Groundnut and Soybean Response to Nutrient Application in West Africa

Core Ideas Leguminous oil seed production is important in West Africa. Well‐determined response functions are important for optimization of profit from nutrient application. Crop response varied across Burkina Faso, Niger, and Nigeria. Nutrient response functions were determined for different production areas. Groundnut (Arachis hypogaea L.) and soybean (Glycine max L.) are important crops in West Africa for food security and marketing. Yields are low, partly due to soil fertility constraints. High net returns to fertilizer use are needed by poor smallholder farmers. Well‐determined nutrient response functions are needed to make profit‐oriented decisions. On‐farm and on‐station trials were conducted in Burkina Faso, Niger, and Nigeria to determine such functions and to diagnose other nutrient deficiencies. All trials included four rates each of P and K. The mean responses to 15 kg ha−1 of applied P for groundnut were 0.40 in Nigeria and 0.36 and 0.19 Mg ha−1 in Niger with and without 2.5 Mg ha−1 manure applied, respectively. Groundnut did not respond to K, S, Zn, and B in Nigeria, to K in Niger, and to all nutrients in Burkina Faso. Mean soybean yield was increased in Nigeria with the application of 15, 5, 1, and 1 kg ha−1 of P, S, Zn, and B by 0.59, 0.23, 0.16, and 0.08 Mg ha−1, respectively, but decreased with K application. The mean yield increases with the diagnostic treatment of N–P–K–Mg–S–Zn–B compared to P–K were 0.11 and 0.36 Mg ha−1 for groundnut in Nigeria and Niger, respectively, and 0.23 Mg ha−1 for soybean in Nigeria. Application of P to soybean in Nigeria and groundnut in Nigeria and Niger has high profit potential but only if some manure is applied in Niger.