Traditional forms of soil fertility maintenance

Several traditional methods of maintaining soil fertility in bean-based cropping systems are reviewed as follows: visoso, large- scale chitemene, ngoro or matengo pit (Mbinga District, Tanzania), mambwe land-use system of northern Zambia (fundikila), mounds of the Wafipas (SW Tanzania), tumba land-use system (southern Tanzania), guie (central highlands of Ethiopia), mafuku in Zaire, termite mounds, agroforestry, relay intercropping systems, coffee- banana-bean cropping system of the Wahayas of Bukoba (Tanzania), removal of maize tassels (northern Malawi), and storage of nutrients in weeds (Arusha, Tanzania). It is evident from the review that, traditionally, farmers producing beans and other crops depended on standing trees and bush vegetation for providing nutrients for the restoration of soil fertility and productivity. In addition to providing nutrients through ash and burning, the vegetation also provided cover for the fragile tropical soils. The oldest form was shifting cultivation (visoso) and its variant chitemene. Although fallowing restored the nutrients almost effortlessly and cost-free, these systems were inefficient, destructive, and had low human carrying capacity. With a reduction in the fallow period, the mambwe or mound cultivation system evolved whereby green manure was composted. Then the era of cheap inorganic fertilizer discouraged the dependence on regenerative agriculture; however, the oil crisis in the mid-1970s and the high attendant cost of agro-chemicals shifted emphasis to agroforestry, an alternative to shifting cultivation, which may be adapted to present day circumstances. (CIAT)