Sorghum-cowpea intercropping: An effective technique against runoff and soil erosion in the Sahel (Saria, Burkina Faso)

In the Central Plateau of Burkina Faso, runoff on bare soil amounts to 40% of annual rainfall and soil losses reach 4 to 8 Mg ha(-1) a(-1), despite sl opes of under 3%. Several studies have shown that mulching the soil surface can reduce runoff by over 60%. However, the scarcity of straw and the inco mpatibility of mulching with mechanical soil preparation have prevented the large-scale adoption of the technique. The study conducted in Saria villag e where annual rainfall is 800 mm, set out to evaluate the efficacy of sorg hum-cowpea intercropping in reducing runoff and erosion. The study design c omprised five plots set up so as to recover runoff and transported solids, on a Ferric lixisol with a slope of 0.7%. Three years results showed that s orghum-cowpea intercropping reduces runoff by 20-30% compared to a sorghum monoculture and by 45-55% compared to a cowpea monoculture. Soil loss is al so reduced with intercropping by at least a half compared to sorghum and co wpea monoculture. Moreover, it transpired that sorghum-cowpea intercropping is also beneficial in agricultural production terms, since the grain yield of the intercropped plots was double that obtained with sorghum or cowpea monocultures. The better crop production can be an asset for the widespread use of this technique in the country. An evaluation of the advantages of t he legume in terms of nitrogen supplies to the cereal (N-2 symbiotic fixati on) and of added soil OM will be useful in improving the cost-effectiveness of such a technique.