Straw return alleviates the greenhouse effect of paddy fields by increasing soil organic carbon sequestration under water-saving irrigation

The comprehensive greenhouse effect depends on the trade-off between greenhouse gas (GHG) emissions and soil organic carbon sequestration (SOCS) of paddy fields. Investigations of the effect of the straw return on GHG emissions and SOCS under different water management regimes help clarify the strategy to alleviate the comprehensive greenhouse effect of paddy fields. Therefore, a two-year field experiment was conducted to investigate the effect of different water and straw management on GHG emissions, SOCS, and rice yield. The greenhouse effect of paddy fields was quantified by calculating the greenhouse gas emission intensity (GHGI) and net greenhouse gas emission (NGHGE). The field experiment included four treatments: CI: controlled irrigation + straw removal; FI: flooded irrigation + straw removal; CI+SR: controlled irrigation + straw return; and FI+SR: flooded irrigation + straw return. The results showed that straw return could increase the SOCS and rice yield of paddy fields under different water management regimes, and the average SOCS and rice yield of CI+SR were higher than FI+SR. Furthermore, compared with FI, FI+SR promoted the GHG emission and increased the average global warming potential by 36.37%, which significantly increased the average GHGI and NGHGE by 19.95% and 22.63%, respectively. However, the global warming potential of CI+SR had no significant difference with FI due to water-saving irrigation could mitigate CH4 emissions, which caused the average GHGI and NGHGE decrease by 22.02% and 38.45%, respectively. Therefore, straw return combined with water-saving irrigation is an effective strategy to alleviate the comprehensive greenhouse effect of paddy fields.