This Publication Issue does not exist in your language, View in: English (en), Français (fr), Español (es),
Or use Google Translate:  
Papia Portugues (mcm) | Change Language (Change Language)
By: Dr. Franklin Martin and Scott Sherman
Published: 1992-01-20


TN 25 Figure 1

Cacao grown under banana trees.Photo by Danny Blank

In simplest language, agroforestry is the production of trees and of non-tree crops or animals on the same piece of land. The crops can be grown together at the same time, can be grown in rotation, or can even be grown in separate plots when materials from one are used to benefit another. However, this simple definition fails to take into account the integrated concepts associated with agroforestry that make this system of land management possibly the most self-sustaining and ecologically sound of any agricultural system. Thus, a second definition of agroforestry would be the integration of trees, plants, and animals in conservative, long-term, productive systems. Agroforestry can be considered more as an approach than as a single, finished technology. Although several finished systems have been devised and tested, such technology may require adjustment for particular situations. The flexibility of the agroforestry approach is one of its advantages.

Why Agroforestry?

Agroforestry systems make maximum use of the land. Every part of the land is considered suitable for useful plants. Emphasis is placed on perennial, multiple purpose crops that are planted once and yield benefits over a long period of time. Such benefits include construction materials, food for humans and animals, fuels, fibers, and shade. Trees in agroforestry systems also have important uses such as holding the soil against erosion and improving soil fertility (by fixing nitrogen or bringing minerals from deep in the soil and depositing them by leaf-fall).

Furthermore, well-designed systems of agroforestry maximize beneficial interactions of the crop plants while minimizing unfavorable interactions. The most common interaction is competition, which may be for light, water, or soil nutrients. Compe- tition invariably reduces the growth and yield of any crop. Yet competition occurs in monoculture as well, and this need not be more deleterious in agroforestry than monoculture systems. Interactions between components of an agroforestry system are often complementary. In a system with trees and pasture, with foraging animals, the trees provide shade and/or forage while the animals provide manure.

Thus, agroforestry systems limit the risks and increase sustainability of both small- and large-scale agriculture. Agroforestry systems may be thought of as principle parts of the farm system itself, which contains many other sub-systems that together define a way of life.

Definitions

Alley Cropping:
Growing annual crops between rows of trees or shrubs
Beautification:
Planting trees for ornamental purposes
Boundary Plantings:
Trees planted along boundaries or property lines to mark them well
Dispersed Trees:
Trees planted alone or in small numbers on pastures or otherwise treeless areas
Earthworks:
Constructions made of earth, usually to conserve or control water
Improved Fallows:
Areas left to grow up in selected trees in trees-crop rotation systems
Individual Trees:
Trees occurring alone, whether spontaneously emerging or planted
Living Fences:
Fences in which the posts are living trees, or in which the entire fence consists of closely-spaced trees or shrubs
Nectar Crop:
Trees valuable as a source of nectar for honey bees
Terraces:
Level areas constructed along the contours of hills, often but not necessarily planted with trees
Vegetative Strips:
Long, narrow areas of any type of vegetation, usually planted along contours for erosion control; may include trees
Woodlot:
An area planted to trees for fuel, or timber

Summary Of Benefits Of Agroforestry

  • Improved year-round production of food and of useful and salable products
  • Improved year-round use of labor and resources
  • Protection and improvement of soil (especially when legumes are included) and water sources
  • Increased efficiency in use of land
  • Short-term food production offsetting cost of establisment of trees
  • Furnishing of shade for vegetable or other crops that require or tolerate it
  • Medium and long-term production of fruits
  • Long-term production of fuel and timber
  • Increase of total production to eat or to sell

Components Of An Agroforestry System

Land

Agroforestry is not a system of pots on a balcony or in a greenhouse. It is a system by which land is managed for the benefit of the landowner, environment and long-term welfare of society. While appropriate for all landholdings, this is especially important in the case of hillside farming where agriculture may lead to rapid loss of soil. If the farmer owns the land, s/he has a vested interest in thinking conser- vatively, how the land can be maintained over long periods of time. Unfortunately, farmers who rent land may have less interest in the long-term benefits of agroforestry and may even fear that making improvements will raise the rent or result in the lease being terminated.

Trees

In agroforestry, particular attention is placed on multiple purpose trees or perennial shrubs. The most important of these trees are the legumes because of their ability to fix nitrogen and thus make it available to other plants. The roles of trees on the small farm may include the following:

  • Sources of fruits, nuts, edible leaves, and other food
  • Sources of construction material, posts, lumber, branches for use as wattle (a fabrication of poles interwoven with slender branches etc.)and thatching
  • Sources of non-edible materials including sap, resins, tannins, insecticides, and medicinal compounds
  • Sources of fuel
  • Beautification
  • Shade
  • Soil conservation, especially on hillsides
  • Improvement of soil fertility

In order to plan for the use of trees in agroforestry systems, considerable knowledge of their properties is necessary. Desirable infor- mation for each species includes its benefits, adaptability to local conditions (climate, soil, and stresses), the size and form of the canopy and root system, and suitability for various agroforestry practices. Some of the most common uses of trees in agroforestry systems are:

  • Individual trees in home gardens, around houses, paths, and public places
  • Dispersed trees in cropland and pastures
  • Rows of trees with crops between (alley cropping)
  • Strips of vegetation along contours or waterways
  • Living fences and borderlines, boundaries
  • Windbreaks
  • Improved fallows
  • Terraces on hills
  • Small earthworks
  • Erosion control on hillsides, gullies, channels
  • Woodlots for the production of fuel and timber

Some very good food-bearing trees for agroforestry are given in Table 1. Table 2 lists some of the best of the non-food producing trees used in agroforestry. Some successful uses of trees in isolation are given in Table 3. Note that any tree can be used; however, in actual practice, very large trees are not key components of most agroforestry systems.

Non-trees

Any crop plant can be used in agroforestry systems. The choice of crop plants in designing such systems should be based on those crops already produced in a particular region either for marketing, feeding animals, or for home consumption, or that have great promise for production in the region. In keeping with the philosophy of agroforestry, however, other values to be considered in crop selection include proper nutrition, self-sufficiency and soil protection. Thus, selection of crops requires a judgment based on knowledge of the crops, adaptations, production uses, as well as family needs, opportunities for barter, and markets.

Any farm animal can be used in agroforestry systems. The choice of animal will be based on the value the farmer places on animal- derived benefits including income, food, labor, non-food products, use of crop residues, and manure. Some examples of the use of trees, crops, and animals together are given in Table4.

Species Common Name Edibility Principle Uses
Anacardium occidentale Cashew flowers, seeds, fruit garden, fence, pasture
Annona muricata Soursop flowers, fruit garden, fence, pasture
Borassus aethiopum Borassus Palm multiple food uses garden, pasture
Cajanus cajan Pigeon Pea seeds, leaves hills, nitrogen fixation, fuel, hedgerows
Carica papaya Papaya flowers, fruit garden, quick shade
Cnidoscolus aconitifolius Chaya leaves rapid hedge
Cocos nucifera Coconut multiple food uses pasture, roadside, construction
Coffea arabica Coffee seeds hedges, hills, fuel
Gliricidia sepium Mother of Cacao flowers living fence, feed, fuel
Leucaena leucocephala Leucaena, Ipil Ipil leaves, green manure hills, alley cropping,fuel, nitrogen fixation
Manihot esculenta Cassava roots,leaves rapid hedge
Moringa oleifera Moringa, Drumstick leaves, flowers, pods fence, garden
Psidium guajava Guava flowers, fruit pasture, fuel
Sauropus androgynus Katuk leaves haie, alley cropping
Theobroma cacao Cacao pulp, seeds understory tree, pasture
Yucca guatemalensis Izote flowers hedge
Ziziphus mauritiana Jujube flowers, fruit erosion control, fuel
Table 1. Trees or large shrubs with edible products for agroforestry systems

 

Table 2.Principle trees for agroforestry systems (especially for hillsides)
Species Common Name Principle Uses
Bursera simaruba Gumbo Limbo living fences, fuel, forage
Calliandra calothyrsus Calliandra vegetation strips, fallows, windbreaks, fuel
Erythrina berteroana Pito living fences, forage, rapid cover, nitrogen fixing
Faidherbia albida Apple-ring acacia terraces, dispersed trees, forage, nitrogen fixing
Gliricidia sepium Mother of Cacao living fences, forage, fuel, hardwood
Leucaena leucocephala Leucaena, Ipil Ipil alley cropping, soil conservation, food, nitrogen fixing, fuel, forage
Moringa oleifera Moringa, Drumstick living fences, rapid cover
Senna siamea Siamese senna terraces, fuel, nitrogen fixing
Sesbania grandiflora Agati rapid cover, forage, nitrogen fixing
Sesbania sesban Sesban planting stakes, quick cover, nitrogen fixing
Table 3. Examples of successful uses of trees on small farms (not necessarily with other crops)
Location System Tree Crop Benefits Other plants
Central America Living fence Erythrina, Yucca, Gliricidia food, feed  
Tropics Windbreaks Casuarina fuel  
Central Africa Dispersed trees Faidherbia albida fuel, feed, erosion control  
Niger Improved fallows Leucaena, Sesbania soil fertility restoration grasses
India Earthworks Dalbergia, Pongamia, Prosopis food, soil conservation grasses (napier, mondo)
Tropical Africa Gully protection Tamarix food, soil conservation grasses
Tableau 4. Exemples de système agroforestiers comprenant arbres, cultures et animaux
Location System Tree Benefits Understory Crops
Costa Rica dispersed trees Cordia alliodora lumber, shade, nutriments coffee
Costa Rica dispersed trees Erythrina spp. nitrogen, fuel, shade, nutrients coffee
Puerto Rico dispersed trees Inga spp. shade, nitrogen, fuel, wood coffee, bananas, root crops
El Salvador dispersed trees Inga spp. fuel, nitrogen, shade coffee, cacao
Amérique centrale dispersed trees leguminous trees lumber, fuel, shade, nitrogen grains, pasture
Malaisie dispersed trees dwarf coconut food, lumber cacao
Tropiques dispersed trees Coconut food, forage pasture
Mexico dispersed trees Brosimum spp. food, lumber many crops, pasture
Haiti home garden Mango fruits rice
Sri Lanka mixed perennials various fruit trees fruits, other products spices, vegetables
Philippines home garden various fruit trees fruits, edible leaves many vegetables
Afrique de l’ouest home garden fruit trees fruits vegetables
Côte d’Ivoire mixed perennials cacao, bananas food yams
Puerto Rico mixed perennials oranges, avocados, bananas food, nutrients coffee, root crops
Tropiques alley crop Leucaena leucocephala erosion control, fuel, nitrogen, nutrients annuals, grasses
Nigeria alley crop Gliricidia sepium erosion control, fuel, nitrogen, nutrients root crops, grains
Rwanda vegetative strips Grevillea, Albizia, and Leucaena spp. lumber, fuel, forage  

Getting Started With Agroforestry Systems

Steps in the decision-making process

  1. Decide whether agroforestry systems are appropriate
    • Describe family and community needs
    • List the needs that could be met with an agroforestry system
    • List the potential benefits, and their relative importance, of an agroforestry system in the region in question
    • Find the limiting constraints in agriculture, including markets and marketing
    • Consider whether the people of the region are willing or capable of adopting a system
    • Then decide if it is worth the effort to develop one
  2. Design a system
    • Select the area
    • Characterize its strengths and weaknesses with respect to existing soil, water, and crops
    • Select the trees, shrubs, or grasses to be used (see Tables 5-7; consider similar local plants)
    • Characterize the minimum space requirements, water and fertilizer needs, and shade tolerance of the desired crops

Further decisions as influenced by anticipated duration of the system

  1. If the system is temporary
    • Plan the features of soil erosion control, earthworks, and gully maintenance first
    • Plan spacing of fruit trees according to final spacing requirements
    • Plan a succession of annual or short-lived perennials, selecting the most shade tolerant crops for the final years of intercropping
  2. If the system is permanent
    • Plan the proportion of the permanent fruit and lumber trees on the basis of relative importance to the farmer
    • Plan the spacing of long-term trees on the basis of final space requirements times 0.5
    • Plan succession of annual and perennial understory crops, including crops for soil protection and enrichment
    • As large permanent trees grow, adjust planting plan to place shade tolerant crops in most shady areas
  3. With both temporary and permanent systems
    • Always keep the ground covered, using various crops-to protect soil from sun and erosion
    • Try the system on a small scale first
    • Measure the inputs and outputs of the system
    • Evaluate whether the benefits expected have been achieved
    • Expand or extend any new system cautiously

Seed And Information Sources For Agroforestry Species

ECHO provides sample (not bulk) packets of seeds of most of the agroforestry species listed in this publication. See our online (www. echonet.org) overseas seed listing. Seed requests can also be emailed (echo@echonet.org) or mailed (17391 Durrance Road, N. Ft. Myers, FL 33917). Other seed sources are listed in Table 5 below. Be aware that many trees that are able to survive under difficult condi- tions may also have considerable potential to become weeds. Management can be critical. For example, pruning minimizes the ability of Leucaena spp. to produce seeds.

Table 5. Suppliers of seed for agroforestry tree species (last updated February 2007)
Seed Supplier Mailing Address Website URL
Australian Tree Seed Centre CSIRO Division of Forestry and Forest Products,
PO Box E4008
Kingston, Canberra ACT 2604, Australia
Phone: +612 6281 8211
Fax: +612 6281 8266
Email: ffp-atsc@csiro.au
http://www.ffp.csiro.au/tigr/atscmain/index.htm
Directory of Tree Seed Suppliers in Indonesia ICRAf, the World Agroforestry Centre Trees and Market Unit
Jl. Cifor Situ Gede Sindang Barang,
P.O. Box 161, Bogor 16001
Phone: 0251-625415, 625417
Fax: 0251-625416
Email: icraf-indonesia@cgiar.org
http://www.worldagroforestrycentre.org/sea/Products/AFDbases/seedsupplier/index.asp
Inland and Foreign Trading Company Block 1090, #04-04/05,
Lower Delta Road
Tiong Bahru Industrial Estate
Singapore 169201
Phone: 65 2722 711
Fax: 65 2716 118
Email: iftco@pacific.net.sg
http://www.iftco.com.sg/#cover
Kimseed 42 Sarich Court, Osborne Park
Western Australia, 6017
Phone: 61 8 9446 4377
Fax: 61 8 9446 3444
Email: kimseed@kimseed.com.au
http://www.kimseed.com.au/frameset.html
New Forests Project World Seed Program – New Forests Project,
731 Eighth Street SE,
Washington, DC 20003, U.S.A.
Phone: 202-547-3800
Fax: 202-546-4784
Email: wsp@newforests.com
http://www.newforestsproject.com/English/wsprequest.html
New Zealand Tree Seeds P.O. Box 435,
Rangiora, New Zealand 8254
Phone: 64-3-3121635
Fax: 64-3-3121638
Email: sales@nzseeds.co.nz
http://www.nzseeds.co.nz/
Raintree Raintree Nutrition, Inc.
3579 Hwy 50 East, Suite 222
Carson City, NV 89701
Phone: 800-780-5902
Fax: 775-841-4022
Email: info@rain-tree.com
http://www.rain-tree.com/rtmprod.htm
Sheffields Seed Company 269 Auburn Road, Route 34,
Locke, New York 13092 U.S.A.
Phone: 315-497-1058
Fax: 315-497-1059
Email: seed@sheffields.com
http://www.sheffields.com
The Banana Tree Inc.
Easton, PA 18042 U.S.A
715 Northampton St.
Easton, PA 18042
Fax: 610-253-4864
http://www.banana-tree.com/
Tree Seed Supplier Directory Supplier information accessed from website by clicking on ‘Botanic Nomenclature’ and then on ‘Botanic’ or ‘Common’ name search http://www.worldagroforestrycentre.org/Sites/TreeDBS/TSSD/treessd.htm
Table 6.Related resources and organizations found online
Type of information

Website URL and or Mailing Address

Information on various species of tree crops
  1. Moringanews:http://www.moringanews.org/moringa.html
  2. Atcros (table of information nutrients, chilling requirements of tree crops) : http://www.wanatca.org.au/atcros/index.htm
  3. California Rare Fruit Growers (information on fruit trees) : http://www.crfg.org/
  4. Noix comestibles (information from the FAO) : http://www.fao.org/docrep/V8929E/V8929E00.htm
  5. EDIS (University of Florida): http://edis.ifas.ufl.edu/
  6. FAO (photos of forage species): http://www.fao.org/AG/Agp/agpc/doc/gallery/pic.htm
  7. Neem Foundation (information aboutneem) : http://www.neemfoundation.org/
  8. NewCROP ( Purdue) : http://www.hort.purdue.edu/newcrop/default.html
  9. New Forests Project : http://www.newforestsproject.com/English/trees.html
  10. Oxford Plant Systematics : http://herbaria.plants.ox.ac.uk/
  11. Raintree : http://www.rain-tree.com/plants.htm
  12. Traditional Tree Initiative : http://www.traditionaltree.org/
  13. Winrock : http://www.winrock.org/fnrm/factnet/factpub/factsh.htm
  14. World Agroforestry Centre : http://www.worldagroforestrycentre.org/Sites/TreeDBS/aft.asp
Organizations involved in agroforestry, many of which provide useful information about their projects.
  1. Agrofloresta.net : http://www.agrofloresta.net/
  2. Agroforestry.net : http://agroforestry.net/links.html
  3. CARE : http://www.care.org/index.asp 650 First Ave., 2nd Floor, New York, NY 10016, USA
  4. ECOTOP: http://ecotop-consult.de/ C. Guillermo Viscarra N° 125 (Casi Uyuni), zona Tupuraya
  5. Floresta : http://www.floresta.org/ Floresta USA, 4903 Morena Blvd, Suite 1215, San Diego, Californie 92117 USA
  6. Garden Organic : http://www.gardenorganic.org.uk/international_programme/ip_agroforestry.phpRyton Organic Gardens, Coventry Warwickshire, Royaume-Uni CV8 3LG
  7. International Society for Tropical Foresters: http://www.istf-bethesda.org/index- english.htm] 5400 Grosvenor Lane, Bethesda, MD 20814
  8. International Union of Forest Research Organizations:http://www.iufro.org/ IUFRO Headquarters, Secretariat, Mariabrunn (BFW), Hauptstrasse 7, A-1140 Vienne, Autriche
  9. KENGO: http://www.iisd.org/casl/CASLGuide/KENGO.htm KENGO, PO Box 48197, Nairobi, Kenya
  10. Roy Danforth : Imeloko Agroforestry Project, B.P. 1377, Bangui, République centrafricaine
  11. RWEDP: http://www.rwedp.org/ FAO/RAPA, 39 Maliwan Mansion, Phra Athit Road, Bangkok 10200, Thaïlande
  12. USDA Forest Service : http://www.fs.fed.us/global/topic/welcome.htm US Forest Service International Programs, Outreach & Partnerships Unit, 1099 14th Street, NW Suite 5500W, Washington D.C., 20005 USA.
  13. Viikki Tropical Resources Institute :http://www.mm.helsinki.fi/mmeko/vitri/ Latokartanonkaari 9 (2. floor), P.O. BOX 27, FIN-00014 University of Helsinki, Finlande
Publications- books, research results and/or information on forestry- related subjects
  1. Agroforestry Options for Small Upland Farms : http:/www.floresta.org/Agroforestry_English_web.pdf
  2. DANIDA : http://www.sl.kvl.dk/Publikationer.aspx
  3. Living fences- by Cornell University : http://ppathw3.cals.cornell.edu/mba_project/livefence.html
  4. Nitrogen Fixing Tree Startup Guide : http://agroforestry.net/pubs/nftguide.pdf
  5. Tropical Tree Seed Manual : http://www.rngr.net/Publications/ttsm
  6. USDA International Institute of Tropical Forestry : http://www.fs.fed.us/global/iitf/library1.html
  7. USDA National Agroforestry Center : http://www.unl.edu/nac
  8. World Agroforestry Center : http://worldagroforestry.catalog.cgiar.org/library/Pubsearch.asp
Table 7. Adaptation and Photos of Principle Tree Species.

Bursera simaruba
hot, dry tropics
TN 25 Figure 2

Callindra calothyrsus

wet tropics

TN 25 Figure 3

Erythrina berteroana
intermediate tropics
TN 25 Figure 4

Faidherbia albida
hot, dry tropics

TN 25 Figure 5

Gliricidia sepium
intermediate tropics

TN 25 Figure 6

Leucaena leucocephala
intermediate tropics

TN 25 Figure 7

Moringa oleifera
intermediate tropics
TN 25 Figure 8
Senna siamea
intermediate tropics
TN 25 Figure 9

Sesbania grandiflora
intermediate tropics

TN 25 Figure 10

Sesbania sesban
intermediate tropics

TN 25 Figure 11

Photos by Tim Motis  

BibliographyandUseful Publications

Buck, L. 1988. Agroforestry Extension Training Sourcebook Cooperative for American Relief Everywhere. (CARE) International New York, N.Y., 540 pp.

Fernandez, Pamela G., guest ed. Sustainable Agricultural Newsletter (September 1990 issue dedicated to agroforestry seeds with an extensive listing of suppliers around the world). CUSO, 17 Phaholyothin, Golf Village, Phaholyothin Road, Bangkhen, Bangkok 10900 Thailand.

Folliot, Peter F. and Thames, John L. 1983. Environmentally Sound Small-Scale Forestry Projects, Guidelines for Planning. Volunteers in Technical Assistance (VITA). Arlington, VA, 109 pp. $9.75 (see CODEL below)

Forestry/Fuelwood Research and Development Project. 1992. Growing Multipurpose Trees on Small Farms. Bangkok, Thailand: Winrock International. 195 + ix pp. (including 41 species fact cards). To order in the USA, call: 703/351-4006 and request book order no. PNABR667.

IITA. (no date) Alley Cropping, A Stable Alternative to Shifting Cultivation. International Institute of Tropical Agriculture, Ibadan, Nigeria, 25 pp. (available for $1.00 from NFTA, see resources).

IIRR. 1990. Agroforestry Technology Information Kit. The International Institute of Rural Reconstruction, 475 Riverside Drive, Room 1270, New York, NY 10115 ($20.00). Kits are probably available as well from their office in the Philippines: IIRR, Silang, Cavite 4118, Philippines.

MacDicken. 1988. Nitrogen Fixing Trees for Wastelands. FAO Regional Office for Asia and the Pacific, Maliwan Mansion, Phra Atit Road, Bangkok, Thailand.

Nair, P.K.R. Classification of Agroforestry Systems. Agroforestry Systems 3: 97-128.

National Academy of Sciences. 1980. Firewood Crops, Shrub and Tree Species for Energy Production, Vol I, Washington, D.C., 236 pp. (available free to those actively working in develop¬ment: BOSTID (JH 217D), National Research Council, 2101 Constitution Avenue, Washington, D. C. 20418, USA).

National Academy of Sciences. 1983. Firewood Crops, Shrub and Tree Species for Energy Production, Vol II, Washington, D.C., 92 pp. (see vol I).

Rockeleau, D., Weber, F. and Field-Juma, A. 1988. Agroforestry in Dryland Africa. International Centre for Research in Agroforestry (ICRAF). Nairobi, Kenya, 311 pp. $31.00

Save The Children/US, Thailand. 1992. Collection, Storage, and Treatment of Tree Seeds: A Handbook for Small, Farm Tree Planters. The FAO Regional Wood Energy Development Programme in Asia, Bangkok, Thailand.

Shankarnarayan, R. A. (ed.). 1984. Agroforestry in Arid and Semi-arid Zones. Jodphur, India, ICAR Central Arid Zone Research Institute, 295 pp.

Teel, W.A. 1984. A Pocket Directory of Trees and Shrubs in Kenya. Kenyan Energy Non-Governmental Organization (KENGO). Nairobi, Kenya, 151 pp.

Thuvesson, D. (ed.). Forests, Trees and People Newsletter, Swedish University of Agricultural Sciences/IRDC, Box 7005, S-750 07 Uppsala, Sweden. (Quarterly publication distributed to those interested in and/or working with community forestry activities).

USAID. 1987. Windbreak and Shelterbelt Technology for Increasing Agricultural Production. United States Agency for International Development, Washington, D. C. 219 pp.

Liegel, Leon H., Venator, Charles R. 1987. A technical guide for forest nursery management in the Caribbean and Latin America, Gen. Tech. Rep. SO-67. New Orleans, LA: U.S. Department of Agriculture, Forest Service, southern Forest Experiment Station. 156p.
Von Carlowitz, P. 1986. Multipurpose Tree and Shrub Seed Directory. International Center for Research in Agroforestry, Nairobi, Kenya. 265 pp. $24.00

VSO. (no date). If a Tree Falls: A VSO Guide to Raising and Planting Trees in Kenya. Voluntary Services Overseas.

Wesley, S.B. (ed.) Agroforestry Today, ICRAF. Nairobi, Kenya, quarterly.

Citethis article as:

Martin, F.W. and S. Sherman 1992. Agroforestry Principles. ECHO Technical Note no. 25.