Evaluation of agroforestry potential in sloping areas

27 Pages·2008·0.65 MB·English

8 Evaluation ofagroforestry potential in
sloping areas
AnthonyYoung
InternationalCouncilforResearchinAgroforestry,P.O.Box30677,Nairobi,Kenya.
Acknowledgements
Beinginthenatureofa synthesis,thispaperowesmuch to theworkofthecolleagues
inICRAF, towhom thanksareextended. Inparticular, Ihavedrawn heavilyondata
gathered by the ICRAF agroforestry systems inventory, and would like to thankits
Director, Dr. P.K.R. Nair, theregionalcoordinatorsandfieldcollaborators, andMr.
E.Fernandesforhishelpinselectingappropriateexamplesandfordiscussionofmeth
ods for agroforestry system description. Where' the present paper departs in detail
from termsusedinthesysteminventory, theresponsibilityismyown.
Abstract
Eightexamplesofagroforestrysystemsin slopingareasared"escribed withtwoexam
ples ofeconomic analysis ofagroforestry systems. The ICRAFdiagnosis and design
methodologyisoutlined,exemplifiedandcomparedwithlandevaluationprocedures.
Distinctive features in land evaluation for agroforestry are that surveys commence
with a phase ofdiagnosis; that the performance ofsystems, and hence the land-use
requirements,cannotbepreciselyspecifiedat present; and thatasa consequence, the
output fromagroforestry surveysis frequently a research programme. The ICRAF/
FAOproject,LandEvaluationforAgroforestry,isoutlined.Classificationofanagro
forestrylandutilizationtypeashighlysuitableforagivenareaisnotrelatedtoenviron
mentalonebutdependsonexistingland-usesystemsandproblems.Themajorbenefit
thatagroforestrycanbringtoslopingareasliesinitscapacitytocombinesoilconserva
tionwithproductivefunctions. Agroforestrymay oftenbe thepreferredfonn ofland
use in sloping lands which have problems of soil erosion, soil fertility decline and
shortages offuelwood orfodder. Slopingareas should be a priority environmentfor
theapplicationofresearchanddevelopmentinagroforestry.
8.1 Questions
The titleofthis papercovers threeentities: land evaluation, agroforestryandsloping
areas. Since relations between two ofthese, landevaluation and slopingareas, is the
subject ofthis symposium, this leaves two other sets ofrelationships as the primary
questions,namely:
I. Howcanlandevaluationbeappliedtoagroforestry?
2. Whatbenefitscanagrofor~stryofferasakindoflanduseinslopingareas?
Anticipating that the answers to these are broadly positive, thatis, that agroforestry
does have a potential in sloping areas and that this potential can be evaluated.
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\
,
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thentwofurtherandmorespecificquestionscanbeasked:
3. Underwhatcircumstances,and in what respects, is agroforestrysuperior to other
kindsoflanduseinslopingareas?
4. Areslopingareasapriorityenvironmentfor theapplicationofresearchanddevel
opmenteffortinagroforestry?
8.2 Agroforestry
,
8.2.1 Agroforestryasamajorkindoflanduse
Agroforestry refers to land-use systems in which trees are grown on the same land
I
as agricultural crops and/or animals, either in a spatial arrangement or a time se
quence, and in which there are both ecological and economic interactions between
thetreeandnon-treecomponents(Lundgren, 1982,modified). Note that'tree'ishere
usedasanabbreviationfor woodyplants,comprisingtrees,shrubsandbamboos.
The secondpart ofthis definition, the need for interactions, is an essential feature
I
I ofagroforestry land-use systems. Economic interactions can mean simply that the
tree and the crop (and/or animal) each supply part of the farmers' needs; or could
involve,forexample,thetreeharvestprovidingcapitalwhichisputintoimprovements
to crop production. Ecological interactions are numerous; examples are fertilization
with litter from nitrogenfixing trees, feeding ofhigh-protein leaflitter to cattle, the
I manure from which is then applied to crops, or the soil conservation functions of
trees.
Isagroforestrymorecloselyrelated toagriculture orforestry? Neither. Mostagro
I
forestry, probably over 90%, is carried out on agricultural land, and by farmers; as
I
willbeillustratedbelow,thecommoneststartingpointforagroforestrydevelopments
t
I isfarmland that has problems. Yetit is thedistinctivefeatures and functions oftrees
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whichare theessenceofagroforestry. Given that theconcept ofa majorkind ofland
f useisinanycaselooselydefined,agroforestrycanusefullyberegardedassuch.
f
f
8.2.2 Terminology
I
t Agroforestry components refer to the three elements of a land-use system, the tree
f (= woodyperennial),herb(agriculturalcroporpastureplants) and animal.Thefirst
two are always present, the last sometimes. This leads toa simple classification of
agroforestrysystems:
Agrosilviculturalsystems: cropsandtrees
I Silvopastoralsystems: pastures,animalsandtrees
r
Agrosilvopastoralsystems: crops,animalsandtrees(withorwithoutpastures)
I Othersystems: e.g.mangrovewithfishing, apicultureintrees.
I
The treecomponent is almost always a multipurpose tree. Afterextensiveconsidera
tionofbothconceptsandexamplesithasbeenfound that theland-usesystemwithin
1
! whicha treeisgrownis an essential part ofthis definition. Hencemultipurpose trees
f (MPTs) are those which are grown, or kept and managed, for more than one major
!
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purpose(productorservice),economicallyand/orecologicallymotivated,inanagro
forestry or othermultipurpose land-use system (von Carlowitz, 1984, modified). Ex
pressedmoresimply,multipurposetreesarethosewhichprovidemorethanonesignifi
cant contribution to the productionand/or service functions ofthe land-use systems
they occupy (Huxley, 1984). The main functions ofmultipurpose trees are listed in
Table8.1.
Table8.1 Functionsofmultipurpose trees. Adapted from the ICRAFmultipurpose treedata sheet(von
Carlowitz,1984).
Wood fuelwood(inc.charcoal)
timber(sawnwood)
poles(domestictimber)
other(e.g.carvings)
Fodder browse }.
cut-and-carry (me.leaves,seeds,shoots)
Food fruit,nuts
oils
beverages
otheredibleproducts
Otherproducts oils,gums,waxes,dyes,tannin
fibres,thatching
latex
medicinaluses
Services shade(fromsun)
shelter(fromwind)
soilconservation(inc.reclamation)
soilimprovement
fencing(= barrierfunction)
moistureconservation
Thus the same tree species can be monopurpose where it is managed to optimize
one outputonly, as ina forest plantationmanaged for timberproducts; ormultipur
pose where management is intentionally directed towards two or more outputs, e.g.
fuelwood, fodder, shelter,conservation.
Agroforestrypracticesarethemorecommonarrangementsofcomponentsinspace
and time,coupledwiththemajorfunctions ofthe treecomponent. Thisismoreeasily
illustratedthandefined,asinTable8.2.
Anagroforestrysystemisasetofagroforestrypracticeswithinaspecifiedphysical.
economic and social setting; the land-use systemitselfmay bebased on agroforestry.
or the agroforestry system may fulfil certain functions within the broadercontext of
the land-use system as a whole. Agroforestry systems are described in terms oftheir
biological,technical,economicandsocialaspects.
This term, widely employed in agroforestry literature, is so nearly equivalent to
thestandarddefinitionofalandutilizationtypethatagroforestrysystemandagrofor
estrylandutilizationtypemaybetakenassynonymous.Aswithlandutilizationtypes.
existingagroforestrysystemsarefrequentlyspecifictoalocalregionbutarepotentially
extendabletootherareaswithsimilarenvironmental,economicandsocialconditions.
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.•.••_u'"-""''''''"'-''-"''"-.
4..0
t
i
T;Jble8.2Agroforestry practices. Adapted from the ICRAF agroforestry systems inventory (ICRAF,
1983d;Nair,1984).
l
Improvedtreefallow
I Taungya
Alleycropping(hedgerowintercropping)
Boundaryplanting
Livefences
\tultipurposetreeson:
. cropland
I
- r;Jngeland
- pastures
- homesteads
Woodlots(withmultipurposemanagement)
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Treesasshelterfor:
! - crops(windbreaks,shelterbelts)
f - animals
i - homesteads
J.
Treesforsoilconservation:
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I - onbunds,terraces
- strips
- hedges
Agriculturaltree/shrubcrops
t .. lower-storeytree/shrubcrops
i
- herbaceouscrop
- upperstoreytrees
- pasturesandlivestock
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i Aquaforestry(mangrove)
Apiculturewithforestry
I
f 8.3 Slopingareas and theirenvironments
I
f SlopingareasarehereassumedtorefertoslopeclassescandbcontheFAa/UNESCO
SoilMapoftheWorld,thatis,areaswithdominantslopesover17°/30%oracombina
f tionofthiswithareasof5°- 17°/8- 30%.Thispaperislargelyconcernedwithsloping
t areasintropicalandsuhtropicallatitudes.
It may be remarked in passing that the slope classes on the world soil map are
f
nottheoutcomeofaprimaryinventoryoflandforms,butaresupplementarytoclasses
~
and map units determined primarily on the basis ofsoil type. Since there are now
f also satisfactory world or continental maps ofgeology, climate and vegetation, the
f lack ofa treatment oflandforms at comparable intensity and coverage is deficiency
I! intheinventoryoflandresources,whichcouldleadtosubstantialerrorsinworld-scale
landevaluationorotherestimatesofproduction.
!
i Within the tropics, sloping areas may be grouped on the basis oftemperature and
,
I altitude into lowland and upland, separated at 1,200 m altitude. These correspond
approximately to the division between Koppen A (hot) and R(warm) climates, and
f
i betweenthe'warmtropics'and'cooltropics'oftheFAaagro-ecologicalzonesinven
tory. On the basis ofamount and duration ofrainfall, these lands may be further
J
I subdividedintohumidclimates(KoppenAf,AmandCa,growingperiod>270days),
~
I andsubhumidclimates(Koppen AwandCw, growingperiod 120-270days). Sloping
lands withsemi-aridclimatesaremainlyofverylow potentialandwill notbeconsid-
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T
ered.Thisgivesthefollowingclassesofslopinglandinthetropicsandsubtropics.
I. Lowlandhumidtropics
Hot, humid for all or most ofthe year, vegetation evergreen or semi-evergreen rain
forest. Reliefcommonly either V-shaped valleys with narrow interfluves or convex
interfluves,steepeningdownslopeuntiltheypassabruptlyintoflatvalleyHoors('demi
orangerelief). Soilsarenormallyferralsolsoracrisols,withniticpropertiesifonbasic
rocks.
This is by far the most extensive tropical sloping-land environment, found in all
continentsbutparticularlyinCentralAmerica,atloweraltitudesintheAndeanstates
ofSouthAmerica, intheWestand EastIndies,thesouth-eastAsia mainland,Pacific
islandsandeasterntropicalAustralia.
Commonland-usesystemsinthisenvironmentare:
- extractiveforestry;
- perennial,non-foodcropplantations;
- shiftingcultivationofannualfoodcrops,cerealsorroots;
oftenwithshortenedfallowandconsequentsoildegradation;
- terracedcultivation,includingswamprice(especiallyinAsia);
- ranching(especiallyinSouthAmerica).
The principal environmental hazard is the very reserve rainfall erosivity. Others in
cluderapidoxidationofsoilorganicmatter,highsoilaciditywithassociatedPfixation
andaluminium toxicity(thelastespecially,for reasons notwellunderstood,in South
America),andrapidleaching.Besidessoilerosion,theremaybeahazardofaccelerated
landsliding.
Themostcommonland-useproblemsarethecuttingofrainforestfasterthannatu
ral ormanagedregeneration,andshorteningoffallows withconsequentsoildegrada
tion and over-grazing, the two latter sometimes leading to soil erosion. Shortening
offallowsisparticularlylikelyinareaswhichlacktheflatvalley-floorlandthatpermits
swampricecultivation.
2. Highlandhumidtropics
This is a less widespread environment, since most high-altitude regions have a dry
season ofsufficient length to fall into the subhumid zone. It occurs in parts ofthe
Andes, andthehighlandsofMalaysiaandtheEastIndies.Ahighproportionofrelief
issloping.Soilbecomehumicferralsolsandhumicacrisolsathigheraltitudes.
Land-usesystems aresimilarto thoseofthelowlandhumidzoneexcept thatcom
mercialforestryislesscommon.Land-useproblemsincludeshorteningoffallowswith
soildegradation;overgrazingandpasturedegradation;andover-cuttingfordomestic
fuelwood and timberleadingto reductionin area and speciesdepletion ofremaining
forests.
3. Lowlandsubhumidtropics
This is the savanna zone ofAfrica and the cerrado ofSouth America, with one or
two wet seasons (Koppen Aw orAw' respectively) and atleast one long dry season.
A high proportion ofthis climaticregion is not sloping, other that on isolatedinsel
bergs.Areasofslopinglandsoccur,however,particularlyinescarpmentzonesseparat
ingerosionsurfaces.
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Commonland-usesystemsinclude:
_cultivationofannualcrops,oftenmoreorlesswithoutsoilrestperiods;
_ certainperennialcrops,mainlytowardsthemorehumidmargins;
_ extensivegrazing(rangingornomadic);
- afforestation.
Although rainfall erosivity is less than in the humid zone, the soil erosion hazard is
almost ashigh, owingtotheslowergrowthand lesscompletecoverofthevegetation.
Droughtbecomesa hazard in thedrier partsofthezone (mean annual rainfall <800
mm).Themostwidespreadland-useproblemsarefirst,declineinsoilfertilitybrought
about by over-cultivation; secondly, degradation of natural deciduous woodlands
through over-cuttingwithconsequentfuelwood shortage;andthirdly,erosion,which
isparticularlycommonongrazingland.
4. Highlandsubhumidtropics
Thisdistinctiveenvironment,sometimeslooselycalledthe'highlandtropics',isexten
sive in East Africa (especially Kenya and Ethiopia), the Andes and the Himalayas,
in the last ofwhichit occursundera climateofmonsoonal origin and regime. Much
ofthisclimaticzoneisnotsloping,beingeitheruplandplateauorintermontanebasins,
butsloping land occurs at the borders ofthese. Notable examples are the extensive,
steeply-sloping and deeply dissected lands of Ethiopia, and the so-called 'foothills'
oftheHimalayas.
Land-use systems include annual crops, perennial crops in the wetter parts ofthe
zone, grazing and commercial afforestation. Terraced cultivation is common in the
Himalayas.
Lossordegradationofnaturalforests isoftenconsiderable,andsoilfertilitydecline
andsoilerosionare bothcommon. The Ethiopianhighlandscombineseveresoilero
sionwith almostcompletedestruction ofnatural forests. Systemsofterracedcultiva
tionhavebecomepoorlymaintainedorabandonedinsomeareas.
8.4 Agroforestry insloping areas
8.4.1 Examples
To illustrate the range ofagroforestry practices and their potential in sloping areas,
eight cases will be described. The first five are existing systems, 'traditional' in the
senseofbeingevolvedlargelybythefarmersoftheareaconcerned,althoughincorpor
atingsome relatively recentlyintroduced crops. The sixth case is a development pro
ject, the seventh an example ofexperimental trials, while the last gives systems sug
gestedinoneoftheICRAFcollaborativedesign projects. Two oftheseexamplesare
drawn from Africa, three from south-east Asia, one from south Asia and two from
South America. In these accounts, some added descriptors for land utilization types
areemployed,explainedinSection6.1 andTable8.5below.
I. Terracedhillfarming,westNepal
The first case has been set out as a formal description of a land utilization type
(Table 8.3).TheTinauwatershedofwestNepalhasalowlandsubhumidclimate,with
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Table8.3Descriptionofanagroforestrylandutilizationtype:terracedhillfarming,Nepal.
Title Terracedhillfarming,westernNepal.
Environment Lowland subhumid climate (Koppen Aw) of monsoonal origin, 7-8 dry
month;slopessteep,20°-35°(36-70%)
Socio-economicsetting Densepopulation,severelandshortage,averagefarmsizeIha,lowincome,
poorinfrastructure
Summarydescription Slopes('bari'land)areterraced,withmaizeandotherrainfedcropsonslop
ing treads, MPTs on risers (contour strips) and farm boundaries (vertical
strips)(Figure8.1).
LUTdescriptors
Outputs Products:maizeandotherrainfedannualcrops,cattleproducts,fuelwood.
Services:soilconservation.
Market Dominantlysubsistence,pluslocalmarketing.
Capitalintensity Low
Labourintensity High
Technicalknowledge ormodernagriculturalmethods,low;moderatelyamenabletoinnovations.
Landholdings Small,averageIha;somehaveseparatelowlandirrigatedriceholding.
Tenure Owner-cultivated.
Landimprovements Terracing;unlikesomeotherpartsofNepal,terracetreadsareinitiallyslop
ing,olderonesbecominglevel.
Infrastructure Low;familyprocessingofproducts;needforroadaccesstolocalmarkets.
requirements
Power Ox-ploughing,plusmuchmanualpower.
Mechanization None.
Inputlevel Low;noartificialfertilizers,mainlylocalseed.
Cropping Maize,withsubsidiarywheat,fingermillet,mustardandlegumes.Numerous
vegetablesandfruitinhomegardens.MPTsonterracerisers,over30spp.
Cultivation Oxploughing,handweeding.Treesprunedforfodder,cutforfuelwood.
Conservationpractices Achievedthroughcontourterraces,stabilizedbytrees.
Irrigation Onlyonseparatelowlandfields,forrice.
Livestock Cattle,buffalos,goats,poultry;forfood,cash,draught,manure.Partlystall
fed,partlygrazed.Contourtreestripsmaysupply40-60%offodder.
Yields Low;samplesurvey,maize930kg/ha,wheat580kg/ha.
Economics Nodata.
Agroforestrydescriptors.
Type Agrosilvopastoral(crops,trees,livestock).
Maininteractions Space,includingoff-site.
Time Static,interpolated.
Space Zonal,row.
AFpractices Main:MPTsforsoilconservation,onterraces.
other:boundaryplanting,MPTsaroundhomesteads,livefence.
Functionsoftrees Soilconservation,fodder,fuelwoodfood,fencing.
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..:.P:---...
.&
the excessive concentration ofrainfall into four very wet months that is a feature of
dimates ofmonsoonal origin. This still further increases the erosion hazard on the
steep slopes. Despite the relief, the region is densely populated, and the remaining
area of natural forest reduced and degraded. Most fanning takes place on sloping
land under rainfed conditions, although some farmers also possess a low-lying area
ofirrigatedrice. Whilstgivingtheappearanceofbeingbasedonannualcrops,chiefly
maize, livestock products also play an important role, both for subsistenceand cash
purposes.
The main agroforestry practice is the planting of trees as strips on two kinds of
sites:alongtherisersofterracesandasvertical(downslope)rowsalongfarmboundar
ies(Figure8.1).Theserowsarequitedenselyplantedandgivethelandscapeacompart
mentedappearance. Over30speciesarerecorded, nearlyall havinga function as fod
der, most also as fuel, and a smallernumberas fruit (not to mention the presumable
medicinal use ofWrightia antidysenterica). Up to halfthe livestock feed comes from
the tree strips, and there is a further interaction in that the manure from stall-fed
animals is returned to the fields. The major service function ofthe trees is ofcourse
soilconservation,through themediumofstabilizingtheterraces.
In addition, the tree rows form aneffectivebarrier, permittinglivestock to beletinto
specificfields, andkeepingoffthoseofneighbours,
Summarizing the agroforestry features, this is an agrosilvopastoral system (crops
+ +
trees livestock), interacting in space, with the trees zoned, as rows, The main
practiceistreesonsoilconservationworks,in thiscaseterracerisers:subsidiaryprac
ticesareboundaryplantingand homegardens. Thefunctionsofthetrees areparticu
larly varied namely fodder, soil conservation, fuelwood, food and fencing. (Source:
FonzenandOberholzer, 1984).
2. Chaggahomegardens, MountKilimanjaro,Tanzania
Farm 1 Farm 2 Farm 3
.
.,.
... "
'
'
~-;-:-;-,:;
<""nr1ll.."'..._ :"i:','::.:'.::::.:;.,.
,',
.,'..
1< 100m
_ Slope
Figure8.1 Planviewandcross-sectionofterracedhillfarming,WestNepal,AfterFonzenandOberholzer
(1984).
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ThissystemoccupiesthesouthandeastslopesofMountKilimanjaro,Tanzania,with
asubhumidclimateandanaltitude rangeextendingfrom lowland to highland. Land
isscarce, incomelow to medium,capitalscarce, marketingfacilities and otherinfras
ructure'moderate. It is a mixed cash and subsistence economy, labour-intensive,
owner-occupied.
The home gardensconsistofa random and dense arrangement that includes food
andcashcrops, and herbaceouscropsand treesofbothplantation(agricultural)spe
ciesandtimber(coffee,othersbeingcardamom,andsurplusbananasandfood crops.
(Figure8.2)Foodcropsincludebananas,maize,beans,rootcrops,vegetablesandfruit.
Farmers deliberately retain and manage numerous species of tree (over 40). Cattle
andpoultryarekept,mainlystall-fedfromtreefodder, bananaandcultivatedgrasses.
Thissystemisagrosilvopastoral,interactinginspace,staticintimeandwithamixed,
densemultistoreyarrangementofthetreeandshrubcomponent.Asitsnameindicates,
it is an example ofthe home garden practice, widely found in humid to the moister
subhumidenvironment(cf.e.g. theKandyhomegardensofSriLanka,andtheexam
ple which follows). The trees fulfil productive functions ofcash crop income, food,
fuelwood and fodder; and besides the soil conservation achieved by the dense, mult
istorey canopy, there is a substantial element ofsoil improvement, or maintenance
of fertility, through incorporation of leaf litter and manure from stall-fed cattle.
(Source: FernandesetaI., 1984).
3. Hillsideagroforestry,westernSumatra
This is a further example ofhome garden practice, chosen for description as being
Xl
ALBIZIASCHIMPERIANA
LIVErNCEj
MORUS
ALBA
CAESAlJ>tNIA
DECAPETALA
Figure8.2Typicalverticalzonationinachaggahomegarden,mountKilimanjaro,Tanzania(Fernandes
etaI.,1984).
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i
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in adifferent continent, a more humidclimate and with differences offunction. The
l
I areaaroundLakeManinjau,inthecentralpartofwestSumatra,hasalowlandhumid
climate (Koppen At), with rainfall >3,000 mm and no dry months. As the slopes
are very steep, reaching to over 40° (84%), it need hardly be said that the erosion
hazard is severe; there isalsoa serioushazard ofaccelerated landslidingifthe slopes
{
arecleared. The forests which remainhave beentaken overbytheState. Thefarmers
f growswampricewherepossible,inconjunctionwiththetreegardensofthehillsides.
Thegardensarelargelymulti-storeytreearrangements,withherbaceouscropsbeing
onlysubsidiary. Amongthecommonestspeciesisthebeloveddurian,cinnamon,cof
fee, nutmeg, and many timber species. These are farmed in various combinations,
atleastpartlyplanned,e.g.durian +cinnamon + timberspecies.Itisanagrosilvicul
turalsystem,interactingmainlyinspace,althoughgardensaresometimesabandoned
or new ones established, giving an element oflong-term fallowing. As in all home
gardens, thespatialarrangementismixedanddense. Thetreesfulfilfunctionsoffood
andcashcropproduction,fuelwoodandtimberproduction,anderosionandlandslide
control.(Source:MichonetaI., 1984).
4. Coffee-Erythrina-Cordiasystems,CostaRica
Systemsofcoffeewithanupperstoreyoftrees,especiallyErythrinapoeppigianaand/
or Cordia alliodora, are widespread in Central and South America, sometimes on
gently-sloping land but often on sloping areas, in part because these provide some
ofthe best sites for coffee. The same two species are also grown with cacao. Such
systems are found in humid to the moistersubhumidlowland andhighlandenviron
ments.TheyareexemplifiedinthevicinityofTurrialba,CostaRica.Thetypicalsocio
economicenvironmentdiffersfrom the precedingexamples. Landisonlymoderately
scarce,incomelevelsatalow-intermediatelevelandinfrastructuremoderate.
The farming system is based on cash-croppingofcoffee. Erythrina and/or Cordia
are planted in the cropland, in some areas as rows, in others on a mixed, random,
open to moderately dense arrangement. Erythrina are pruned several times a year,
keeping them as a low stubby life form, and the prunings laid asmulch. Cordia are
allowed to grow into tall trees. Erythrina is a nitrogen-fixing tree,and its use for soil
fertilitymaintenanceisintentional.
Thisisanagrosilviculturalsystem,interactinginspace,with thecomponentseither
inamixedarrangementorasrows. Thefunctionsofthetreesare:
Erythrinapoeppigiana CordiaaIliodora Coffee
Shade Shade Cashcrop
Soilimprovement Timber
Mulch Fuelwood
Soilconservation Soilconservation
(Sources:Budowski,1983;Escalante,inpress).
5. Improvedtreefallow,Philippines
InCebuProvince,Philippines,asystemofimprovedtreefallowusingLeucaenaleuco
cephala (leuco) is found. Although lowland subhumid, it is wetenough (1,620 mm)
for rapid growth ofleuco. Part ofthe farm is undercrops, partplanted to leuco for
aboutthreeyears.Theleafproductionrestoressoilfertility.Whenthetreesarecleared,
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