Shamie Zingore, Lydia Wairegi and Mamadou Kabirou Ndiaye

Rice systems cropping guide

2015Revised Edition

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Africa Soil Health Consortium: Rice systems cropping guideBy Shamie Zingore (International Plant Nutrition Institute (IPNI)), Lydia Wairegi (CAB International (CABI)) and Mamadou Kabirou Ndiaye (AfricaRice).

© CAB International 2014

Updated May 2015

Please cite this publication as: Zingore et al. (2014) Rice systems cropping guide. Africa Soil Health Consortium, Nairobi.

This publication is licensed under a Creative Commons Attribution 3.0 Unported License.Creative Commons License

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Limits of liabilityAlthoughtheauthorshaveusedtheirbesteffortstoensurethatthecontentsofthisbookarecorrectatthetimeofprinting,itisimpossibletocoverallsituations.Theinformationisdistributedonan‘asis’basis,withoutwarranty.

Neither the authors nor the publisher shall be liable for any liability, lossofprofit,orotherdamagescausedorallegedtohavebeencauseddirectlyorindirectlybyfollowingtheguidelinesinthisbook.

About the publisherTheASHCmissionistoimprovethelivelihoodsofsmallholderfarmers through adoption of integrated soil fertility management (ISFM)approachesthatoptimizefertilizeruseefficiencyandeffectiveness.

ASHCbooksareavailableatspecialdiscountsforbulkpurchases.Specialeditions,foreignlanguagetranslationsandexcerptscanalso be arranged.

ISBN(paperback):978-1-78064-548-3 ISBN(e-book):9781780645919 DesignbySarahTwomey

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Addresses of authors

Shamie ZingoreInternational Plant Nutrition InstituteICIPE CompoundDuduville-KasaraniP.O.Box30772-00100NairobiKenyaszingore@ipni.nethttp://ssa.ipni.net

Lydia WairegiCABICanaryBird,673LimuruRoad,MuthaigaPOBox633-00621NairobiKenya ASHC@cabi.orgwww.cabi.org/ashc

Mamadou Kabirou NdiayeAfricaRice-SenegalStationBP96Saint LouisSenegalK.Ndiaye@cgiar.org

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Acknowledgements

ThepreparationofthisguidewassupportedbytheBill&MelindaGatesFoundation.

Wethank:

• Farmersforinformationandforallowingphotographstobetakenontheirfarms.

• Jimmy Lamo, NaCRRI, Uganda for information and for facilitatingatriptoricefieldsduringwhichsomeofthephotosinthebookweretaken.

• Shamie Zingore (IPNI), Grace Omondi (CABI), Jill Rischbieth (CABI) and Lydia Wairegi (CABI) for photographs.

• IPNIforgivingpermissionforuseofnutrientdeficiencyphotographs from the IPNI library.

• Keith Sones for editing the guide. • IPNI,AfricaRiceandCABIforthetimetheauthorsspentwriting

this guide.

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Contents

1. Introduction 1

2. Rice cropping systems 3

3. Growing conditions for rice 6

4. Land preparation and planting 8

5. Rice management 20

6. What can go wrong 46

7. Rice production economics 60

1

1. Introduction

ThiscroppingguideisoneinaseriesbeingproducedforextensionworkersbytheAfricanSoilHealthConsortium(ASHC).Theseriesalsocoversbanana-coffee,maize-legumes,sorghum-andmillet-legumes,andcassavasystemsbutthisguideisfocusedonrice–uplandrainfed,lowlandrainfedandlowlandirrigated.

Extensionworkerswillfindthishandbookparticularlyusefulfor guiding their clients as they shift from producing rice under traditional,subsistencecroppingsystemstomoremarket-orientedsystemsthroughsustainableintensification.

Theguideaimstoprovide,inasinglepublication,allthemostimportantinformationneededtoachievehigheryieldsofriceinasustainableandcost-effectivemanner.

AlthoughASHC’sworkisfocusedontheneedsofsmallholderfarmersinAfrica,emergingandestablishedcommercialfarmerswillalsofindthecontentsrelevantanduseful.

TheASHCmissionistoimprovethelivelihoodsofsmallholderfarmers through adoption of integrated soil fertility management (ISFM)approachesthatoptimisefertiliseruseefficiencyandeffectiveness.TheoverarchingframeworkfortheguideisthereforeprovidedbyISFM.

Theoverallobjectiveofthehandbookistoprovidesimple,usefultipsonhowsmalltomedium-scalefarmerscanintensifytheirriceproductiontoincreaseyieldstoaround80%ofthepotentialyield,whiledecreasingunitcostsandincreasingprofitability–itisusuallynotcosteffectivetoaimtoachievethemaximumpotentialyield.TheaveragecurrentandattainabletargetyieldsforthethreemainricesystemsareshowninTable1.

2

Current yields are limited by multiple factors that constrain rice productivity.Toachieveimprovedyieldsandincome,asetofmanagementpracticestermed‘bestpractices’shouldbeusedforlandpreparationthroughtoharvestingandgrainstorage. Best practices include:

• Good land preparation • Useofqualityseedofimprovedvarieties • Establishing the correct density of plants by correct spacing at transplantingorsowing

• Timely planting • Effectiveweeding • Effectivepestanddiseasemanagement • Effectivewatermanagement,especiallymaintainingcorrectwaterlevelsatdifferentstagesofgrowth(forirrigatedsystems)

• Correctuseoffertilizerandgoodmanagementofcropresiduesand other organic material

• Correctandtimelyharvestingandpost-harvestpractices.Thisricesystemscroppingguideprovidesinformationonthesebestmanagementpracticesandhowtheycanbeusedtoensurefarmersachievethebestriceyieldsforirrigatedandrainfedlowland,anduplandproductionsystems.

Table 1. Yieldsinrainfedupland,rainfedlowlandirrigatedlowlandrice.

Rice system Current average yields(tonnes per hectare)

Attainable yields with ‘best practices’ (tonnes

per hectare)

Rainfed upland 1 2

Rainfed lowland 2 3–4

Irrigated lowland 5 6–8

3

2. Rice cropping systems

There are three main types of rice production system (Photo 1):

• irrigatedlowland • rainfedlowland • rainfed upland.Thereisafourthsystem,themangroveswamp,butthisrepresentsonlyabout6%ofthericegrowingarea.

Note:‘lowland’referstotheproductiontechnique(ricegrownonlandthatisfloodedorirrigated)notaltitude–lowlandproductionoccursataltitudesupto2000mabovesea-level.

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Table 2. Main features of the three rice systems.

Rainfed upland Rainfed lowland Irrigated lowlandEstimated%ofglobal land area planted to rice

10 30 60

Estimated%of global rice production

5 20 75

Estimated%ofAfrica land area planted to rice

40 46 14

Estimated%ofrice production in Africa

20 47 33

Ecologieswhereused(seefigure1)

Uplands,fromlow-lyingvalleystosteepslopes

Swampy,lowlyingareas that collect a lot ofwater

Floodplains,valleybottoms and terraced fieldswherethereissufficientwaterandwatercontrolinfrastructuretoallowirrigation

Crops per year and yields

1 crop per yearYieldslowerandmorevariablethanlowland

1–2cropsperyearOne rice crop plus otherdiversifiedcropsYieldslowerthanirrigated

1–2cropsperyearHighest yields

Water Soilnotcoveredwithwaterformostofgrowingseason

Soil submerged for part of cropping season, depending on rainfall and groundwater

Layerofwateriscontrolledandcoverssoil for most of growingseasonActivewatermanagement

Main factors impacting yields

HighriskofdroughtSubsistencefarming–lowuseofinputs

Competition from weedsandriskofdrought reduces yields

Reducedriskofcropfailuregivesfarmersconfidencetouse

Key management practices

No puddling or irrigation and soil not intentionally submerged Seeds broadcast or dibbled in dry soil prior to or during rains

Soils ploughed after onset of rainsBunds used to containwater,butnoactivemanagementofwaterTransplantation of seedlings or direct seeding in dry or puddledfields

PuddlingTransplantation or direct seedingManagementofwaterlevelsthroughoutcropping seasonMechanicalweedcontrol

5

 

Upland  rice   Rainfed  lowland     Irrigated  lowland  

bund  

Figure 1. Ecologieswhereupland,lowlandrainfedandirrigatedlowlandriceisgrown.

A B

C D

Photo 1. Rice growing in the three systems. (A)Upland,well-drainedsoil(photo:CABI) (B)Rainfedlowland,poorlymanagedwater(photo:CABI)(C)Irrigatedlowland,wellmanagedwater(photo:CABI)(D)Irrigatedrice–irrigationcanal(photo:CABI).

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3. Growing conditions for rice

Soil type: Ricecanbegrowninawiderangeofsoiltypes.Soilswithgoodwaterretentioncapacitiesarebest–soclaysoilswithhighorganicmattercontentareideal,butsoilswithhighsilt contents are also suitable. Sandy soils are not ideal for rice production.

Soil pH:RicedoesbestinsoilswithanearneutralpH(6–7)–thatis,theyareneithertooacidicnortooalkaline–butlowlandricecanbegrowninsoilswithpHvaluesintherange4–8.

ThepHvalueismostimportantinuplandrice.Here,ifitistoolow(i.e.tooacidic)thereisariskofaluminiumtoxicityandlowphosphorusavailability(phosphorusisessentialtopromotegoodrootgrowthandtillering1).

Inrainfedlowlandrice,irontoxicityisamajorproblemwhichlimitsyields.Irontoxicityoccursinacidicsoilsandcanbemanagedbyapplyinglimeandgrowingiron-tolerantricevarietiesamongstother techniques.

Inirrigatedlowlandricesystems,wheresoilsaresubmergedforlong periods, pH is not usually a problem. Submerged soils tend tobecomeneutralirrespectiveofwhethertheywereoriginallyacidicoralkaline.

ClimateRiceneedsawarm,moistclimatewithabundantsunshinetodowell.

1Tilleringmeansshootswhichgrowfromthebaseofthericestem.

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Rainfall:Anaverageof200mmrainfallpermonthisneededforlowlandrice;100mmamonthforuplandrice.

Flowersopeninthemorninganditisbestnottohavemorningrainduringflowering.Forexample,inWestAfrica,seedofearlyvarietiessowninearlyJulywillflowerinSeptember–Octoberwhenmorningrainfallislesslikely.

Temperature:Iftemperaturesaretoohigh(over35°C)flowersfailtosetseed.Ifitistoocold(below15°C)growthisslowandplantsfailtoflower.Ideally,theoptimaltemperaturesrangeshouldbebetween20and30°C;however,ricetoleratesdaytemperatureupto40°C.Theoptimumtemperatureis22to23°Cforfloweringand20to21°Cforgrainformation.

Sunshine: Ricedoesbetterwhenthereisbrightsunshine,especiallyinthe45daysbeforeharvestwhenatleast6hoursofsunshine are needed each day.

Key messages

• Ricedoesbestinsoilswithgoodwaterretentioncapacities,e.g.claysoilswithhighorganicmatter.

• TheoptimumpHis6-7butlowlandricecanbegrowninsoilswithpHvaluesintherange4-8.

• Amount of rainfall required is about 200 mm per month for lowlandand100mmforuplandrice.

• Rice production is seriously reduced if temperatures are below15°Corabove35°C.

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4. Land preparation and planting

Land preparation

Theobjectivesinpreparinglandforricecultivationaretocontrolweeds,makeagoodbedforriceplantstogrow,achievetheright soil structure and to incorporate crop residues, manure and mineralfertilizerintothesoil.Toodeepploughingshouldbeavoided.Adepthof15–20cmisenoughforrice:deeperploughingrisksmovingthemostfertilesoiltoodeepforthericetobenefit.Ploughingshouldbefollowedbyharrowing.

Forlowlandrice,becausericeisgrownunderfloodedconditions,itisbestgrownonlandthatisnearlylevel.Wherethelandhasasteepslopeorhasanunevensurface,thefieldshouldbelevelledtoaslopeoflessthan1%(i.e.adropoflessthan1mforevery100mlength)toenablefloodingtoanevendepth(Photo2).Toachievealevelforanewfield,thetopsoilshouldbemovedtoanotherposition,thesub-soillevelledandthetopsoilthenreturned.Foroldfields,levellingisdoneduringtillingandharrowing.Alternatively,dykesorbundscanbebuilttoseparatethefieldintoanumberofdifferentlevelsections.

Landpreparationpracticeswillalsovarydependingonwhetherriceisfirstgrowninanurserybedandthentransplanted,ordirectsowingtakesplace.

Lowland rice:Landpreparationstopsatharrowingifdirectseeding.Ifpreparingfieldfortransplanting,harrowingisfollowedbypuddlingandlevelling.Puddlingmeanstillingthefloodedfieldwiththeobjectiveofdevelopingahardpantoreducewaterloss through percolation into the ground. Puddling is especially effectiveinclayeysoils.

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Upland rice:Landpreparationstopsatharrowing.

WhensoilpHislow(acidic),limingtoachievetheoptimalpHrange is required and is best done during land preparation. Soil aciditycanreducenutrientavailability,especiallyphosphorus,whilecausingaluminiumtoxicityinuplandsoilsandirontoxicityinlowlandsoils.About2tonnesoflimeperhectareisrequiredtoincrease pH by one unit on clayey soils, but less is required for loamy soils. The lime should be applied by broadcasting and incorporatingintothetop15–20cmofthesoilduringploughing.

Choice of varietiesRicevarietiesshouldbeselectedthathavegraincharacteristicssuitableforthemarket;forexample,grainthatiswhiteifriceistobemilledandsoldtoconsumers,orgrainwithayellowtintifriceisforparboiling.Thevarietyshouldalsobesuitableforthelocalecologyandhavedesirableplantcharacteristics;forexample,forfamerswhoharvestbyhand,plantsofaheightthatallowsforeasyharvesting–thatis,about1.1mtallatmaturity–aresuitable.Thevarietychosenshouldalsohavehighyieldpotential.

Seed selection and plantingSeedcaneitherbefarmer-savedfromthepreviousharvestorimprovedvarietiescanbepurchasedfromseedproducersorseedcompanies. Preferably, fresh seed should be obtained to ensure theseediscleanandofthedesiredvariety.Useofseedthatisamixtureofdifferentvarietiesshouldbeavoidedastheymatureatdifferenttimes,whichcomplicatesharvesting.

Seedfromsomevarietiesdoesnotgerminatewellifharvestedand planted immediately but germinates better if stored for some timebeforeplanting.Thisperiodduringwhichseedgerminationispoorisreferredtoasthe‘dormancyperiod’.Somevarietieshavea

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A B

C

E

D

F

Photo 2. Land preparation. (A)Makingbundsforwatermanagement(photo:CABI) (B)Tractorscanbeusedtomakebunds(photo:CABI)(C) In the irrigated system, land can beploughedsoonafterharvesting,andthenextcropplanted(photo:CABI)(D)Levellingcan be done manually (photo: CABI/IPNI) (E)Awellpreparedfieldforirrigatedriceshouldbelevel,andtheheightofwatershouldbeuniform(photo:CABI)(F)Depthofwaterisnotuniform (photo: CABI).

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dormancyperiodof2–3weeksafterharvesting.Ifplantingfreshlyharvestedseed,itshouldbedriedinthesunfor1–2daystobreakdormancy.

Priortosowingagerminationtestshouldbeperformed.Forthis,100riceseedgrainsshouldbeplacedonwetpaperinawaterproofcontainer.Afterfivedaysthenumberofgerminatedseeds is counted. To calculate the germination rate:

Ideally,germinationratesshouldbe80–100%;if60%orbelow,thefarmershouldeitherobtainfreshseedoradjusttheseedrateaccordingly.Forexample,ifthetargetseedrateis80kgperhectareandgerminationis60%,thentheamountofseedtobesownperhectareis:80kg×(100/60)=133kg.

Beforeplanting,theseedshouldbewinnowedtoremovechaff.Toremoveunfilledgrains,placeseedinwater:unfilledgrainswillfloattothesurfaceandcanberemoved.

Riceseedcanbedirectsownasdryseed,directsownas pre-germinatedseed,ortheseedcanbestartedoffinanurseryandtheyoungseedlingstransplantedtothefieldlater.Eachhasadvantagesanddisadvantagesandissuitedtodifferentsituationsandsystems(seeTable3).

Direct sowing:Thisisalwaysdoneforuplandriceandcanalsobedoneforlowlandrice.

Foruplandrice,drysowingcanbedonebybroadcasting,orplantinginrows.Ifplantinginrows,seedscanbeplacedinholesorfurrows.Forbroadcasting80–100kgseedperhectareisapplied.Ifplantinginholes,spaceat20–30cm(betweenandwithinrows)with2–3seedsperhole:thiswillrequireless

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!"#$%&  !"  !""#!  !"#$  ×  100  

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seed,just40–50kgperhectare.Ifplantinginfurrows,spacefurrowsat25–30cmandplaceseedsat5cmintervalsalongthefurrow:thiswillrequireabout75–80kgofseedperhectare.Afterbroadcastingtheseediscovered,forexamplewiththeuseofaspine-toothedharrow.Forrowsowing,thedistancebetweenrowsisdeterminedbythewidthoftheweedingimplementused.

Forrainfedorirrigatedlowlandrice,dryseeding(thatis,plantingofdryseedintodryormoistsoil;dryseedisseedthathasnotbeenpre-germinated)canbedoneinrowsorbroadcast.Inrows,80kgperhectaredryseedisused;forbroadcasting100–120kgseed per hectare is used.

Note:Ifwatercontrolanddroughtareproblems,transplantingispreferabletodirectsowing.

Transplanting:Transplantingseedlingsisoneoptionforlowlandricesystems.Hereseedsaresowninanurserybedandseedlingstransplantedintothefield.

Nursery for seedlings

Thenurserybedcaneitherbeinthemainplot(Photo3),orsomewhereelse:insomericegrowingschemesthereisonesiteforallthefarmers’nurseries.

Ifinthemainplot,selectalocationnottoofarawayfromtheirrigationcanalforeasyaccesstowater.

Becauseofriceyellowmottlevirus,itisbettertohavethenurseryawayfromthefieldborder.Thisisbecauseinsectslivinginthebordercaninfectplants;weedsintheborderprovidegoodhabitatforinsectsastheborderisalwaysmoistduetotheclosenesstothe drain.

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There are three main options for producing seedlings:

1.Sowingdryseedindrynurserybeds,whicharethenflooded.Seedlingsgrowninthiswayhavedeeperroots,whichmakesthemmoredifficulttotransplant.

2.Sowingpre-germinatedseedsontowetmud.Seedlingsgrowninthiswayhavemoreshallowrootsandarethereforeeasiertotransplant.Seedcanbebroadcastedonthemuddyseedbedinsteadofplantinginrowstosaveonlabour.Iftheseedbedis 1mwide,forevery10mlengthofseedbeduse1kgseed.

3.Sowinginadapognursery,alsoreferredtoasamatnursery,forwhichanumberofdifferentmodificationshavebeendeveloped.Thenurseryismadeonafirmsurfacethatrootscannoteasilypenetrate and hence uprooting seedlings from the nursery is easierthanfromdryorwetmudnurseries.Thenurserybedcanbeconstructedoversheetsofplastic,bananaleavesoraconcretesurface.Beforeplanting,awoodenframecanbeusedtocreatecells,eachmeasuring30cmx50cmand4cmdeep.Amixofsoil,well-rottedmanureandricehullsisplacedintheframeandtheframeisthenremoved.Alternativelythesoilmixturecanbeplacedonthefirmsurfacewithoutusingthewoodenframe.Pre-germinatedseedsarethensowninthenurserybybroadcasting.Iftheseedbedis1mwide,forevery10mlengthofseedbeduse10kgseed.

Photo 3. Nurserycanbesetupinthefield(photo: CABI/IPNI)

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A

D

G

J

B

E

H

K

C

F

I

Photo 4. Pre-germinating seed. (A) Get clean paddy rice seed (photo: CABI) (B) Wash theseed.Removedebrisandfloatingseed(photo:CABI)(C)Soakseedinwaterfor24hours (photo: CABI) (D)After24hours,pouroutwater(photo:CABI)(E) Place seed in bag (photo: CABI) (F)Rollbagwithseedinside(photo:CABI)(G)Placebaginbucket,oranother container (photo: CABI) (H)Seedcanstayinbucketfor24hours(photo:CABI)(I)Periodicallychecktheconditionofseed(photo:CABI)(J)Iftoodry,addmorewater(photo: CABI) (K) Sprouting seeds (photo: CABI).

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Thewidthofthenurserybedshouldallowforworkingwithoutsteppingonthebed(Photo5).Awidthof1misidealandthebedshouldberaisedtoabout5cmabovethegroundsurface.

Thesizeofthenurserydependsonthetypeofnurseryandtheareatobeplanted.Ifseedingonwetmud,thenurseryshouldbeaboutatenthoftheareatobeplanted;ifseedingusingthedapogmethod, the nursery should be about a hundredth of the area to be planted.

How to pre-germinate rice seedTopre-germinatericeseed,submergeajutesackcontainingseedinwaterfor24hours(Photo4).After24hours,removethebagfromwaterandplaceinashadyplacewheretheaircancirculatearound the bag. Ensure than the temperature of the bag does not exceed42°C.Afteranother24hoursthepre-germinatedseedisreadyforsowing:thisshouldbedonebeforetherootsaremorethan5mminlength.

Thereisnoneedtoapplyfertilizerinthenurseryiftheseedlingswillbetransplantedatninedays.If,however,seedlingsaretobeplantedinafieldwherewatercontrolisnotgood(e.g.whichisnotlevelledproperlyorthathasahighdepthofwater)applyfertilizer(suchas50gdiammoniumphosphate(DAP)persquaremetre)tomaketheplantsgrowfasterandtallersothattheycanbetterwithstandthewater.

Transplanting seedlingsSeedlingsshouldbetransplantedbetween9and21daysfromsowingforseedlingsgrownfrombothpre-germinatedseedanddryseed.Ifcrabsinmangroveareaproblem,allowseedlingstogrowformore than 21 days so they can better resist predation. If transplanting after21days,fertilizercanbeappliedtothenurseryifnutrient

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A B

C D

Photo 5. Seedlings in nursery bed. (A)Seedscoveredwithbananaleavestopreventdryingofsurfacewhenseedsaresprouting(photo:CABI)(B)Avoidcoveringseedbedwithricestraworgrass.Strawandgrassmayhaveseedwhichcangrow,contaminatethecropandmaybedifficulttocontrol(photo:CABI)(C)Newlyuncoveredseedlings(photo:CABI)(D)Dormancycanbeaproblemwithseedofsomericevarieties–forexample,3rdand7throwfromleftinthephoto(eachrowisavariety).Ifdormancyissuspected,waitforatleast2–3weeksafterharvestingseedbeforeplantingit(photo:CABI).

deficienciesareexpected(forexample,50gDAPpersquaremetre).

Wet-bedseedlingsshouldbeplantedatadepthof1.5-3cmanddapogseedlingsatadepthof1.5cm.Thisisbecausetherootsofdapogseedlingsdonotgrowasdeepasthoseforwet-bedseedlings.

Itisbesttoplantseedlingsoutinthericefieldsinrows,withregularrowandbetween-plantspacing(seeTable4forsuggestedplantarrangements).Rowplantinghasanumberofadvantagesoverrandomplanting:itmakesweedingandfertilizer,herbicideandinsecticide application easier and also helps ensure optimal planting density.Toensurestraightlinesandcorrectspacing,wire,twineorwoodenplantingguidescanbeused(Photo6).

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A

D

G

B

E

C

F

Photo 6. Transplanting seedlings from nursery. (A) Seedlings in nursery ready for transplanting (photo: CABI) (B)Seedlingsuprootedfortransplanting–iftootall,cutofftipsto encourage seedlings stray upright on transplanting (photo: CABI) (C) Seedlings can be spacedat20cmbetweenrowsand20cmalongrows.Thisplantingropeismarkedat20cmintervals(photo:CABI)(D)Place2–3seedlingsateachpoint(photo:CABI)(E) Place theseedlingsgentlyintothemud,withthenoderemainingabovethewater(photo:CABI)(F) Seedlings spaced at 20 cm (photo: CABI) (G)Seedlingsinrows(photo:CABI).

Formechanizedtransplanting,thedapogtypenurseryisrequired.Theseedlingsareraisedinasoilmixtureonafirmsurface.Whentransplanting, seedlings are uprooted in a mat and placed into the rice planter.

Extraseedlingsshouldbetemporarilyplantedaroundtheedgeofthefieldandusedtofillanygapsafteraround10days.

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Table 3: Characteristicsofdryandpre-germinatedseedsowingandtransplanting.

Dry seed sowing Pre-germinated seed sowing

Transplanting

Features Dry seed broadcast orsowninrowsintodry soil

Seedsarepre-germinated, then sowninawetbed

Seedsarepre-germinated,grownin a seedbed, then seedlings are transplanted to a wetfield

Advantages Less labour required than transplanting

Increases rate and percentage of seedling emergenceLess labour requiredcomparedwithtransplanting Requires less waterduringlandpreparation

Goodplantgrowth,tillering and yieldOptimum plant density obtainedLessweedcompetition as seedlingsgrowaheadofweedsGoodweedcontrolUniform maturity

Disadvantages Seeds are placed on the soil surface and can be eaten by birds and other animalsWeeds can be a problem as both weedsandriceemerge at about the same timeLodging can be a problem as plants maynotbefirmlyanchored to ground

Weeds can be a problemWaterlogging can be a problem, especiallywhencrop is young if land isnotlevel

More labour required

Suitability for upland Suitable Not suitable Not suitableSuitability for rainfed lowland

Suitableifwateriswellmanaged

Suitable Suitable

Suitability for irrigatedlowland

Suitable Suitable Suitable

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Table 4. Optimalspacingfordifferenttypesofvarietyandseasons.

Variety Dry season: fertile soil

Dry season: poor soil

Wet season: fertile soil

Wet season: poor soil

Tall,leafy,heavytillering, susceptible to lodging

30x30cm 25x25cm 35x35cm 30x30cm

Short, lodging resistant

20x20cm 20x15or 20x10cm

20x20cm 20x15or 20x10cm

Key messages

• Ploughsoiltoadepthof15–20cm,andthenharrow.Avoiddeep ploughing.

• Forlowlandrice,levelfieldtoaslopeoflessthan1%. • Foruplandrice,alwaysplantseedsdirectlyinfield. • Lowlandricecanbesowndirectly,orseedcanfirstbegrowninaseedbedandthenseedlingstransplantedtofield.

• Ifdirectseeding,seedscanbepre-germinatedorplantedbeforepre-germinating.

• Fornurseryseeding,pre-germinateseedsbeforeplanting. • Noneedtoapplyfertilizerinnurseryiftransplantingwithintherecommended9–21daysaftersowing.Iftransplantinglaterorintodeepwater,apply50gDAPpersquaremetretonursery.

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5. Rice management

Water management: irrigated lowland riceActivewatermanagementisonlypossibleinirrigatedlowlandrice.Theobjectivehereistokeepawaterlayertocontrolweeds:thewateractslikealayerofweed-suppressingmulchforlandplants.

Itisimportanttoensurethatthepointatwhichnodesstartshouldnotbeunderwater.Thewaterlevelmustincreasewiththeheightoftheplant:maximumdepthshouldnotexceed 10 cm.

Fromtransplantingtopanicleinitiationmaintainadepthof 2–3cmofwater,afterpanicleinitiation5–7cm,thendrainfield7–14daysbeforeharvesting.Aftertillering,raisingthewaterlevelfrom2–3cmto5–7cmdoesnothaveanyimpactonplantdevelopment.

Whenapplyingfertilizer(seepage22),drainwater,applyfertilizer,thenwaitatleastthreedaysbeforelettingwaterbackin.

WeedingWeeds can be controlled mechanically, pulling by hand or using a machine, or by use of herbicides.

Herbicidescanbeusedtocontroldifficultweeds,suchasoryzaweeds(e.g.wildrice)andgrasseswithrhizomes.Ifusingherbicide,applynon-selectivetypesbeforeploughingtodestroyalltypesofweeds.Theweedsarethenploughedin21daysafterapplying the herbicide.

The decision on the type of herbicide to use should depend ontimingandtypeofweeds.Someherbicidescanbeapplied

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beforeweedsemerge;forexample,butachlor,apre-emergenceherbicide, does not harm rice but controls many annual grasses, sedgesandbroadleavedweeds.Alternatively,aselective post-emergentherbicidecanbeusedaftercropestablishmentwhenweedsstarttoappear;forexample,propanil,apost-emergentherbicide,controlsgrassesbutnotbroadleavedweeds.Theherbicideshouldbesprayedwhenweedsareatthe2–3leafstage.Thiscontrolsweedsforaboutonemonth.Later,weedscan be controlled by pulling out by hand or using a mechanical weeder.

Thefieldmustbekeptweed-freeuntilharvest(Photo7)asweedsaffectthequalityofricegrainsorseed.Somefarmersstopweedingwhenthericehasflowered,butthisisnotrecommended.

Manurethatisnotwelldecomposedcanbeasourceofweedseeds.Weedseedscanalsobecarriedtoneighbouringfieldsthroughirrigationwater.Toavoidintroducingweedsintoricefields,manureshouldbewelldecomposedandweedsshouldbedestroyed before they form seeds.

Forirrigatedlowlandrice,farmersshouldmaintainashallowlayerofwater.Farmersoftenusetoomuchwaterthinkingtheycancontrolweedsbetterthatwaybutthisisbadpractice.Withgoodlevellingofthesoil,awaterdepthofabout2–5cmcanbemaintainedtocontrolweeds.

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A B

C D

Photo 7. Weeding. (A)Uplandriceunweeded(photo:CABI)(B)Inirrigatedrice,weedscanbecontrolledtosomeextentbymanagingwater(photo:CABI)(C)Manualweedingusing hoe (photo: CABI/IPNI) (D)Pullingoutweeds(photo:CABI/IPNI).

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Nutrient managementToensuresustainableproductionandavoiddepletinganddegradingthesoil,thenutrientsremovedwhenthericecropisharvestedneedtobereplaced.

Foreverytonneofricegrainsplusstrawharvestedaround22kgofnitrogen(N),phosphorusequivalentto10kgofP2O5 and potassium (K)equivalentto27kgofK2Oaretakenupfromthesoilbythecrop.

These nutrients can be replaced by application of mineral fertilizersandorganicmatter(suchasmanureandricestraw)tothesoil,andalsobytheuseofnitrogen-fixinglegumessuchasgreen manures and in crop rotations.

Notallthefertilizerappliedtothesoilisavailabletothecrop.Toallowforthis–whichisknownas‘fertilizeruseefficiency’-foreveryadditionaltonneofgrainharvested,fertilizercontainingaround60kgN,30kgP2O5and30kgK2O needs to be applied to supportlong-termsustainablecropping.

Fertilizer useTheoptimaltypeandamountofmineralfertilizerthatisneededwillvaryindifferentlocationsandsituations.Somegeneralguidelinesareprovidedinthetablesbelow–seeThe4Rs:rightsource,rate,timeandplace,below.

Theaimoftheseguidelinesisnottomaximiseproduction;ratheritis to increase yields by about one tonne per hectare for upland and rainfedlowlandrice,andbyupto3tonnesperhectareforirrigatedlowlandrice(seeTable5).Althoughhigheryieldsarepossible,aimingtoincreaseyieldsbybetween1and3tonnesperhectareismorecost-effectiveandalsolikelytobewithinthereachofsmallholder farmers.

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Theserecommendationsarebasedontheuseoffivefertilizersthatarecommonlyusedonrice:diammoniumphosphate(DAP);muriateofpotash,alsocalledpotash(MOP);ureaintheformofsmall granules (about 2mm in diameter) and urea in the form of ‘supergranules’orpellets(3-5geach);andNPK15-15-15.

Table 5. Averagecurrentyieldsandachievableyieldswhengoodseedandfertilizerareusedotherandgoodagronomicpracticesarefollowed.

Rice system Average current yield tonnes per hectare

Achievable target yield tonnes per hectare

Upland rice 1 2

Rainfed lowland rice 2 3-4

Irrigated lowland rice 5 6-8

Fertilizer response curvesThewaythatcrops,includingrice,respondtofertilizercanbedescribedbyafertilizerresponsecurve(seeFigure2):thisshowstheimpactofincreasingamountsoffertilizeronyield.

 

 

 

 

3.5  

3.7  

3.9  

4.1  

4.3  

4.5  

4.7  

0   10   20   30   40   50   60  

Yield  

Amount  of  fertlizer  applied  

Maximum  benefit  per  dollar  invested  

Maximum  yield  

Figure 2. Fertilizer response curve.

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Asthefigureshows,tobeginwiththeyieldincreasessteeplyasmorefertilizerisadded,butastheamountoffertilizerappliedincreases,theextrayieldachieveddecreases.Eventuallyaddingmorefertilizerwillhavenofurtherimpactonyield.

Thebestreturnoninvestmentinfertilizerisachievedwheretheresponsecurveissteepest–herethegreatestincreaseinyieldisachievedperunitoffertilizeradded(circledinyellowinthediagram).Sotherecommendationsgivenbelowaimtofallonthis,thesteepestpartofthecurve.

Actualincreasesinyieldwill,however,varydependingonmanyvariables.Theseinclude:

• thecharacteristicsofthesite,forexamplethesoilmaybelocallydeficientinoneormorenutrientsinadditiontoN,PandK(whicharethefocusoftheserecommendations)

• weather–especiallyrainfallandamountofsunshine• pests and diseases present• othermanagementpractices,suchasvarietiesused,water

managementandweeding• incorporation of organic matter to the soil, including

livestockmanureandricestraw• qualityofmineralfertilizerbeingused:somefertilizers

aresub-standard–theymaynotcontaintheamountofnutrientsshownonthelabel.Fertilizershouldthereforeonly be purchased from trusted sources, such as local agro-dealershops.

So,iftargetyieldsarenotachievedfollowingtheserecommendations,thenexpertassistanceshouldbesoughttoworkoutwhatfactorisholdingbackproduction.

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Short term gains and sustainable croppingIncomparisontouseoflittleornofertilizer,thefertilizerrecommendationsgivenbelowarelikelytoincreaseyieldsandgenerate higher incomes from sales of surplus production in most situations, at least in the short term.

Althoughadoptingtherecommendationsprovidedbelowisbetterthanapplyinglittleornofertilizer,thesoilmightstillbe‘mined’–morenutrientsmightbetakenoutwiththecropthanarebeingreplaced each season by application of mineral and organic fertilizer.

Ideally farmers should, therefore, use these recommendations for afewseasonsonly.Afterthistheyshouldconsiderreinvestingsomeoftheirincreasedprofitsfromtheirhigheryields,forexamplebypayingforlaboratorysoilandleaftests.Theresultsofthesetestscanbeusedbyexpertstodesignmuchbetterfertilizerrecommendationssuitedtotheirfarmswhichwillmaintainsoil health and support sustainable production in the future. In somecasesmulti-locationnutrientomissiontrialstodeterminesoil nutrient supply potential and N, P and K responses may be possible, but these are outside the scope of this guide.

The 4Rs: right source, rate, time and placeIfsitespecificfertilizerrecommendationsareavailabletheseshouldbefollowed.Incasethesearenotavailable,thissectionprovidessomeexamplesofbasalandtop-dressingoptions.

Theguidelinesbelowaresimple,blanketrecommendationsbasedonthe‘4Rs’-thatistherightsource,rightrate,righttimeandright place of nutrient management.

Usuallynitrogenisthefirstmostlimitingnutrienttoriceproduction

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followedbyphosphorusandpotassium,andsotheseguidelinesfocusonthesethreemajornutrients.

Theseguidelinesareintendedforuseinsituationswherethesoilpreparationandplantingadvicegiveninthiscroppingguidehasbeenfollowed;inseasonswhererainfallisclosetonormaland/orirrigationwaterisavailableinadequateamounts;andthesoileitherhasnoproblemwithsoilalkalinityorsalinity,orappropriatestepshavebeentakentoaddresstheseissues(seeSection6,What can go wrong).

Thefertilizerrecommendationsbelowareprovidedasbothkgperhectare and g per square metre1.Farmersare,however,likelytofinditdifficulttomeasureoraccuratelyestimatesmallamountsoffertilizer.Tohelpovercomethisproblemseebox,Farmerfriendlyfertilizermeasurements,whichshowshowcheap,locallyavailableitemscanbeusedascalibratedscoopstomeasurefertilizer.

Basal fertilizerisappliedwhentheplotisbeingpreparedforplantingoratthetimeofsowingorplanting.Itprovidesnutrientsneededbythecropearlyinitsgrowingcycleandalsonutrientswhichareslowlyreleasedoverthegrowingseason.Forlowlandrainfedrice,wherewaterlevelscannotbemanaged,allfertilizerhastobeappliedasbasalfertilizer.

Top-dressing isapplicationoffertilizerafterthecrophasstartedgrowing.Itprovidesnutrients,especiallynitrogen,whichareneededlaterinthecrop’sgrowingcycle,forexamplewhenthepanicle(grain)isformingandalsonutrientswhich,ifappliedearlier,wouldbelostintotheairorwater.

Upland rice:Thefollowingtablesgivesomeexamplesoftherightamountsofbasalandtop-dressingfertilizersforuplandrice.1 There are 10,000 square metres in a hectare: grams per square metre is therefore the amountinkgperhectaredividedby10,000

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Applyingthesefertilizerscanhelpfarmerstoincreasetheiryieldsfrom about one tonne per hectare to about 2 tonnes.

ThecombinationofeitherExample1basalfertilizerplusExample1topdressing,orExample2basalfertilizerplusExample2topdressingwillbothsupplyatotalofabout60kgN,30kgP2O5 and30kgK2O per hectare.

Basal fertilizers for upland ricekg per hectare

(number of 50 kg bags) grams per square metre

Example 1 200 kg (4 bags) NPK 15-15-15 20 g NPK 15-15-15

Example 265 kg (1.3 bags) DAP

AND50 kg MOP (1 bag)

6.5 g DAPAND

5 g MOP

Basalfertilizershouldbeappliedwhenthesoilisbeingpreparedfortheuplandricecrop.Thefertilizerisbroadcastandthenharrowedintothesoil.

Thetop-dressingshouldbeappliedintwoequalsplits:thefirstaround 21 days after seeding and the second at panicle (seed head)initiation,around45-50daysafterseeding.Top-dressingshouldbeappliedafteragoodrainwhenthesoilismoist:donotapplytodrysoil.Ifamechanicalweederisbeingused,thetop-dressingcanbeappliedatthesametimeasweeding.

Top-dressing for upland ricekg per hectare

(number of 50 kg bags) grams per square metre

Example 165 kg (about 1.3 bags) urea split into 2 equal

applications

6.5 g urea split into 2 equal applications

Example 2 100 kg (about 2 bags) urea 10 g urea split into 2 equal applications

Lowland rainfed:Becausethewaterlevelcannotbemanagedin

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thissystem,allfertilizerneedstobeappliedwhenthesoilisbeingpreparedforthericecrop(basal)–notop-dressingisapplied.

Thefollowingtablegivetwoexamplesoftherightamountsofbasalfertilizersforimproved,high-yieldingvarietiesgrowninlowlandrainfedricesystems:eitherExample1orExample2should be applied.

Applyingthesefertilizerscanhelpfarmerstoincreasetheiryieldsoflowlandrainfedricefromabout2tonneperhectareto3to4tonnes.Inbothexamples,thebasalfertilizerwillsupplyabout60kgN,30kgP2O5and30kgK2Operhectare.Thebasalfertilizershouldbebroadcastandthenharrowedintothesoil.

Basal fertilizer for lowland rainfed ricekg per hectare

(number of 50 kg bags) grams per square metre

Example 1

200 kg (4 bags) NPK 15-15-15AND

65 kg (about 1.3 bags) urea

20 g NPK 15-15-15AND

6.5 g urea

Example 2

65 kg (1.3 bags) DAPAND

100 kg (about 2 bags) ureaAND

50 kg MOP (1 bag)

6.5 DAPAND

10 g ureaAND

5 g MOP

Iftraditional,tallvarietiesaregrown,whicharepronetolodging,justtheurea(100kgperhectare)canbeused.

Lowland irrigated: Thefollowingtablesgivesomeexamplesoftherightamountsofbasalandtop-dressingfertilizersforhigh-yieldingvarietiesgrowninlowlandirrigatedricesystems.

Applyingthesefertilizerscanhelpfarmerstoincreasetheiryieldsoflowlandirrigatedricefromabout5tonneperhectaretoupto8tonnes.Thecombinationofeitherofthebasalfertilizeroptions

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plusExample1ofthetopdressingoptionswilltogethersupplyabout150kgN,45kgP2O5and45kgK2O per hectare.

EitherofthebasalfertilizeroptionscanalsobecombinedwithtopdressingExample2:althoughthissupplieslessN,thisoption(ureasupergranules)ismoreefficientandsoeithertopdressingoptionwillsupportsimilarlevelsofproduction.

Thebasalfertilizershouldbeappliedbybroadcastingbeforepuddling.

Basal fertilizer for upland irrigated ricekg per hectare

(number of 50 kg bags) grams per square metre

Example 1100 kg (2 bags) DAP

AND30 kg (0.6 bags) MOP

10 g DAPAND

30 g MOP

Example 2 300 kg NPK 15-15-15 30 g NPK 15-15-15

Fornormalgranulatedurea(Example1,below),thetopdressingshouldbeappliedintwoequalsplits:thefirst10-15daysaftertransplantingandthesecondatpanicleinitiation.Toapplyurea,thefieldshouldbedrainedsoitismuddy,theureaappliedbybroadcastingand,after2–3days,thefieldre-flooded.UreashouldnotbebroadcastonfloodedfieldsasthiswillleadtohighlossesofN.

The pellets (also called super granules) used in the deep urea placement(DUP)method(Example2,Top-dressing for upland irrigated rice)aremuchlargerthannormalureafertilizergranules–typically3to5grams.TheyreleaseNslowlyandlossesarereducedcomparedtoordinarygranules;theyarealsomoreefficient,resultinginlargerincreasesinyieldperunitofureaapplied–solessureacanbeusedwhenpelletsareusedinplaceofgranules.Forthe DUP method, the urea is applied once only at the tillering stage. One3gramsupergranuleshouldbeplacedbetweeneveryfourplantsineveryotherrowatadepthof7-10cm3.

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Cropsgrowninirrigatedlowlandsystemsinthedryseason,whensunshineisabundant,needmoreNthancropsgrownintheloweryieldingwetseason.RicethatisdeficientinNispalerthanhealthycrops (see Nutrient deficiencies, page 32).

Top-dressing for upland irrigated ricekg per hectare

(number of 50 kg bags) grams per square metre

Example 1 230 kg urea split into 3 equal applications

23 g urea split into 3 equal applications

Example 2187.5 kg super granules for DUP in one application at

tillering only

19 g super granules for DUP* in one application at

tillering only*Assuming row and plant spacings of 20 cm x 20 cm, that is 250,000 plants per hectare. One 3 gram urea pellet between every 4 plants in every other row (equivalent to one pellet per 4 plants) totals 62,500 x 5 g = 187,500 g (187.5 kg) per hectare.

Note:Iftraditionalvarietiesaregrown,onlyuptoamaximumof100kgureaperhectareisrecommended:applicationofhigherlevelsofnitrogentotraditional(tall)varietiesisnotadvisablebecausethesevarietiestendtolodge(fallover).

Farmer friendly fertilizer measurements

Itisdifficultforfarmerstoknowwhatsmallamountsoffertilizer,suchas10gofurea,lookslikeandtheywillnothaveaccesstoweighingscales.

Thesolutiontothisproblemistoidentifyalocallyavailablecontainer,suchasmetalcrowncorkbottle-topforbeeror soda3.Thebottle-topcanthenbeusedasascoopformeasuringfertilizer.

Forlargeramounts,discardedwaterbottlesmakeusefulcontainers.

Differentfertilizershavedifferentdensities,sowhileabottle-topfull(level,notheaped)ofNPK15-15-15willweigh3g,abottle-topfullofDAPwillweighjustunder5g.

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Forthosewithaccesstotheinternet,atool(theOFRAfertilizercalibrationtool)isavailableatCABI-ASHCwebsite(www.africasoilhealth.cabi.org).Thistoolenablestheusertocalibrateanycircularcontainerthatcanbefilledwitharangeofdifferentfertilizers.

Seetable,below,forotherfertilizers:valuesinthistablehavebeen calculated using the CABI tool.

Fertilizer type Weight of fertilizer (g) per metal beer or soda bottle-top full

CAN 3DAP 5MOP 6

NPK 15-15-15 3SSP 3.5TSP 7Urea 4

So,forexample,toapply10gofureapersquaremetreofsoil,twoandahalfbottle-topsfullofnormal(granular)ureafertilizerareneeded:2.5x4g=10g

Toapply20gofNPK15-15-15,justunder7bottle-topmeasuresareneededpersquaremetre:7x3g=21g.Forlargeramounts,acut-offplasticwaterbottlewillbeamoreconvenientmeasure,butthiswillneedtobecalibratedusingtheOFRA fertilizer calibration tool.

Oncefarmershavesomeexperienceofusingthemeasuretheywillknowwhattheappropriateamountofagivenfertilizerlookslike.Theycanthenstopusingthemeasureandapplyathree-fingerpinchoffertilizerwhichcorrespondstotherightamount.Fromtimetotimeitwouldbeadvisabletocheckthattheirpinchisdeliveringtherightamountoffertilizer.

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Use of CAN and other nitrate fertilizersNitrate-containingfertilizers,suchasammoniumnitrateorcalciumammoniumnitrate(CAN)arenotsuitableforricewhenappliedatorbeforeplanting.Unlikeammonium-containingfertilizers(suchasDAPandammoniumsulphate,andalsourea,whichishydrolysedtoammonium),thenitrogeninnitrate-containingfertilizerscanbelostquicklybydenitrificationoncethefieldisflooded.Theycan,however,beusedfortopdressingwhenuptakeofnutrientsisproceedingrapidlyasthetopsoiliscoveredwithamatofrootsandNlossesarethereforeminimized.

A B

C ED

Photo 8. Applying fertilizer. (A)Topdresswithnitrogenfertilizerattilleringandpanicleinitiation (photo: CABI/IPNI) (B)Applyingnitrogenfertilizerinformofpelletsreducesnutrientlossesandsynchronisescropdemandwithnutrientrelease.Thesizeofpelletcanbevariedtotakeintoconsiderationtheamountoffertilizerrequired(photo:CABI/IPNI) (C) The pellets can be pushed into the ground by hand or an applicator (photo: CABI/IPNI) (D)Fertilizerisplacedinthefunnel(photo:CABI/IPNI)(E) The funnel containingfertilizeristhenplacedintotheground(photo:CABI/IPNI).

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Use of manureWhenavailable,animalmanurecanbeanimportantresourceforimprovingriceyields.Additionofmanurehelpstomaintainsoilorganicmatteratgoodlevels.Manureisalsoanimportantsourceofnutrients,whicharemostlyreleasedfollowingitsdecomposition.

However,manurecontainsalowerdensityofnutrientscomparedwithmineralfertilizersandtheamountofnutrientscontainedinmanureavailableonsmallholderfarmsisusuallyinsufficienttosustainrequiredlevelsofriceproductivity.Ifmanureispurchaseditcanbemoreexpensivethanequivalentamountsofmineralfertilizerandisalsomuchmorebulky,whichmakestransportexpensive.

Usingmanureincombinationwithfertilizergivesbetteryieldsthanusingeitherinputalone.Ideally,5–10tonnesofanimalmanureperhectare(0.5to1kgpersquaremetre)shouldbeappliedeachyear on the surface and incorporated during ploughing. Some studieshavesuggestedthatwithadditionofmanureatthislevel,therequirementformineralfertilizerscanbereducedbyhalf.So,farmerswhoapplymanureinthiswaycouldreducetheamountofmineralfertilizersuggestedinthetablesbyhalf.

Thenutrientcontentofmanure,however,variesconsiderably.So,iffarmersreducemineralfertilizertheyneedtobeonthelook-outforsignsofnutrientdeficiencies,especiallyofN,intheirricecrop;seeSection6,Whatcangowrong,fordescriptionsandphotographsofricecropswithvariousnutrientdeficienciesanddetailsofwhattodowhenthesesignsareseen.

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Use of green manureGreenmanuresaremostlynitrogen-richlegumecropsgrowntoprovidenitrogenforthenextricecropandtoaddorganicmattertothesoil.Greenmanuresareplantedbeforeorafterrice,whenthelandisvacant,allowedtogrowforsometime,thenslashedand either left on the soil surface or ploughed into the soil.

Althoughgreenmanurecanbeusedinallricegrowingsystems,theyareespeciallyusefulforimprovingpooruplandsoils,whichare often acid or easily eroded. They are also useful in situations wheretimelyavailabilityofmineralfertilizersisunreliable.GreenmanuresshouldbeconsideredwhensoilorganicmatterandNlevelsarelowandfertilizerpricesarehigh,particularlyinregionswithlonggrowingseasons.

Incorporation of a green manure crop before planting rice can add theequivalentofaround2bags(100kg)ofureaperhectare,sothetop-dressingcanbeadjustedaccordinglysavingthefarmersignificantamountsofmoney.Foruplandricethegreenmanurecouldsavealltheureatopdressing;forlowlandrainfedriceitcouldsavealltheureainbothbasalfertilizerexamples;andforlowlandirrigatedriceitcouldreducetheamountoftopdressingureabyabout40%.

If farmers plan to use green manure as part of their nutrient managementpackagetheyneedtochosetherightgreenmanure:• Itneedstosuittheirgrowingconditions–theclimate,soiland

wateravailable.• Itmustbeeasyandcheaptogrow.• Goodqualityseedthatgerminateswellneedstobereadily

available.• Itneedstogrowwithoutneedforirrigation,fertilizeror

pesticides.

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• Itsgrowingseasonmustfitthetimeavailablebetweenricecrops: it must not delay rice planting

• Thebenefitintermsofnitrogenfertilizersavedmustbesignificantlygreaterthanthecostofseedandlabourneeded.So,ifthegreenmanureprovides100kgNperhectare,thecostof seed and labour should be no more than the cost of about 2 bag of urea per hectare.

Someexamplesofgreenmanurecropssuitableforuseinricecropping systems in Africa include:

Sesbania (Sesbania rostrata):Asmallsemi-aquaticleguminoustreethatnaturallyoccursinAfrica.Ithasnitrogenfixingnodulesonbothstemandroots.Sesbaniaisfastgrowthandabletoconvertlargeamountsofatmosphericnitrogenintoausableformforplants–theequivalentof1to2bagsofureaperhectareinbetween40and60days.Aconstrainttogrowingthisgreenmanurecanbeavailabilityofseed.

Sesbaniaseedisbestbroadcastattherateof30kgperhectare(3g per square metre) before the onset of rains. The better the land isprepared,thebetterthecropestablishes;alsotheseedratecanbereducedonwellpreparedseedbedsto16kgperhectare.Germinationratesareimprovediftheseedisimmersedinveryhotwater(100°C)forjust3seconds.Inirrigatedsystems,watershouldbeappliedifthesoilcracksandleavesareshed.Thecropisincorporatedintothesoilbeforeitbecomestoowoody,whichisbetween45and60daysaftersowing.Todothisthecropcanbeslashedbyhandpriortoploughing;alternativelyitcanbeknockeddownusingaplankdrawnbydraftanimals,andthenploughedin.Ifavailable,machinessuchashydrotillersortractorsandrototillerscan be used.

Other legume crops: Various legume crops, such as soybeans,

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pigeonpeasandmungbeans,canbegrownasfastgrowinggreenmanurecropsthatcanaccumulatesignificantamountsofnitrogenwithin45−60daysofsowing.

Residue managementIffarmersareabletoreturnthericestrawtothefieldandusemineralfertilizersthenthesoil’snutrientbalancewillbemuchimproved.However,demandforalternativeusesforstraw,includingasfuelforcooking,asathatchingmaterialandasfeedforlivestock,maymakethisdifficultorevenimpossible.

Ricestrawandstubblecontainsabout40%ofthenitrogen(N),33%ofthephosphorus(P),85%ofthepotassium(K),44%ofthesulphur(S)and85%ofthesilicon(Si)takenupbyriceplants.Incorporationofstrawintothesoilthereforereturnsmuchofthenutrientstakenupbythecrop.Thestrawshouldbespreaduniformlyinthefieldtoavoidcreating‘nutrienthotspots’.

Wheremineralfertilizersareusedandallthestrawisincorporated,reservesofsoilN,PandKaremaintainedorevenincreasedandmicronutrients(e.g.zinc)arealsoreturnedtothesoil.

BurningstrawresultsinthelossofalmostalltheNcontent,butlossesofP,KandSaresmaller.Burningalsoresultsin‘hotspots’ofnutrientaccumulationinpartsofthefieldwherethefiresoccurredwhileotherpartsofthefieldsgetdepleted.Burningis,however,lesslabourintensivethanincorporatingstrawintothesoil.

Early,dry,shallowtillage(5–10cmdepth)toincorporatecropresiduesandenhancesoilaerationduringfallowperiodshasbeenshowntoincreaseNavailabilityuptothevegetativegrowthphaseofthesucceedingricecrop.Shallowtillageofdrysoilrequiresafour-wheeldrivetractorandshouldbecarriedoutupto2–3weeksafterharvestincroppingsystemswherethedry-moistfallow

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periodbetweentwocropsisatleast30days.

Note:IncorporationofstrawandstubblewhenwetsoilisploughedresultsinatemporaryimmobilizationofN.Cropestablishmentshouldbecarriedout2–3weeksafterstrawincorporation;alternatively,urea(asasourceofN)shouldbeappliedalongwithstraw.However,thebenefitstoyieldfromincorporation of crop residues are greater in the long term.

A B

Photo 9. Residue management. (A)Apileofstrawreadyforburning(photo:CABI) (B)Ferryingricestovertofeedlivestock(photo:CABI).

Crop rotationsIn upland rice:Ricecanberotatedwithcropsincludingmaize,sorghum,millet,cottonandlegumes,suchascowpeasandbeans.

Farmerstendtoprefertoapplynutrientstoriceandmaizeratherthansorghumandmilletasthereturnstoinvestmentarehigher.Riceisthemostprofitablecroptoapplyfertilizerbecauseitrespondswelltofertilizerandalsobecauseofthehighpriceitattractsinthemarket.Althoughminimalamountsofnutrientsareappliedtolegumes,legumesthatfixnitrogencancontributetoimprovedsoilfertilityandhenceindirectlyleadtoimprovedriceyields in subsequent rotations.

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In lowland rainfed rice:Ricecanberotatedwithvegetableslikepotatoes(sweetandIrish),okra,tomatoesandaubergine,andalsowithlegumessuchasbeans(Photo10).

A

B

Photo 10. Rotating rice with other crops. (A)Growingsweetpotato(right)afterrice(left)helpsinmanagementofweeds,pestsanddiseases(photo:CABI)(B)Ricegrownafteralegumecropgivesbetteryieldsthanafteranotherricecrop(photo:CABI).

Inlowlandirrigatedrice:Aricecropcanbefollowedbyanotherricecrop,orvegetablessuchasonions(shallots),tomatoesandokra.Vegetablestendtobemoreprofitablethanrice.Farmers

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tendtoapplymineralfertilizersandalotoforganicfertilizerstovegetablesandlessonrice,butricegrownafteravegetablecropcanbenefitfromtheresidualfertilizer.

Nutrient deficienciesSeechapter6,What can go wrong, for table listing the symptoms, situationswheretheyarelikelytooccurandremedialmeasuresforthemostcommonnutrientdeficienciesthataffectrice.

Salinity managementSalinesoilscontainhighamountsofsodiumchloride;varyingamounts of sodium sulphate, calcium chloride and magnesium chloride can also be present.

Salinityisnoteasytoidentifyinthefieldbutcanbediagnosedorconfirmedinthelaboratorybymeasuringsoilelectricalconductivity(EC),pHandsodiumexchangecapacity,allofwhichare higher in saline compared to normal soils.

SalinityleadstodeficienciesofKamongstotherdeficiencies.This is not a problem for upland rice, but it can be a problem for lowlandrainfedrice(e.g.inmangroves).Herethesolutionistoimprovedrainageortousetolerantvarieties.Itismostlyaproblemwithirrigatedlowlandrice.

Salinitycanbeduetoevaporationofirrigationwater,saltywaterandahighwatertable.Ifitisduetoahighwatertable,asystemofdrainageshouldbeinstalled.Ifsalinityisduetoirrigationwaterevaporatingandthedissolvedsaltsbecomingconcentrated,freshwatershouldbeadded.

Tocontrolsodiuminalkalineandsodicsoilsusegypsumororganicmanure.Organicmatterhelpsdissolvecalciumfromthe

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soil and gypsum supplies calcium. The calcium displaces sodium, makingitmoreeasilyleachedfromthesoil.

Tolerantvarietiescanalsobegrownifsalinityisaproblem.

Salinityisaproblemincoastalcountriesandalkalinityandsodicity(highsodium)inlandlockedcountries(e.g.inMali).

Use of manureWhenavailable,animalmanureisanimportantresourceforimprovingriceyields.Additionofmanurehelpstomaintainsoilorganicmatteratgoodlevels.

Manureisalsoanimportantsourceofnutrients,whicharemostlyreleasedfollowingdecomposition.However,manurecontainsalowerdensityofnutrientscomparedwithmineralfertilizersandtheamount of nutrients contained in manure on smallholder farms is usuallyinsufficienttosustainrequiredlevelsofriceproductivity.Butusingmanureincombinationwithfertilizergivesbetteryieldsthan using either input alone.

Ideally,5–10tonnesofanimalmanureperhectareshouldbeappliedeach year on the surface and incorporated during ploughing.

Bird scaringBirds feeding on rice grains tend to be more of a problem if a mixtureofvarietiesofriceisgrown(Photo10).Thedifferentvarietiesmatureatdifferenttimesbuttheyallneedtobeharvestedatthesametime.Thismeansearlymaturingvarietiesaremostlikelytobeattackedbybirdsastheyremaininthefieldlongerasthelatermaturingvarietiescatchup.Birdsalsotendtoattacktallervarietiesbeforemovingontoshorterones.

Birds can be scared using a combination of methods, such as

42

scarecrows,hangingtins,cassettetapesorreflectiveribbonsandpeoplemakingnoise.Thericeshouldbemonitoredregularlyafterfloweringforbirddamage.

A

B

Photo 11t. Plants in field – mixed varieties. (A)Mixedvarietiescanmatureatdifferenttimes,canalsodifferinheightmakingharvestingdifficult(photo:CABI)(B) Presence and absenceofawnsisacharacteristicthatcansometimesbeusedtotellvarietiesapart (e.g.wildAfricanricehasawns)(photo:CABI).

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HarvestingFarmersneedtoknowtherighttimetoharvest:riceisreadyforharvestwhen80%ofthepanicleishardandbrown.Othersignsarethatgraintakenfromthetopofheadisfirmtothebitebutnotbrittle(moisturecontentofsuchricegrainsisabout20–25%),somegrainremainsinhandwhenthepanicleissqueezed,andtheheadmakesarattlingsoundwhenshaken(Photo11).Riceisreadyforharvestingataboutfourweeksafterflowering.

Toharvest,thestemiscutbelowthericehead(Photo12).Thelength of stem retained on the head depends on the method of harvestingused;forexample,ifharvestingbyhandusingasmallknife,about7.5cmofstemisretained,butifharvestingusingamechanicalharvester,stemsarecutclosetotheground.

Ifharvestingirrigatedlowlandricewithacombineharvesterthefieldshouldbedrained15daysbeforethedateofharvestingsothatthestrawisdryenoughtoallowforthreshing.

Afterharvesting,thericeheadsshouldbedriedforabout3–7days inthesunifthreshingisbyhand(Photo13).Ifthreshingismechanisedthisshouldbedoneonthedayofharvesting.Thegrainsneedtobedrier(haveamoisturecontentof16–18%)ifthreshing is by hand.

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A B

C

Photo 12. Time to harvest. (A)Ricepanicles,ready(browncolour)andnotready(greencolour)forharvesting(photo:CABI)(B)Ricepaniclesreadyforharvestingmakeadistinct‘chachacha’soundwhenshaken(photo:CABI)(C)Delayedharvestingcanresultinlossofgrains.Somevarietiesaremorepronetothisproblemthanothers(photo:CABI/IPNI).

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A B

C D

Photo 13. Harvesting and threshing. (A)Manualharvesting(photo:CABI)(B) Mechanicalharvesterandthresher(photo:CABI)(C)Harvestedriceplantsdryingbeforethreshing (photo: CABI) (D)Ricecanbethreshedmechanicallyandbaggedinfield(photo:Kabirou Ndiaye, AfricaRice).

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A

B

Photo 14. After threshing. (A)Riceisbaggedandtransportedfromthefield (photo: CABI) (B) After drying, paddy can be placed in bags, and bags can be stored in a cooldryplaceonwoodenpallets(photo:CABI).

DryingThethreshedgrainshouldbedriedto12–14%moisturecontent.This can be done by putting the paddy (that is, grain enclosed bythehusk)outinthesunorbyusingadryer.IntheSahelthemoisturecontentcanreachaslowas8%:ifitbecomestoodry,thequalityofriceislowduetoalargeproportionofbrokenriceatmilling.

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Thegrainshouldbespreadinthinlayers,2–5cmdeep,andturnedevery1–2hours.

Ifsun-dryingseed(forplantingnextseason)morecareisneeded:theseedshouldbeturnedmoreoftenandnotexposedtotemperaturesabove42°C.Ifsuchhightemperaturesoccurthenthe seed should be dried in the shade, not full sun.

Ifusingadryer,careneedstobetakensoasnottousetoomuchheat as this can burn the grain.

Theharvestedcroporpaddyshouldbekeptawayfromtherain.Rainorothersourcesofwatercancausethegraintogerminateorthe quality can become poor as the grain gets discoloured.

Post-harvest value additionParboilingriceisaprocessusedtoincreasethenutritionalvalueofricegrainsthathavenotbeendehulled.DuringparboilingBgroupvitaminsmovefromthepericarp(bran)tothegrain.Parboilingthereforeresultsinhigherlevelsofsomemineralsandvitaminsthannormalrice.Parboilingalsochangesthetaste,texture(firmerandlesssticky),appearance(whiter)andsmell(odourless),andreducesthecookingtimeofrice.Parboiledricegrainsarealsomoreresistanttostoragepestattackthannormalgrains.Parboilingalsoreducesbreakageatmillingwhenthebranisremoved.

However,parboiledricecanbemoreexpensiveduetotheadditionalcostofparboiling,especiallylabourandenergy.Huskremovalisalsomoredifficultandcostsmore.

Parboiled rice is preferred by some but not all consumers. Parboilingtendstobeacommonpracticeinplaceswherericeisatraditionalcrop,forexampleNigeria,theNigerdelta,TheGambiaandBenin.Ittendsnottobedoneinareaswherericeisanon-traditional crop, such as parts of Senegal and Mali.

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There are many methods of parboiling rice, but the basic steps are soaking,steaminganddrying(Photo14).Beforeparboiling,thericegrainsarefirstwashedandfloatingdebrisisremoved.Thericeisthensoakedfor10–24hours,drained,thenplacedinboilingwateruntilitgelatinizes–thatis,thestarchbecomeslikeajelly.Atthisstagethehuskspartlysplitopen.Thericeisthendrainedanddried,afterwhichitcanbestoredandmilledlater.

A B

C

Photo 15. Parboiling to improve the value of paddy. (A)Thericeiswashedtoremovechaffandotherforeignmaterials,andalsounfilledgrain(photo:CABI)(B) Boiling rice (photo: CABI) (C) The paddy is dried, then milled (photo: CABI).

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MillingMillinginvolves:

1.Removalofchaffandforeignmaterials,suchasstones

2.Removalofhusksandpolishingofgrain

3.Sortingintogrades,i.e.brokenandwholegrains

4. Weighing and bagging.

StorageRicegrainstoresarevulnerabletoattackfrompestsincludinginsects(suchasrust-redflourbeetle,Tribolium castaneum), rodents and birds, and also fungi.

Topreventdamageoccurring,grainandpaddyshouldbestoredinacleanstorewithgoodventilation.Jutebagsarebestastheyallowgoodaeration;alternatively,hermetic(air-tight)bagscanalsobe used.

Parboiled rice is less susceptible to damage during storage than rawrice.

Grainstoresmusthaveadamp-prooffloorandwaterproofwallsand roof. It is preferable to be able to seal the store so fumigation is possible should the need arise. Sealing the storage also helps excluderodentsandbirds.Examplesofricestoragecontainersinclude bags and airtight metal containers. Where grain is to be storedinbags,thebagsshouldbestackedonpalletsatleast50cm awayfromthewalls.

Hermeticstoragesystemshaveprovedtobeaneffectivemeansofstoringgrain.Byhavingasealedatmosphereanyinsectspresentinsideutilizetheoxygen,expirecarbondioxideandeventuallydie

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throughsuffocationanddehydration.Thiswilloccurwithin5–10days dependingonthelevelofinsectinfestation.Otherbenefitsofahermetic system are that the moisture content of the grain and storageenvironmentremainsconstant,andthesealedsystemreduces the chance of damage by rodents and birds.

Toavoidmycotoxinproblems,whichareassociatedwithcertaintypes of fungi, grain should be dried to a safe moisture content (12–14%)beforestorage.Reducingphysicaldamagetothegrainduringharvestingandstorage,andensuringclean,dryinsect-proofstorageconditionswillalsohelppreventmycotoxincontamination.

Seed productionIfgrowingriceforseed,plantsthatarenotofthedesirabletypemustberoguedoutbeforeharvesting.Afterharvestinganddrying(moisturecontent12-14%),threshingneedstobedonecarefullyusingaslowerspeedthanusedtothreshriceforconsumptiontoavoiddamagingtheseed.

Seedshouldbestoredaspaddyineitherjuteorhermeticallysealedbags.Ifusingjutebags,seedshouldbeprotectedfrominsectattackbyapplyinginsecticide,suchasneem,whichisaplant-basedproduct;chemicalsarenotneededifusinghermetically sealed bags.

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Key messages

• Inirrigatedlowlandrice,maintainadepthof2–3cmofwaterlayerfromtransplantingtopanicleinitiation,5–7cmafterpanicleinitiation,thendrainfield7–15daysbeforeharvesting.

• Keepfieldweed-freeuntilharvest. • Foruplandriceapplybothbasalfertilizer(PandK)atploughingandtopdresswithN(urea)attillering.

• Forlowlandrainfedriceallfertilizer(N,PandK)needstobeapplied at ploughing.

• Forirrigatedlowlandricebasalfertilizer(PandK)isappliedbeforepuddlingandtopdressingwithN(urea)in2splitsattillering and panicle initiation, or only at tillering if using urea super granules.

• Inirrigatedlowlandrice,drainfieldbeforeapplyingurea,andre-floodfield2-3daysafterapplyingurea.

• Tocontrolsalinityduetoahighwatertable,improvedrainageortousetolerantvarieties.Ifsalinityisduetoirrigationwaterevaporatingandthedissolvedsaltsbecomingconcentrated,addfreshwater.

• Ifavailable,apply5–10tonnesofanimalmanureperhectareeach year.

• Reducegrainlossestobirdsbyscaringthebirdsaway,harvestingwhengrainisready,andbyavoidingplantingmixturesofvarieties.

• Harvestwhen80%ofthepanicleishardandbrown,graintakenfromthetopofheadisfirmtothebitebutnotbrittle,somegrainremainsinhandwhenthepanicleissqueezed,andtheheadmakesarattlingsoundwhenshaken.Thisisataboutfourweeksafterflowering.

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• Ifharvestingirrigatedlowlandricewithacombineharvester,drainthefield15daysbeforethedateofharvesting.

• Ifthreshingbyhand,drythericeheadsforabout3–7daysinthesunafterharvestingbeforethreshing

• Drythreshedgrainto12–14%moisturecontentbyputtingthepaddyoutinthesun.Iftemperaturesareabove42°C,dryriceinthe shade, not full sun.

• Storegrainandpaddyinclean,dry,storewithgoodventilation. • Ifgrowingriceforseed,rogueoutundesirable(abnormal)plants,threshcarefullyusingaslowspeedandstoreseedaspaddy.

• Ideally,incorporatestrawintothesoilandrotatericewithothercrops.

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6. What can go wrong

Riceproductioninvolvesmanyprocesses,manyofwhichhavebeendescribedinthisguide.Evenifthefarmerhasdoneeverythingright,unexpectedproblemscouldstilloccur.Someoftheseproblemsandexamplesofhowtorespondtothemarepresentedinthefollowingtables.

Table 6. NutrientdeficienciesNutrient Symptoms Where likely to occur What to doNitrogen (N)(Photo16)

Stunted plants Leavesbecomesmallandpale greenSymptomsappearfirstonolderleavesPaleyellowcolourdevelopsatthetipofoldleavesandproceedstocovertheleavestowardsthe leaf baseEventuallyyellowleavesturnbrown,dryanddieReduced tillering

SoilswithloworganicmatterLighttexturedsandysoils,whichhavebeenleachedbyheavyrainfallorexcessiveirrigationSoilsexhaustedbyintensivecroppingWaterlogged conditions

Applynitrogenfertilizer,such as DAP or ureaDeficiencycanbecorrectedwithonlyalimitedyieldreduction if remedial action istakenearlyduringtheseasonInclude legume crops (e.g. grain legumes) in rotation withrice

Phosphorus (P) Stuntedplants,withnarrowanderectleavesLeaveswithblue/purplecolourSymptomsappearfirstandbecomemoresevereonolderleaves;youngleavesusually remain healthyOlderleavesturnbrownand dieNumber of tillers, panicles and grains per panicle are reduced

Coarse-texturedsoilshavingloworganicmatterandsmallPreservesSaline, sodic and calcareous soilsSoilsexhaustedbyintensivecroppingAcid soils and highly weatheredsoilsErodedsoilswheretopsoilhasbeenremovedanddegradedlowlandsoils

CorrectingPdeficiencywhensymptomshavealready appeared is not veryeffective;however,application of soluble Pfertilizers,suchasammonium phosphate, canreducetheeffectsofPdeficiencyRemedial action should be takenforthenextcropApply correct amounts of PasbasalwithPfertilizerssuch as DAP, NPK, TSP or SSPApplyrockphosphateApply manureCorrect soil problems, such as acidity and salinity

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Nutrient Symptoms Where likely to occur What to doPotassium (K) (Photo17)

PlantscanbedeficientwithoutshowingsymptomsSymptoms appear only inseveredeficiencyconditions and mostly duringlatergrowthstagesYellowbrowncolourontheedgesoftheleavesBrowncolourbeginsfromtipofleafandadvancesdowntheedgestowardsthe baseSymptomsappearfirstonoldleaves

Sandy soilsSoilslowinorganicmatterSoilsthatreceiveexcessiveuseofNorN+PfertilizerswithinsufficientapplicationofKfertilizersHighlyweatheredacidsoilPoorly drained soils

ApplyKfertilizers,includingNPK, MOP or SOPRice residues contain large amountsofK;recyclingresidues add K to the soilAddorganicmanureswellbefore planting

Sulphur (S) (Photo18)

Stunted plantsInyoungplants,wholeplantbecomesyellowand symptoms can be confusedwithNdeficiencySymptomsappearfirstandbecomemoresevereonyoungerleaves;differentfromNdeficiencywhichaffectsolderleavesfirstTheyoungleavesbecomedullorbrightyellowbutoldleavesusuallyremaingreen

SoilshavingloworganicmatterSandysoilswhichhavebeenleachedbyheavyrainfallorexcessiveirrigationSoilsexhaustedbyintensivecropping

Apply correct quantity of S mixingintothesurfacesoilwellbeforesowingusingelemental S, SSP or gypsumIndeficientstandingcropsapply ammonium sulphate, magnesium or potassium sulphate

Iron(Fe) (Photo19)

SymptomsappearfirstonyoungerleavesDeficiencysymptomsappear as discoloured stripesonyoungleavesWholeemergingleavesbecome discoloured in severeconditionsofirondeficiency

Mainly a problem in upland soilswhichhavelowconcentrationofsolubleFeFeavailabilityincreasesafterfloodingLoworganicmatterstatusof soilsAlkalineorcalcareoussoils

GrowFe-efficientcultivarsIn high pH upland soils, use ammonium sulphate fertilizerinsteadofureatosupply N Ammonium sulphate is an acidifyingfertilizerwhichincreasesFeavailabilityApply ferrous sulphate fertilizerbroadcastattherateof30kgFeperhectare

Zinc (Zn) (Photo 20)

Symptomsoccur2-4weeksaftertransplantingManydustybrownorbronzespotsappearonthe leafSpots become bigger and eventuallycoverwholeleafIn later stages entire leaf turnsbronzeanddriesZincdeficiencyalsocauses stunted plant growth

Leached sandy soils AlkalinesoilsLevelledsoilswheresub-soilisexposedforcultivation:availableZnintop-soilisoftendoublethatinsub-soilSoilwithheavyandexcessiveapplicationofP-fertilizers,whichreduceavailabilityofZnduetoZn-phosphates formationExcessivelylimedsoils

Problematicalkalinesoilsshould be reclaimedUse2kgzincsulphateperhectare in the nurseryApply25-30kgzincsulphate per hectare in Zn deficientsoilsDonotmixZn-fertilizerswithP-fertilizersIfdeficiencyappearsinstanding crop apply Zn as a foliarsprayat5kg/ha

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A B

C D

Photo 16. Nitrogen deficiency. (A)Nitrogendeficientplantsarepale(foreground)whilethosewithadequatenitrogenaregreen(background)(photo:ShamieZingore,IPNI) (B)Olderleavesorwholeplantsareyellow,tilleringisreduced(photo:ShamieZingore,IPNI) (C)Yellowingstartsfromthetipoftheleaf,progressestowardsthebase,withthemiddleoftheleafyellowingbeforetheedges.Theyellowingprogressesina‘V’shape(photo: Shamie Zingore, IPNI) (D)Leaveseventuallydie(photo:ShamieZingore,IPNI).

A B

Photo 17. Potassium deficiency. (A)Thelowerleavesstartyellowing(photo:ShamieZingore, IPNI) (B)Theyellowingstartsfromtheleafmargins(photo:ShamieZingore,IPNI)

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A B

C

Photo 18. Sulphur deficiency. (A)Plantsarepaleyellow,youngerleavesaffectedmore.ThisisunlikeNdeficiencywhichaffectslowerleavesandtheyellowcolourisdeeper (photo: Shamie Zingore, IPNI) (B)Theyoungestleaf(middle)showingdeficiencysymptoms (photo: Shamie Zingore, IPNI) (C)Theyellowingonleafcanbeuniform,buttipscan die (photo: Shamie Zingore, IPNI)

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A

D

G

B

E

C

F

Photo 19. Iron deficiency. (A)Plantsbecomepaleandyellow(photo:ShamieZingore,IPNI) (B)Onsomeleaves,leafveinsremaingreen,yellowing(orpaleness)betweenveins–leafhasgreenandyellow(pale)stripes(photo:ShamieZingore,IPNI)(C) Tips of emerging leavesdryup(photo:ShamieZingore,IPNI)(D)Tipsofemergingleavesdryup(photo:Shamie Zingore, IPNI) (E)Developingpaniclesandflagleafarepale(photo:ShamieZingore, IPNI) (F)Paleleavesdevelopbrownstreaks(photo:ShamieZingore,IPNI) (G)Healthygreenleaf(left),streaksshowingmoderatedeficiency(middle),palecolour-signofseveredeficiency(right)(photo:ShamieZingore,IPNI).

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A B

C

Photo 20. Zinc deficiency. (A)Brownpatchesonlowerleaves(photo:ShamieZingore,IPNI) (B)Lightbrowncolouronleaf(photo:ShamieZingore,IPNI)(C)Brownstripesonleaf,whitestripesclosetothemid-rib(photo:ShamieZingore,IPNI)

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Table 7.Examplesofinsectpeststhatdamagerice

Insect Damage Control

Stem borers (Photo 21)

LarvaeenterthestemandeatitfromwithinGrowingpartsofyoungshoots may die (dead hearts)Floweringaffected(deadheads,whitepanicles)Plantsmayfallover

Floodingandharrowingorploughinginofstrawtoreducecarryingoverofinsects from one crop to thenextRoguingofvolunteerplants3betweencroppingseasonsPlanting early maturing varieties

African gall midge Cylindricalswellings,knownasgalls,about3mmindiameter, can be short or upto1–1.5mlong,causedbymaggotswhichhatchfrom eggs laid by female midgesOftensilverywhiteandaregenerallyknownas‘silvershoots’or‘onionleafgalls’

Early and synchronised plantingRoguingofvolunteerplantsbetweencroppingseasonsPloughinginofstrawtoreducecarryoverinsectpopulations

Termites AttackbothyoungandoldplantsDamagerootsandfilltheinsideofthestemwithsoil

Use pesticideFloodingoftermiteholesDigging up termite mounds and destroying nest and queen

Riceweevil&largergrainborer (storage pests)

Attackpaddyandgrainafter millingThelarvaeeattheinsideof the grain, emerging as adults through holes

Removeinfestedresiduesfrom last seasonTreat grain before storing withpesticideStore grain in airtight containers

Rice grasshopper (Photo 22)

The nymphs and adults eat leaves

Cultivatepartsofthefieldthatarenotcultivatedasthiswillreduceareaforadults to lay eggs

Ricestinkbug (Photo23)

Attacksstems,leavesandfillinggrain

Removealternatehostssuch as grasses on bundsForrainfedrice,plantearlyat the beginning of the rains

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A

D

G

B

E

C

F

Photo 21. Stem borers. (A)Therearemanytypesofstemborersthataffectrice,forexamplediopsis(photo:CABI/IPNI)(B)Anotherstemborer–amoth(photo:CABI/IPNI)(C)Larvaofstemborer(photo:CABI)(D) Stem borer damages inside of stem (photo: CABI) (E)Stemborerdamage,‘whitehead’–emptypanicle(withoutgrain)(photo:CABI) (F) Stem borer damage, empty panicle (photo: CABI) (G)Normal–paniclewithgrain (photo: CABI).

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Photo 22. Ricegrasshoppercausesdamagetoleaves(photo:CABI/IPNI).

Photo 23. Ricestinkbugsreduceyieldbyfeedingonthedevelopinggrains(photo: CABI/IPNI).

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Table 8. Examplesofricediseases

Symptoms Control

Rice blast (Photo25)

Onleaves,longlesionswithpointedendsandgreyorwhitecentres;dark-greentoreddish-brownmargins,sometimeswithayellowhaloIfsevere,lesionsmergeandleavesdie;leafsheathsdryupandwholeplantsmaybekilledSeverelyinfectedfieldshaveascorched appearanceOn leaf collars, rotting may result in premature leaf fallOnlowernodes,rottingcauses‘whiteheads’Onpanicles,whiteheadsorpartiallyfilledheads;lateinfectionaftergrainfillingresultsin‘brokennecks’

ResistantcultivarsAvoidexcessiveNfertilizerand droughtFieldsanitationSynchronizedplanting

Falsesmut(Photo26)

Symptomsobservedongrainsafterflowering:smallgreenballsupto1cmin diameter appear on grain, the balls burst, become orange, then green

Use tolerant or resistant varietiesAvoidexcessiveNfertilizer

Brownleafspot Evenlydistributedoval-shapedlesions,up to 1 cm in lengthThespotsarebrown,withgreyishcentreswhenfullydevelopedYounglesionsappearassmall,dark-brownspotsLesions on the panicles may lead to blackspotsongrain

ResistantvarietiesUse disease free seedsApply good balance of inputs (e.g. supply micronutrientsifdeficient),also combine organic and inorganicfertilizers

Narrowbrownleaf spot (Photo 27)

Narrowbrownelongatedspots,2–12mmlongand1–2mmwideappearontheleaves,leafsheaths,panicle

Planting early maturing varietiesEarly planting

Riceyellowmottlevirus(Photo28)

Leavesyellow-orange,sometimesfollowedbyrollingPlantsstunted,reducedtillering,non-synchronousflowering,spikeletsdonotfillwithgrainDisease can be transmitted by insectsYoung plants are most susceptible

Destroy crop residues (e.g. by burning) and uproot volunteerplantstocontrolinsect pests and plant material that could be carrying the diseaseDelay planting timeUsetolerantvarietiesUse pesticides to control insectvectors

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A B

C

Photo 25. Rice blast. (A)Thelesionshaveagreycentre,andbrownborder(photo:CABI/IPNI) (B)Inseverecases,lesionsonleafmergeandleafdies(photo:CABI/IPNI) (C)Nodesaffectedbydisease–ifthenodebelowtheheadisaffectedbeforegrainfilling,thegrainmaynotfill,ifaffectedaftergrainfilling,theheadmaydroopdownwards (photo: CABI/IPNI)

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Photo 26. False smut (photo: CABI).

Photo 27. Narrow brown leaf spot (photo: CABI).

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A

B

Photo 28. Rice yellow mottle virus (RYMV). (A)PlantsinfectedbyRYMVcanbeyellow,andaremorelikelytobeattackedbyotherdiseases–inthiscasebrownspot(photo:CABI) (B) Leaf of plant infected by RYMV (photo: CABI).

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7. Rice production economics

RiceisamajorfoodandcashcropinAfrica:farmersgrowricefor sale but some of the rice can be used to meet household food requirements.

Manyofthechangesrequiredforimprovedproductionrequireuseofscarceresourcessuchasfertilizer,manure,seedsandlabour.Forexample,ifgrowingimprovedricevarietiesthatgivebetteryieldsthanlocalvarieties,morefertilizermaybeneededtoreachthehighyields.Butuseoffertilizershouldalsobeaccompaniedbygoodmanagementpractices(e.g.timelyplanting,goodwatermanagementandkeepingthefieldsweed-free).

Itisimportanttohaveanideaofwhetheranewfarmingpracticewillbeprofitable(beforeintroduction)andwhetherthetechnologyisactuallyprofitable(afterintroduction).Thelikelybenefitsofanewpracticearecalculatedbasedondatacollectedelsewhere,whileactualbenefitsarebasedondatacollectedaftertheintroductionofthenewfarmingpracticeon-farm.

Theminimumincreaseinyieldrequiredtorecoverexpensesincurredfromimplementingthenewtechnologycangiveanideaofwhetherthenewpracticecouldbeworthwhile.

Forexample,ifafarmerhasbeentopdressinganimprovedricevarietywithtwobagsofureaandgetting3.8tonnesofgrainperhectare,butwouldnowliketoapplytwomorebagsofurea,theincreaseinyieldrequiredtorecovertheadditionalcostoffertilizer(assumingthepriceofureaisUS$50per50kgbagandpriceofriceisUS$500pertonne)canbecalculatedas:M!"!#$#  !"#$%&'%  !"  !"#$%  !"#$%!"&   !/ℎ! = !"#$  !"  !"#$  !"#$%&%'"#

!"#$%  !"  !"#$=     !  ×  !"

!""= 0.2  

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So,inthiscaseifthefarmerachievedanadditional200kgofriceperhectare,thiswouldcoverthecostoftheadditionalurea.

Theextracostsincurredwithuseofanewtechnologycanalsobecomparedwiththeadditionalbenefitsgotbyuseofthetechnology(benefit-costanalysis).

Forexample,ifintheabovecasethepreviousyieldswere 3.8tonnesperhectarebutwithadditionaltwobagsofureayieldshaveincreasedto4.5tonnesperhectare,thevalueofadditionalyieldwithfertilizercomparedwiththecostoffertilizer,thebenefit-cost ratio (BCR), is calculated as:

As a rule of thumb, a BCR greater than 2 is needed for an investmenttobeeconomicallyattractivetofarmers–thatistheextrariceproducedisworthatleasttwiceasmuchastheinputsusedtoproducethem.InthiscasetheBCRis3.5,sothisisaveryattractiveinvestment–foreveryUS$1investedinfertilizerthefarmergotareturnofUS$3.5.

Ifadditionalinformation,forexampleoncostsoflabour,weedingandpestcontrolisavailable,moredetailedcalculationscanbecarried out. Remember, the best use of a resource should be exploredinordertogetthebestreturnfromtheinput.

A point to note is that prices of inputs and produce, and also yieldsofcropscanvary.Forexample,goodincomecanbeobtainedbystoringproduceafterharvest,sellingwhenthemarketisnotoversuppliedandpricesarehigher.Also,lessfertilizershouldbeappliedwhenrainsarelateanddroughtisexpected,andmorefertilizercanbeusedwhenrainsareontimeandareexpectedtobeadequate.

!"# = !"#$%  !!"!  !"#$%&%'"#  !  !"#$%  !"#!!"#  !"#$%&%'"#    !  !"#$%  !"  !"#$!"#$%&  !"  !"#$%&%'"#  !""#$%&  !  !"#$%  !"  !"#$%&%'"#

= !.!  –  !.!  ×  !!!(!  ×  !")

 =  3.5  

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For more information see:

http://www.knowledgebank.irri

A good source of additional information on rice production.

Defoer,T.,Wopereis,M.C.S.,Jones,M.P.,Lancon,F.andErenstein,O.(2003)Challenges, innovation and change: towards rice-based food security in sub-Saharan Africa – pp219-234.InProceedingsofthe20thsessionoftheInternationalRiceCommission,Bangkok,Thailand,23-26July2002,Rome,Italy,FAO.

Figure 1 on rice ecologies adapted from this reference.

Fairhurst,T.H.,Witt,C.,Buresh,R.J.andDobermann,A.(2007)Rice: A Practical Guide to Nutrient Management. International Rice Research Institute, International Plant Nutrition Institute and International Potash Institute.

http://bit.ly/1jLAZzg

Important reading material on nutrient management for rice. Estimates of nutrient content in rice stover presented in this guide were based on data presented in reference. The reference also has a good collection of photographs on nutrient deficiencies in rice.

Africa Soil Health Consortium – improving soil fertility, improving food production, improving livelihoodsTheAfricaSoilHealthConsortium(ASHC)workswithinitiativesinsub-SaharanAfricatoencouragetheuptakeofintegratedsoilfertilitymanagement(ISFM)practices.ItdoesthisprimarilybysupportingthedevelopmentofdowntoearthinformationandmaterialsdesignedtoimproveunderstandingofISFMapproaches.ASHCworksthroughmultidisciplinaryteamsincludingsoilscientistsandexpertsoncroppingsystems;communicationspecialists,technicalwritersandeditors;economists;monitoringandevaluation;andgenderspecialists.ThisapproachishelpingtheASHCtofacilitatetheproductionofinnovative,practicalinformation resources.ASHC defines ISFM as: A set of soil fertility management practicesthatnecessarilyincludetheuseoffertilizer,organicinputsandimprovedgermplasmcombinedwiththeknowledgeonhowtoadaptthesepracticestolocalconditions,aimingatoptimizingagronomicuseefficiencyoftheappliednutrientsandimprovingcropproductivity.Allinputsneedtobemanagedfollowingsoundagronomicandeconomicprinciples.

The Integrated Soil Fertility Management Cropping Systems Guide series is an output of the Africa Soil Health Consortium (ASHC), which is coordinated by CABI.

Thisguidewasfirstpublishedin2015byASHCCABI,CanaryBird,673LimuruRoad,Muthaiga,POBox633-00621,Nairobi,Kenya

Tel:+254(0)20-2271000/20Fax:+254-20-7122150Email:Africa@cabi.org Website: www.cabi.org/ashc