Abstract

Better land and crop management systems are needed to resolve actual problem of land and environmental degradation in Africa. Assessment of required technology must consider both impacts on crop yields and the different environmental compartments (soil, water and atmosphere). With these concerns, an experimental study was conducted on these basis at Cinzana research station (13° 15’N; 5° 57'W), Mali. Effects of five crop management systems (treatments T1 to T5) are compared from 1992 to 1997 in a split-plot arrangement with two tillage levels (simple ridging and tied one): sorghum monoculture with crop residues export (T1); crop residue restitution every two years (T2); rotation cowpea – sorghum (T3); rotation green manure sesbania – sorghum (T4); rotation green manure dolic – sorghum (T5). All treatments received Tilemsi rock phosphate (300 kg ha^-1) in 1995. Soil samples were analyzed and sorghum yields quantified. Between 1990 and 1996, pH increased in T2 and T3 and decrease in T1 and T4. All treatments improved slightly and equivalently, soil organic carbon (SOC) (0.3%), decreased the cation exchange capacity (CEC) and bases (except Ca) and increased available P. Grain sorghum yields decreased in monoculture (23 and 14%), and increased in rotations (6 to 12%). The results confirmed the value of leguminous and green manure with addition of Tilemsi rock phosphate in improving sorghum productivity.

Key words: Sudano-Sahelian zone, Mali, sorghum, green manure, Tilemsi rock phosphate, soil quality.