Nonpoint pollution under extreme climate conditions and possible mitigation

Climate change significantly alters agricultural processes, impacting the movement and loss of essential nutrients like nitrogen (N) and phosphorus (P) in farming systems. This study investigates nonpoint source pollution associated with three major crops—rice, maize, and wheat—across global watersheds, focusing on the effects of extreme climate conditions through model-based analysis. The results show that nutrient losses exhibit nonlinear responses to precipitation changes. Under dry conditions, nutrient losses decreased steadily with reduced precipitation, without abrupt drops under extreme dry conditions. In contrast, wet conditions led to progressively higher nutrient losses, with N and P losses surging significantly under extreme wet conditions (P: 63.8–115.6%; N: 32.7–106.7%). Extreme wet years occurred more frequently than extreme drought years, exerting a greater impact on agricultural systems. Despite varying climate conditions affecting total nutrient loss, the proportional contributions of pathways like runoff and erosion remained relatively consistent. Further analysis revealed significant differences in nutrient loss patterns under extreme wet conditions across watersheds. Regions with high absolute nutrient losses tended to show smaller relative increases, while regions with smaller absolute losses often experienced larger relative increases. This variation highlights the need for tailored mitigation strategies. In areas with high absolute nutrient losses, the focus should be on controlling total loss through measures like precision fertilization, optimized nutrient management, and conservation tillage to reduce runoff and erosion. Meanwhile, regions with high relative increases, due to their sensitivity to extreme wet conditions, require dynamic nutrient management strategies aligned with precipitation patterns. Utilizing residual soil nutrients effectively and avoiding fertilization during wet periods can minimize additional losses. Enhancing system resilience by improving soil organic matter content is also critical, as it strengthens water retention and erosion resistance. By addressing the distinct needs of different regions, these strategies provide a solid foundation for reducing nutrient loss under extreme climate conditions, supporting sustainable agriculture and enhancing the resilience of farming systems to climate variability.