Runoff and sorghum performance as affected by the spacing of stone lines in the semiarid Sahelian zone

Crop yields are primarily water-limited in dryland production systems in semiarid regions. This study was conducted in a catchment located in the "plateaucentral" of Burkina Faso to assess the impact of the space between stone lines on runoff and crop performance. The experimental design consisted of four plots in which stone lines were installed. The spacing between the lines was 100 m in the first plot, 50 in in the second, 33 m in the third, and 25 m in the last plot. The soil was a Ferric lixisol and the slope, which is characteristic of the area, was about 1-3%. Subplots placed at regular and fixed distances from the lines were used to monitor soil water content and crop yield. Runoff from all plots was measured using a water discharge recorder. It was found that 31% of rainfall was lost through runoff in plots without stone lines. The efficiency of stone lines in checking runoff and in improving soil water storage increased with reduced stone line spacing (runoff was reduced by an average of 5% on plots where the space between the lines was 33 m, but was reduced by 23% when the stone line spacing was 25 m). Soil water content decreased with increasing distance from the stone line. Sorghum (Sorghum bicolor (L.) Moench) performance was greatly affected by stone line and plant straw and grain yield were doubled in plots with stone lines compared with those of plots without stone lines. At an area of about 6 m from the stone lines (upslope), where organomineral sediments were collected, sorghum grain yields were 60% greater than that obtained at 19 m from stone lines. The stone line technique seems to be a sound option to mitigate water stress during dry spells. (Résumé d'auteur)