10. Agroforestry in africa's humid tropics - three success stories.
Agroforestry Today, April-June 1991, pp. 4-6
This article describes three traditional agroforestry systems that combine multipurpose woody species with food-crop production on low-fertility soils in humid tropical Africa.
Efforts to increase food-crop production in the humid tropics by importing high-input 'modern' technologies have repeatedly led to disappointing results. For this reason, there has been a resurgence of interest in the traditional farming systems that have proven successful over the years.
The traditional slash-and-burn cultivation system of tropical Africa appears to be biologically stable as long as there is enough land to allow sufficient periods of natural fallow. The productivity of the traditional system declines rapidly with intensification of land use. In response to increasing pressure on land, farmers in some parts of the region have developed innovative production systems combining trees and crops. These systems are well adapted to prevailing soil and climatic conditions and help meet local needs for food and other products.
In Benin's Mono Province bordering Togo, the Adja people practice an improved-fallow system involving the replacement of the traditional bush fallow by densely planted oil palms (Elaeis guineensis). They grow these trees primarily to produce palm wine, which is often further distilled to make a popular local drink. Fruits from the trees also provide palm oil and the leaves are used for fodder, fencing, roofing, and baskets.
When the trees are felled, the trunks, roots, and other biomass left in the fields help renew soil fertility.
Acioa barteri is one of the three most important woody species in the bush-fallow system of southeastern Nigeria.
This shrub is planted or retained by farmers for nutrient cycling, weed suppression, staking, browse, and domestic uses.
Farmers plant acioa in hedgerows at intervals of 2 to 3 metres. At the beginning of the cropping cycle, the shrubs are burned and the stems cut to a height of 10 to 20 centimeters above ground. Some stems are collected for yam staking or for sale. Plots are then interplanted with yam, cassava, and sometimes maize. During the second cropping year, only the cassava remains, growing between the acioa hedgerows. In the third year, the hedgerows cover the entire field.
Farmers have practiced this rotational hedgerow-intercropping (alley-cropping) system for generations.
In the Bas-Zaire region of southwestern Zaire, pigeonpea (Cajanus cajan) is the third most important grain legume after groundnut and phaseolus beans. Pigeonpea is grown most intensively along with cassava in the Songololo area. It fills a crucial protein gap in the local diet between September and December before the harvest that follows a long dry season. After the pods are harvested, farmers apply the leaves as green manure on intercropped cassava.
This pigeonpea/cassava system of Bas-Zaire, which produces food and a little cash, may be a candidate for wider adoption. Experiments are in progress at M'Vuazi and Kimpese, Zaire, to test different spatial arrangements and timing of operations that might improve the traditional system.
These three examples show that farmers are fully capable of developing agroforestry systems that are well suited to their environmental and economic conditions - and without chemical inputs. Although the practices described here may not be as productive as more intensive, high-input systems, they achieve effective nutrient cycling and a degree of sustainability by combining deep-rooted woody species with food crops.
It might be possible to make these traditional systems more productive without losing their advantages, for example by adding low levels of fertilizer or other inputs, or by incorporating more nitrogen-fixing trees. There is a danger that these systems will be replaced by unstable 'modern' approaches, emphasizing short-term gains at the expense of long-term sustainability.
Research on these well-adapted traditional systems might lead to ideas for making them even better. Insights gained in these areas might also provide a basis for developing more sustainable and productive food-production systems in other parts of the region.
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Review, developing countries, fuelwood production, biomass energy, forestry, firewood species, farm forestry, community forestry, woodlots, land-use systems
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