Direct seeding, residue management, and mungbean integration for sustainable intensification of irrigated rice systems in the derived savannah of West Africa

Context
Rice is a staple crop in West Africa, but its production faces significant challenges, including sub-optimal cropping practices, low yields, nutrient depletion, and excessive water use.
Objectives
This study evaluated the impact of alternative rice-based cropping systems—incorporating direct seeding, residue management, and legume integration—on crop productivity, resource use efficiency, and profitability in the derived savannah agro-ecological zone of West Africa.
Methodology
A three-and-a-half-year field experiment in Bouaké, Côte d’Ivoire, assessed eight treatments, including puddled transplanted rice (PTR) systems with different residue management and crop rotations, including single rice cropping with fallow, double cropping, and triple cropping with continuous rice or mungbean integration, as well as direct-seeded rice systems (wet, dry, or no-till) combined with mungbean. Residue management ranged from complete removal in conventional systems to 50 % residue retention in integrated systems. Key parameters evaluated included system rice equivalent yield (SREY), water use efficiency (WUE), partial productivity of nitrogen, protein output, and benefit-cost ratio (BCR).
Results
Continuous puddled transplanted rice with residue removal exhibited a gradual decline in yield over time, whereas integrating mungbean and residue return under wet or dry direct seeding enhanced productivity, input use efficiency, and profitability. Wet or dry direct seeding of rice in both rainy and dry seasons followed by mungbean cultivation and 50 % residue retention, resulted in the highest system rice equivalent, productivity efficiency, water use efficiency, and protein output. These improvements were 47–53 %, 27–32 %, 83–92 %, and 37–41 % greater, respectively, compared to double cropping, puddled transplanted rice with residue removal. Besides, these practices enhanced economic benefits by 109–120 % and increased the benefit-cost ratio by 82–88 %, while reducing water use by 16–23 %. No-tillage system reduced water use but led to lower mungbean yields and overall productivity.
Conclusions and Significance
Rice–rice–mungbean under wet or dry direct seeding with 50 % residue retention offers a promising strategy for sustainable intensification in the derived savannah agro-ecological zone of West Africa. This approach enhances productivity, water use efficiency, protein output, and profitability in irrigated rice systems. Further, long-term studies are recommended to evaluate the impact of these practices on soil health and greenhouse gas emissions.