Crop diversification in the Sahel through use of environmental changes near Faidherbia albida (Del) A Chev

Pearl miller [Pennisetum glaucum (L.) R. Br.] is well adapted to the harsh environment of the West African Sahel but has relatively low genetic yield potential and market value. Crop diversification is desirable, but alternative crops generally cannot tolerate the harsh climate and soil conditions that pearl miller can. This study tested the hypothesis that alternative crops could be grown near Faidherbia albida (Del.) A. Chev. (syn. Acacia albida), a tree species of semiarid Africa, because of its ameliorating effects on the surrounding environment. Octants around trees were sown to pearl millet, maize (Zea mays L.), sorghum [Sorghum bicolor (L.) Moench], and cotton (Gossypium hirsutum L). Crop, soil, and climate measurements were made periodically during the growing season. Soil fertility and fine-particle content decreased with distance from trees. Inside the canopy, irradiance was reduced by 0.5 to 1.0 kW m(-2) and daytime soil temperature at a depth of 0.05 m was reduced by as much as 6 degrees C. Improved conditions within the tree canopy were reflected by increased crop yield. Sorghum and maize tended to use less soil water than millet. Sorghum and maize yielded more than 120 g m(-2) near the tree bole, whereas millet yielded approximate to 80 g m(-2). Near the edge of the tree canopy, where pearl millet maintained yields of 40 g m(-2), the other crops tended to fail. Faidherbia albida trees can be used to diversify cropping systems and increase yields in the Sahel, but adoption of this agroforestry system may be constrained by modern social factors which have disrupted traditional land husbandry practices.