Title : Integrated water and nutrient management in tropical rainfed agroecosystems: A systematic review of yield responses and resource use efficiency
Abstract:
Tropical rainfed agriculture supports over one billion people, yet yields remain below 30% of genetic potential due to interconnected water and nutrient constraints. Understanding which integrated water-nutrient management approaches generate consistent benefits across diverse contexts remains poorly synthesized, limiting evidence-based intensification strategies. This meta-analysis synthesized 43 field studies (1990-2024) selected through ROSES guidelines from Scopus and Dimensions. Inclusion required experimental trials combining water conservation and nutrient management in tropical rainfed conditions with yield data across multiple seasons. Random effects models estimated mean effects by intervention category, with meta-regression identifying moderating factors. Studies from South Asia (44%) and East Africa (28%) generated 53 intervention comparisons across seven categories: conservation tillage, integrated fertilization, organic fertilization, topographic modifications, mineral fertilization, cropping systems, and mulching. Here we show that integrated fertilization combining organic and mineral sources demonstrated superior robustness (1.34 t ha-¹; 95% CI: 0.37 to 2.30), consistently outperforming mineral-only approaches (0.60 t ha-¹; 95% CI: 0.07 to 1.12) despite substantial heterogeneity (I² = 98.4%). Study duration emerged as the primary moderator (F1,27 = 15.90; p < 0.001), with meta-regression revealing 0.063 t ha-¹ additional gain per season (R² = 0.23; p < 0.001). This is the first quantitative synthesis demonstrating that short-term trials (≤4 seasons, 77% of studies) systematically underestimate cumulative benefits. These findings provide evidence-based guidance for sustainable intensification while highlighting those long-term experimental trials exceeding ten seasons are essential to capture cumulative soil fertility improvements in tropical rainfed systems.
