Effects of straw management practices on soil organic carbon fraction dynamics and greenhouse gas emissions in a double-season rice cropping system
摘要
Straw form affects both SOC fraction dynamics and GHG emissions. GSR enhances MAOC and leads to the lowest net greenhouse effect. CSR promotes rapid decomposition and elevated greenhouse gas emissions. pH, Fe mineralogy, cellulase activity are key drivers of carbon-climate trade-off.
Although straw return enhances soil carbon accumulation, its net climatic effect depends on the balance between carbon stabilization and greenhouse gas emissions, which is influenced by the management practice. This study investigated the impact of four straw return methods: straw removal (SR), granulated straw return (GSR), chopped straw return (CSR), and in-situ burning (ISB) on soil organic carbon fraction dynamics and greenhouse gas emissions in a coastal double-season rice paddy. Changes in soil carbon fractions, dissolved organic matter composition and greenhouse gas fluxes were analyzed. Results showed that GSR progressively increased the stable mineral-associated carbon pool, achieving the lowest global warming potential in the following full growing season and suggesting a favorable trajectory for long-term sequestration. CSR enhanced carbon association with crystalline iron oxides but also stimulated rapid decomposition, leading to sustained higher emissions. ISB minimized short-term emissions but failed to contribute to stable carbon accrual. Multivariate analysis identified soil pH, Fe mineralogy and microbial cellulolytic activity as key regulators of the carbon-climate trade-off. Our findings demonstrate that straw processing determines its environmental fate, and that practices which promote slow substrate release and mineral stabilization are more effective in reconciling soil carbon accumulation with climate change mitigation in paddies.