Optimizing Fertilization in Double‐Rice Systems: Balancing Grain Yield, Soil Organic Carbon and Greenhouse Gas Emissions

ABSTRACT

Addressing the urgent need to balance high yields with environmental sustainability in the Yangtze River's double‐rice systems, this study evaluates fertilization strategies combined with a decomposition agent. We aim to identify an optimized regime that enhances grain yield and soil organic carbon while reducing greenhouse gas emissions, and to elucidate the underlying metabolic mechanisms. This study conducted a field experiment with four treatments: T1 (conventional fertilization), T2 (conventional fertilization + decomposition agent), T3 (optimized fertilization I, elemental fertilizer + decomposition agent) and T4 (optimized fertilization II, novel slow/controlled‐release fertilizer + decomposition agent). The results showed that T4 significantly increased rice yield, with the total double‐season yield increasing by 5.7% compared with T1 treatment. In addition, T4 treatment significantly increased soil organic carbon, total nitrogen and available potassium content. The increase rates for early rice and late rice were 19.8% and 21.05%, 28.57% and 20.00% and 76.36% and 77.78%, respectively. The T4 treatment reduced the global warming potential (GWP) and greenhouse gas intensity (GHGI) by 30.5% and 29.5%, respectively, while significantly increasing the activities of nitrate reductase (NR) and glutamine synthetase (GS) in early rice leaves, enhancing nitrogen assimilation capacity. Metabolomics analysis showed that optimized fertilization altered the crop's metabolic profile, characterized mainly by lower abundances of metabolites mapped to lipid and amino acid pathways. In summary, while T3 maximizes immediate emission reduction, the T4 represents a superior comprehensive strategy by synergistically sustaining high crop yields, sequestering soil organic carbon and effectively mitigating global warming potential.