a review of soils and crops in the bukidnon highlands of northern

BASE Biotechnol. Agron. Soc. Environ.201418(4),544-557 Focus on:

AreviewofsoilsandcropsintheBukidnonHighlandsofNorthernMindanao,thePhilippinesGuadalupeM.Dejarme-Calalang(1),GillesColinet(2)(1)XavierUniversityCollegeofAgriculture.DepartmentofAgriculturalEngineering.CorralesAvenue,9000.CagayandeOroCity(Philippines).E-mail:[email protected](2)UniversitédeLiège-GemblouxAgro-BioTech.DépartementScienceetTechnologiedel’Environnement.SystèmesSol-Eau.PassagedesDéportés,2.B-5030Gembloux(Belgique).

ReceivedonFebruary25,2014;acceptedonNovember3,2014.

Introduction.ThisarticlereviewssoilandcropproductioninformationfromBukidnon,NorthernMindanao,thePhilippines.ItfocusesontheparentmaterialsinvolvedinformingBukidnonsoils,clayformingminerals,soilclassification,typesandlocationdistribution,physico-chemicalcharacteristics,soilpotentialitiesandconstraints,andtheyieldsofthemajorcrops.Literature. The informationdiscussedwas gathered fromon-line journals, a compilationof agricultural research reportspublished inNorthernMindanao, published theses, government data and reports, and books. Bukidnon has existing soilinformationthatcouldbeusefulforassessingandmonitoringsoilfertilityandinestablishingaregionalLandInformationSystem(LandIS).SoilsintheProvinceareclassifiedaccordingtoSoilOrder,GreatGroupandsoiltypeundertheUSDASoilTaxonomicClassification.Dataoncropproductionyieldsarealsoavailable.Soilinformationisintendedmoreforcropfertilizationplanningatthebroaderscale.Studiesongeomorphopedologyandtheinteractionsofelementswithinthesoilarescarce.Therelationshipbetweensoilformationanditscharacteristicsandplantresponsesisnotdiscussedhere.Conclusion.The recommendations arising from this study are: (1) to conduct in-depth geomorphopedological studies inmarginalareasofundifferentiatedsoils,(2)tostudytherelationshipbetweensoilcharacteristicsandcropresponsesincludingnutrientassimilationbyplants,focusingonphosphorus(P),and(3)todevelopagenericprotocolandestablishaLandISformountainareasthatcanbereplicatedinotherareasinMindanao,thePhilippines.Keywords.Soilmorphology,soilclassification,soilchemicophysicalproperties,mineralogy,crops,landinformationsystems,Philippines.

Sols et plantes cultivées dans les hautes terres du Bukidnon à Mindanao nord, Philippines (synthèse bibliographique).Introduction.Cetarticleconstitueunerevuesurl’informationexistantequantàlagéomorphopédologieetlaproductiondesculturesduBukidnon,Mindanaoseptentrional,Philippines.Celle-citraitespécifiquementdesmatériauxparentauximpliquésdanslaformationdessolsduBukidnon,desminérauxargileux,declassification,typeetdistributiondesols,descaractéristiquesphysiquesetchimiques,despotentialitésetcontraintesdesoletdesrendementsdesprincipalesculturesconduites.Littérature.Cette informationaété rassembléeàpartirde journauxen ligne,de lacompilationde rapportsde rechercheenMindanaoseptentrional,demanuscritsdethèsespubliées,dedonnéesgouvernementalesetdelivres.Bukidnondisposed’informationsurlesolquipeutêtreutilepourévalueretassurerlesuividelafertilitédessolsetétablirunsystèmerégionald’informationsurlesterres,lesterrains(LandIS).Lessolsdelaprovincesontclassésselonl’ordre,lesgrandsgroupesetlestypesdesoldelaclassificationtaxonomiqueaméricainedessols(USDA Soil Taxonomy).Lesdonnéessurlesrendementssontdisponibles.L’informationsurlessolsestdavantageorientéeverslaplanificationenfertilisationdessolsàlargeéchelle.Lesétudesdegéomorphopédologieetsurlesinteractionsentreélémentsdanslesolsontrares.Lesrelationsentrelaformationdessolsetlescaractéristiquesdelaréponsedesplantesnesontpasétudiées.Conclusion.Ilestrecommandéde(1)conduiredesétudesgéomorphopédologiquesdétailléesdanslesairesmarginalesdesolsindifférenciés,(2)d’étudierlarelationentrelescaractéristiquesdessolsetlaréponsedesplantesincluantl’assimilationdesnutrimentsparlesplantesavecuneattentionparticulièrepourlephosphoreet(3)dedévelopperunprotocolegénériqueafind’établirunLandISpourlesairesdemontagnequipourraitêtretransposéàdesairessimilairesdeMindanao,Philippines.Mots-clés.Morphologie du sol, classification des sols, propriété physicochimique du sol,minéralogie, plante de culture,systèmed’informationfoncière,Philippines.

SoilsandcropsofBukidnon,thePhilippines 545

1. INTRODUCTION

Thisreviewfocusesontwotopics:theimportanceofagricultural lands inBukidnonand thedataavailableforuseindevelopingaLandISfortheProvince.Theinformationpresentedwasgatheredfromlibraryon-linejournal collections on Andosols, geomorphology,PhilippineandBukidnongeology,thesoilsandcropsof Bukidnon; a compilation of agricultural researchreportsonhighland soils, vegetables andother cropsinBukidnonandNorthernMindanao;publishedthesesonagriculturaldevelopmenthistory,andthesoilsandcropsofBukidnon;websitesofPhilippinegovernmentagencies for regional and provincial agriculture,economy and demography; Bukidnon provincialgovernment soil and agricultural reports; and booksonearthandsoilsciencetopicsandonvegetablesandcrops.

1.1. Significance of the review paper

Theconversionofprimaryagriculturallandstootheruses and the increasing population in the highlandshave prompted the use of marginal lands for foodproduction.Marginal landsarecharacterizedby theirremoteness from markets and population centers.They have high transport costs, a lack of resourcesand poorly defined property rights (Briones, 2011).Marginal lands constitute the frontiers of Philippineagriculturalproduction(Raymundoetal.,1985).

ThePhilippinearchipelagohas7,107islandswithalandareaof~30Mha.Itseconomyhasalwaysbeendeeplyentrenchedinagricultureand,sincetheSpanishregime,Filipinofarmershaveraisedfoodcropsforself-sufficiencyandforexport to the internationalmarket(Merino, 1952). The country’s population censusrevealedthatin2010therewere93.4millionFilipinosliving in the country (NSO, 2012a). Rapid changesinthelandrequirementsforfoodtookplaceoverthelast century. In 1910, the Philippines was sparselypopulated(28persons.km-2);by2003ithadbecomeadenselypopulatedcountry(273persons.km-2)(Kastneretal.,2010).Withinthespanof10years–from2000(205persons.km-2) to 2010 (308persons.km-2)– thecountry’s population density increased by 20.7%(NSO,2012b).

BukidnonisthefoodbasketofNorthernMindanaoandisthelargestcontributortotheregionalagriculturaleconomy.Initsearlyhistoryofagriculture,theProvincehad already been identified as suitable for the largescaleproductionof food forexport (Lao,1992).TheProvincialpopulationrosefrom30,974in1907(Lao,1985)to1.3millionin2010(NSO,2012a).Aspartoftheearlygovernment’smovetofast trackagricultureand to utilizeBukidnon’s timber resources,migrantshad been invited to cultivate the soil, prompting the

original inhabitants to integrate themselves into themainstream. Those who were unable to adapt wentdeeper into the forest,where theyundertook shiftingcultivation(Lao,1992).ShiftingcultivationispracticedinmanypartsofthePhilippines,includingBukidnon,but there is no estimateof its areal extent (Schmidt-Vogtetal.,2009).AgriculturallandsintheProvincearesocially,economicallyandenvironmentallyimportant,notonlyforBukidnon,butalsofornearbyprovincesand nationally. Upstream locations of significantwatershedsthatfeedintothewatersupplyofCagayande Oro City and adjacent provinces are located inBukidnonandactivitiesinthehighlandsconsequentlyaffectlowlandenvironments.

Research on geomorphopedology can yield basicinformation in creating a working knowledge of thelandandsoil.DataareessentialinputstothebuildingofaLandIS(a“one-stop-shop”informationsystemforlandandsoildata)inordertofacilitatebetterdecision-makingonlanduse.However,lessattentionhasbeengiventothiskindofstudy,becausesuchanapproachdoes not yield tangible results that can directlycontribute to increased crop production. In order tounderstand the nature of soil and its dynamics, it isimperativetoimproveitssustainableuse,toanticipatedegradation trends, to spot problematic areas andto provide sound bases for land evaluation and landconversiondecisions.Inputdataforlanduseplanningandmanagementcanonlybeusefulifthesearebasedon reliable measurements. The relationship betweenplants and inherent soil fertility provides essentialinformation for developing effective strategies andpractices in crop production and management. ALandISthereforeneeds tobeestablishedinorderforstakeholderstoeasilyaccessinformation.

1.2. Structure of the review paper

This review discusses the information currentlyavailableforuseinthedevelopmentofaLandISintheBukidnonhighlandsandidentifiesissuesofconcerns.Thesectionsofthepaperarestructuredasfollows:– geography, topography and climate of Bukidnon, relatingtoitsgeographicalposition,ecologicalzones withrespecttoelevation,andtheclimaticconditions oftheProvince;– geologicalbackgroundandassociatedrocks,relating tothegeologicalformation,theBukidnongeological mapandtheparentrocksofBukidnonsoils;– a discussion of Bukidnon soils, presenting their mineralogical properties, the location and distri- butionofsoilsintheProvince,soilmorphology,the physicalandchemicalcharacteristicsofsoil,andthe potentialitiesandconstraintsofBukidnonsoils;– an examination of the major crops produced in Bukidnon,thebackgroundonthecontributionmade

546 Biotechnol. Agron. Soc. Environ. 201418(4),544-557 Dejarme-CalalangG.M.&ColinetG.

bytheProvincetotheNorthernMindanaoeconomy, andthesuitabilityofthecropstothesoilenvironment;– thesignificanceoftheuseofaLandISinreaching scientificallybasedandthereforeobjectivedecisions inlanduseplanningandissuesofconcern;– theconclusionsummarizesthemainfindingsofthe article. It presents the authors’ opinion on the findingsandalsomakesrecommendationsforareas offutureresearchtoaddresstheissuesidentified.

2. LITERATURE REVIEW

Thissectionexaminestheliteraturedescribingthedataavailable foruse in creatingaLandIS forBukidnon.It also presents the authors’ view on the existinginformationandhighlightstheissuesofconcern.

2.1. Geography, topography and climate of Bukidnon

Bukidnon is one of the five provinces of NorthernMindanao,withatotallandareaof8,294km2,extendinggeographically from 7°20’-8°40’ to 24°30’-125°30’.Figure 1 presents a map of Northern Mindanao,showing the Province of Bukidnon. Bukidnon is alandlockedprovinceandissubdividedintothreeagro-ecologicalzones(Holmer,1997),whichcomprise:– the mountainous zone of Mt. Kitanglad and Mt.KalatunganandtheCentralCordilleraofEastern

Bukidnon at elevations from1,200-2,950mabove sealevel,– the high altitude volcanic plains, terraces and footslopes surrounding Mt. Kitanglad and Mt.Kalatunganwithelevationsrangingfrom600- 1,200m,– the low altitude volcanic plains, terraces and hills withelevations<600m.

The Province is drained by three rivers and theirdistributaries. FromMt.Kitanglad, theCagayan andTagoloan Rivers and their tributaries are the mainstreamsdrainingthenorthernpart.TheeasternsectionisdrainedbytheManupaliRiverfromMt.Kalatungan.The Maladugao and Muleta Rivers drain the south-easternpartoftheProvinceandeventuallycontributetothedischargeintothePulangiRiver.

Climateaffectstherateofrockweatheringandsoilformation(Grotzingeretal.,2007).ThePhilippineshasatropicalandmaritimeclimate,whichisclassifiedintofour types (PAGASA-DOST, 2014). Type I has twoseasons,dryfromNovembertoAprilandwetduringtherestoftheyear.TypeIIhasnodryseason,buthasaverypronouncedmaximumrainperiodfromDecembertoFebruary.TypeIIIhasnopronouncedmaximumrainperiod,buthasadryseasonlastingbetweenonlyoneand threemonths. Type IV has rainfall that is moreor less evenly distributed throughout the year. Twotypesofclimateprevail inBukidnon,Type III in thenorthern part andType IV in the south.The 30-year

Figure 1.MapsofMindanaoandNorthernMindanaoRegion,thePhilippinesinset—Cartes de Mindanao et de la Région Nord de Mindanao, insertion au sein des Philippines(CourtesyofMarkAlexisO.Sabines,GeomaticsUnit,XavierUniversityCollegeofAgriculture,Philippines).


meanannualrainfallhasbeenrecordedatMalaybalayWeatherStationas2,569mm,withthewettestmonthsbeingfromJulytoOctober(PAGASA-DOST,2014).The1994-1996annual rainfalldata for theManupaliWatershedat1,500maslwas2,825mmandduringthatperiod,onlyonemonthhadalevelofrainfall<100mm(Poudeletal.,2000).Temperatureandrelativehumidityvary with elevation. Mean annual temperature andrelative humidity have been recorded at <500m aslas27°Cand74%, respectively (CMU,2012).Meanannual temperature in areaswith elevations >500masl have been recorded as 18-28°C, with a relativehumidityof~80%(SustainableWatershedEcosystemsManagementResourceCenter,2013).Theareasaroundthevolcanicslopesexhibitsemi-temperateconditions,whichcansupportabroadrangeofhighlandtropicalcrops(SustainableWatershedEcosystemManagementResourceCenter,2013).

2.2. Geological background and associated rocks

ThePhilippinearchipelagoislocatedwithinthecircum-Pacific seismic belt where plate tectonicmovementsand lithospheric collisions are very active. Thearchipelagoiswedgedbetweentwoconvergingplates:theoceanicnorthwest-movingPhilippineSeaPlateintheeastandtheSundaBlock/EurasianPlateinthewest,whichresultedintheformationofthePhilippineFault(Yuet al., 2013).According toAurelioet al. (2012),the archipelago is the outcome of a complex seriesofgeologicalevents that involvedcontinentalrifting,oceanic spreading, subduction, ophiolite obduction,arc-continent collision, intra-arc basin formationand strike-slip faulting. The archipelago becamesubdivided into two tectono-stratigraphic blocks, thePalawan-Mindoro Continental Block (PCB) and thePhilippineMobileBelt(PMB).

Cretaceous ophiolites of the PMB strung alongthe eastern Philippines, which include northern andsouthern Mindanao and foraminiferal limestone thatrepresents the Paleocene, have been found in thedrillcoresintheAgusan-DavaoBasin(Aurelioetal.,2012).Reeflimestoneformations,inassociationwithrocksofdifferentagesarefoundinthehighmountainsofthePhilippines,includingalongthecommonborderof Bukidnon, Agusan, South Cotabato and DavaoOrientalinMindanao(Raymundoetal.,1985).Youngandesitic todaciticvolcanism,mostly representedbyash and lapilli and domes, are emplaced along thePhilippine Fault (Sajona et al., 1997). Subductionrelated volcanism during the Pleistocene depositedvolcanicrocks(basalt,andesiteanddacite)andrelatedpyroclasticproductsthroughoutthePhilippines,exceptfor north-east Luzon (Aurelio et al., 2012). CentralMindanao isanexampleofayoungcollisionof twoisland arcs, which are devoid of the old continental

basement(Sajonaetal.,2000).TheCentralMindanaoVolcanicFieldischaracterizedbynumerousPliocene-Quaternary basaltic to andesitic strato-volcanoes andminor parasitic dacite cones (Sajona et al., 2000).ThewholeofBukidnon isofvolcanicorigin, exceptfor the southern part, which consists of sedimentarymaterials and limited alluvial plains along the rivers(Marianoetal.,1955).Figure 2showsthegeologicalmapofBukidnon.AnalysesofrocksamplesfromMt.Kalatungan have revealed that these are fresh calc-alkalinebasalt(Sajonaetal.,1997).Thismeansthattherocksareunder-saturatedmelanocrate,withabundantolivine,labradorite,slightlycalcic-augiteandricherinNa2OandK2Othanthetholeiticfacies.RocksamplesfromMt.Kitanglad aremoderately fresh shoshoniticbasalt(withNa2OandK2O)andandesite(Sajonaetal.,1997).InnorthernBukidnon,thelowgrassyhillseastofMalaybalay,aremainlymetamorphic(schist)rockswithcappingsoflimestone,whichformthelowhillsinthelocation(Marianoetal.,1955).

2.3. Bukidnon soils

ThefirstsoilresourceinventoryinthePhilippineswascreated in Batangas in 1903 by ClarenceW.Dorseyand focused on soils for abaca (Raymundo et al.,1985). Much progress was made in the late 1920s,whenDr.RobertPendletonworkedonthesugarlandsofNegros Islandand simultaneously trainedFilipinostudents (Raymundo et al., 1985). The actual soilinventory in the country began in the provinces in1934, when the soil survey committee was created,but progress was interrupted by the Second WorldWar(Caratingetal.,2014).Thesoilseriesisthekeypedological unit for soil mapping (Mariano et al.,1955).

Mineralogical properties.Soilistheresidueofrockweathering,and theparentmaterials,consolidatedorunconsolidated, influence soil formation (Grotzingeret al., 2007). Knowing the associated rocks andminerals is useful in identifying the degree ofweathering. The elements found in soils may beverified by soil laboratory analysis. The PhilippineArchipelagoisoneoftheregionsinthePacificBasinwhere Andosols are found (Driessen et al., 2001).AndosolsrepresentsasoilgroupthatisrecognizedintheWorldReferenceBase (WRB).Andosols includesoils developed from volcanic ejecta or glass underanyclimate,whichoccurinvolcanicregionsalloverthe world and may also develop in other silicate-rich materials under acid weathering in humid andperhumidclimates(FAO,2006).AndosolisequivalenttoAndisolintheUSDASoilTaxonomicClassification(SoilSurveyStaff,2010).MostBukidnonsoilsareofvolcanicorigin.However,Bacatioetal.(2005)noted


thatinMindanao,fewstudieshavebeenconductedonthe physico-chemical and mineralogical properties,genesisandclassificationofsoils.Severalstudiesonsoils derived from volcanic material have revealedthepresenceofallophanesandimogolites(Poudeletal.,1999;Bertrandetal.,2008;Kimseyetal.,2011;Levardetal.,2012;Miletietal.,2013).ThemineralsidentifiedintheCentralMindanaovolcanofieldwereolivine, pyroxene, plagioclase and other phases,such as titanomagnetite, hemo-ilmenite, amphiboleranging frommagnesio-hornblende to tschermakitesand apatite, which were observed in western andeasternandesiticanddaciticrockoutcrops(Sajonaetal.,2000).InastudyofthesoilinIntavas,Impasug-ong,Bukidnon,which is situatedat1,200masl, theprimary minerals were found to be predominantly

opaque minerals (Bacatio et al., 2005). Hornblendeandheavymineralsandweatheredparticlescomposedofmica,quartzandvolcanicglass for lightmineralswere found here, while for clay soils, gibbsite andhalloysiteweredetected (Bacatio et al., 2005).Clayformingminerals identified in the soil of a volcanicslope within the Manupali Watershed of Bukidnonwere halloysite, gibbsite, goethite, hematite andcristobalite and the presence of allophanes andimogoliteswasalsoobservedinallthestudiedpedons(Poudel et al., 1999).The presence of both goethiteandhematiteindicatesastateofmineralevolutioninanecologicalsituation.

Soil distribution location.TheSoilSurveyReportofBukidnonwas published in 1955. Soils are grouped

Figure 2. Geological map of Bukidnon, the Philippines— Carte géologique de la Province du Bukidnon, Philippines (BukidnonProvincialDevelopmentStaff,1985).


according to: (1) soil series, (2) soil type, (3) aphase of a soil type, and according to (4) complex,(5) miscellaneous undifferentiated soils from roughbroken lands andmountains (Mariano et al., 1955).TheUSDASoilTaxonomicClassification isused innamingPhilippinesoils.TheNationalBureauofSoilandWaterManagementhasidentifiednineSoilOrdersin thecountry,namely: Inceptisols (39.9%),Ultisols(26.6%),Alfisols (17.1%),Entisols (8.1%),Vertisols(4.5%),Mollisols (3.3%),Andisols (0.23%),Oxisols(0.2%)andsomelimitedHistosols(PCARRD,2006).Figure 3 shows the soilmapofBukidnonProvince.Soil Orders/Great Groups and their distribution inBukidnonarepresentedintable 1.

Soil morphology.Volcanicmudflowsor laharsfromMt. Kitanglad and Mt. Kalatungan underlie thegreaterpartof theBukidnonPlateau,and therestofthe Province with other kinds of igneous materialsand a few localmetamorphic rocks (Mariano et al.,1955).Themoderateweatheringofmainlypyroclasticmaterials produces soils with andic properties.However, some soils develop these properties fromnon-volcanicmaterials, including loess, argillite andferraliticweatheringproducts (FAO,2006). Inorderforasoil tobedefinedashavingandicproperties, itmustmeettheFAO(2006)diagnosticcriteria:– >2%Alox+½Feoxvalue,– abulkdensityof<0.90kg.dm-3,– phosphateretentionof>85%,– organiccarbon<25%bymass,– itmustmeettherequirementsofanalbichorizonif occurringundertephricmaterials.

Poudel et al. (1999) reported that, according tothe USDA Soil Taxonomic Classification, the soildevelopment gradient in the Manupali Watershedranged from Inceptisol in the mountains to UltisolandOxisolatlowerelevations.Moreover,theauthorsidentified theSoilGreatGroupsasHumitropeptandHapludult in themountains,Kandiudox in theupperfootslopes, Acrudox and Hapludox in the lowerfootslopesandAcrudoxandKandiudoxinthealluvialterraces. Soil in Intavas, which is representative ofcultivated,highlandmarginalsoil,hasbeenclassifiedasfineclayey,acid,isothermic,gibbsittic,andasOxicDystrudepts(Bacatioetal.,2005).

In the Bukidnon soil map, no soil is classifiedundertheAndisolSoilOrderorAndosolSoilGroup,although many parent rocks come from volcanicmaterials.Furthermore,thedescriptionsofthesesoilsdonotpresent“andic”properties.Mineralweatheringcandramaticallychangesoilmineralogyandchemistry(Mileti et al., 2013).Poudel et al. (1999) stated thatduring the weathering process, Andisols lose someoftheiruniquepropertiesandchangeintootherSoil

Orders, including Inceptisols, Alfisols, Entisols,Oxisols,Spodosols,Vertisols,MollisolsandUltisols.Therefore,becauseofweathering, soils inBukidnonmayhavelosttheir“andic”characteristicsduringthisprocess.

Andicpropertiescanberetainedifthesoilispro-tectedorundisturbed.Tsuietal.(2013)foundthatofthe60pedonstheystudiedinYMSNationalParkinTaiwan,40pedonswereclassifiedasAndisols.Theyalso discovered that these Andisols were generallyfoundatelevations>700masl,withgentleorsteepslopes, possibly because a thick growth of plantsprovidedprotectionforsoils.Raymundoetal.(1985)statedthat“InthePhilippines,agoodnumberofsoilshave been previously classified asAndepts. HydricDystrandepts (inclusion of the Tigaon series) arefoundontheslopesofMt.Isarog,theHystrandeptsataround800melevationinMt.Makiling(unclassified)area,andpossiblyEutrandeptsovertheslopesofmanyvolcanicpeaks.TheTagaytay,TaalandTupiseriesinCotabatomaybeclassifiedasAndisols”.Pedologicalresearch in Bukidnon hasmade little progress; thusinformation on soils with “andic” characteristics isunavailable. In addition, the soils in some areas ofthecountryareunclassified,suchasinMt.KitangladandMt.Kalatungan,which are volcanicmountains.None of the areas bordering theAgusan andDavaoProvinces, thePantadonRangeorMt.Malambohasbeenstudiedandthereisthereforenosoilinformationavailablefortheseareas.

Soil physical characteristics.Mariano et al. (1955)summarizedthephysicaldescriptionofsoilsaccordingtothedepthofsoilhorizons,color,texture,moisture,stoniness, compactness, soil structure, consistency,root penetration, presence of mottles, and externalandinternaldrainage.ThephysicalcharacteristicsofBukidnonsoilsdiffersignificantlyfromthisdescrip-tionbecauseoftheirparentmaterialsandtopographi-callocation.Poudeletal.(1999)describedthesoilinthemorphologicalunitintheManupaliWatershedasfollows:thesurfacehorizonsofallpedonswerebrowntodarkbrown,withafinetomediumgranularstruc-ture and a very friable to friablemoist consistency.Subsurface horizons were a brown to reddish colorwithaweaktomoderatesub-angularblockystructure.Theywerefriabletoveryfriablewithslightlystickyandslightlyplasticmoistconsistency.Waterretentionwasfoundtobehigh,whichtheauthorsattributedtothepresenceofallophanesandallophane-likemateri-als (Poudel et al., 1999).The profile of Intavas soilhasverydarksurfacehorizonsthatbecomelighterinlowerhorizonswithafineloamytexture.Bacatioetal.(2005)foundthatthissoilhadaconsistencythatwasslightlystickyandplasticwithabulkdensityrangingfrom0.85to1.18g.cm-3.


Figure 3.SoilmapofBukidnonProvince,thePhilippines—Carte des sols de la Province du Bukidnon, Philippines(Marianoetal.,1950).


Tabl

e 1.DistributionlocationsofsoilsinBukidnon—O

ccur

renc

e de

s sol

s au

sein

du

Buki

dnon(1Marianoetal.,1955;2 PCARRD,2006).

Topo

grap

hic

grou

psSo

il se

ries

Pa

rent

mat

eria

l1So

il or

der/

soil

grea

t gro

up2

Dist

ribu

tion

loca

tion1

Alluvialplainso

ilsMaapagseries

Alluvium

Inceptisol

LowlandplainsinM

anagok,M

inlawan,Simaya,Nabago,

MaapagandDagatkidavao

SanManuelsiltloam

Recentalluvium

deposit

Inceptisol/Dystropepts

SmallareasalongPulangiRivernearV

alenciaandsouth-

eastofD

ologon

Mailagclayloam

Anabandonedriverbed

Inceptisol

OccursinM

ailagandinpartoftheplainsouthwestof

Maram

agSoilsonaplateau

Adtuyonclay

Volcaniclavaorlahars

composedofmixedboulders

(basaltandandesite)

Ultisol/Paleudults,

Hapludults

CoversalmostextensivelytheentireBukidnonPlateau.

Totalarea205,124ha,covering25.52%

oftheProvince

Kidapaw

anclayloam

SimilartoAdtuyonclay

(presenceofboulders)

Ultisol/H

apludults

Secondm

ostextensivesoil.Totalareaof139,189haor

17.30%

.Occursonthelow

erslopesofK

itangladand

KalatunganandinthesouthandwestofK

ibaw

eJasaanclay

Volcanicmaterials

Ultisol/H

apludults

OccursinAlaeanditsvicinityinthenorthcentralpart

adjoiningMisam

isOriental

Calauaigclay

Metam

orphicrocks(schist)

(noclassification)

Occursinthelow

grassyhillseastofM

alaybalay.Total

areais4,363haor0.54%

oftheProvince

Faraonclay

Limestone

Inceptisol/Eutropepts

Occursinthelow

limestonehillsbetweenKisolonand

Tankulanan

dinthreeseparatep

lacesalongSayreHighw

ay

andKibaw

einthesouthernpart.Totalareais10,296haor

1.28%oftheProvince

Bolinaoclay

Limestoneresidues


Occursinthen

orth-westernpartofB

ukidnonandoccupies

1,952haor0.25%

oftheProvince

Alim

odianclay

Sedimentaryrocks(shale)

Alfisol/H

apludalfs

Lowsmoothhillsnorthandnorth-westofTankulanand

thehillsofKiliog,covering15,726haor1.79%

ofthe

Province

LaCastellanaclay

Igneousm

aterials(m

ainly

basaltandandesite)

Alfisol/H

apludalfs

CoversM

usuanV

olcanoandsimilarhills,westofM

aram

ag

Poblacion.Totalareaof45,254haor5.63%

oftheProvince

Taclobanclay

Shaleandassociatedrocks

Alfisol/H

apludalfs

Occupiestheso

uthernpartofadjoiningCotabatoProvince

withatotalareaof4,447haor0.55%

oftheProvince

Macolodclay

Weatheredproductso

fvolcanicmaterials


OccupiesthesouthernpartoftheProvinceonbothsides

ofthePulangiandM

uletaRiversandcoversanareaof

52,921ha,6.58%

oftheProvince

Miscellaneousland

types

Roughbrokenland

OccurseastofImpasugongcontinuingtoalargeportionofM

alitboginthenorthernpart

oftheProvince

Mountainsoils,undifferentiated

Mt.Kitanglad,M

t.KalatunganandthewholeportionborderingAgusanandDavao

Provinces:PantadonRangeandM

t.Malam

bo


Soil chemical properties. Earlier studies on thechemical characteristics of Bukidnon soils wereconductedinconjunctionwiththeSoilSurveytoidentifyand classify soil types based on theirmorphologicalandgenetic characteristics, as theyoccur in thefield(Marfori et al., 1955). The soil chemical parametersanalyzed were: soil reaction (pH), soil organicmatter content (SOM), total nitrogen (N), availablephosphorus(P),availablecalcium(Ca),potassium(K),magnesium(Mg),iron(Fe),andmanganese(Mn).Thereport alsopresented recommendations regarding theadditionoflimeandfertilizertosoils.

SoilpHis themost indicativemeasurementof itschemicalproperties in termsofecologicalprocesses,because of its influence on nutrient availability. SoilpH values derived from recent studies are shown intable 2.BusdiandSt.PeterarelocatedneartheCentralCordillerainEasternBukidnon.SungcoandKibangayare on the slopes of Kitanglad andKalatungan. TheManupaliWatershedislocatedwithinKitangladatthenorth-westboundaryandKalatunganinthesouth-west.TheMiarayonRegionisonMt.Kalatungan.

In Bukidnon, SOM content ranges from low tohigh,dependingonlocation.SoilsathigherelevationsgenerallyhaveahigherSOMcontent(Holmer,1997).Thesoilorganiccarbon(SOC)contentofIntavassoilis4.3%,whichirregularlydecreasesatdepth(Bacatioet al., 2005). Thirteen soil surface horizon samplesfrom theManupaliWatershed revealed that the totalcarbon in mountain pedons ranged from 8.2-13.2%,while at the lower elevations the levels ranged from2.5-5.3%(Poudeletal.,1999).IntheirstudyofsoilsintheMiarayonregion,Tatoyetal.(2001)foundthatthetotalSOCvalueswere:inLirongan,9.3%,Miarayon,17.2%andSanMiguel18.3%.ResultsofSOCanalysesfrom fields in these villages were derived from theexamination of four composite samples that weretaken from representative locations in each village.Volcanic soils generally have higher SOM content

levels of organic matter compared to non-volcanicsoils,whichmaytendtobufferexcessivedepletionofSOC(Sandovaletal.,2007).Theslowmineralizationof SOM in volcanic soils inhibits excessive releaseofcarbon(C)overtimeandthereforeCisconservedin the soil.Bukidnon is relatively cool, especially inthemountainousareas,becauseof itshighelevation.CooltemperaturesinthemountainousregionsfurtherretardsSOMmineralization,whichmakesitsmineralcomponentsavailableonlyslowlytoplants.

VolcanicsoilshaveanextremelyhighPretentionrate, so that85-90%of inorganicPadded to thesoilremains unavailable to crops (Mejias et al., 2013).UnavailableformsofPaccordingtoPCARRD(2006)are:– apatite,anoriginalsource,– Ca, Fe and Al phosphates, which are secondary sources,– organiccombinations.

AtalowpH(<5.5)phosphateionscombinewithFeandAl,andatahighpH(>8.0)withCa to formcompounds that are not readily available to plants(Landon, 1984). Phosphorus deficiency commonlyoccursinlateriticredsoilsinabouthalfoftheuplandareasofthePhilippines(PCARRD,2006).Inhisstudy,Holmer (1997) discovered that only 3% of the totalsamplesanalyzedhadavailableP>25mg.kg-1.Poudeletal.(1999)foundoutthatPretentionbysurfacehorizonsofmountainpedonsrangedfrom94-98%,whilethatofother values ranged from 63-81%. For Intavas soils,Bacatioetal.(2005)foundthatPretentionrangedfrom58-78%,withtheplowlayerhavingthehighestvalues.Tatoyetal. (2001)foundthatresultsofsoilanalysesof composite samples taken from four representativelocations in each village in the Miarayon regionshowedPconcentrationsof:Lirongan,1.5,Miarayon,24.7 and San Miguel, 11.9mg.kg-1. The challengesregardinglevelsofPavailabilityinsoilliefirstly,inthe

regularity of the releases of thenutrientandsecondly,inhowfastP is replaced in the soil solutionand is able to become availableforcropsbefore it issequesteredby Fe/Al complexes. High Pimmobilization forces farmersto use significant amounts ofphosphate fertilizers in orderto obtain suitable yield targets(Mejiasetal.,2013).Tocounteractthis limitation, soil ameliorationtoincreasepHtoalevelsufficientto dissociate the nutrient fromtheFe/Alcomplexesneeds tobeundertaken. It should be notedthatinallthereferencesgathered

Table 2.ThepH(inH2O)valuesofsomelocationsinBukidnon—Valeurs de pH eau pour quelques contextes de sol du Bukidnon.Location pH H2O SourceBusdi,Malaybalay 6.6-6.9 CAO,2010St.Peter,Malaybalay 5.5-6.0 CAO,2010IntavasTDF,Impasugong 4.8-5.6,atplowlayer5.0 Bacatioetal.,2005Sungco,Lantapan 5.5 Holmer,1997Kibangay,Lantapan 5.6 Lapootetal.,2010ManupaliWatershed,Lantapan 4.2-6.3,mean5.4 Poudeletal.,1999Miarayon,Talakag 5.1 Tatoyetal.,2001

Lirongan,Talakag 4.9 Tatoyetal.,2001SanMiguel,Talakag 5.1 Tatoyetal.,2001


for theProvinceregardingsoil research,onlyPoudeletal.(1999)studiedtheassociationofaluminum(Al)andFe in termsof thePfixationcapacityof soils inBukidnon.

Cation Exchange Capacity (CEC) is an overallassessment of soil potentiality, which assesses thesoil’s possible response to fertilizers. It is aguide inidentifyingthekindofclaymineralsandtheimpactofSOMin termsofbothquantityandquality (Landon,1984).Poudeletal. (1999)reported thatCECvaluesin the mountains ranged from 7.5-50.4cmol.kg-1, inthe upper footslopes, 5.0-21.7cmol.kg-1 and for thelower footslopes, 9.0-24.2cmol.kg-1. Lapoot et al.(2010)reportedaCECvalueinKibangay,Lantapanof6.34cmol.kg-1.Intheirstudy,Bacatioetal.(2005)foundthat Intavas soil had a CEC range of 7.4-17.3cmol.kg-1,with thehighestvaluebeing in the topsoil.Theaforementioned values are useful references whenevaluatingthepotentialfertilityofBukidnonhighlandsoils.

Soil potentialities and constraints. Based on theinformationgatheredinthisreview,wecanconcludethat mountain soils in Bukidnon have potentialities,suchasahighSOMwithoptimalC/Nratios,highCECvalues,lowbulkdensityandhighwaterretention,butwithrapiddrainageduringrainfall.Lowbulkdensityresults in high porosity, which is essential for theexpansion of plant root systems, enabling them toextractmorewaterandnutrientsfromthesoil.Ahighwater retention capacity enables soils to hold morewater,whichactsasamoisturereserveforplantsduringperiodsofdrought.Rapiddrainageisalsofavorableforplantssensitivetowaterlogging.

The soil constraints in Bukidnon are a too lowbulk density, stoniness and rock outcrops, a low pHandpossibleincreasingrisksofAltoxicityandhighPretention.Lowbulkdensitysoilscanbeassociatedwitha risk of soil erosion.After long periods of drought,thesplasheffectsofheavyrainscaneasilyslakesoilaggregates and transport thedebris, togetherwith itsnutrients,fromthesurface.Soilerosionpredominatesinareaspresentingsteepslopeswithsparsevegetation.In recent years, rapid land use changes in the upperManupaliWatershed have caused the heavy siltationof the Manupali River Irrigation System (Lanticanetal.,2003).Soils intheseareasareshallowandareunsuitableforcultivationandhenceareusedaspasturelandsforcattle.

WhenpHislow,certainmetallicelementspresentin soil will bemobilized.These can easily be takenupbyplantsandsomeoftheseelements,suchasAl,can block root absorption sites. A soil pH of <5.5indicatesapossibleriskofAltoxicity(Landon,1984).Phosphorus is classified as a major plant nutrientand most farmers in Bukidnon spend money on P

fertilizersforcropmaintenance.Becausesoilderivedfromvolcanicmaterial retainshighamountsofP, itsnutrientdynamicsneedtobestudiedfurtherinordertoascertainitseffectiveuseinfarming.

2.4. Major crops in Bukidnon

Bukidnon is the primary producer in NorthernMindanao of maize/corn (Zea mays L.), rice (Oryzasativa L.), sugarcane (Saccharum officinarum L.),pineapple(Ananas comusus [L.]Merr.),banana(Musa sapientum L.)andhighvaluecommercialvegetables:carrots(Daucus carota L.var.sativus),potato(Solanum tuberosum L.), cabbage (Brassica oleracea L. var.capitata) and tomato (Lycopersicon esculentumMill.var.esculentum).Pineapple (A. comusus) andbanana(M. sapientum) are the two crops grown for export.Rubber (Hevea brasiliensis [HBK] Müll.Arg.) is amajorindustrialcrop.

Table 3showsproductiondataforthemajorcropsofBukidnonandNorthernMindanao.Rice(O. sativa)isthemainstaplefoodinthecountry.With88,975haof production in the Province, the irrigated areasoccupy 78,891ha, and the rain-fed areas 10,084ha.TheProvince’scontribution to theproductionof ricein Northern Mindanao is 57.5%. The yellow maize(Z. mays)yieldisdoublethatoftheyieldofthewhitevariety(Table 3),whichmakesyellowmaizeamoreattractive crop for farmers to plant. Because yellowmaize(Z. mays)hasahigheryieldthanthewhitevariety,there is a disproportionate areal extent of theyellowcompared with the white varieties in the Province.Theareaplantedwithyellowmaizeissixtimeslargerthan that for white maize (Table 3). The Provinceproduces the only sugarcane (S. officinarum) in theregion.Theproductionofpineapple(A. comusus)andbananas (M. sapientum) ismanagedbymultinationalagro-industrialcorporations.MuchemphasisisplacedontheCavendishbananabecauseitistheonlyvarietygrown for export.The regional production of rubber(H. brasiliensis)islargelyfoundintheProvince.

Bukidnonisaproducerofhighvaluecommercialvegetables,whichare largelygrownon theslopesofMt. Kitanglad andMt. Kalatungan in Lantapan andTalakagandinImpasug-ong.Tomato(L. esculentum),carrot(D. carota)andcabbage(B. oleracea)represent77, 86, and 83%, respectively of the total regionalproduction. Bukidnon is the sole producer of potato(S. tuberosum) in the region. The production datashowthattheProvincehashigheraverageyieldsthanNorthernMindanaoandtherearesomecropsthatareonlyproducedwithintheProvince.

Table 4 shows the indicative soil requirementsof the major crops planted in the Province. Rice(O. sativa) is found in alluvial plains in Bukidnon,andmostof theareas (89%)are servedby irrigation


systems, thus making the land suitable for theproductionof thiscrop.Generally, soils inBukidnonpossess the aforementioned characteristics requiredby crops. The higher crop yields in the Provincecomparedtoregionalvaluescanbeattributedtotheseenvironmentalconditions.However,todate,nostudyhas identified the links between soil formation andcharacteristicsandcropyields.

2.5. The significance of a LandIS

Inordertoidentifythebestuseofland,itisessentialtoknowwhatqualitiestheareahasandwhatimpactsonthelandanditsenvironmentaparticulardevelopmentmay bring. The classical land evaluation approachis based on qualitative models, requiring only basicstructuralknowledgeofthespecificlandscapeandthe

Table 4.SoilrequirementsformajorcropsinBukidnon—Exigences pédologiques des principales cultures du Bukidnon.Crop Soil requirement pH ReferenceRice(Oryza sativa) Heavysoils 5.0-5.6 Landonetal.,1984Maize/corn(Zea mays) Welldrained,nowaterlogging 5.0-7.0 Landonetal.,1984Sugarcane(Saccharum officinarum) Deep,wellaeratedbutrelatively

toleranttoperiodicflooding4.5-8.5,optimum6.5 Landonetal.,1984

Pineapple(Ananas comusus) Sandyloamwithalowlimecontent 4.5-6.5 Landonetal.,1984Banana(Musa sapientum) Deepwelldrainedloamwithout

stagnantwater5.0-7.0 Landonetal.,1984

Rubber(Hevea brasiliensis) Deep,wellaerated,permeable acidsoils Landonetal.,1984Cabbage(Brassica oleracea) Welldrained,optimum 6.0-6.5 Landonetal.,1984Potato(Solanum tuberosum) Welldrained,aeratedandporous

soils4.0-5.6 Landonetal.,1984

Tomato(Lycopersicon esculentum) Lightloam,welldrainedwithoutwaterlogging

5.0-7.0 Landonetal.,1984

Carrot(Daucus carota) Moist,welldrained,loam,sandyloam

6.0 Rubatzkyetal.,1999

Table 3. MajorcropsofBukidnoncomparedtoNorthernMindanao,thePhilippines—Principales plantes cultivées au Bukidnon et comparaison au sein de la Région Nord de Mindanao(2012).Crop Area(ha) Yield(t.ha-1)

Bukidnon N. Mindanao Bukidnon N. MindanaoRice(Oryza sativa) 88,975 154,712 4.12 4.19Corn(Zea mays),white 27,546 195,578 2.37 1.86Corn(Zea mays),yellow 164,554 183,284 4.74 4.72Sugarcane(Saccharum officinarum) 76,372 76,372 52.97 52.97Pineapple(Ananas comusus) 21,000 21,530 60.90 60.17Banana(Musa sapientum),total 20,373 51,433 56.74 33.42Banana(Musa sapientum),Cavendish 16,481 16,628 66.59 66.30Rubber(Hevea brasiliensis) 6,639 6,851 1.58 1.58Tomato(Lycopersicon esculentum) 1,985 2,728 19.51 18.36Potato(Solanum tuberosum) 550 550 11.91 11.91Carrot(Daucus carota) 104 137 10.72 9.50Cabbage(Brassica oleracea) 371 494 13.67 12.33Source:BureauofAgriculturalStatistics(2013).


object of evaluation and thus must be rearranged ifthelanduseischanged(Mannaetal.,2009).Butlandevaluationhastofocusnotonlyonoptionsforfoodbutalsoonecological,environmentalandsocialconcerns,as these are becoming increasingly important in theplanningprocess(Rossiter,2008).

A LandIS represents the pooling of informationregarding the land, which is a prerequisite whenplanning for land resource surveys, and whichleads to the physical evaluation of the land for itssuitability. If there is no information about criticallandquality, researchmustbe initiated (FAO,1989).The Environmental Impact Statement System of thePhilippines classifies areas of primary agriculturalland as environmentally critical areas,which requirean environmental impact assessment wheneverdevelopment projects are proposed. Soil and landinformation are inputs in identifying environmentalrisksthatcanbeassociatedwiththedevelopmentandhowtheseriskscanbemanaged.

The soil survey of Bukidnon is the earliestcomprehensivedocumentthatpresentsprovincialsoilinformation(Marianoetal.,1955).Thisreportcontainsthe state of agriculture of the Province, soil surveymethods, soils and their morphology, productivityratings and information regarding physical landevaluation, land use and soilmanagement. It furthercontains erosion surveys and information regardingthe soil chemical characteristics with fertilizerrequirements for provincial soils. In that report, andeven to date, there are areas that are still unmapped(the mountainous areas). These are the frontiers ofagricultural production and are areas that are beingincreasingly used for farming in the Province. Latersources of information on soil fertility managementpresentusefuldataandinformationonPhilippinesoilsand soil fertility management strategies (PCARRD,2006). However, this reference does not contain thesameinformationforalltheprovincesinthecountry.Thescaleofinformationneedstobenarroweddowntofieldlevelinorderforittobeasuitablesourceofadviceforfarmersonsoilfertility,potentiality,suitabilityandconstraints.Aswehaveseen,soilresearchhasalreadybeen conducted and has yielded someuseful results.However, the scale of investigation, associated datadensityandtheintegrationofalltypesofinformationneeds to be considered in order to provide holisticknowledgeaboutthesoil.

3. CONCLUSIONS

The information gathered in this paper presents thebackground of Bukidnon’s geology and associatedrocks, soilmorphology, physico-chemical properties,potentiality and constraints and suitable crops.

NamingofsoilsinthePhilippinesfollowstheUSDASoil Taxonomic Classification and the pedologicalunit used in mapping is the soil series. Rocks andminerals in Bukidnon soils are associated withvolcanicparentmaterials.However, the soils arenotclassifiedasAndosols/Andisols,nordotheyhavethe“andic”propertiesqualifier,althoughresultsofrecentpedologicalstudiesinthehighlandshavecorroboratedthat those soils are remnants of that particular SoilOrder/Great Group. Crop yields at the macro-levelindicate that Bukidnon has advantages in terms ofcommercialagriculturecomparedwithotherprovincesin Northern Mindanao. Few geomorphopedologicalstudies have been carried out on Bukidnon soils.Althoughtheavailableinformationrelatesmoretosoilfertilitystatus,whichisusedinfertilizationplanning,nodetailedanalysisisavailableonthedynamicsandinteractions of nutrient elements within soils. Soilsinmarginallandsareincreasinglybeingusedascropproduction areas in the Province. However, thesesoils are still undifferentiated. Results of previoussoil research found that the low level of available Prepresents a limitation in Bukidnon soils. Althoughcropyielddatasuggest thatBukidnonsoil issuitablefor certain crops, information needs to be gatheredat field level.Based on thefindings of our literaturereviewwemakethefollowingrecommendations:– With increasing utilization of marginal lands and undifferentiated soils, geomorphopedological studies need to be conducted in order to obtain a detailedanalysisofsoilevolutionandtherelationship between its physico-chemical characteristics and itsenvironment.Amoredetailedexaminationofsoil propertiesisneededinordertoidentifytheenabling anddisablingcharacteristicsofthenutrientsusable for plants. Such informationwouldprovideuseful inputs in formulating strategies in managing soil resourceswhenlanduseschange.– AlthoughthecharacteristicsofBukidnonsoilsshow potentialities for crop production, there are cons- traintsthatneedtobeaddressed.Itisrecommended to study soil characteristics and plant response in ordertoidentifycropsuitabilityusingyieldsatplot levelasindicators.Thisshouldalsoincluderatesof nutrientassimilationbyplantsasawayofassessing fertilitylevelsandmonitoringsoilstatus.Becauseof the volcanic origin of Bukidnon soils, P is highlightedasalimitingnutrient.SincePisessential forplantgrowth,farmerscurrentlyhavenochoice buttoinvestinthisagriculturalinputasafertilizer. ItisrecommendedthatthedynamicsofPnutrients insoilsbestudiedinordertodeterminetheoptimal quantityandtimingofPfertilization.– With the information that would be gathered as a result of the aforementioned recommendations, aLandISwithgeoreferenceddatawouldneedtobe


established and implemented in land use planning and the management of highland soils.A generic protocol would need to be developed for the LandIS, which could then be replicated in other marginalareasofMindanao.Thecostofdeveloping suchaninformationresourcemaydependonthelevel ofdetailrequired.Inordertoavoidtheunnecessary use of resources, site representativeness should be animportantconsiderationinchoosinginvestigation sites.

Acknowledgements

TheauthoracknowledgesthesupportoftheCooperationofUniversities forDevelopment – InterUniversity Program,theUniversityofLiege-GemblouxAgro-BioTech,BelgiumandXavierUniversity,PhilippinesforherPhDstudies.Theauthorwouldalsoliketoexpressherthanksfortheassistanceof other EPaM project partners: the Catholic UniversityofLouvain and theUniversity ofNamur inBelgium, andEnvironmental Science for SocialChange, andAteneo deDavaoUniversityinthePhilippines.

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