Synergistic impact of irrigation regimes and agro-ecological nutrient management practices on rice yield and water use efficiency in inland valleys.

This study evaluates the effects of irrigation and agro-ecological nutrient management practices on rice yield and water use efficiency (WUE) over two cropping seasons (2022 and 2023) in southwestern Benin. Field experiments were conducted at two contrasted sites, Matekpo (in-season) and Sewahoue (off season), using a split-split-plot design with three replications. Treatments included four irrigation regimes—Continuous Flooding (CF), Soil Saturation (SS), moderate Alternate Wetting and Drying (-15 kPa, AWD15), and severe (-30 kPa, AWD30)—and eight nutrient treatments: Control (C), recommended Mineral (M), Mineral Micro-dosing (MM), COmpost (CO), Rice Straw (RS), Biochar plus Compost (BCO), Rice Straw plus Compost (RSCO), and Mucuna biomass (BM). Daily water dynamics were monitored throughout the production cycle, and grain yield was measured at maturity. Linear models in R 4.4.2 were used for data analysis. Results revealed that In-season rice yield (3.3 t/ha) were higher than that of off season (3.1 t/ha). AWD15 reduced water inputs by 1.84 times at Matekpo (in-season) and 1.3 times at Sewahoue (off season) compared to CF, while maintaining comparable yields across season and years. AWD30 yielded the lowest at both seasons and sites. Mineral fertilizer (M) significantly outperformed organic amendments (BCO, RSCO, CO) in 2022, producing 1.86, 1.75, 1.63, and 1.67 times higher yields, respectively, compared to the control. However, in 2023, organic amendments achieved yields comparable to mineral fertilizers. AWD15 combined with organic fertilizers, particularly BCO, CO, and RSCO, maximized WUE. Integrating Mucuna biomass with AWD15 increased WUE from 0.83 kg/m³ in 2022 to 1.19 kg/m³ in 2023. Mineral nutrients performed better with CF, while agro-ecological organic fertilizers excelled with AWD15. These findings emphasize the role of agroecological practices, such as alternate wetting and drying and organic nutrient amendments, in fostering sustainable rice production