Conservation tillage increases corn and soybean water productivity across the Ohio River Basin

Optimizing agricultural management practices is imperative for ensuring food security and building climate-resilient agriculture. The past several decades have witnessed the emergence of conservation tillage practices to combat soil erosion and degradation. However, the effects of conservation tillage on crop water productivity (CWP) remain uncertain, especially from a regional-scale perspective. Here, we used an improved process-based agroecosystem model (DLEM-Ag) to quantify the long-term effects of conservation tillage (e.g., no-tillage, NT; reduced tillage, RT) on CWP (defined as the ratio of crop productivity to evapotranspiration) of corn and soybean across the Ohio River Basin during 1979–2018. Our results revealed an average increase of 2.8% and 8.4% in CWP for corn and soybean, respectively, under the NT adoption scenario. Compared to the conventional tillage scenario, NT and RT would enhance CWP, primarily due to reductions in evapotranspiration, particularly evaporation. Further analysis suggested that, although NT and RT may decrease surface runoff, these practices could also increase subsurface drainage and nutrient loss from corn and soybean farmland via leaching. These results indicate that conservation tillage should be complemented with additional water and nutrient management practices to enhance soil water retention and optimize nutrient use in the region's cropland. Our findings also provide unique insights into optimizing management practices for other areas where conservation tillage is widely applied.