Nutrient management for sustainable food crop intensification in African tropical savannas

Abstract

AbstractIncreased fertilizer use is often an essential component of sustainable intensification for improved food security and economic growth in the upper elevation tropical savanna (UTS) and lower elevation tropical savanna (LTS) of Africa. The UTS and LTS are large “breadbasket” areas with little fertilizer use due to financial and other constraints. Farmers’ perceptions of high profit opportunity with low risk are often major drivers of adoption. Representative crop nutrient response functions are needed to maximize farm‐level profits from fertilizer use. Such functions were determined from results of past research, and profit potentials were evaluated. The mean yield increases due to fertilizer application at the economically optimum rate, relative to yield with no fertilizer applied, were as follows: 41% for cassava (Manihot esculenta Crantz), 18% for cowpea [Vigna unguiculata (L.) Walp.], 16% for groundnut (Arachis hypogaea L.), 67% for maize (Zea mays L.), 50% for lowland rice (Oryza sativa L.), and 39% for sorghum [Sorghum bicolor (L.) Moench] in LTS, and 46% for bean (Phaseolus vulgaris L.), 81% for groundnut, 58% for maize, 96% for upland rice (Oryza sativa L. or Oryza glaberrima Steud.), 32% for sorghum, and 48% for soybean [Glycine max (L.) Merr.] in UTS. The profit potential varied greatly across nutrient rates applied to individual crops making optimized crop–nutrient–rate choices especially important for cases of financially constrained fertilizer use. Considerations for achieving widespread adoption of increased fertilizer use are discussed. Increased fertilizer use needs to be complemented by mitigation of diverse yield and socioeconomic constraints to meet the growing demand for food.