Exploiting rainy season potential from the onset of rains in the Sahelian zone of West Africa

Abstract

Field studies were conducted at the ICRISAT Sahelian Center, Niamey, Niger, during 1986 and 1987 to test the methodology described earlier by Sivakumar (1988) that the potential of the rainy season in the Sahelian zone of West Africa can be determined from the date of onset of rains. We tested an early onset of rains treatment (imposed with supplemental irrigations) with the natural onset of rains. In 1986, natural onset was early while in 1987 it was considerably late. In both the seasons, dry matter production of millet ( Pennisetum glaucum (L.) R. Br.) in the early onset of rains treatment reached 7 t ha −1 while late onset of rains resulted in only 3 t ha −1. Data on soil water profiles showed that at the time of the millet harvest in the early rains treatment, profile soil water is adequate to establish a second crop of cowpea ( Vigna unguiculata (L.) Walp.) for hay. This enables efficient exploitation of soil moisture. In addition, the combined water use of the two crops in the early rains treatment was much higher. Results of this study suggest that by tailoring management tactics to weather conditions, in years with early onset of rains it is possible to establish a second crop of cowpea for hay in the Sahelian zone where the farmers traditionally grow only millet. The implications of the suggested methodology for other climatic zones in West Africa and its limitations are discussed.