Soil science and agricultural development in Rwanda: state ... ?· Soil science and agricultural development…

Download Soil science and agricultural development in Rwanda: state ... ?· Soil science and agricultural development…

Post on 03-Sep-2018

212 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

  • BASE Biotechnol. Agron. Soc. Environ.201418(1),142-154 Focus on:

    SoilscienceandagriculturaldevelopmentinRwanda:stateoftheart.AreviewPascalN.Rushemuka(1,2),LaurentBock(2),JeremiasGasperMowo(3)(1)RwandaAgriculturalBoard(RAB).Box617.Butare(Rwanda).E-mail:Rushem2005@yahoo.fr(2)Univ.Liege-GemblouxAgro-BioTech.DepartmentSciencesandTechnologiesoftheEnvironment.Soil-WaterSystems.AvenueMarchalJuin,27.B-5030Gembloux(Belgium).(3)WorldAgroforestryCentre.Box30677.Nairobi(Kenya).

    ReceivedonApril19,2012;acceptedonSeptember18,2013.

    PooragriculturalproductivityremainsacrucialprobleminRwandainspiteofnumeroustechnologicalinterventions,includingaspectsof soilmanagement.Theobjectiveof this studywas todraw lessons from thepastwith theview tobetterorientfuture interventions insoil fertilitymanagement.Theliteraturereviewanditerativefieldobservationswere thesourcesofinformation.Findingsfromthisstudyshowthatsubstantialprogresshasbeenmadeintheidentificationofdifferentsoiltypesandtheirspatialdistribution.Factorsrelatedto lowlevelofproductivityhavebeenidentifiedandsustainablesoil fertilitymanagementoptionshavebeendevelopedatplotlevel.However, thewidespreadadoptionofthesetechnologieshasbeenproblematic.Themainreasonisthefailuretotailorsoilfertilitymanagementtechnologiestospecificsoiltypes.Thestudyhasdemonstrated that thesoilmapofRwanda(CPRforCarte Pdologique du Rwanda)1:50,000offersaremarkablepotentialtoconstituteatooltosolvethisproblem.Inpracticehowever,theCPRremainsunderutilized,mainlybecauseofitsinaccessibilitytoitspotentialusers(e.g.policymakers,soilfertilityexperts,agronomistsandextensionists).Foritseffectiveuse,thefollowingisrecommended:Rwandansoilscientistsneedtoincreasepolicymakersawarenessabouttheusefulnessofthissoilmap;agriculturalresearchneedstoadaptfromtheconventionalmodeltoatrulyparticipatoryandintegratedapproach;theCPRlegendshouldbeelucidatedbyprovidinginformationonthelandunitsinwhichsoilsoccurandbybridgingSoilTaxonomywiththefarmerssoilnomenclature;regionalsoilreferencesystemsshouldbeestablishedthatallowlinkingsoiltypeswiththefertilitystatusofarablelandandcropyields.ThisimpliestheneedfortrainingofRwandansoilscientistsinbothSoilTaxonomy(thelanguageoftheCPR)andthefarmerssoilnomenclaturesothattheycanserveasinterpreterforscientistsfromotherdisciplinesandfarmers.RwandansoilscientistsshouldbetrainedintheuseofGeographicInformationSystem(GIS)softwaretoenablethemtoexploitthedigitizedversion/softcopyoftheCPRandtobecomefamiliarwiththeRwandanbiophysicalenvironment.Keywords.Soilsciences,soilmap,agriculturalresearch,informationexchange,ruraldevelopment,Rwanda.

    Science du sol et dveloppement agricole au Rwanda : tat de la question (synthse bibliographique). AuRwanda,malgrplusieurs interventions techniques, encecompris lesaspectsde lagestiondes sols, la faibleproductivitagricoleresteunproblmecrucial.Lobjectifdecettetudetaitdetirerlesleonsdupassenvuedemieuxorienterlesinterventionsfuturesengestiondelafertilitdessols.Larevuedelalittratureetlesobservationsitrativessurterrainontservidesourcedinformation.Lesrsultatsdecettetudemontrentquunprogrssubstantielatralisdanslidentificationdesdiffrentstypesdesolsetdeleurrpartitionspatiale.Lesfacteursresponsablesdufaibleniveaudeproductivitdesterresonttidentifisetlesoptionsdegestiondurableonttdveloppeslchelledelaparcelle.Cependant,leuradoptiongrandechelleestresteproblmatique.Laraisonprincipaleapparaittrelincapacitdadapterlestechnologiesdegestiondelafertilitauxdiffrents typesdes sols.Cette tudemontredoncque laCartePdologiqueduRwanda (CPR) -1:50000 constitueunoutilpossiblepourrsoudreceproblme.Enpratiquecependant,laCPRrestesous-utilise,principalementcausedesoninaccessibilitsesutilisateurspotentiels(planificateurs,expertsengestiondelafertilit,agronomesetvulgarisateurs).Poursonutilisationeffective,lesrecommandationssuivantesonttformules:lespdologuesduRwandadevraientsensibiliserlesplanificateursproposdelutilitdecettecartedessols;larechercheetvulgarisationagricolesdevraientpasserdelapprocheconventionnelleuneapprocherellementparticipativeetintgre;lalgendedelaCPRdevraittreexpliciteenyincluantlesunitspaysagiques/morphologiquesetentablissantdespontsdecommunicationentrelalgendetaxonomiquedelaCPRetlesnomsvernaculairesdessols;dessystmesrgionauxderfrencesurlessolsdevraienttretablis,quipermettentdemettreenrelationlestypesdesols,ltatdefertilitdesterrescultivesetlesrendementsobtenus.Ceciimpliqueunbesoin

  • SoilscienceandagriculturedevelopmentinRwanda 143

    1. INTRODUCTION

    Soil is studied from both fundamental and appliedpointsofview.Theknowledgeacquiredbybasicsoilscience is published in scientific journals and books.However, theway the information generated by thisscientific sub-discipline is used to formulate soundpolicies and translated into soil-specific and user-tailoredtechnologiesinappliedsoilscienceiscomplexandcontroversial.

    While Hartemink (2006) maintained that soilscience has contributed to the increase in worldagricultural food production over the last 50years,manyotherauthors(Papadakis,1975;Leeuwisetal.,2004; Ruellan, pers. com.) asserted that the increasein agricultural food production in the industrializedworld was made possible less by progress in soilscienceandacademicresearchthanbytheagronomicsciences, which developed responsive fertilizervarieties, pesticides and intensive use of fertilizers,agricultural engineering, value chain developmentandmarkets.Theproblem is that thiscapital-ledandnonsoil-specificintensificationoffoodproductionhasoccurredat theexpenseof thecapacityof thesoil tosustainablyproducefoodandsupportlife(Rainaetal.,2006;Ruellan,pers.com.;Herren,2011).

    Despite the above concerns, in those developingcountrieswherefoodproductionhasstagnatedoverthelast50years,thereisagreattemptationtoimitatethedevelopedworld.Forinstance,intheAfricanFertilizerSummit, the conclusions of which were endorsedby theAfrican Heads of State atAbuja, Nigeria, in2006,itwasarguedthatforagreenrevolutiontotakeplace inAfrica, fertilizerusemustbe increased fromthe then mean of 8kg.ha-1 to ~ 50kg.ha-1 by 2015.Accordingly, African governments were encouragedto takeconducivemeasures to increase fertilizeruse.Following these recommendations, several Africancountries have used subsidies in efforts to increasefarm-levelfertilizerapplications(Marenyaetal.,2012).It is also in this context that Rwanda has promoteda policy of agricultural modernization and cropintensificationwithlandconsolidation,mechanization,mono-cropping,highyieldingcropvarieties,intensiveuse of fertilizers and irrigation (MINECOFIN, 2000;MINAGRI,2002;MINECOFIN,2007).

    Agro-ecologists,whilesharingthesameconcernsaboutregardinglowagro-systemproductivity,wouldprefer not to see developing countries repeatingthe past errors of the developed world.Within thiscontext, they consider agro-ecological solutionsor Ecological Agriculture (EA) (minimum useof fertilizers and investment in agroforestry) tobe superior to conventional agriculture based onchemicals or Industrial Agriculture (IA). Theythus propose measures to governments to lead thedevelopmentandadoptionofsuchapproaches(Altieri,2002;deSchutter,2010;Herren,2011;Marenyaetal.,2012). Soil scientists, for their part, maintain thatagro-ecological solutions are unable to contributesignificantly to food securityandpovertyalleviationwithin the context of acid and inherently poor soils,such as those found in many parts of sub-SaharanAfrica (Drechsel et al., 1996; Rutunga et al., 2006;Breman,2011;Keatingetal.,2011).

    Several questions arise: is the debate about IAversus EA new? Has any progress been achieved?Whatpositionshouldgovernmentstake?Shouldtheywait forscientists toreachacompromise,or isevenanycompromisepossible?

    The objective of this study is to analyze howsoil science has evolved in Rwanda, what has beenachieved, how these achievements have contributedtoagriculturaldevelopment,whattheconstraintshavebeen,andwhatmightconstitutethewayforward.

    2. METHODOLOGICAL APPROACH

    A literature review, including unpublished reports,maps and journal articles, was the main source ofinformation for this study. A historical perspectiveapproachwasusedtoanalyzethecontributionofsoilscience to agricultural development inRwanda.Thehistorical time-frame covers a period of ~80years(1930-2010).Threeyears(2010-2013)ofiterativefieldactivityobservationswereundertaken to support theliterature reviewwith concrete and recent examples.Figure 1 presents the location of Rwanda withinAfrica,theAgro-EcologicalZones(AEZs)ofRwanda(Verdoodtetal.,2003a)andthemainsitescitedinthetext.

    pouruneformationdespdologuesduRwandalamaitrisedelaSoil Taxonomy (langagedelaCPR)etdelanomenclaturevernaculairedessolsafinquilsserventdinterprtespourlesnon-pdologuesetlespaysans.Aummemoment,ilsdevraientaussi recevoirplusdeformationsur lutilisationdes logicielsdeSystmesdInformationGographiques(SIG)afindtrecapablesdexploiterlaversiondigitalise/lectroniquedelaCPRetdevenirfamiliersaveclemilieubiophysiquerwandais.Mots-cls.Sciencesdusol,cartedesols,rechercheagricole,changedinformation,dveloppementrural,Rwanda.

  • 144 Biotechnol. Agron. Soc. Environ. 201418(1),142-154 RushemukaP.N.,BockL.&MowoJ.G.

    3. SOIL SCIENCE COMPONENTS AND ACHIEVEMENTS IN RWANDA

    Soil science, as applied in agricultural research anddevelopmentinRwanda,istraditionallysubdividedintothreemaincomponents:soilsurvey,soilconservation,andsoilfertilitymanagement.

    3.1. Soil survey

    ThefirstsoilsurveyinRwandawasundertakenbytheteamoftheInstitut National dtudes Agronomiques au Congo (INEAC), beginning in 1955 at RubonaStation(Figure 1).AfterIndependence(1962),INEACactivitieswerecontinuedbytheInstitut des Sciences Agronomiques du Rwanda (ISAR), which wasintegratedin2012intotheRwandaAgricultureBoard(RAB).By1963,themajorsoiltypesofthecountryhad

    been described (VanWambeke, 1963). In the 1980s,almost all soil knowledge acquired by the INEAC-ISARteamwassynthesizedintoasoilassociationmapat a scale of 1:250,000 (Prioul et al., 1981).Duringthe same period, Pietrowicz (1985) undertook a soilsurveyinthemandateareaoftheprojectProjet Agro-Pastoral (PAP) Nyabisindu(Figure 1).

    During the period 1981-1990, the project Carte Pdologique du Rwanda(CPR)(Birasaetal.,1990)conducted a comprehensive soil survey of Rwanda.The CPR project produced a soil association and amedium scale (1:50,000) soil map (43sheets) undertheSoilTaxonomyclassificationsystem.TheCPRdatabase was created in 1990-1994. In 2002, thesoil map was digitized and the associated databasepublished (Verdoodt et al., 2003b). In 2003, a set ofsoil suitabilitymapswas published (Verdoodt et al.,2003a).

    Figure 1.LocationofRwandawithinAfrica,RwandaAgro-EcologicalZonesandsitescitedinthetext(adaptedfromVerdoodt,2003aandSchrry,1991)Localisation du Rwanda par rapport lAfrique, Zones Agro-cologiques du Rwanda et sites cits dans le texte (daprs Verdoodt, 2003a et Schrry, 1991).

    20 10 0 20 40 60 80km

    LegendPAPMandateArea

    Sites with terracesKisaroKigemeMuniniRubonaRuhandeKanyirandoriKigali

    Agro-ecological zonesImboImparaKivulakeborderCongo-NileWatershedDivideEasternplateauBirungaBuberekahighlandsIslandKivulakeMayagaandperipheralBugeseraCentralPlateEasternSavannaandCentralBugesera

    N

  • SoilscienceandagriculturedevelopmentinRwanda 145

    3.2. Soil conservation and erosion control

    ErosioncontrolhasbeenformallypracticedinRwandasince 1937 at INEAC research stations (Kabiligi,1985).In1947,theprogramwaswidenedtothewholecountry and many extensionists (mostly known asMONAGRIS1)wererecruited.In1947,thecolonialadministrativeresidentdecreemadethecreationofditchesandtheplantingofgrassandtreesobligatoryforalllandholders.

    After Independence (1962), erosion control wasabandonedandmanyerosioninfrastructureswereevendeliberately destroyed (Kabiligi, 1985). In 1966, thegovernmentofRwandarevivedanationalprogramofsoilerosioncontrol.Followingthis,severalcompulsoryfive-year programs (1966-1970; 1977-1981; 1982-1986)wereimplemented.

    In 2005, as the countrywas recovering from the1990-1994civilwarandgenocide,theerosioncontrolprogramwasre-startedwiththesameapproach.Sincethen,manybench terraceshavebeenconstructed.Asaresult,inmanyregionsofthecountry,thelandscapehas changed remarkably. At the same time, the oldinfiltrationditcheswererenewed.

    Infiltration ditches. One of the most ancient andcommonexamplesoferosioncontrolinfrastructureinRwandaisintheuseofinfiltrationditches(imingoti)stabilized by grass verges parallel to contour lines(Figure 2). In addition to being labor-intensive andlackingpositiveimpactsoncropyields,themethodisinefficient incontrollingsoilerosiononsteepslopes.Infact, theditchesdonothaveanyimpactontillagepractices(therootcauseofhuman-inducederosion)or

    onphysicalsoilproperties(e.g.improvementofwaterinfiltrationrate).

    Thus,whensoilswith loworganicmattercontentonsteepslopesarecultivated(to~60cmdepth),atthebeginningoftherainyseasonwhenlandisbare,theyareexposedtohigherosionrisk.Itiscommonfortheditchestofillupwithinafewdays(Rooseetal.,1993).

    Bench terraces. Bench terraces (Figure 3) wereintroduced in Rwanda in 1973 in the mountainousregion of Buberuka AEZ at Kisaro hill (Figure 1).In this region, terraceshavebeengreatlyappreciatedas an effective way of controlling soil erosion andmaintaining or progressively improving soil fertility.Since1992,theuseofbenchterraceshasbeenexpandedtotheunproductivesoilsofthetopographicallysimilarmountainous region of the Congo-Nile watersheddivideAEZ,atKigemehill(Figure 1).Inthisregion,incontrast,benchterraceshavenotbeenadopted,andtheterracedterrainshaveremainedunused.

    More recently (2006), under the Food forWorkSystem, many Districts and Non GovernmentalOrganizations (NGOs) have created bench terracesonlargeareasinallAEZs.However,bothancientandrecently constructed terraces have led to a situationwheresometerracesareusedeffectively,whileotherswere totally abandoned just after their construction.This has been reported as embarrassing for policy-makers andothernon-soil scientists interested in theadoption of terraces (Bizoza, 2011). However, foran informed soil scientist, inorder for terraces tobeusedeffectively,theywouldneedtobeconstructedonproductivesoils,whichcanstillberesponsivetofarmerinput (organic input or organic input + fertilizers).Alternatively,effectiveterraceswouldbeconstructedon very strongly acid and inherently poor soils, butwith appropriate input supply (limestone, organicinput, fertilizers and improved seeds). Terraces that

    Figure 2. Fields on a steep slopewith infiltration ditchesand grass verges parallel to contour lines for erosioncontrolChamps sur forte pente avec fosss dinfiltration et bandes enherbes parallles aux courbes de niveau pour lutter contre lrosion.

    1MONAGRISreferstomoniteursagricoles.

    Figure 3. Bench terraces with farmers harvesting Irishpotatoes at Munini Terrasses radicales avec les cultivateurs rcoltant la pomme de terre Munini.

  • 146 Biotechnol. Agron. Soc. Environ. 201418(1),142-154 RushemukaP.N.,BockL.&MowoJ.G.

    becomeabandonedwouldbethoseconstructedonverystronglyacidic,depletedandunproductivesoilswithoutadequateinputsupply.Indeed,ithasbeendemonstratedthatwhereappropriateinputs...

Recommended

View more >