Abstract
A trial was conducted during the growing seasons of 1985 and 1986 in the Sudan Savannah of Burkina Faso, West Africa, to evaluate the effect of rock bunds and tied ridges constructed by donkey-traction on soil water content and soil properties. Soil water content was measured by gravimetric sampling at 7-10-day intervals during the season. Soil sampled from 0-0.05 m depth at the termination of the trial was analysed for particle size distribution, organic matter content and soil water retention. Rock bunds increased soil water content in the surface 0.30 m immediately above a rock line by an average of 32% in both 1985 and 1986. Away from the rock lines, bunds had no effect whereas tied ridges increased soil water content. At 2 m below a rock line, soil water content was increased by an average of 23 and 19% in 1985 and 1986, respectively, and midway between two rock lines by an average of 11 and 18% in 1985 and 1986, respectively. Both rock bunds and tied ridges improved water conservation in the short-term, with the latter being more efficient. Soil water retention and clay content in the surface 0.05 m were, however, greater with rock bunds and greatest when tied ridges and rock bunds were combined. Sand, silt and soil organic matter were not affected by either rock bunds or tied ridges. Sorghum grain yield was increased only by tied ridges, and was due primarily to increases in soil water content during flowering. Yield was greatest, however, when tied ridges were combined with rock bunds. It was concluded that tied ridges were more efficient than rock bunds in increasing soil water content during the growing season. Rock bunds were, however, more efficient in reducing loss of clay particles in surface runoff.
