Tillage and soil physical properties in semi-arid West Africa

In the semi-arid zone of West Africa, the growth of annual crops is severely constrained by soil and climatic conditions. Soil physical properties, specifically low porosity resulting from the particle-size distribution and predominantly low-activity clay, restricts root system development and crop growth. Using intensive mechanical tillage is an effective method in enhancing soil porosity and physical properties. This paper summarizes the results of tillage experiments conducted for about 30 years in West Africa. Tillage methods evaluated involved deep plowing with motorized equipment or animal powered tools using tined equipment and ridgers for earthing up. Soil properties and plant characteristics evaluated were porosity, root development, microbial life, soil-water reserves, and crop yields. Results of no-tillage and minimum-tillage studies are also discussed. Application of reduced tillage techniques did not produce satisfactory results. Several mulch farming systems, using dead or living vegetative covers, were also tested in regions where annual rainfall exceeds 1000 mm. The results obtained support the conclusion that soil tillage is an excellent means of improving soil physical properties and crop yields in the semi-arid regions of West Africa. However, adaptation of this technique by resource-poor small farmers poses several technical and logistical problems