Water distribution within soil-plant-atmosphere system enhances water use efficiency at various nitrogen levels in...

Various nitrogen (N) fertilizer applications aim to achieve higher yields, reduce carbon emissions, or improve N use efficiency. However, enhancing water use efficiency (WUE) remains a significant challenge in Chinese paddy fields, with current N practices largely overlooking this aspect. Thus, this study aimed to estimate WUE by examining water transpiration, evaporation, leaching, and runoff across N application levels of 0-400 kg N ha^-1 in Chinese rice fields using a data-intensive approach and the denitrification-decomposition (DNDC) model to optimize water resource utilization for sustainable rice production. Results revealed distinct WUE patterns: N inputs of 50-100 kg N ha^-1 (N50-100) exhibited the highest WUE (10.38 kg mm^-1), while 150-200 kg N ha^-1 inputs (N150-200) achieved a high WUE (8.31 kg mm^-1). In contrast, 250-400 kg N ha^-1 (N250-400) showed the lowest WUE (7.74 kg mm^-1). N50-100 reduced water transpiration, leaching, and runoff by 13-21 %, and increased water evaporation by 3 % compared to other N levels. These synergistic effects improved WUE; however, N50-100 may disrupt water equilibrium and kinetic fractionation by affecting water transpiration and leaching to limit the water productivity potential. N150-200 minimized evaporation by 38 % while sustaining high transpiration, thereby maintaining both water productivity and WUE. Conversely, N250-400 elevated water losses through transpiration, evaporation, and leaching, leading to reduced WUE. In conclusion, optimizing deeper soil water dynamics by limiting leaching and improving transpiration, especially within the widely practiced N150-200 range, shows promise for enhancing WUE potential in Chinese paddy fields. This study offers valuable insights into optimizing water resource utilization through targeted N fertilizer practices to achieve sustainable, low-carbon, and high-efficiency rice production.