.... 25 Years of Improvement

Part VI. Agroforestry

Agroforestry research begins and ends with the farmers; characterization and diagnosis exercises help researchers understand the needs and problems of the farmers in an area. Researchers also catalogue indigenous knowledge of rapidly diminishing species trees and shrubs that farmers value and collect information on indigenous agroforestry systems that have worked well for centuries, and focus their efforts on policies that can help safeguard these environmentally and economically successful systems.

In other areas, researchers identify appropriate technologies and suitable tree and shrub species and test them on station and on farm, through researcher- and farmer-managed trials. Researchers work closely with farmers to ensure that trees and technologies meet their needs and their approval. Strategic research helps them understand the processes behind tree-crop interactions. This means national researchers are able to predict which species, arrangements and management techniques will work best in any given setting.

ICRAF research and dissemination activities are going on in 19 countries in Africa, Asia and Latin America. Apart from its activities at headquarters and the Machakos research station, ICRAF collaborates with national research organizations, universities and NGOs. All the planning, priority setting and implementation of the work is done jointly. Constant input from national teams - and from farmers - ensures that the research is relevant to the problems of the ecoregion and the country.

This means, for example, that in the densely populated and mountainous region of Central and East Africa, research focuses on reducing soil erosion and degradation on steep slopes, using trees on contours that can perform these services at the same time as they ease the perennial shortage of timber and the seasonal shortage of fodder. In southern Africa, where there is a problem of decreasing soil fertility and declining crop yields and where the cost of fertilizer is prohibitive for subsistence farmers, researchers have developed a system that can reverse these trends; it involves the tree - Sesbania sesban - planted as improved fallows that increase subsequent maize yields and provide valuable fuelwood. These fallows also help save remaining stands of the miombo woodlands that once covered much of the Southern African plateau.

Similarly, researchers in Indonesia are examining the intricacies of complex agroforests that simulate natural forests in their wealth of biodiversity but which are planted for profits; they are also looking at ways government policies can protect these invaluable farming systems. And in Latin America, where slash-and-burn agriculture contributes so much to deforestation and to emission of greenhouse gases, researchers are coming up with alternative farming systems that involve multi-layered systems of leguminous pastures, under trees that provide various valuable products.


A tree revolution

One particularly exciting area of work, and a new dimension of ICRAF's research, is that of domestication and improvement of indigenous tree species. These valuable trees are known as Cinderella species, since they have been largely overlooked by researchers and their full potential has yet to be realized. Fruit, medicines, high-grade timber, food additives, oils, fibres, resins and fodder have long been harvested from trees, and they often have important local markets. These are trees with high-value and low-volume products, with enormous potential for regional and even international markets. Some notable examples are

- the bush mango (Irvingia gabonensis), a West African species with edible fruits whose cotyledons are used for thickening soups and stews and to make a staple bread, while seeds are used as spices

- peach palm (Bactris gasipaes), a Latin American palm that produces fruits, heart of palm, medicines from the roots and wood for parquet floors

- masuka (Uapaca kirkiana), a southern African tree that is valued for its edible fruits, eaten fresh or used to make wine, borer- and termite-proof timber, and roots that produce extracts for treating indigestion

- camu camu (Myrciaria dubia), an Amazonian species that produces berries with 40 times the concentration of vitamin C as citrus fruits- pygeum (Prunus africanus), an African highland tree whose bark extracts are used in the treatment of prostate cancer

ICRAF is working to tap these high-value tree resources, to start what researchers like to call a tree revolution, to follow up on the Green Revolution of the past few decades in which agricultural crops were so successfully domesticated and improved. The challenge is to identify the most valuable species and to learn about them from the people who know them best - the farmers. Research therefore involves extensive ethnobotanical surveys that reveal farmers' own priorities in tree species and even identify individual trees that farmers feel are superior.

Together with national partners, ICRAF researchers make collection missions, to obtain the material needed to begin the domestication of trees. Trees are propagated using simple vegetative methods, using stem cuttings, followed by clonal selection. In this way, high-quality and productive varieties can be developed relatively quickly, much faster than with traditional breeding methods. The current focus of the research is on indigenous fruit trees, which farmers would like to flower and fruit earlier. To achieve this, trees must be propagated from mature shoots that have acquired their reproductive capacity. Unfortunately, these mature shoots are the most difficult to propagate, and research on reproductive biology and phenology is in its infancy in many cases. Pioneer work is concentrating on the physiology of aging.

Optimism is high for this research program, which aims to produce cash income for farmers. Not only that, fruit trees grown on farms - in home gardens and in complex multi-layered agroforests - can be a lasting and practical alternative to slash-and-burn agriculture. ICRAF is also investigating the possibility of linking with the private sector in this enterprise.


ICRAF research emphasizes management of natural resources, and is working with several technologies that can maintain and improve soil fertility. In many parts of Africa, low farm income and high costs for fertilizer pose serious threats to the soils; farmers simple cannot afford to fertilize their fields and population pressure on land precludes the use of long fallows to restore nutrients to soils depleted by intensive cultivation. Under these conditions, soil fertility declines, and the land produces little. It is possible to turn this trend around, to make these areas productive again? On most African soils, the two nutrients that tend to be most lacking are nitrogen and phosphorus. ICRAF has been studying agroforestry systems that restore both nutrients back to the soil. This "recapitalization" of vital nutrients is an investment in natural resources, similar to that made in irrigation systems.


Agroforestry systems can add nitrogen directly to soils in two ways: biological nitrogen fixation from the air and nitrates captured deep in the subsoil, beyond the reach of crop roots. Trees accumulate these nutrients in their leaves, nutrients which are then transferred to the soil when the leaf litter is incorporated. Organic nitrogen inputs have an advantage over inorganic nitrogen fertilizer because they come together with carbon - carbon that is used by soil microorganisms to incorporate the nitrogen not used by crops - in active pools of soil organic matter. Research indicates that the slow accumulation of soil organic nitrogen from agroforestry systems can have long-term benefits in building up nitrogen capital.

Researchers are exploiting these principles to develop short-duration fallows to regenerate soil fertility. Recent research has highlighted the potential of Sesbania sesban, a fast-growing African legume. In Eastern Zambia, two-year sesbania fallows show remarkable results -doubling maize yields each season for 3-4 seasons following the fallow. In 1995, over 180 farmers in the area are working with the Zambian Ministry of Agriculture and ICRAF, raising their own seedlings to plant and test improved sesbania fallows. But the excitement is so high among farmers that more than 500 have already begun trying - and experimenting with -sesbania fallows.

Where farms are too small and land pressure too great for any fallows, research focuses on improving soil fertility without interrupting the cropping cycle. One of the most promising technologies for this niche appears to be "relay cropping," a system in which sesbania seedlings are established at the same time as maize. During the rainy season, the trees grow slowly in comparison with the crops, making for little competition. After the maize is harvested, the sesbania grows more rapidly, surviving on residual moisture in the soil. About 2-3 tons of fuelwood are harvested every year, for use at home or for sale in the market, and the leaf and twig litter from the trees is incorporated into the soil before the next crop of maize is sown. The resulting seasonal input of organic matter from the trees has more than doubled maize yields over those where the maize is not fertilized. Farmers are enthusiastic about this technology and the research project in southern Malawi is working with 46 farmers to evaluate relay cropping on their farms.

The phosphorus story

Many soils in Africa are sorely limited by the lack of phosphorus, to the extent that other inputs cannot have any significant effect. Research indicates that agroforestry can only supply up to half the phosphorus needs of crops on soils deficient in phosphorus - the rest has to come from inorganic sources. For this reason, ICRAF is a major actor in the World Bank-funded "Phosphorus Initiative" the aim of which is to use African phosphate rock sources as a one-time application to recapitalize African soils. The application is seen as a capital investment that should permit farmers to reap returns - in the form of increased harvests - for up to ten years. Removing phosphorus as the limiting factor in these soils will have a multiplier effect on other inputs, including biological nitrogen fixation. Researchers are also working on developing and testing complementary technologies, such as contour hedgerows and vegetative strips, to control soil erosion and keep phosphorus on the farm. Other research will look at biological technologies to control weeds and accessibility to improved tree germplasm, to guarantee the initial investment. Biophysical research will concentrate on interactions between inorganic and organic sources of phosphorus in the soil, and country case studies conducted with partners in national agricultural research institutions during 1995 will assess the economics of the initiative, taking environmental costs and benefits into account.

Where water is scarce

In many agroforestry systems competition between crops and trees for water is a major concern. However, trees that tap water from below the crop rooting zone - water that is unavailable to the crop - increase the use of the available water and the nutrients it carries. Recent research at ICRAF's Machakos Research Station in Kenya has demonstrated that a pure maize crop uses only 30 percent of the available rainfall, while a system with maize and Grevillea robusta trees uses 76 percent. This is an exciting result with important implications for areas where water is a limiting factor, as it is, for example, in subhumid areas of Eastern and Southern Africa and the semi-arid lowlands of West Africa where ICRAF is working. Current research focuses on quantifying water uptake by various components of agroforestry systems and develops models to predict and extrapolate how and where water will be used within an agroforestry system. This knowledge can be used when trees and crops are being selected, based on their appropriate architecture and ecology, for agroforestry technologies in any given area.


ICRAF assesses the effects of its work by measuring impact in three areas: impact on science, impact on capacity building and impact on development. Researchers are developing ways to measure the overall impact of their work, including social and ecological effects on a community and in a region. Environmental accounting methods that put values on factors such as decreasing greenhouse gas emissions, increasing carbon sequestration, decreasing stream sedimentation and eutrophication, and preserving biodiversity, are being developed.

The link between research and development is key; ICRAF is particularly interested in the rates at which farmers are adopting agroforestry technologies - because adoption and experimentation by farmers are the real test of a technology. By validating technologies on farms, researchers are able to learn from farmers and adjust technologies to fit their needs, and farmers themselves learn about the technologies. Such tests also reveal policies that encourage - and in some cases discourage - adoption of sustainable and positive technologies. There are many examples of areas where on-farm experimentation has peaked farmer interest in agroforestry, and led them to take on the technologies. In southwest Uganda where there is an acute shortage of fuelwood, farmers are keen to develop nurseries and grow trees to supply fuelwood for home use and for sale. In Zambia, where declining soil fertility is a problem, farmers are so enthusiastic about sesbania for fallowing that the technology has already spread far beyond the confines of Chipata where the research began. In the central highlands of Kenya, where prices for dietary supplements for dairy cows are prohibitive to the small-scale farmer, farmer interest in fodder trees is more than keeping up with the pace of the research itself.

Farmer demand for research is intense - be it biophysical geared towards tangible options that solve their problems, socio-economic aimed at improving production on their farms so that they can cover education and medical costs for their children, or policy research that can identify constructive policies that encourage good management of natural and farm resources. ICRAF researchers, together with their national partners and NGOs and because of their close working relations with farmers, are trying to keep up with the demand for lasting solutions to the problems of rural poverty, land degradation and deforestation in the tropics.


One of the most severe limitations on the establishment of a lasting capacity for agroforestry research and development is the shortage of a knowledgeable and skilled staff. Since agroforestry is a new but rapidly developing science, the shortage of expertise is acute.

In 1994, ICRAF built up the African Network for Agroforestry Education (ANAFE), a unique endeavor to strengthen agroforestry education for the next generation of agroforesters. Membership has grown rapidly, and now includes 74 universities and technical colleges in 31 African countries - 18 anglophone, 12 francophone and 1 lusophone.

ANAFE supports curriculum review and implementation; specialists have been developing teaching materials in a host of national and international workshops. Staff exchanges and research internships are arranged between educational institutions and national agricultural research systems. ANAFE is supporting 18 postgraduate fellowships at 8 African universities for MSc students of agroforestry. These students are doing their thesis research at agroforestry network sites and are supervised by both ICRAF and university staff.

But research and training activities are not limited to academic and institutional circles. ICRAF's information division concentrates on making all its research activities and findings known to the broadest possible audience. Policy documents and research reports that highlight major breakthroughs are published and made available to policy- and decision-makers, who, by keeping abreast of the latest findings, are able to make sound decisions affecting the welfare of their constituents and the environment. Information specialists also put together a quarterly magazine that provides specialists and practitioners of agroforestry with easily digestible and applicable information on new technologies, trees and trends. In 1995, broadcast-quality videos are being produced, which should reach television viewers around the world, making "agroforestry" a household word.

In all of these ways, ICRAF research, training and information programmes are a small but important part of the movement that emerged from the Earth Summit in Rio de Janeiro in 1992 - a movement for sustainable development that aims to improve living standards through sensible management of natural resources throughout the tropics.

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