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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.

Water and soil fertility are the most limiting biophysical factors affecting crop production in semi-arid West Africa. . This study was conducted in Nadion (south Sudan zone of Burkina Faso) to assess the impact of tillage practices (no-till, tied ridging; ripping and conventional tillage) combined with soil fertility management options (compost, NPK + Urea, crop residues, Compost+ NPK + Urea and a control) on soil moisture content and sorghum yield. The soil moisture was monitored weekly using the Time Domain Reflectometer (TDR) method and the soil bulk density was evaluated 30 days after planting. Zero tillage increased the soil water storage capacity compared to the other tillage practices at 0-30 cm depth. Sorghum straw residues application improved soil water content by 20%. Conventional tillage decreased surface soil (0-10 cm) bulk density. Compost + NPK + Urea application increased sorghum yield by 74% over the control while, NPK + urea and compost increased sorghum grain yield by 50% and 29%, respectively relative to the control (no soil amendment). Conventional tillage led to decrease in yield compared to zero tillage after two years of experimentation. The zero tillage combined with compost, NPK and urea increased sorghum yield by 28% compared to tied-ridging regardless of the fertility management options. Zero tillage is a promising option for sorghum production in the South Sudan agro-ecological zone of Burkina Faso.