Productivity and nutrient use efficiency of maize, sorghum, and cotton in the West African Dry Savanna

Sustainable agricultural practices are needed to improve food security and support livelihoods in West Africa, where soil nutrient deficiencies and rainfed production systems prevail. The objective of this study was to assess the productivity and nitrogen (N) and phosphorus (P) use efficiencies of three dominant crops (maize, sorghum, and cotton) under different soil management strategies in the dry savanna of northern Benin. Data were collected for each crop in experiments with (1) an un-amended soil as control, (2) a low use of external inputs, (3) an integrated soil-crop management practice, and (4) a high mineral fertilizer use, as treatments. Data were collected through researcher-managed and farmer-managed on-farm trials in 2014 and 2015, and analyzed using linear robust mixed effects model and Pearson's correlation. Above-ground biomass accumulation did not differ significantly among the control, integrated soil-crop management practice, and high mineral fertilizer use up to 30, 50, and 60 d after planting for maize, cotton, and sorghum, respectively. Thereafter, the differences in growth were substantial for each crop with highest biomass monitored with high mineral fertilizer use and lowest with the control. Biomass and economic yields at harvest were highest under high mineral fertilizer use and integrated soil-crop management practice, although the magnitude was crop-specific. With the integrated soil-crop management practice and high mineral fertilizer use, N and P uptake by all crops was higher than for the un-amended soil conditions. Inter-seasonal changes in N uptake were higher for sorghum and cotton, but lower for maize. The highest agronomic efficiency and apparent recovery of N and P as well as positive N and P partial balances were obtained with the integrated soil-crop management practice for all three crops tested. The integrated soil-crop management strategy gave the highest yields and significantly improved N and P use efficiencies. The findings can contribute to formulating site and crop-specific recommendations for sustainable agricultural practices in the Dry Savanna zone of West Africa.