REHABILITATION OF A SEMIARID ECOSYSTEM IN SENEGAL - 2 - FARM-PLOT EXPERIMENTS

In the Sudano-Sahelian zone of western Africa, characterized by semi-e xtensive agriculture and subhumid climate, soil degradation and water shortages are widespread features. Soil and water conservation practic es are introduced to the farmers, but often abandoned thereafter. Some interesting results have been obtained, on a hillside scale, in the s outhern part of the cropping basin of Senegal. As a supplement to the experimental design, two small watersheds (2.5 ha) were delineated and equipped in representative hillside locations. In 1988, both the wate rsheds were planned and submitted to an hydrological survey. One of th em, located on a colluvial/alluvial terrace, was also submitted to soi l water storage and grain yield monitoring. Results highlight a decisi ve effect of soil and relief features on the efficiency of conservatio n measures. Relevant results were obtained on the terrace, but upstrea m areas still generated marked soil and water losses. These phenomena, in addition to socioeconomic constraints, partly explain farmers' beh aviour noticed on the hillside scale. (C) 1998 Published by Elsevier S cience B.V. All rights reserved.