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1. RESEARCH, REVIEWS,PRACTICES,
POLICY AND TECHNOLOGY
Agrosilvopastoral Systems:
A Practical Approach
Toward Sustainable Agriculture
Ricardo 0.Russo
ABSTRACT. The practical objective of agrosilvopastoral (ASPS)
systems, in areas fundamentally devoted to cattle production, is to
produce goods, traditionally forestry goods such as fuelwood, poles,
and timber. These goods are used to solve immediate domestic
needs, to provide for local needs and also to alleviate the pressure on
natural forests.
By definition, ASPS is a collective name for land-use systems,
implying the combination or deliberate association of a woody com-
ponent (trees or shrubs) with cattle in the same site. Essentially,these
systems are a model of production and conservation based on silvi-
cultural practices complementary to pre-existing agricultural activi-
ties. From this point of view, these practicesmay be applied in a wide
range of ecological and productive conditions. Based on this frame-
work, several activities to achieve ASPS are proposed. [Article copies
available jiwm The Haworlh Document Delivery Service: 1-800-342-9678.
E-mail address:getinfo@haworth.com]
Ricardo 0.
Russo is affiliated with Escuela de Agricultura de la Region Tropi-
cal Humeda(E.A.R.T.H.) University,P.O.
Box 650990 Miami, FL 33265.
Journal of SustainableAgriculture, Vol. 7(4) 1996
O 1996 by The Haworth Press, Inc. All rights reserved. 5

2. 6 JOURNAL OF SUSTAINABLE AGRICULTURE
KEYWORDS. Agrosilvopastoral systems, trees
INTRODUCTION
Agroforestry systems (AFS), which include agrosilvopastoral com-
binations, are not a new thing in Central America, Mexico, or the Carib-
bean. Thcir roots are in Mayan civilization, where farmers practiced
"roza-tumba-quema" or cutting the forest to cultivate corn from one to
three years, after which the abandoned cropped area was allowed to
regenerate naturally (Kellogg, 1963; Parsons, 1976; Reyes-Rodriguez,
1979). Mayan farmers also cultivated multispecific gardens with more
than 20 multipurpose species in their "milpas" (Gomez-Pompa ct al.,
1987). Agroforestry practices continued into the Spanish colonial times.
In Mexico, they were practiced in the state of Tabasco (Arias, Lau, and
Sepulveda, 1987), where cocoa was cultivated under shade in natural
forest. Today in the Mexican humid tropics, more than five millon hect-
ares are under the "roza-tumba-quema" system, where the cultivated
areas are used to produce food, while the fallow areas are utilized for
forest, wildlife, and animal production purposes (Hernandez X. et al.,
1987).
DEFINITIONS
Under the name of agrosilvopastoral systems (ASPS), there exists a set
of land-use techniques implying the combination or deliberate association
of a woody component (tree or shrub) with husbandry and/or crops in the
same site (Combe and Budowski, 1979; Nair, 1985, 1989). Such systems
contain significant ecological and/or economic interactions (Kapp, 1989)
orjust biological interactions (Somamba, 1990).These combinations may
be simultaneous or alternate in time and space, and aim to achieve sustain-
able production. If only tree and animal components are prescnt, they are
referred as to silvopastoral systems (SPS). ASPS also may be considcred
as a set of silvicultural practices complementary to other activities (agri-
cultural or cattle) alrcady established in a farm or in a region. From a
sustainable agriculture viewpoint, ASPS should be considered as a biolog-
ical strategy in search of sustainability.

3. Research, Reviews, Pructices. Policy and Technology 7
INTERACTIONS AMONG SYSTEM COMPONENTS
Multiple interactions occur among components of ASPS (Borel, 1987;
Bronstein, 1983). The flow diagram (Figure I), redrawn from Bronstein
(1983), allows a quick and clear view of inputs, outputs, and relationships
among components.
Some of these interactions, as summarized by scveral authors (Borel,
1987; Bronstein, 1983,Montagnini, 1992; Torres, 1985),are as follows:
1. Trees supply organic matter to the soil through the periodic decay of
leaves, flowers, fruits, branches, and dead roots. In addition, roots
absorb elements from deeper soil laycrs and bring them to the sur-
face, making them more available to the pasture. In the case of nitro-
gen fixing trees (NFT), soil nitrogen levels are increased.
2. Trees create a microclimate favorable for animals (shade and lower
temperature). Shade intensity depends on tree density, crown diarne-
ter, and crown structure. Shade protects animals from excessive
heating from direct radiation and reduces internal temperature
stress. Changes in animal thermal balance, that is, lower air temper-
ature than body temperature, leads to lower food consumption (De
Alba, 1959). Whether or not this contributes to higher animal pro-
ductivity is a point of controversy.
3. Trees may compete with pasture for water, nutrients, light, and
space. Competition effects will be stronger if the requirements of
both are similar. Natural leaf fall and pruning help to increase the
availability of water, light, and nutrients to system components. Ap-
propriate selection of species and the selective prunings (in season
and intervals) help to ameliorate competition.
4. High numbers of animals or trees arranged in groups can lead to ani-
mals crowding together looking for shade. Trampling may result
and can affect plant cover and cause soil erosion and soil compac-
tion. These conditions can deter tree growth.
5. Feed preferences of animals can affect forest composition. Over
time, those species rejected by cattle can dominate.
6. Animal component changes can accelerate some aspects of nutri-
ment cycling by returning manures and urine to the soil.
7. Animals can spread seeds, or scarify them, which favors germination.
8. Generally, grass species growing beneath the tree canopy yield
more, have a lower root:shoot ratio, and are of a different composi-
tion than those outside the canopy (Pinney, 1989).

4. FIGURE 1. Simplified Flow Diagram of an Agrosilvopastoral System. Redrawn from Bronstein (1983).
ds, fertilizers, herbicides,

5. Research,Reviews, Practices. Policy aud Technology 9
ADVANTAGES AND DISADVANTAGES
OF AGROSZLVOPASTORAL SYSTEMS
Several authors have analyzed advantages and disadvantages of ASPS
(Borel, 1987; Bronstein, 1983; Ruiz, 1983; Torres, 1985). According to
Ruiz (1983), some of the factors that favor cattle components in ASPS are:
Diversification of production activities within the farm reduces risk
of economic disasters.
Small farmers, with land limitations, may use the forest to produce
food from animal origin (milk, meat) without sacrificing areas dedi-
cated to crops.
In addition to direct advantages, farmers may also obtain economic
benefits from fuelwood, timber, posts, and forage, which are used
eventually on the farm for cattle management.
Cattle keep pastures and weeds from competing with young trees. In
the case of fruit trees or palms, grazing also facilitatesthe harvest of
fruits.
Grazing of cover vegetation reduces fire risks.
In the case of associations of cattle with crops, the principal advan-
tage is that between 60 and 70% of plant biomass can be used as feed
for cattle without causing competition problems with crops for hu-
man consumption.
In the particular case of cattle associated with nitrogen-fixing trees,
it is logical to assume that these species will contribute to soil fertil-
ity, in addition to being a protein supplement when their edible parts
are utilized as forage.
It is important to realize also that disadvantages exist (Ruiz, 1983).
Most important are:
Compaction effects on the soil are harmful but could be compen-
sated for by the effect tree roots have on soil porosity, infiltrationca-
pacity, and soil aeration. However, this topic requires more research.
Velocity and size of water drops from tree crowns to plants or crops
under them can cause damage to flowers and fruits.
Cultural practices, such as mechanized harvest of crops, "henifica-
cion," or "ensilado," are interfered with by the trees. Planning with
sufficient space is necessary.
Sometimes ASPS has been considered a subsistence practice. This
negative connotation may prevent wider acceptance. Furthermore,
effects to improve these systems can be interpreted as a means to
maintain the poverty status of the subsistence small farmer.

6. 10 JOURNAL OFSUSTAINABLE AGRICULTURE
The low levcl of knowledge on agrosilvopastoral techniques and the
lack of trained personnel makes systems improvement difficult.
Also, formal experimentation with these combinations is complex,
not only from a practical point of view, but biometrically. They also
require a long term commitment which not too many institutions are
willing to assume.
Where young timber trees are planted in pasture lands, problems oc-
cur due to trampling and browsing by grazing animals (Heuveldop,
19871.
- - - .
An obvious bottleneck for small farmers in rural areas is the lack of
availability of suitable plant material (Heuveldop, 1987).
IMPORTANCE OF AGROSILVOPASTORAL SYSTEMS
IN COSTA RICA
It is difficult to talk about ASPS without referring to husbandry in
Costa Rica. The cattle census of 1988 accounted for 2.19 millon head:
64% for meat, 22% double-purpose and 14% for milk (MAGISEPSA,
1990). These activities occupied an area of 2.4 millon hectares of grass-
lands. However, in many farms the presence of forest fallows is common,
especially when cattle activities are discontinued because of low market
prices for meat. It is estimated that around 400,000 hectares of abandoned
pasture lands are under fallows of different ages (Miiller et al., 1992).
Although these statistics exist, it is unknown at the farm level what area
percentage is managed under ASPS or has a forest component. A one-year
follow-up study of 38 farms showed that 84% had forest or forest species
as livinifences, shade, or for forage in pastures. In terms of forest utiliza-
tion, only 69% of farmers used the forest for production and 3 1%said they
only have patches of forest because of lack of time or resources to convert
it to crops or pastures (Avila et al., 1979).
In 1978, the Tropical Agriculture Center for Research and Training
(CATIE) established an agroforestry project and started studies of ASPS.
Almost ten years later, a Silvopastoral Systems Project was established in
the lowlands of the Atlantic Region of Costa Rica to develop low-risk,
low-cost ASPS (CATIE, 1991).
At the government level, the National Program for Development of
Meat Cattle, started in 1990 (MAG-SEPSA, 1990), opened an avenue of
opportunity to deepen the knowledge on ASPS. A research component on
natural resources with emphasis in forests, soil, and water was added.
Silvopastoral systems found most frequently in Costa Rica are: (a) trees
in pastures, including grazing in secondary forests and fallows; (b) grazing

7. Research, Reviews, Practices, Policy and Technology 11
in forest and fruit plantations; (c) living fences; (d) perimeter shelter-
woods; and (e) crop and utilization of forage trees and shrubs.
An example of the first c a s d e e s in pastures-has been evaluated in the
grasslands of the College of Agriculture of the Humid Tropical Region
(known as EARTH in Spanish), Las Mercedes de Guacimo, Costa Rica,
where 29 different tree species have been identified within an area of
approximately 400 hectares (Table 1).
Other examples of successful ASPS that have remained throughout
time are:
(a) One developed in the highland areas of Costa Rica, on volcanic soils,
where alder (Ainus acuminata) is planted with pastures of kikuyo grass
(Pennisetum clandestinunz) and green forage such as elephant grass (fi
purpureum). The alder trees, selected for their fast growth (in 15-20 year
rotations trees reach 35-40 cm diameter), provide timber, fuelwood, and
also have the added advantage of being an actinorhizal tree (it is host to the
nitrogen-feg actinomycete Frankia in nodules of their root tissue); and
(b) Another one developed in the Atlantic lowlands, where laurel (Cor-
dia alliodora) is frequently found in pastures. Duringpasture maintenance,
farmers favor its natural regeneration, leaving it to grow. The tree is
currently a valuable timber cash crop and it is said that it contributes to the
maintenance of soil structure and pasture productivity.
FIGURE 2. Trees in Pasture Lands at E.A.R.T.H. Colleae in the Atlantic
Lowlands of Costa Rica.
- -- --

8. 12 JOURNAL OF SUSTAINABLE AGRICULTURE
TABLE 1. Tree species identified in pasture lands at E.A.R.T.H. College, in
the Atlantic lowlands of Costa Rica.
Latinname Localname Family
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Burserasimaruba
Castillaelastica
Cecmpiaspp.
Cedrellaodorata
Ceibapentandra
Cordiaalliodora
Dipteyxpanamensis
Ficuswerkleana
Goethalsiameiantha
Guareaspp.
Hieronymsalchorneodes
Huracrepitans
lnga edulis
Jacarandacopaia
Lueheaseemani
Ochmmapyramidale
Pentaclethrarnacroloba
Pithecelobiumlongifolium
Pithecelobiurn
saman
Psidiumguajaba
Pterocarpushayesii
Raphiataedigera
Sirnarubaamara
Spondiasmombin
Sterculiaapetala
Striphnodendronexcelsum
Terrninaliaamazonia
Virola koschnyi
Zanthoxylonmayanun
indiodesnudo
hule
guarurno
cedmamargo
ceiba
laurel
almendm
chilamate
guacirnoblanw
ocora
pil6n
jabillo
guaba
gallinazo
guecimocolorado
balsa
gavilan
sotacaballo
Cenizaro
guayaba
sangrillo
caminadora
aceituno
job0
panama
vainillo
guayabon
fwtadorada
lagarlillo
- - - - - - - - - - ,
Burseraceae
Moraceae
Moraceae
Meliaceae
Bombacaceae
Boraginaceae
Fabaceae
Moraceae
Tiliaceae
Meliaceae
Euphorbiaceae
Euphorbiaceae
Fabaceae
Bignoniaceae
Tiliaceae
Bombacaceae
Mimosaceae
Mimosaceae
Mimosaceae
Mirtaceae
Fabaceae
Palmae
Simarubaceae
Anacardiaceae
Sterculiaceae
Mimosaceae
Combretaceae
Myristicacae
Rutaceae
GENERAL CONSZDERATIONS WITHIN
A FRAMEWORK OF SUSTAINABILITY
First o f all, natural resources and environmental degradation can not be
isolated from economic processes. The importance o f economics i
n envi-
ronmental studies and production has lead various researchers to integrate

9. Research,Reviews, Praclices, Policy ajld Technology 13
the social and natural systems (Forrester, 1973; Lonergan, 1981, 1988;
Lakshmanan and Ratick, 1980). These integrated economic-ecological
models, although constrained by their positivist approach (Harvey, 1974),
in which physical models are used to simulate economic behavior (Loner-
gan, 1988), have been useful. They improve the understanding of natural
resources problems, the environment, and the production process.
On other hand, the worldwide drastic reduction of forest areas, concur-
rent, with the increased demand for forest products, leads to a paradigm:
production and supply of forest products. Because most of the farmers in
the humid tropics live on and farm small parcels, it is financially too risky
for them to experiment with small plantations of trees. Even a plantation of
2 or 3 hectares would replace other uses. This represents a large financial
decision. Farmers have to see that the planting of trees is both technically
and economically feasible.
Within this framework, AFS should be considered as a palliate for the
domestic and community supply of woody resources in an ecological,
economical, and social framework:
Ecological, because of its multispecific and sometimes multistrati-
fied structure. AFS increases the efficiency of radiation capture and
utilization of horizontal and vertical space of the agroecosystem.
Economic, because of its production, not only of food, protein, and
fiber of the agricultural component, but also the production of the
woody component such as fuelwood,timber, forage, poles, shade,and
the contribution of organic matter to the soil, which saves fertilizer.
Social, because the trees (in particular timber trees) represent a re-
serve of standing capital which is a stability factor contributing to in-
ternal security for the socio-economic component of the system-the
rural family. Also, because of its external projection, AFS could
ameliorate the needs of timber supply at the community level.
Agroecosystem sustainability means profitable production without
damaging the environment. So, the minimum requirement to achieve this
goal must encompass the productive, environmental, and economicissues.
Still, it would be incomplete if no consideration is given to the social,
political, and cultural issues as well.
However, one has to be aware that ASPS is not a total solution to
tropical problems. It is rather an appropriate alternative that in certain
cases will solve some of the problems caused by the disappearance of the
forest resource, but only on a farm scale. It is not logical to think that trees
integrating ASPS can replace forest plantations for pulp and paper produc-
tion, but they can ameliorate local needs of timber and fuelwood.

10. 14 JOURNAL OF SUSTAINABLE AGRICULTURE
The 20th FA0 Regional Conference for Latin America and the Carib-
bean, held in Recife, Brazil October 2-8, 1988 had as its central topic
"Agroforestry for Improvement of Agriculture". In this meeting, the bio-
logical-productive importance of AFS was recognized, and strong support
was given to a series of recommendations leading to promote the active
participation of rural communities in the preparation and application of the
most appropriate AFS for each given situation.
The conditions to further ASPS applications are nearly ideal: (a) forest
legislation in effect in almost all tropical countries gives importance to
forest plantations; (b) there is an alternative in motivating the active partic-
ipation of rural communities through incentives to use the timber from
forest plantations that result from agroforestry practices; (c) there exists
the need for looking at adequate and practical solutions that promote a
productive, ecological, and social equilibrium; (d) the Tropical Forestry
Action Plan (TFAP) of the FA0 exists to implement programs of restora-
tion, reforestation, and conservation within a prioritized productive frame-
work; (e) there exists an actual experience in AFS in many countries, in
addition to the willingness and the opportunity of planting trees by many
of the farmers, and, finally; (f) there exists an organization structure in
different countries.
Therefore, it is proposed:
a. To capitalize on the valuable experience of existent people through a
diagnostic and evaluation process of all those current practices that
can be considered successful agroforestry;
b. To identify the most relevant practiccs with the idea of extending
them to othcr situations where they can be applied;
c. To establish research networks among higher education institutions
and research centers that are already working with ASPS, to set re-
gional and local ASPS data bases;
d. To motivate interest and participation of the rural community in or-
der to achieve community involvement in conservation;
e. To reforest or to intercultivate rows of valuable timber trees (VTT)
with annual or perennial crops everywhere possible;
f. To intercultivate VTT in perennial crops already established or in
the establishing process, replacing to a degree the traditional shade
trees;
g. To evaluate the foragc from existing living fences and to promote
the establishment of live fence posts where they are still not familiar
to the farmers;
h. To establish VTT in pastures;

11. Research,Reviews,Proclices,Policy and Teci~~tology 15
i. To evaluate the alternative of using ASPS as buffer zones in the
boundaries of conservation areas;
j. To teach and to train on AFS and ASPS at elementary school level;
k. To do extension activities and a planned follow-up of agroforestry
activities;
1. To integrate a network of demonstration plots and validation, in-
cluding existing multipurpose modules;
m. To permit alleys of natural regeneration in areas where cattle raising
has been discontinued, as a way to restore deforested areas, and to
enrich them with VTT using all available promotional benefits;
n. To increase the use of agricultural technology and to take advantage
of the technical services given by the national governments and in-
ternational organizations..
Finally, the current challenge is to produce and concurrently preserve
natural resources. These objectives seem to be divergcnt, but with the
appropriate use of known agroforestry practices, it may be possible to
accomplish both production and conservation goals.
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REVISED: 08131194
ACCEPTED: 09/07/94