Large Potential for CH₄ Mitigation and Yield Improvement in China's Paddies Through Locally Optimized N Management

Nitrogen (N) management is critical for ensuring food security and mitigating greenhouse gas (GHG) emissions. In rice paddies, the effectiveness of N management in maximizing yields and minimizing N losses is highly dependent on local environmental conditions and thus varies widely across regions. However, the influence of optimized, site-specific N management on methane (CH₄) emissions remains poorly quantified and is not reflected in current IPCC Tier 1 methodologies. Here, we synthesize data from multiregional field experiments and conduct a meta-analysis to show that locally optimized N management practices-such as delayed fertilizer application, reduced N input, and deep placement-reduce CH₄ emissions from rice paddies by 16%-21%. The experiments further show that these practices suppress CH₄ emissions by lowering soil N availability and organic matter decomposition, thereby limiting substrates for methanogenesis. Combining survey data from 155 counties with machine learning models, we estimate that implementing optimized N strategies across China's rice-growing regions could reduce CH₄ emissions by 16% while simultaneously increasing rice yields by 7%. These findings underscore the dual benefits of locally optimized N management for agricultural productivity and climate change mitigation, and provide a foundation for improving CH₄ emission estimates under diverse management regimes.