Model-based assessment of nitrogen input reduction for sustainable paddy rice production using DSSAT and DNDC: Yield, environmental and economic trade-offs

Intensive paddy rice production often relies on high nitrogen (N) inputs to maintain yield, but excessive fertilization causes diminishing agronomic returns, environmental burdens and external costs. This study developed an integrated sustainability assessment framework to evaluate N-input reduction pathways in a single-season rice system in the Taihu Lake Region. Rice yield and N productivity were simulated using the CERES-Rice module of the Decision Support System for Agrotechnology Transfer (DSSAT). Greenhouse gas emissions and reactive N losses were estimated using the DeNitrification-DeComposition model (DNDC). Model outputs were integrated through environmental footprint accounting, ecosystem economic evaluation and the Food-Economy-Environment Nexus Index (FEENI). Using a 40-year climate sequence (1981–2020), we compared N application rates, fertilizer sources and application patterns across dry, normal and wet years. The high N input of 270–300 kg N ha −1 was associated with declining N productivity and increasing environmental damage costs. Reducing N input to 230 kg N ha −1 provided the most balanced production-stage outcome, maintaining high yield and achieving the highest net ecosystem economic benefit (3019.7 $ ha −1 ) while retaining relatively low greenhouse gas and reactive N intensities. However, the relative advantage of the fertilization practices varied among climatic year types. Conventional split application at 230 kg N ha −1 performed best in dry and normal years, whereas partial organic substitution performed better in wet years. Taken together, these findings indicate that moderate N reduction combined with climate-responsive fertilization can improve the balance among productivity, economic viability and environmental performance in intensive paddy rice systems.