Contoured ridge-tillage increases cereal yields and carbon sequestration

In southern Mali, under a semi-arid climate, contour-ridged tillage can reduce soil erosion and substantially increase the infiltration of rain water, which causes in increased growth of the crops and the trees associated with the crops in the traditional farmed landscapes. Permanent contour ridges, covered with perennial grasses, are maintained in the fields, thus giving the main frame for drawing the contour lines. The farmers follow those permanent ridges when dressing the annual contour ridges for their crops. Contoured ridges increased infiltration of rain water up to 10% of the total annual rainfall (800 mm), even in fields with a gentle slope between 1 to 2%. Crop growth of was improved. Cereal yields (millet, sorghum and maize) were increased in average by 30%, and over 50% during the dry years. The rain water better replenished water stocks in the subsoil through contour ridging, which increased the growth of existing trees (Vitellaria paradoxa and other valued species) in the traditional cultivated tree parks. This cropping technique facilitated the germination of seeds from those trees and the establishment of seedlings. The ligneous bio-mass was increased, contributing to carbon sequestration. Therefore, contour-ridge-tillage, increasing cereal yields and carbon stocks in the soil, promotes a more sustainable small scale farming in semi-arid Western Africa. (Résumé d'auteur