofsummerabstractions.

Mostreservoirsareclaylinedandconstructedwheretheneedforcostlyprovisionforpeakfloodflowsthatrequirelargeoverflowarrangementscanbeavoided.Wherenosuitableclayisavailableageotextileunderlayneedstobeusedtoprotecttheartificiallinerfromstonedamage.

Reservoirsthathaveacapacityof10,000m3ofwaterstoredabovethelowestsurroundinggroundlevelnowcomeundertheFloodandWaterManagementAct2010


Section 2

andtheReservoirsAct1975.MoreinformationcanbefoundontheEnvironmentAgencywebsite:(www.environment-agency.gov.uk/business/sectors/118421.aspx)thismeans:

•Onlythosereservoirsassessedasahigherriskaresubjecttoregulation

•Allundertakerswithreservoirsover10,000m³mustregistertheirreservoirswiththeEnvironmentAgency

• Inspectingengineersmustprovideareportontheirinspectionwithin6months

•Allundertakersmustprepareareservoirfloodplan

•Allincidentsatreservoirsmustbereported.

ThereservoirsectionsoftheFloodManagementAct2010are,however,dependentupononthedevelopmentofsecondarylegislation(regulationsandorders)beforethelawcanbefullyimplemented,soitislikelythatmanyoftheprovisionsintheActwillnotcomeintoforceforsometimeyet.Dependingonscale,siteconsiderationsandtheneedforlining(whichcanaccountfor60%ofthetotalcost)costscanvaryfrom£2-£4m3.

CranfieldUniversityiscurrentlydoingsomeR&DintocollaborativeapproachesandreservoirsforDefrawiththeresultsduein2013.FurtherinformationcanbefoundontheprocessofconceptthroughtobuildingreservoirsintheEnvironmentAgency/CranfieldUniversitypublication

Thinking about an Irrigation Reservoir? A guide to planning, designing, constructing, and commissioning a water storage reservoir.

2.3.3 The need for water and how much to supplyThreemainfactorsaffectcropwatersupply:

•Thelevelofwaterdemand,expressedasevapo-transpiration(ET)

•Theamountofwaterinthesoil

•Theabilityoftherootsystemtoextractwaterfromthesoil.

2.3.4 Evapo-transpiration (ET)Thedemandforwaterbyaplantisreferredtoasevapo-transpiration(ET)andconsistsoftranspirationfromplants(cropET)andevaporationfromthesoilsurfaceandair(ET0).

ETisusuallycalculatedfrommeteorologicaldataandisexpressedasthedailyrateofwaterusedinmm.ETdataisavailablefromsourcessuchastheMeteorologicalOffice,theinternet,andbyusingin-fieldoron-farmETgaugesandcomputerisedirrigationschedulingprograms.

Source: Calculating Readily Available Water: Note 543 Newman, H 2012

Field capacityWilting point

Saturated soilDry soil

Refill point

No

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C

rop growth slows Best crop growth Crop growth slo

ws

RAW

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Section 2


2.3.5 The water held in the soilTheamountofwaterthatsoiliscapableofretainingdependsonitstextureandstructure.Inasaturatedsoil,allspacesbetweenparticlesarefilledwithwaterbutdrainageprogressivelyremoveswaterfromthelargerporesbetweenparticlesfirst.Afterafewdaysdrainage,theonlywaterleftisthatcontainedinporessufficientlynarrowthattheforcesholdingitaroundthesoilparticlesareinequilibriumwithgravity.

Thisisknownas‘fieldcapacity’(FC)andrepresentstheupperlimitofavailablewaterinthesoil.Asdrainageandcropextractionproceed,apointisreachedwhentheplantcannotextractanymorewater(thepermanentwiltingpointorPWP).ThesoilwateravailableforthecropistheamountheldbetweenFCandPWPandisdescribedastheavailable water capacity (AWC):thusAWC=FC–PWP.

SandysoilsholdrelativelylittlewaterastheirtextureallowswatertodrainfreelydownthesoilprofileandthesesoilshaveasmallAWC,however,bytheadditionoforganicmatter,theAWCcanbeimproved.Heavierloamandclaysoilsareequallyporousbyvolumebutbecausethisporespaceiscomposedofmuchnarrowerpores,

theyareabletoretainmorewateragainstgravity.ThesesoilshavealargerAWC.

Readilyavailablewater(RAW)isthewaterthataplantcaneasilyextractfromthesoil.RAWisthesoilmoistureheldbetweenfieldcapacityandanominatedrefillpointforunrestrictedgrowth.Inthisrangeofsoilmoisture,plantsareneitherwaterloggednorwater-stressed.

2.3.6 Typical soil Available Water Capacity (AWC)AnestimateofAWCforacroprootingto700mm,with330mmoftopsoiland370mmsubsoil(soiltypesandysiltloam)wouldbecalculatedasshowninthetableabove.

DepletionoftheAWCbelow50%wouldresultinalargeyieldpenalty.Ifconditionsarehotanddrytheevapo-transpirationrateswillbehighandasignificantyieldpenaltywouldoccuratlowersoilmoisturedeficits.Thisneedstobetakenintoaccountwhenschedulingirrigation.

Topsoil AWC % (readily available %) Subsoil AWC % (readily available %)

Siltloam 23(15) 22(14)

Mediumsandysiltloam 19(11) 17(11)

Clayloam 18(11) 16(10)

Mediumsandyloam 17(11) 15(11)

Loamymediumsand 13(9) 9(6)

Loamycoarsesand 11(7) 8(6)


Soil horizon Depth AWC% Available water

Topsoil 330mmx 19%= 63mm

Subsoil 370mmx 17%= 63mm



Section 2

2.3.7 Soil Moisture Deficit (SMD)SoilMoistureDeficit(SMD)isanindicatorofthemoisturestatusofthesoilandisthekeymeasurementusedinirrigationscheduling.

Whenwaterislostfromthesoilbyevaporationandtranspiration,watercontentisreducedandaSMDdevelops(belowFC).Waterfromthelargerporestendstobeextractedfirst,becauseitisheldlesstightlybythesoil.Asthisprocesscontinuesonlytightlyretainedwaterremainsandeventuallytheplantclosesitsstomatatoreducewaterloss.Thepointatwhichthisoccursisknownasthe‘criticalSMD’.Closedstomataresultsinlowerratesofphotosynthesisandpotentiallyloweryields.Ifthesoilisallowedtodrybeyondthe‘criticalSMD’,therateofwateruptakedecreasesandplantgrowthiscompromised.

TheSMDshouldbemonitoredandirrigationtriggeredbeforeitreachesacriticallevel.TheamountofirrigationthatshouldbeappliedatanyonetimeislimitedbythecurrentSMDaswellastheinfiltrationrateofthesoil,ieirrigationshouldnotbeappliedatafasterratethancanbeacceptedbythesoil.Forexample,thereisnobenefitfromapplyingmorethan20mmofwateratanSMDof20mm.

Howeverbyapplyingless,ie15or18mm,thisallowssparecapacityinthesoilshouldrainfalloccurafterirrigationhasbeenapplied(thoughamountsbelow18mmareconsideredimpracticalforrainguns).Irrigatingwithmorewaterthanthesoilcanacceptisnotonlyawasteofresourcebutlikelytocauserunoffanderosion.

IRRIGATION AND DRAINAGE SYSTEM. Match the irrigation methods, crop choice and site characteristics to design a system for optimal water use efficiency. Reuse water where feasible.

2.3.8 Irrigation system optionsIrrigationsystemsincludesurfaceflow,sprinklersandvariousformsoftrickle/dripirrigation.Eachhasitsownspecialapplications,meritsandlimitations.

Surfaceflow(floodorfurrow)irrigationisveryrarelyusedintheUKandtendstobeusedincountrieswherethegeneralinfrastructureislow.Thistypeofirrigationisbestsuitedtoheavysoilswithlimiteddrainageandtheapplicationoflargevolumesofwatertolargeareas.Energycostsarelowasthisoptionreliesongravitytomovethewater.

Sprinklertypeirrigationsystemsrangefromrainguns,linearandcentrepivots.Largeareascanbewateredand

theyarereasonablypreciseinhowtheydeliverwater.Theyrequirewaterunderpressuretooperateandconsequentlyenergycostsarerelativelyhigh,asaretheinfrastructurecosts.

Driportrickleirrigationallowsveryprecisewaterdeliverytoplantsandtheirroots.Theycantobeusedinavarietyofsituations.Thisoptionrequiresapressurisedwatersupplywhichcanbeexpensivetoinstallbuttheyareveryefficientonwateruse.

2.3.9 Design of systemTheirrigationsystemchosenmustmatch:

•Thewatersupplyanddeliverysystem

•Thesoiltypeandtopography

•Thecroprequirements.

Automation,maintenanceandfittinginwithotherfarmingoperations(egplantingandharvesting,etc.),alongwithpriceandoperatingcostsareotherfactorsthatneedtobeconsideredwhendesigningasystem.

Theirrigationsystemneedstosuitthemanagementskillsandthegoalsoftheirrigator.Forexample,apoorlymanagedtrickleirrigationsystemcanbelessefficientthanwell-managedfloodirrigationontheappropriatesoils.

Mostwelldesignedsystemsaimtoachievehighlevelsofuniformityindeliveringwaterandtypically85-95%consistencyoverafieldisrealised.Thismeansthatthepotatoplantsarewateredevenly,eliminatinganygapsthatwouldlowerthewateruseefficiency.

Itisimportanttomatchpumpsandmotorstothesizeofthejobandtomaintainthesystemregularlyasenergyconsumption(iecostofdiesel)hasamajorimpactontherunningcostandgreenhouseemissions.

2.3.10 Uniformity of application across the crop areaIrrigationshouldbeappliedasevenlyaspossibletoensureauniformcropresponse.Variableapplicationsoftenleadtoover-wateringofsomeareaswhileotherpartsreceiveanadequateamount.Thiscanalsoleadtolowercropyieldandpoorerquality,aswellascreatingpondingonthesurfaceandpossiblerun-offproblems.

Uniformityisverydifficulttovisuallymeasure,soisoftenoverlooked.Applicationuniformitymustbecheckedperiodicallytoidentifyanyspatialvariabilitythatmayhavearisensincethelastcheck.Thenthesetup(eglane

23

Section 2


spacing,etc.)andoperation(egwaterpressure)ofthesystemcanbecheckedandimprovementsmadeasnecessary.

Uniformityisinfluencedbythreemainfactors:

•Correctoperationofequipment(pressure,trajectoryandsectorangle)

•Lanespacing–theareaofwettedoverlap(howfarthewaterisbeing‘thrown’)

•Localweatherconditions,includingwindspeedanddirectionduringirrigation.

2.3.11 Applying irrigation water efficientlyMostgrowers(approximately70%)stilluseraingunsfittedwithhosereelsbecausetheyareflexible,robustandfitinwellwiththerotationalpatternofcroppingintheUK.

2.3.12 Getting the best from rain gunsItisvitalthatraingunsareoperatedattheirdesignpressure,providingagooddistributionofmanysmalldropletsthatwilllandgentlywhichpercolatethroughthesoil.Ifpressuresaretoolow,largerdropletsareformed,andcancausesoilcappingorerosion.

Allraingunnozzleshaveadesignpressurethatislinkedtoawaterthrowradius.Thiscanbefoundininstructionsprovidedwiththemachine.However,asageneralguide,thepressureneededattheraingun(notthehose-reel)willbeapproximately4.5-5bar.Aspigotisusuallyfittedontheriseroftherainguntrolleysothatapressuregaugemaybeattached.

It is worthwhile fitting a gauge here to ensure that the correct pressure is being achieved at the rain gun.

Thereisalwaysapressuregaugeprovidedontheintaketoahose-reelandthisshouldalsobecheckedtoensurethatwaterpressureatthemachinematches

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themanufacturersrecommendations.Thisvaluevariesdependingonthemachineandmaybebetween8-10bar,thoughsomemachinesmayhavehose-reelconnectionpressuresofaslowas5.5bar.

2.3.13 Problems that may occur with rain guns

2.3.13.1 Low PressureThemainreasonsforlowpressureare:

•Rain gun/nozzle size:incorrectselection:toolargewillallowtoomuchwateroutflowandnotpermitadequatesystempressurerisetoachievethedesiredtrajectory.Applyingwaterthoughraingunsatamountsgreaterthan25mmperpassmayaggravatetheoverallpressure/flowbalancewithinthesystem,causinginstabilityofthemachine,whichmayinturncauseproblemsduringreelwind-in

•Pipe size:Innarrowborepipes,frictionalpressurefromthepipewallreducesflowrateinthepipeforanygivenpumppressure.Tomaintainflowratestherefore,pumppressureshavetobeincreased

•Pipe lengths:Aslengthincreases,morepipeisincontactwithwaterandthusmoreenergyisneededtooffsettheincreasedfriction.Thisisoftenaproblemwith‘new’fieldsfurtherawayfromthepumpingsource

•Land contours:Every10mriseinthelandisequalto1barpressurewithinthepipe.Thismustbeconsideredwhenlayingoutpipesforseasonaluseorwhenplanningtheroutingofanysystem.Pressureis,ofcourse,increasedwithinthepipeforadownhillslopeinthelandsurface(anextra1barfora10mfall)

•Pump:incorrectspeed:poorpumpselectionorworncomponentscanallresultinreducedwaterpressure.Excessivesuctionliftatthewatersourcecanalsolimitpumpperformance.

2.3.13.2 Pipe sizes and lengthsEnergyislostwithindistributionpipeworkduetothefrictionofwaterpassingthroughitbutagooddesignshouldallowfornomorethan10%ofthepumpenergytobelostinthisway(inadditiontotheequipmentconnectionpressureandanyliftsinvolved).

•Selectthelargestinternaldiameterpipe(thatisconsistentwithcostandotherpracticalfactors)tominimisefrictionlossesandreduceenergyconsumption

•Examplesoftheamountofenergyused(expressedasheadlosses)attwoflowratesandforthreeinternalpipediametersareshownintheTablebelow.Itcanbeseenthattheenergydoesnotrelatelinearlytopipediameters,whichmeansthatforarelativelymodestincreaseindiameter,thepressurelossdropsconsiderably.Thereisonly15-20%reductionin

PRESSURE LOSS PER 100M PIPE

Pipe internal diameter (mm) Water flow 15 litre per second Water flow 30 litre per second

100 2.8 10

150 0.5 1.5

200 0.12 0.3

Note:10metrepressure=1bar(1atmosphere).Allpipessizesshouldbecheckedtomakesureitistheinternaldiameterwhichisusedforcalculations.

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pressurelossfora50%increaseindiameter(from100to150mm),buta95-97%reductionforadoublingofdiameter(from100to200mm).

•Mostgrowershavetoacceptsomeconstraintonwherecropsaregrownandhowwaterisdeliveredtothefield.Goodplanningshouldensurethatthefurthestlocationswillbeservedbythelargestaffordablediameterpipe

•Blockcroppingwillconcentratethedemandonthedistributionsystem,sooperatorsneedtoconsiderwhetherpipesizeislargeenoughforthedemandsofsuchalayout.Aringsystemdesignallowswatertoflowwithintheringcircuitineitherdirectionatlowerflowrateswithinthepipe.Thisreducesenergyconsumptionduetofrictionandprovidesmorepumpenergyfortheirrigationequipment.

2.3.13.3 PumpsAllpumpshaveanoperating‘window’intheiroriginalspecificationtooptimiseflowrate,pressure,operatingefficiencyandpowerinput,thisisdesignedaroundafixedoperatingpumpspeed.

•Checkthepumpisn’toperatingoutsidethiswindow,tryingtosupplyavolumeofwaterinexcessofitscapacity,tomeettheneedsoftoomanyhose-reelsornozzles.

2.3.13.4 Lane spacingAllhose-reel/rainguncombinationswillworkatvaryinglanespacings.Thisislistedwithintheequipmentinstructions.IntheUKalanewidthof72miscommonlyselected,whichallowstherainguntrolleyorsledgetofollowpairsofpotatorowsoronebed.Littledamagetocropsisnormallycaused,thoughincreasedattentionisbeingpaidtothispotentialproblem,especiallyforhighvaluecrops(egwithoffsetequipment).

Othergrowersnowleavetheserowsunplanted,acceptingtheproductionlossisbalancedbythereducedamountofgradingoutrequired.

• It is critical that the lane spacing remains unaltered during irrigationandalladjustmentstotheequipmentpermitcorrectoverlapofwaterfromlanetolaneat72m.Generallythismeansthatthewatershouldhaveathrowofapproximately43m.

2.3.14 Checking water distribution•Checkinthefieldusing5litrecatchcans,spacedat3m

intervalsacrossthefullwettedarea,andcoveringtheoverlapofadjacentpulls.Measurementsofthevolumeofwatercollectedateachpointcanthenbeplottedtoshowtheareasofnon-uniformityonagraphicalimage

•AvaluecalledtheCoefficientofUniformity(CU)iscalculatedfromthesemeasurements.Thelargerthefigure,themoreeventheapplication–thoughmuchhigherthan90%wouldnotbeexpectedinthefield

• Ifgunpressureispoorthenthepatternshowninthechartabove,takenfromafieldstudy,mayresult(seethechartsabove).ThispoordistributionwillresultinagreatercumulativedisparityintheSMDifrepeatedovertime

•Acorrectlysetupraingunwithcorrectoperatingpressureattheguntomatchthechosenlanespacing,producesamuchbetterperformance

AsuitableCUtargetforraingunsis80-85%.Simplecheckstouniformity–andtheamountactuallyapplied–maybefoundbyusinganumberofsimpleraingauges,or‘catchcans’.Resultsgreaterthan75%areacceptablebutlowerfiguresshowscopeforimprovement.

0

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Poor rain gun overlap due to low pressure 72m line spacing, CU = 63%

Good rain gun uniformity at correct pressure 72m lane spacing, CU = 90%


Section 2

2.3.15 Calculating the Coefficient of Uniformity (CU)TheCUcanbecalculatedbycarryingoutasimplefieldinterceptionofwateracrossanirrigator’swettedarea.Thisisdoneoutbyputtingout‘catchcans’–normally5litrepaintpotsat3mintervalstoensurethatthewholedistributionisintercepted.

Thevolumeofthe‘can’mustbeknown,sothatthe‘depth’ofwatercollectedcanbecalculated.Forexample,acanwithanopeningof20cmdiameter(radiusofr=10cm)willhaveanareaof314cm2(area=∏r2)(∏=3.142)andso10mmofrainwillgiveavolumeof314mlinthecan.Thereforethevolumeof‘rain’inthecan(measuredasmlorcc)shouldbedividedby1/10ofthearea(cm2)toobtainthedepthofraininmm.

Fora72mraingunlanewidth,thewettedarea(assumingnosidewindeffect)willprobablybearound85-90minwidth.Thusaround30canswillberequired,placedatrightanglestotheirrigatortraveldirectionasitisdrawnacrossthefield.Oncetheirrigatorhaspassedoverthelineofcans,thevolumeofwaterineachcanismeasuredusingagraduatedmeasuringcylinderandthevolumerecordedforeachcan.Thevolumepercanmustthenbecalculatedintoadepthpercanbydividingbytheknowncollectingarea(openingsize).

TheCoefficientofUniformity(CU)asapercentagecanbecalculatedusingtheformula:

CU = (1 – (∑ (x – xm)) / y) x 100

where,∑meansthesumofthefollowingeg∑x=x1+x2+x3...xnn=numberofcansx=depthof‘rain’foundineachcan(mm)xm =meandepth(mm)forallcans(xm=∑x/n)y=totalofdepth(mm)fromallcans(y=∑x)andx-xmisalwaysexpressedasapositivevalue(eg if x=5 and xm=6 then 5-6=1 not –1)

Fewercanscanbeusedbuttheresultwillbelessaccurate.

2.3.16 Mitigating for wind effectsTheirrigationseasonintheUKwillmostcertainlyincludemanydaysofwindyweather,whenwaitingforstillconditionsmaynotbefeasible.Toreducetheeffectofwindonuniformity,farmersshouldaimto:

•Settheraingunsectorangleat210ºormore(ratherthanthenormal180º).Thisallowstherainguntocovertheendsofthecycleforlonger,depositingmorewater

attheedgesofthelanewidth.Anyriskofpossibleoverwateringismorethanoutweighedbybetterdistributioninwindyweather

•Makethemostoftheopportunitytoirrigateatnight,whenthemeanUKwindspeedisabouthalfofthatfoundduringtheday

•Plantoincludemostofthelonger‘pulls’atnight,wherepossible,sothatagreaterareareceiveswatermoreuniformly

•Wherenewer‘variableangle’raingunsareused,lowertheangle(toaround15ºfromthehorizontal,comparedwiththenormalangleofaround22º)whentheweatheriswindy.Incalmconditionsthesegunsmaybeincreasedtoa25ºangletomaximizethrow,thusachievinggoodoverlap

•Onexposedsites,betteruniformitycanoftenbeachievedbyadoptingalanespacingnarrowerthan72m.Thismay,inturn,affectotherfarmoperationssuchassprayingandfertilisingbutoften60or66mspacingcanofferimprovedapplicationuniformity.

2.4 Alternatives to rain guns

2.4.1 BoomsBoomequipmentcanoffermoreevenwaterdistributionthanaraingunandregularlyoperatesataCUof90%whensetupcorrectly.Thisisbecauseaboomcarriesalargenumberofsmallnozzlesorsprinklers.Thetrajectoryfordropletstothesoilisshorterandagoodoverlapalongtheboomprofileisachieved.Boomswillgenerallyproducealargernumberofsmalldropletsthatcreatelessdamagetosoilandplants,mainlyduetothedropletshavinglessenergy.

Whencomparedtoraingunuse,boomsaregenerallymoreefficientandtendtoresultinmoreuniformandhigherqualitycropswithcleanerfoliage.However,boomsdonot‘throw’waterfromtheunitasfarasaraingunandthisreductioninthewettedfrontastheboommovesmeansthatthesoilmustacceptthewateroverashorterperiodifoperatedatthesameforwardspeedandapplicationrate.Onafewsoiltypesthiscanbeaproblem,suchassoilwithahighsiltcontentorwhereslopesaresignificant,ieover5%.

Obstructionssuchaspolesortreesarechallengestoboomusage,asarefieldsthatareoddlyshaped.However,itisworthcheckingjusthowmuchofthefieldareaisaffected,asoftentheproportioncanbequitesmall.Inaddition,boomscanbesuppliedwithacentral

27

Section 2


raingunsothatwhereobstructionsarefoundtheboomsmaybefoldedandtheraingunused.

Thecostofboomequipmenttendstobemorethanforaraingunbutovera10yearlife(includingextralabourcosts)theextracostperhectarecanberecoupedincropqualityandyieldimprovements.Inaddition,boomstendtooperateatalowerpressurethanrainguns(around3bar),whichresultsinenergysavingsandmoreefficientwateruse.

2.4.2 Sprinkler and drip irrigationMobilesprinklersystemsrequiringhandmovementbetweenapplicationsarenotverycommon.Theycanbeusedonsmallareasieawkwardfieldextremities,vegetablesorhardyornamentalstock.‘Solidset’orfixedsprinklersystemsaremorecommon,astheyalmosteliminateseasonaldamagetothesoilorcropandprovidegooduniformity.Therecentavailabilityofsinglemovingpartsprinklerswithlateralstypicallyspacedat18mandwithgooduniformitycharacteristics,mayheraldarenewedinterestinsprinklers.

Driportrickleirrigationsystemsnormallyplacethewaterdirectlyintothesoilorontothesoilsurface,givingminimalriskofrun-off.Alldripsystemscanaccommodate

growingtechniqueswithlittleornomodificationandfieldlengthsarenotnormallyaproblemduetotheavailabilityofpressurecompensatingsystems.Dripirrigationinvolvingsoilsurfaceorburiedpipesisunaffectedbywindand,inaddition,placeswaterclosetotherootingzone(limitingevaporativeloss).AcorrectlydesignedandinstalledsystemshouldeasilyachieveaCUabove90%.However,thesesystemsareoftenmoresusceptibletopoormanagementduetothecomplexityandthepotentialblockagesofindividualdrippers,withconsequentimpactsonuniformityandthecostandpracticalissuesofpipeinstallationandretrievalcurrentlychallengeitsmorewidespreadadoption.

2.5 Irrigation techniques

Irrigationsystemsthatalloweachnozzletoapplyvariableratesofwateraccordingtosoiltypeandmoisturedeficitarehelpinggrowersuselimitedwatermoreefficiently.Irrigationiscentraltothesuccessofmostpotatocroppingsystems.Withlowrainfallduringthegrowingseasonandthepotentialofwindsremoving5-8mmofmoistureaday,byapplyingwaterfarmershavebeenabletotakeunreliablelowmoisture-holdingsoilsintousefulproduction.However,wateruseisrestricted,whichmeansfarmersneedtobeefficientinusingit.


Section 2

Thatrequirement,plustherealisationthatsoiltypescouldbeextremelyvariableunderlargeirrigationsystems,suggestedthatvariablerateirrigationcouldhelp.Usingelectromagneticmappingtoanalysesoiltypeunderirrigationsystems,creatingzonesinwhichsoilmoistureprobesareplacedthatwirelesslytransmitmoisturedeficitinformationfromtwodepthsbacktoacentralbasestation.Itgivesreal-timemoisturemonitoringaccessiblethroughawebsiteandtheinformationcanthenbeusedtoproduceirrigationmapsfortheamountofwaterneededtobeappliedineachzone.Thewaterrequiredisthenappliedusingavariablerateirrigationsystemwhichindividuallycontrolseachsprinklerheadtoapplythecorrectamountofwater.

Instudies,farmsusingthissystemhavesavedupto20%water,withnolossinyield.Withawatersavingandthesameyield,thereisanincreaseinwateruseefficiency.Measurementsontwoboomsusingwatermeterssuggestedasavingofaround12litres/second.Potentiallythewholesystemcouldbeautomatedtoapplywateratadesignatedsoilmoisturedeficit.FurtherinformationcanbefoundinthewaterwisedocumentpublishedbytheEnvironmentAgency:http://publications.environment-agency.gov.uk/PDF/GEHO0307BLVH-E-E.pdf

2.6 Drainage

Excessirrigationwaterwilldrainawaybelowthecrop,flowoffassurfacewaterandpotentiallywashawayridgesandbedscausinggreeningofthepotatotuber.Ifdrainageisimpededbelowtherootzonethentheremaybeapossibilityofwaterlogging,salinisationandtheeventualinstallationofasub-surfacedrainagesystem.Thedesignofdrainagesystemsismucheasierifyouhaveanunderstandingofthesite’ssoilandgeology.

Ifdrainagewaterisofsuitablequalityitcanbeharvestedandre-usedforirrigation.Byre-usingthewater,theoverallwateruseefficiencyisimproved,savesnutrientsthatwouldotherwisebelostandreducesthecontaminantsreachingwatercourses.Moreinformationondrainagecanbefoundat:www.ofwat.gov.uk/future/sustainable/drainageandwww.environment-agency.gov.uk/business/sectors/136252.aspx

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Section 3

Irrigation management

29

Irrigation requires regular decisions about when to irrigate and how much. These decisions must balance the availability of water with the needs of the crop, the capacity of the system to deliver the water, how, where and when required.

3.1 Water benchmarking

Thefirststepinirrigationistodevelopawaterbudget.Thebudgetcomparesthecroprequirementforwaterwiththewaterthatisexpectedtobeavailable.Intimesofdroughtthisisacrucialtoolandcanbemodifiedifthecircumstanceschange.Budgetscanbeusedonanannualbasisorbrokendownintomonthlyintervals

Itisessentialthatthebudgetallowsforallthecomponents,includingallpotentialwatersources(rainfall,irrigationandre-use),theinitialstoreofwaterinthesoilandlossessuchasevaporationfromreservoirs.Aswellastheplantrequirement,drainagealsoshouldbefactoredin.

3.2 When to start irrigating

Startdatesforirrigationhavebecomeearlierinthelifeofthecrop.Themaindriverforthishasbeenqualityandthecontrolofcommonscabinboththepre-packandprocessingsectorswheretolerancelevelshavemarkedlydeclined.

Irrigationshouldbetargetedtobeginshortlyafteremergenceandnomorethan15%cropcover,toensurethattopsoilisclosetofieldcapacitybythetimetuberinitiationoccurs.However,thereisariskofnitrogenleachingfromthesoil,particularlyiftheweatherturnswet.Withlittlegroundcover,evapo-transpirationratesarelowandtheriskofleachingwillbehigh,withsoilsatornearlyatfieldcapacity.IfirrigationneedstostartearlierthantheabstractionlicenceallowsthenitisessentialthattheEnvironmentAgencyiscontactedasearlyaspossible(03708506506)sothatchangestothelicencecanbemade.

3.3 How much water and when?

Around40%ofgrowersthatirrigatestilldonotuseanyformofscheduling,whichshouldformthebasisofplanningwateruseduringtheirrigationseason.Itwouldbeunwisetorelysolelyonschedulingwithoutexaminingsoilinthefieldbutequallybasingirrigationdecisionssubjectivelyongutfeeling,whattheneighboursdo,experienceorwalkingthecrop,willnotensureoptimumwaterapplicationorcropresponse.

Theaimofschedulingistoapplythe‘rightamountofwaterattherighttime’andthreebasicapproachesareusedeitherontheirownorincombination:

•Calculatingcropwaterrequirementsbasedonclimateandevapotranspiration

•Monitoringsoilmoisturelevelsintherootzone

•Monitoringtheplantsthemselves.

Thekeyistousearangeoftoolsandindicators,whilestillkeepinganeyeonthebasicssuchasweatherforecastsandvisuallyinspectingthecrop.

3.4 Soil moisture monitoring techniques

Optimisingtheuseofwaterforbothcropsandtheenvironmentoftendependsonsomeonerecordingrainfall,checkingequipmentandschedulingtheirrigationequipment.Arangeofsophisticatedtechniquesandtoolsareavailabletomeasuresoilwatercontentandscheduleirrigationtoassistinoptimisingwater,cropyieldandqualityandenvironmentalcare.

Thereareseveralsoilmoisturemonitoringmethods,thatcanbeusedbasedondifferenttechnologies.Thetwobroadcategoriesaredirectmethodswhichusetechniquesformeasuringthesoilwatercontentortensionandindirectmethodswhichrelyonenvironmentalmeasurementstoestimatecropwaterloss.


Section 3


Section 2

30

Section 3

3.4.1 Direct methodsThisequipmentmeasuressoilmoisturedirectlyanddependsonthesitingofequipmentatpointsthataretypicaltothesoiltypeandirrigationapplied.Variationsinthesoiltextureortheamountofwaterappliedacrossthefieldoftencausesdifficultiesininterpretingdata,thoughitisnormaltohaveanumberofmeasuringpointstoovercomethis.

3.4.1.1 Neutron probesThistechniqueisbasedonfastmovingneutronscollidingwithhydrogenatomsinwaterandslowingdown.Theneutronprobehasbothanemitteranddetectorwhichisusedtocounttheneutronsslowedfollowingcollisions

withthehydrogenandenableanestimationoftheamountofwaterinthesoil.

Afterthepotatocrophasbeenplantedholesaredrilledintheground,usuallythreeperfieldandaluminiumtubesinserted.Atregularintervalsduringthegrowingseason,theneutronprobeislowereddownthetubesandreadingstakenatvariousdepthstoproduceaprofileofsoilmoisture.

However,thetechniquehaslimitationswhenusedforschedulingirrigation.Theprobeneedstobecalibratedwhenthesoilisatfieldcapacityandoftenpotatofieldsdonotnaturallyreturntofieldcapacityfollowingplanting,soanestimatewouldhavetobemade.Anymeasurement

When to irrigate decision tree.

Irrigate Delay irrigation

Monitor soil moisture

Does soil monitoring indicate it is time to irrigate?

Will crop yield or qualitybe seriously reduced if irrigation is delayed?

Will water supply be adequate for remainder

of growing season

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Section 3

ofsoilmoisturebyneutronprobesonlyrelatestotheareaimmediatelyadjacenttotheaccesstube.WhereirrigationisappliedunevenlyasinglepointreadingisoflimitedusewhentryingtoaccuratelymeasureSMD.Thisproblemcanbereducedtosomeextentbytakingreadingsfromseveralareasofthefieldstoprovideamorerepresentativepictureofthesoilmoisture.Thetechniquealsodoesnotworkwellclosetothesoilsurface,especiallyifthesoilprofileisdry.

A licence is required to use a neutron probe due to the radioactive source.

3.4.1.2 TensiometersThesearerelativelycheapinstrumentsthatmeasurethetensionofthewaterheldinsoil.Thegreaterthetensionthedrierthesoil.Themeasurementisusefulasitdirectlyrelatestothecropuptakeandabilitytoextractwaterfromthesoilatthetimeofthereading.Thetensiometerconsistsofaporousceramiccupfilledwithwater,placedinthesoilandattachedtoanuprighttubeofwaterwithavacuumgauge.Assoildries,waterisdrawnoutofthecupcausingavacuuminthetube.

Tensiometersareusedinpairs.Onesitedintheupperthirdoftherootzoneandtheotherinthelowerthird.Irrigationtimingcanthenbedeterminedbyreferencetothesoiltensionsmeasuredonthevacuumgauge.Thesystemaimstoallowtheapplicationofwaterbeforecriticaltensionisdetectedintheupperthirdoftherootzone.Thelowersitedtensiometerhelpstodeterminehowmuchwaterisneededtore-wetthesoilprofile.

Themainlimitationsoftensiometersare:

•Theyonlyprovidepointmeasurementsofthesoilwater

•Theyrequirein-fieldservicingduringthegrowingseason

•Theyprovidelittleadvancewarningofwhenirrigationisneededsoplanningaheadasregardsequipmentandwhereit’sneededcanbeanissue.

3.4.1.3 Capacitance probesTheseprobesconsistofanelectrodeconnectedtoanoscillatorcircuit.TheyareinsertedverticallyintothesoilwithinaPVCtubeatarangeofdepthswithinthesoilprofile.Asignalissenttotheprobeandthereturningsignalisalteredbythewatercontentofthesoil.Aftercalibrationtheoutputfromtheprobecanbeconvertedtomeasurementsofsoilmoisture.Thissystemhastheabilitytocontinuouslymonitorsoilmoisturechangesatarangeofdepthsusingadataloggerandapowerunit.

Thedatagatheredcandescribesoilmoistureconditionsthroughouttherootingprofileandassistintheschedulingofirrigation.Limitationsagainoccurwhenirrigationisappliedunevenly,asinglepointreadingisoflittleusewhenplanningirrigation.Thevolumeofsoilmeasuredisevenlessthanfortheneutronprobeswhichcanleadtoinconsistencies,especiallywheretherearelotsofstonesorvariationinsoiltexture.

3.4.1.4 Time Domain Reflectrometry (TDR) and Frequency Domain Reflectrometry (FDR)Thesetechniquesestimatethevolumetricwatercontentofthesoil.Highfrequencypulsesaresenttoparallelelectrodesplacedinthesoil.TheTDRsystemhasmicroprocessorsusedtomeasurethetimetakenforthesepulsestotraveltotheendoftheprobesandthenbereflectedbacktotheirorigin,whichisaffectedbysoilmoisture.InFDRsystems,changesinfrequencyaremeasuredwhichagainareaffectedbysoilmoisture.Theinformationisthenusedtocalculatetheaveragesoilwatercontentoverthelengthoftheprobes.

Accuracyisdependentonthemaintenanceofaconstantdistancebetweenthetwoprobesandagoodcontactbetweenthesoilandtheprobes.Ifthisdoesn’thappenthereadingstendtobeameasureoftheprobe’scontactwiththesoilinsteadofthemoisturestatus.Anumberofreadingswillbeneededtogainarepresentativepictureofawholefield.Neitherofthesemethodsarecommonlyusedforcommercialirrigationschedulingofpotatoes.

3.4.2 Indirect methods

3.4.2.1 Manual water balance sheetThisapproachisbasedontheconceptofwaterbalance.Waterenteringthesoil,eitherbyrainorirrigation,istreatedascreditandwaterthatexitsasevapo-transpiration,drainageorrunoffisadebit.ThedifferencebetweenthetwoisusedtocalculatetheSMD.Rainfallandirrigationhastoberecordedonadailybasis.Evapo-transpirationfigurescanbepurchasedorestimatedfromcharts.

Adjustmentisneededwherecropshavenotattainedfullleafcoverandthereareseveralmethodsofestimatingthis.Unfortunately,thereisalossofaccuracyandmanualbalancesheetsoftenhavesignificanterrorswhichincreaseastheseasonprogresses.Themainerrorsareestimatingevapo-transpirationandassumptionsthatthecropisabletoextractsoilwaterataconstantratenomatterwhattheSMDis;whereasthecrophasincreasingdifficultyabstractingwaterfromdryingsoil.AnaccumulationoferrorscanleadtosignificantinaccuraciesintheestimationofSMDandconsequentlyirrigationwaterapplications.


Section 2

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Section 3

3.4.2.2 Computerised water balance methodsThesearesophisticatedmanualbalancesheetsthatarecapableofdealingwiththecomplexitieswhichmanualsheetscan’t.

Anumberofcomputerisedsystemsareavailablethatusecrop,meteorological,rainfallandirrigationdatatocalculateratesofevapo-transpirationandsoilmoisturedeficits.TheyareallbasedonamodifiedPenman-Monteithequationwhichhasbeenshownfromresearchtoaccuratelypredictratesofevapo-transpirationacrossarangeofconditions.

Theirmainlimitationisthattheycalculateestimatesofsoilmoisturestatuswhicharenotverifiedbyactualmeasurements.Caremustbetakentoensurethatthedatafedintotheprogrammeisaccurateotherwisediscrepancieswilloccur.

3.4.2.3 New innovationTheuseofnewmonitoringtechnologieshasresultedinimprovedschedulingofirrigationandcombinedwiththetechnicaladvancesinthedeliveryandcontrolofwater,opportunitiestogetthemostoutofirrigationsystemshasimproved.

Twonewinnovationsare:

•PrecisionIrrigation:Theefficientandaccuratedeliveryofdifferentamountsofwateracrossafieldtopreciselymeettheneedsoftheplant

•Fertigation:Fertigation(supplyingnutrientsviairrigationwater)suppliesnutrientsonanalmostcontinuousbasisthroughregularirrigatedapplications.

Bothmethodsaimtomeettheplantsneedsinordertoincreasecropyieldandqualityandultimately,profit.Monitoringandcontrolareimportantfactorsforbothapproaches.

3.5 Precision irrigation

Yieldsvaryacrossafieldduetodifferencesinsoils,availablewater,vigor,pestsandplantvarieties.Precisionirrigationisusedtomeetthespecificrequirementsoftheplantsindifferentmanagementzonesacrossafieldtoultimatelyachievehigherproduction,betterqualityandincreasedwateruseefficiency.Schedulingforprecisionirrigationdealswithseveralquestionssuchas‘when,how,andwheretoirrigate’byrelyingonrealtimeinformationofwhatevermaybelimitingproductionatalltimesandallpartsofthefield.

Precisionirrigationrelieson:

•Acquiringaccuratedatabymonitoringthesoil,plants,andweatherandtheirvariationsacrossthefield

• Interpretation:oftenusingcomputermodels

•Controlledapplication:viaautomaticcontrollerslinkedtosensorstherateorlengthoftimeofirrigationisvariedaccordingtoneed

•Evaluation:monitoringtheapplications,soil-waterandcropresponsetofinetunefutureapplicationsofwater.

Precisionirrigationhasbeenfoundtoimprovewaterefficiencyby8-20%.Ithasthepotentialtoincreaseyieldbutthevariationissogreatthatnoconclusiveresultscanbedrawn.Thustheprofitabilityofprecisionirrigationisalsouncertain.Largein-fieldvariabilityintheyieldorqualitymaybenecessarytojustifytheuseofthisinnovation.

3.6 Fertigation

Fertigationiswherethenutrientsareprovidedasmineralsaltsdissolvedintheirrigationwaterviadrip/trickleirrigation.ThenutrientsolutionisusuallyadjustedtoaspecificpH.Theplacementofthedrippersandthefrequencyofwaterdeliveryrestricttheactiverootzonetoamuchsmallervolumethanisusual.Thesoilisheldnearfieldcapacityatalltimesbyregularlypulsingwaterthroughthesystemoroperatingthesystemcontinuouslythroughouttheday.

Thistypeofsystemseekstomatchthesupplyofmineralnutrientstotheplantsneedsandgrowthstagesandhasthepotentialtosignificantlyincreaseproduction,improvequalityandallowearlierharvesting.However,thedownsidetothissystemisthatitrequiresclosemanagement.Lossesinproduction,leachingofnutrients,acidityandrootzonesalinitycanresultifnotmanagedcorrectly.

33

Section 2


Section 4

Crop and soil management

33

Plant Performance – understand crop growth and development cycles, seasonal requirements and how to maximise tuber numbers. Determine and meet plant nutrient requirements, while ensuring no wastage of fertiliser.

4.1 Plant growth

Understandingthedevelopmentstagesofpotatoes,howtheychangethroughtheseasonandhowtheyfunctioniscrucialtoeffective,efficientirrigation.Knowinghowthepotatoplantdevelopsallowstheapplicationofwatertobetimedandmeasuredaccordingtotheplantsneedsandallowsthegrowertomanipulatethecroptoimproveyieldand/orquality.

4.2 Nutrition

Withmodernirrigationtechniquestheprecisedeliveryofwaterhasmadeitpossibletousethesametechnologyfortheprecisedeliveryofdissolvednutrientswithintheirrigationsupply.

Fertigationisincreasinglycommonwithinthesoftfruitsectorandcanbeusedforthosepotatoesirrigatedviatrickle/dripmethod.Fertigationcanleadtogreaterefficiencyandopportunitiestofinetuneplantnutrition,reducetrafficandfuelsavings.Itcanalsoreducenutrientlossthroughleachingandrunoffwheretheycanpollutewatercoursesandaquaticecosystems.

Thetrade-offsincludehighcapitalcostsformixingtanksandinjectionequipment,thetimetomixthefertiliserandhavingtousehighgradematerialstoavoidblockages.Themoreapplicationsmade,themorecomplexthedecisionsthathavetobemadeaboutratesandtiminganditisessentialthatincompatiblenutrientsarenotmixedtogether,resultinginprecipitationandblockeddrippers.

4.3 Soil condition

Soilstructureandtexturearekeyelementsindeterminingtherateofwaterinfiltration,theamountofreadilyavailablewaterinthesoilandconsequentlyrootgrowthandrootfunction.

Sou

rce:

ww

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Sprouting inititation and emergence between

15 and 30 days of planting

Tubers inititation between 15 and 30 days

of emergence

Tubers filling between 45 and 90 days of emergence

Areal development

Growth of green plantGrowth of tuber Crop closing between

35 and 40 daysof emergence

Tubers development

Maturity and harvest between 90 and 120 days of emergence

Stolonsinititation occurs simultaneously

then the emergence


Section 4


Section 2

34

Section 4

4.4 Infiltration

Watershouldnotbeappliedataratefasterthanthesoilcanabsorbitorinamannerthatdamagesthesoilsurface,aspondingandsoilerosioncouldfollow.Soilswithlowinfiltrationrates(lessthan1mm/hr)resultsinpooruptakeofwaterandarepronetoextendedperiodsofwaterlogging.

Thefateofwaterthatpassesbeyondtherootzoneandlostas‘deepdrainage’shouldalsobeconsideredasgroundwatercanbecontaminated.Drainsmaybeneededandeffortstoimprovethewaterholdingcapacityofthesoilsuchasaddingorganicmatterwouldberecommended.

Soilswithpenetrationresistanceof0.5MParesultinunrestrictedrootgrowthbutthosesoilswithvaluesofover2.0MPaarealmostimpenetrable.Thosesoilswheretheporesareplentifulenabletherootstogrowunimpededandalsoensurethatthereisenoughoxygenfortherootstorespire.Measuredasair-filledporosity,theamountofoxygenshouldbeabove10%foradequateaeration.

Byhavingagoodsoilstructuretheabilityofplantstomakebestuseofwaterisgreatlyincreased.Poorstructuredsoilsareeithertoodryandhardortoowetandsoggy,deprivingtheplantsofoxygen.

Infiltrationcanbeimprovedbycultivationsystemswherethesoiltilthisleftslightlyrough(orasapressedsurfacewhereappropriate).Thereareanumberofwaysinwhichwaterinfiltrationcanbeimproved:

•Compactionandruttingcausedbypreviouscultivationsshouldbeminimised

•Tyresandpressuresshouldbechosentosuitloadsbeingcarried,toexertaslowagroundpressureaspossible

•Avoidingcompactionshouldbeanintegralpartofastrategicsoilplanforanybusiness.Oncecauseditcanbedifficulttocorrect,becauseofalackofopportunity,orpowerforsubsoiling(aswellasthecost)

•Maintainingthecorrectraingunpressurewillensurecorrectatomisationandlimittheproductionoflargedroplets

•Boomirrigatorsproducealargerproportionoffinedroplets,whichreduceserosionrisk

•Growingcropsinflat-toppedorcentre-dishedbedsallowsthesoiltoreceivethewaterwithlessrun-offanderosionriskandsomeextrabenefitfollowsfrommorewaterbeingheldinthesoilandavailableforrootuptake

•Theadditionoforganicmattercanimproveinfiltrationratesandtheaerationofsoilpromotingrootgrowth.

4.5 Slopes

Slopingland,particularlywhencompactedbywheelings,willleadtowaterrun-off.Irrigationlayoutsshouldbeassessedfortheamountofsurfacerun-offproducedand,whereslopinglandispresent,thedifferencesininfiltrationratebetweendifferentsoiltypesmaybeaccentuated.Wherepractical,croproworbedalignmentacrossaslopeshouldbeadoptedtolimitrun-off.

4.6 Reduce run off and soil erosion

Run-offcanalsobelimitedbytheuseoftiedridges.Thesearesmalldamsofsoilformedapproximatelyeverymetretobridgethegapbetweenbeds.Theseholdirrigationwaterandrainfallandallowittotheninfiltrateslowlyintothesoil.Slopesassteepas10°haveshowngoodwaterretentionfollowingtheuseoftiedridges.Thefrequencyofthesetiedridgesalongtherowensuresthatretainedwaterdoesnotaccumulateinalargeenoughmasstostarterosionbyitself.Asimplefrontmountedsingletineorhoeontheharvestertractorcanthenbeusedtobreakdownthedamsandtherebyallowtheharvesterpassage.

Acultivationtooldevelopedtoassistinfiltrationisthe‘Aqueel’(SimbaInternationalLtd.),whichcanbeusedoverthewholesoilsurfacearaisedbedsurface,oronthetopofpotatoridges.Smalldepressionsarecreatedonthesoilsurface,whichactasreservoirs(ofabout1litre)tointerceptthewaterandallowinfiltrationintothesoilwithlesschanceforlateraldisplacementandrun-off.Justunder200,000minireservoirsareformedperhectareandtheeffectcanpersistoverthewholeseason,dependingonsoiltypeandamountofwaterintercepted.Thepolymerwheelsareself-cleaningandcanbefittedtocultivators,bedformers,drillsandplanters.

Thewheeltrackrollerisanothercultivationtoolthatiscurrentlyunderdevelopment.Tinesruntothesideofthecompactioncausedbythetractor,impartingminimalsurfacedisturbancebutgeneratingachannelthroughwhichthesurfacewatercanescapeintotheadjoiningcrops.Theuniqueself-cleaning,plasticrollerformsangled,elongatedreservoirstoholdthesurfacewaterandatthesametimecreatesfissuresenablingthedissipationofthewaterintothesoil,whichremainssoftaroundthechannelsgeneratedbythetines.

35

Section 2


Section 5

Monitoring

35

Monitoring – Monitor and respond to aspects of the system performance, management, production and environment. Every farm is different – by picking key performance indicators that are of most use eg production, finances (gross margins), the environment (water quality) and human aspects (number of accidents), then performance can be measured.

Allaspectsofanirrigationenterpriseneedtobemonitoredsomanagementcanbefine-tuned.

5.1 Record-keeping of water use

Acomprehensivefarmirrigationwaterplancanhaveanumberofaimsbutallofthemshouldcontributetoanoverallobjectiveofimprovingfarmmanagementandprofitability.Theprimaryneedoftheplan,though,istosimplykeepanaccuraterecordofwaterusedonthefarm.(Mostabstractionlicencescarryaconditionthatrequirestheuseofametertomeasuretheamountofwaterthatisabstracted.)THIS IS A LEGAL REQUIREMENT FOR ABSTRACTION LICENCES.

Fromthissetofrecords,manyotherbenefitswillfollow,inparticularaplanshouldbeableto:

•Recordactualwaterusecomparedwithplannedandsoprovideabasisforincreasingefficiency

•Demonstratetheresponsibleuseofwater

•TakeaccountofenvironmentalconsiderationssuchasSitesofSpecialScientificInterest(SSSI)

•MeettherequirementsofCropAssuranceProtocols

•Provideacomprehensiverecordofmanagementandstafftraining.

Suchrecordkeepingisnowessentialonfarmsandthereisagreaterrelianceplaceduponitwhendemonstratingtheenvironmentallyresponsibleandsustainablenatureoffarmingtothewidercommunity.

TheEnvironmentAgencyhasdevelopedanewonlinereportingsystemforabstractors.ThissystemiscalledGenericOperatorReturns(GOR)andmorecanbefoundoutaboutitontheirwebsiteatwww.environment-agency.gov.uk/business/topics/109520.aspx

5.2 Basic farm irrigation planning

Therangeofinformationthatitisadvisabletokeepfallsintotwocategories.Thefirstcanbeconsideredtheminimumsetofbackgroundinformationthatwillbeusefulaccumulatedovermanyyearstodemonstratetheefficientuseofwateronfarmandwillhelptojustifytheneedforwaterforcropproductionatthatlocation.


Section 5S

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Section 2

36

Section 5

5.2.1 Daily work planningThesecondcategoryofinformationisanexpandeddatasetthatcanbekeptforonlyalittlemoreeffort.Thisprovidesadditionalinformationvaluableintheefficientdailymanagementofbothsoilandwater.Thestartingpointforthisinformationis‘daysheets’,whichencourageboththedailymanagementandoversightofirrigationandthehabitofrecordkeeping.Suchadatasetmaycomprisetheinformationlistedbelow.

5.2.2 Background information•Farminformation;includingsoiltypesandcropped

andirrigatedareas

•Abstractionlicenceinformation;licensedamountsandratesforabstraction,togetherwithactualamountsabstracted;shouldincludestoredwateraswellasseasonal

•Actualmeterreadingstocalculateaboveinformationandforlicencechecking(howmuchwaterthebusinessisactuallyusing)

•Annualsummaryofirrigationwaterappliedandonwhichfieldsandcrops(includingthatforaidinggermination,transplanting/cropestablishmentandharvesting),includingdatesofapplication

•Soilmanagementandenvironmentalconsiderations

•Trainingrecordsofalloperators.

Thereisnowaneedinmanyassuranceschemestodemonstratethatappropriatetrainingisundertakenbyboththosewhomanageirrigationandbyoperators.Annualtrainingrecords,includingcertificatesofattendance,arevaluableindemonstratingwateruseefficiencyandinsupportingirrigationabstractionlicencerenewal.Inaddition,amapshouldbekeptshowingthelocationofwatercourses,reservoirs,conservationareas,naturereserves,SSSIs,etc.

Thisinformationmaycompriseof:

5.2.2.1 Daily soil and water management information•Dailyrainfall,accumulatedovermonthsandyears

(multiplesheets)

•Dailyrecordofirrigationamountsapplied;accordingtofieldareasandcrops,anddetailsofequipmentusedandtiming

•Dailymaintenancechecksonequipment

•Occasionalrecordkeepingoflonger-termmaintenanceofpumpsandmeters,includinganyrepairstothesystem.

Atlessfrequentintervals,itwillbenecessarytokeeparecordofallmaintenanceandcalibrationworkcarriedoutonthepumpstationandapplicationequipment.Guidanceforirrigatorsaboutmeteringabstractionscanbefound:www.environment-agency.gov.uk/business/topics/water/123416.aspx

5.2.3 Additional useful informationOtherinformationsuchasthatlistedbelowmaybeusefulinplanningwateruseonthefarmanddemonstratingthatallpossibleoutcomesofmanagementactionshavebeenconsidered.Atleastsixyearsofrecordsshouldbekept,inaccordancewiththe(CAMS)reviewcycle,andpreferably12years(whichwillbethenormalrenewalperiod).

5.2.3.1 Additional management information•Farm/fieldmapshowingwatercourses,waterdisposal

andpotentialrisksandinfielddrains

•Timingandamountofapplicationarecompatiblewithinfiltrationrate

•Weatherdata(dailyrainfallandEvapoTranspiration)toaidcalculationofirrigationneed

•Evidencethatirrigationschedulingsystemdatainputsareaccurate,thesystemisdeliveringtherequiredinformationandthatitiscost-effective.

37I R R I G A T I O N A N D W A T E R U S E ( B E S T P R A C T I C E G U I D E F O R P O T A T O E S )

Section 2

37

Section 2

Appendix

37

Expectation Benefit to the farming business

Improvement to the environment

Action (dependent on local situation)

Access to advice and support

Manage your water usage effectively

Reducethecostsofusingwateronyourfarm.

Increasetheprospectofyourabstractionlicencebeingrenewed.

Reducetheriskoflicencerestrictions,ensuringscarceresourcesareavailableforlonger.

Reducetheimpactsofoverabstractiononyourlocalenvironmentandreducetheriskofenforcementaction.

Waterisavaluableresource.Usingexcessiveamountsdeprivesothersandtheenvironmentofmuchneededwater.

Wastingwatercostsyoumoneyandcouldtriggerearlyrestrictions.

Failuretohavewaterattherighttimereducescropyields.

Checkforleaks,insulatepipework.

Scheduleyourirrigationandensurethatwaterisappliedtocropsefficiently.

Recordthevolumeofwateryouusewithawell-maintainedmeter(ifyouhaveanabstractionlicencethisisrequired).

WaterwisebookletfromtheEnvironmentAgency

Useafreebenchmarkingtool.Toregister,gototheUKIAhomepage–www.ukia.org

Plan for your longer term water needs

Findoutwhatriskslesswaterwillposetoyourbusiness.

Planandpreparefortheseriskstomaintaintheprofitabilityofyourbusiness.

Investoveralongtimescaletoprotectyourbusiness.

Maintainwatercoursessotheyfunctionforyourfarm

Climatechangethreatenstochangetheavailabilityofwateryoucanabstract.Forexample,wemayexperiencemoredroughtsorsuddenhighflows.

Watercoursesareimportantforwatersupplyandfordrainage.

Considerplantingdroughttolerantcrops,harvestingrainwater,ordevelopingahighflowstoragereservoir,especiallywithotherabstractors.

Increasetheconnectivityofexistingsources.

ConsiderbuyingwaterfromanotherabstractorandsettingupaWaterAbstractorGroupwithyourneighbours.

Usemoreefficientirrigationtechniquessuchasscheduling,trickleirrigation,andapplyingatnight.

Applytoextendyourlicensedabstractionseasontomatchyourirrigationseason.

Considerwhetheryoucantakehighflowsinsummerifyoualreadyhaveareservoir.

Considerthetargetedplantingofshelterbeltstoreducewaterstressoncropsduringdroughtperiods.

Getadviceandapplyforconsentsandregisteringforexemptionstoundertakeyourownwatercoursemaintenance.

NationalPermittingServiceorAreaEnvironmentPlanningteams.Telephone03708506506.

LeafletsonWaterRightsTrading,Rainwaterharvesting–anonfarmguide,WaterAbstractionGroupsandReservoirsareavailablefromtheEnvironmentAgency

Farming & ForestryImprovementGrants(Defra),CSFgrants

WoodlandforWater(ForestryCommissionandEnvironmentAgency)

ContactEnvironmentAgencypartnershipandstrategicoverviewteams(toobtainflooddefenceconsentsandadviceonmaintenance).Registerforwastelicenceexemptionsatwww.environment-agency.gov.uk/business/sectors/32779.aspx

6.1 Irrigation essentials – Environment Agency

Section 6



Section 2

38

Section 6

6.2 General farm irrigation template

Farm contact and address Environment Agency Region and CAMS

Maincontact EARegion

Farmname CAMScatchment

AddressAbstraction licence entitlement and pumping capacity for 20**

Totallicensedvolume(m3)

Totalabstractedvolume(m3)

PostcodePeakabstractionrate(m3/dayorm3/month)

Telephoneoremail Arethereanyconstraintsonirrigation(egin-fieldequipment,pumpcapacity,licence)?

Irrigation water sources Comments

Water sources % of total volume

Riverabstraction

Borehole

Mainswater

Other(pleasespecify)

TOTAL

Reservoir storage

Type Number Total capacity (m3)

Unlinedorearth-linedreservoirs

Reservoirswithsyntheticlining

TOTAL

39

Section 2


Section 6Vari

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Section 2

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Section 6

6.3 Pests and diseases associated with irrigation

Common scabCommonscableadstomajorfinanciallosseswithinthepotatoindustry,duetothereductionintuberquality.ThediseaseiscausedbyStreptomycesspp.Soilmoistureduringandshortlyaftertuberinitiationhasadramaticinfluenceoncommonscabinfection.Thediseaseismorecommononlightsandysoils.

Recommendation•Maintainasoilmoisturestatusclosetofield

capacityduring4-6weeksfollowingtuberinitiation,toinhibitinfection.

Late BlightLateBlightisthemosteconomicallyimportantdiseaseofpotatoesintheUK.ItiscausedbyPhytophthora infestans Allpartsoftheplantbecomeinfected.Prolongedperiodsofsurfacewetnessor100%RHandmoderatetemperatures(10-25°C)willencouragethespread.

Recommendations•Controlfoliageregrowthonwastedumps

•Fungicideprogrammesshouldbeginwellbeforeblightbecomesestablished

•Planirrigationandblightcontrolprogrammestooperateinharmonyduringthegrowingseason.

Powdery scabPowderyscabiscausedbySpongospora subterranea.Itdevelopsbestunderdampconditionsandproducespimplelikeswellingsthatenlargeanderuptreleasingsporesintothesoil.Theorganismsurvivesmanyyearsinthesoil.Canalsobetransmittedviainfectedseed.

Recommendations•Avoidplantinginfectedseedinfieldswhichwillbe

irrigated

•Avoidgrowingirrigatedcropsofsusceptiblevarietiesinsoilswithahistoryofthedisease

•Avoidoverirrigation.

Fungal rots (Pink rot, Watery wound rot, Rubbery rot etc.)Pinkrot(Phytophthera erthroseptica),Waterwoundrot(Pythiumspecies)andRubberyrot(Geotrichum candidum),areallproducedbysoilbornefungi.PinkrotisaparticularproblemintheWestMidlandswhereitcancausesevereyieldlosses.Therotsdevelopinsoilsapproachingfieldcapacity,especiallywhentemperaturesarehigh.Poordrainageorsoilcompactioncanworsentheseverityofthesediseases.

Recommendation•Wherethereisahistoryofoneormoreofthese

diseasesinthefield,irrigatetoleaveasignificantSMDinthemid-latesummerperiod.

Blackleg and bacterial soft rotsBlacklegandsoftrotsarecausedbyErwinia species. Thesebacteriaarecarriedinorontubers.Contaminatedtubersshownosymptomsuntiltheybecomestressedordamagedinthefieldorwhenstored.Rottingisencouragedunderconditionswhereafilmofwaterispresentaroundthetuberandtemperaturesare>20°C.Inthefield,rottingtubersreleasebacteriaintothesoil.

IrrigationcancompoundthesituationbyallowingmovementofErwiniaacrossthefield.Blacklegdevelopswhenthepathogenismovedupthexylemintothestem.Bacteriacanbebroughtinfromnearbypotatocrops,dumpsorcontaminatedirrigationwater.Overheadirrigationandraincanalsospreadthediseasebysplashandaerosoleffect.

Recommendation• IfBlacklegbecomesaprobleminacrop,consider

reducingorevenstoppingirrigation.

1. Commonscab

2. LateBlight

3. Powderyscab

4/5.FungalRots

6. Blacklegandbacterialsoftrots

7. SilverscurfandBlackdot

8. Spraing

9. Cutworm

10.Slugs

11. InternalRustSpot

12.Growthcracking

13.Raisedlenticels

14.Greening

15.Bruisingandmechanicaldamage

16.Brownrot

Key for photographs opposite

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Section 6

Internal Rust SpotInternalRustSpot(IRS)appearstobeastressrelateddisorderassociatedwithrestrictedcalciumuptake.PCLresearchhasshownthatperiodsofdroughtcanreducecalciumuptakeintotubers,thereforeawellscheduledandexecutedirrigationregimecanreducethelevelofIRS.OtherfactorsthatcancauseIRSarenematodes(freelivingandPCN).

Recommendation•UsewellscheduledirrigationtoreducetheriskofIRS.

Growth crackingHighinternalpressurewithinthetuberduringrapidgrowth,oftenfollowingaperiodofslowergrowth,splitsthesurfacetissues.Unevenwatersupplyisoneoftheprimecausesofgrowthcracking.Significantrainfall/irrigationwhichpushessoilsabovefieldcapacitycaninducegrowthcracking.Thisempathisestheneedtomarryirrigationmanagementtoweatherforecasts.

Recommendation•Usewellscheduledirrigationtoreducetheriskof

significantgrowthcracks.

Raised lenticelsThelenticelsbecomewhiteandraisedandenlargedinpartiallywaterloggedsoil.Theyareasymptomofwatermanagementthathasbrokendown.Lenticelswhichareraisedforanylengthoftimeleaveobviousspotsonthetubersurfaceatharvestanddetractfromtheappearance.Thesecanbecomesunkenandinfectedwithbacteriacausingrots.

Recommendation•Avoidpushingsoilsabovefieldcapacity,especially

frommidseasononwards.

GreeningGreeningoccurswhentubersareexposedtolightandproducechlorophyll.Thisalsomeansthatthepotatoeshavealsobeenproducingglycoalkaloidswhichbothtastebitterandaremildlytoxic.Greeningoccursbecauseoferosionoftheridgesbeforefullcanopyandasthecanopysenesces.Actioncanbetakenattheplantingstagetominimisegreeningintermsofplantingdepthandtheridgeprofile(flatterandwider).Erosionismadeworsebytheraingunnozzlebeingtoobigandthepressureattheguntoolow.

Silver scurf and Black dotSilverscurf (Helminthosporium solani)andBlackdotareblemishdiseases.Especiallyimportantinthepre-packmarket.Infectionsoftheskinoccurpriortoliftingsoharvestinginatimelymannerisimportant.Thereissomeconflictinginformationthatdiseaselevelsincreaseordecreaseduetoirrigation,soitsbesttofocusonmethodsotherthanirrigationmanagementtominimisethesediseases.

Recommendation•Timelyharvestratherthanirrigationmanagement

offersabettermeansofdiseaseminimisation.

SpraingSpraingmanifestsitselfasbrownarcsinthefleshofthetuberandinseverecasesonthetubersurface.ItiscausedbyPotatoMopTopVirus(PMTV),transmittedbythesporesofPowderyscaborbyTobaccoRattleVirus(TRV)transmittedbyfreelivingnematodes.Thefreelivingnematodesdependonmoistureformovement.WetssoilssoonaftertuberinitiationcanincreasetheriskofspraingwhereTRVnematodesarepresent.

Recommendation• Irrigation,especiallyforcommonscabcontrol,can

increasetheriskofspraing,sowherethisisathreat,takenecessaryprecautionarymeasurestocontrolit.

Cut wormCutwormsarethecaterpillarsofseveralmothspecies.Newlyhatchedcaterpillarsinitiallyfeedonleavesbutthenmovedowntothesoilwheretheyfeedontubers,producinglargeholes.Youngcutwormsdieinwetsoilsoirrigationcanbeeffectivecontrol.

Recommendation•Correctlytimedoverheadirrigationcanlargelyeliminate

theriskofcutwormdamage.

SlugsSlugscausedamagebypenetratingthetubersandexcavatingcavitiesintheflesh.Theriskofdamageisincreasedifsoiliskeptmoistbyirrigation.Heaviersoilstendtohavethegreaterpopulationsofslugs.Earlyharvestreducestheperiodoffeedingavailabletoslugs.

Recommendation• Irrigationincreasestheriskofslugdamage,soother

controlmeasuresuchasslugpelletsneedtobeused.

43

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Section 6

Recommendation•Therightirrigationequipmentoperatedatthe

rightpressures

•Avoidirrigationduringcanopysenescence.

Bruising and mechanical damageTheriskofbruisingcanbemadeworsebyendingirrigationtooearlyintheseasonandallowingSMD’storisepriortodesiccation.Turgorpressuredecreasesasthetubershavedifficultyextractingmoisture.Thenduringharvestcelldeformationmoreeasilyoccursresultingindamagetocellmembranesleadingtoenzymicreactionscausingblackmelaninpigmentstobeformed.

Levelsofbruising/mechanicaldamagecanbehighintheabsenceofacushionofsoilontheharvesterwhenconditionsaredry.Irrigationjustaheadofharvest,canalleviatetheseproblems.

Recommendation• Irrigateuptodesiccationandagainpriortoharvestif

necessary,toreducebruisingandexternaldamage.

Brown rot

rapiddryinganddeathofthewholeplant,althoughwiltinghasrarelybeenobservedinEuropeancrops.

Recommendations•Plantonlyclassifiedseed

•Donotirrigatewithcontaminatedwater

•Controlgroundkeepers

•Goodhygiene.Don’tdumpwasteonagriculturalland.

6.4 ReferencesBaileyJ,BradshawN,BuckleyD,GrovesS,PetersJ,2005.Irrigation Best Practice Management for Potatoes: A Guide for Growers.

BasfordB,KingJ,PerkinsS,TiffinD,2007.Irrigation Best Practice: A water management toolkit for field crop growers.

ChambersB,GouldingK,LeakeA,2012.Simply Sustainable soils.

CranfieldUniversity2007.Save water and money – irrigate efficiently.

CranfieldUniversityandEnvironmentAgency2009.Thinking about an Irrigation Reservoir? A guide to planning, designing, constructing and commissioning a water storage.

EnvironmentAgency2007.Waterwise on the farm.

EvansR,SneedR.E.,CasselD.K.,1996.Irrigation Scheduling to Improve Water- and Energy-Use Efficiencies

JensenM.E.,BurmanR.D,AllenR.G.,1990.Evaporation and Irrigation Water Requirements. ASCE Practice No. 70. ASCE.

KnoxJ.W.,WeatherheadE.K.,2003.Trickle Irrigation in England and Wales.

ManningLetal,2013.Simply Sustainable Water

NewmanH,2012.Calculating Readily available Water, Note 543.

NationalProgramforSustainableIrrigation,2012.Irrigation Essentials Updated.

SmithR.J.,BaillieJ.N.,McCarthyA.C.,RaineS.R.,BaillieC.P.,2010.Review of Precision Irrigation Technologies and their Application.

StalhamM.A.,AllenE.J.,GazeS.R.,1999.Scheduling and efficient use of water in potato crops.

Thebacteriumcancausewiltingofthepotatoplantbutthesymptomsyouaremostlikelytoseeareinthetuber,theinitialsymptomisbrownstainingofthevascularring(hencethename‘brown’rot)thatstartsfromthestolon(heel)end.Apale,creamybacterialexudatemayoozefromthecutvasculartissues.Insevereinfectionsthevasculartissuesrotawaycompletely.Bacterialexudatemayoozefromtheeyesandtheheelend(wherethetuberwasattachedtothestolon).Wiltingoftheleavesstartstowardsthetopoftheplantandmaybeinitiallyconfinedtoonesideofaleafortoonlyonestem.Thiscanleadto

This is a quarantine disease of potato that is listed in the EC Plant Health Directive and is notifiable in the UK.

Yieldlossesaremostlycausedbytuberrottingand,inmanywarmerareasoftheworld,itisoneofthemainlimitingfactorsinpotatoproduction.Theeffectonourseed-potatoindustrycouldbesubstantial,especiallyforexports,ifthediseasebecameestablishedintheUK.Onceestablished,thecostsofcontrolcouldalsobehigh.Controlofthisdiseaserequiresvigilancefromallsectorsoftheindustry,fromgrowersthroughtomerchants,packersandretailers.

© Agriculture and Horticulture Development Board 2013. All rights reserved. Potato Council is a division of AHDB. Registered in England and Wales No 6410734. Registered Office: Agriculture and Horticulture Development Board, Stoneleigh Park, Kenilworth, Warwickshire, CV8 2TL.

Potato CouncilAgriculture and Horticulture Development Board

Stoneleigh ParkKenilworth

WarwickshireCV8 2TL

Tel: 0247 669 2051Web: www.potato.org.uk Twitter: @PotatoCouncil

Concept by: Chris Steele

Written by: Chris Steele, Potato Council

and contributions from the Environment Agency

While every effort has been made to ensure that the information is accurate, no liability can be accepted for any error or omission in the content of this guide.

£80.00 where sold

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