Impact of land use on soils quality and erosion-sedimentation balance in the malian cotton zone (case of Bélékoni Watershed)

Bélékoni watershed (120km2 ) is located in the upper basin of Niger River in Mali. The climate context (Sudanian zone) justify cotton production program. Analysis of last decades agricultural evolution impacts is the objective of the present study. Research methods include in situ observations and measurements and laboratory analysis. According French soil classification of 1967, three main soil types are distinguished in the watershed: Lithosol (soil1), Ferruginous Tropical Soil (soil2) and Mineral Hydromorphic Soil (soil3). Sol1 is marginal for cropping and wood development and the two others soils are indicated for actual agricultural intensification. Concerning land use, there are mainly cropland and land under natural vegetation, subjected to vainly grazing. The general trend is the soil degradation whereas land use. Carbon stock is low (20.2 t.ha-1 in the first 30 cm of soil profile). Soil 1 and 2 are affected by erosion, respectively 2.7 and 5.7 t.ha- 1 .yr-1 or 0.4 and 0.2 cm.yr-1 ; Soil3, located in the depression along river system is a sedimentation site: 10.1t.ha-1 .yr-1 or 0.7 cm.yr-1 . Major process currently affecting Bélékoni watershed are land use change, soil degradation and sedimentation in the river. (Résumé d'auteur