9. African bean-based cropping systems conserve soil.
CIAT Annual Report 1989, pp. 49-52
Low soil fertility is as important as disease in limiting bean production in Africa. This is especially true in areas of high population growth. More people to feed means that land that once could be left fallow and allowed to recover its nutrients must be constantly used. Less good land to farm leads to more cultivation of steep slopes and marginal soils.
In response to the need to increase production and conserve the soil, CIAT is strongly promoting sowing climbing beans in the Great Lakes area. These beans generally yield higher than traditional bush beans; and when climbing beans grow upward rather than spreading across the ground, the plants are better protected from soil-borne pathogens and the damage caused by standing water.
But climbing beans need something to climb on. Having enough vegetative material suitable for making stakes is a major impediment to farmers growing this kind of bean. Appropriate kinds of trees are needed to plant to solve the stake shortage.
These trees or bushes would have several purposes: they would serve as stakes; they would conserve the soil by fixing nitrogen; they would produce organic matter which would be used as green manure or animal feed; and they would counter erosion by stabilizing the soil with their roots and by providing windbreaks.
Research conducted on Rwandan farms has shown that timely manure applications are important in increasing yield and reducing erosion.
Studies show that if manure is applied at a certain stage of growth of the bean plants - the third trifoliate stage - yields can be increased by 60%. This can help farmers maximize the benefit of their limited fertilizer resources.
Traditional soil conservation practices are studied so that accepted methods can be used as guidelines for proposing improvements. For example, in Zambia, farmers concentrate soil fertility through dirt mounds consisting of organic compost. On the other hand, Tanzanian farmers dig pits and compost grass to enrich the soil. In other areas, farmers grow their crops on contoured ridges which reduce erosion.
But population pressures on land are threatening these traditional systems and, in turn, increasing soil erosion. Finding solutions to these problems is vital so that the demands on the land do not ultimately destroy the very foundation of farming: the soil itself.
1262 92 - 13/60
Erosion and desertification control
Latin America, Ecuador, study, soil conservation strategies, mountain environment, climatic factor, basic terms, farmer practices, socio-economic factors, DESFIL, USAID
STAVER, C.P. et al.
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