Characteristics of nitrogen dynamics and impact of nitrate enrichment in the agri-food system of the Taihu Basin

Effective nitrogen (N) application is fundamental to agri-food production in the basin. However, excessive use of N, coupled with gentle slopes and intricate water flow patterns during rainfall, including inflow, outflow, and in–out-flow rivers, results in considerable N loss to water. To elucidate the characteristics of N dynamics and the impacts of nitrate–N (NO₃⁻-N) enrichment in the agri-food system in the Taihu Basin, a dynamic N flow model integrating measurement and modeling was developed, combining inflow, outflow, river removal, and N storage. It distinguishes between ammonium-N (NH₄⁺-N) and NO₃⁻-N fractions. Combined with principal component analysis, the N sources were identified and targeted management strategies were accordingly developed. Scenario analysis was employed to quantify the potential reduction in N loss. The study’s findings indicate a substantial increase of 29.18% in overall N loss, up to 16,427 t during 2000–2007, followed by a decrease of 53.55% to 7631 t by 2021 in the Taihu Basin. The share of NO₃⁻-N increased by 16.94% from 70.29%, shifts in N sources like animal manure and land use changes. Consequently, the study proposes tailored, zoned N management strategies and maps. Scenario analysis results indicate that an increase in the manure returned to the field rate by 5% and the self-produced fodder rate by 30% by 2030 could reduce N loss to water by more than 24%.