Mechanisms of water-saving irrigation and material return in regulating net greenhouse gas emissions from paddy fields in the black soil region

Against the backdrop of global climate change and the “dual carbon” targets, greenhouse gas emissions from paddy fields in the black soil region have increased markedly, highlighting an urgent need to develop green production modes that integrate water saving, carbon sequestration, and emission reduction. This study aimed to elucidate the regulatory effects and underlying mechanisms of water-saving irrigation and material return on greenhouse gas emissions from paddy fields through controlled field experiments combining different irrigation regimes with biochar and organic fertilizer return, and to systematically quantify their impacts on methane, nitrous oxide, and carbon dioxide emissions, soil organic carbon accumulation, and rice yield formation. The results showed that water-saving irrigation effectively suppressed anaerobic methane production by improving the soil redox environment in paddy fields, whereas the concomitant enhancement of aerobic processes led to a certain increase in carbon dioxide and nitrous oxide emissions; biochar and organic fertilizer exhibited differentiated regulatory effects on the emission pathways of the three greenhouse gases, with biochar showing the most pronounced advantages in reducing net greenhouse gas emissions and enhancing soil carbon sequestration, while organic fertilizer was more conducive to increasing rice yield. Overall, the combined application of water-saving irrigation and biochar return simultaneously achieved carbon sequestration, emission reduction, and yield enhancement, significantly lowering net greenhouse gas emissions from paddy fields, thereby providing a scientific basis for establishing an integrated “water saving–yield increase–carbon sequestration and emission reduction” management mode in paddy fields of the black soil region and offering important insights for regional agricultural green transformation and sustainable development.