Soil organic matter: A review of research results

The role of soil OM is reviewed, with special reference to bean production. Soil physical properties, chemical properties, and biological effects are covered. The different interactions of soil management practices with soil OM, such as the implications of seasonal effects on decomposition, nutrient cycling in cereal- legume crops, minimization of losses of OM and nutrients, sources of OM, and management of crop residues, are also indicated. The benefits of composting are also reviewed; although few field trials on composting have been reported in Africa, the few research results obtained so far are summarized. Research needs for Africa, with particular reference to bean production, include (1) N and P balance studies in major cropping systems, (2) improved utilization of OM, (3) on-farm verification of management techniques with kraal or boma manure, (4) surveys of local sources of OM potentially for composting, (5) evaluation of different legumes and nonlegumes for green manuring and mulching, (6) determination of the effect of several OM sources on soil physicochemical properties, and (7) determination of the duration of surface-applied mulches. (CIAT)