Short-term residual effects of integrated phosphorus and manure management in soybean on subsequent maize productivity and profitability in Northern Benin

Résumé fourni par la source

Soybean-maize rotation enhances productivity and soil fertility through biological nitrogen fixation, but this benefit is constrained by low soil phosphorus levels and poor soybean fertilization practices in Sub-Saharan Africa. This study evaluated the short-term residual effects of integrated phosphorus and manure management in soybean on subsequent maize productivity and profitability across three agro-ecological zones of Northern Benin over three years (2019-2021). A split-split-plot randomized complete block design with three replications was established at three sites (Baka, Ina, Kommon), comparing two soybean varieties (improved TGX1019-14F and local), six phosphorus and manure fertilization applied to soybean, and two maize mineral fertilization levels. Phosphorus fertilization applied to soybean was the factor most strongly associated with system performance across all sites, accounting for up to 47% of the variance in soybean grain yield, 47% of the variance in maize grain yield and 67% of the variance in net profit. Manure nearly doubled system net profit and increased subsequent maize grain yield by up to 0.37 t ha -1 across sites. The improved variety TGX1019-14F consistently outperformed the local across Baka, Ina, and Kommon in all seasons, while enhancing system phosphorus use efficiency. No significant additional benefit was observed between P10 and P20 at the more favorable sites (Baka and Ina), confirming P10 as the optimal rate at these locations. A consistent gradient in yield performance emerged across sites (Baka > Ina > Kommon), with site environment associated with up to 15% of the variance in grain yield. Combining the improved soybean variety with manure and phosphorus fertilization represents the most productive, efficient, and profitable strategy for soybean-maize rotations in Northern Benin.