Abstract
Under the escalating pressures of climate change and freshwater scarcity, understanding how irrigation management alters greenhouse gas dynamics in agricultural ecosystems has attracted increasing attention. This study conducted a comprehensive meta-analysis based on 76 field-derived publications across Chinese coastal and inland regions. We evaluated the impacts of water-saving regimes-including deficit, alternate, and intermittent irrigation-on field emissions of methane (CH 4 ), nitrous oxide (N 2 O), and carbon dioxide (CO 2 ), with random forest (RF) modeling and path analysis employed to disentangle the underlying mechanisms. The results demonstrated that water-saving practices induced a distinct biogeochemical divergence in field agroecosystems, characterized by a significant comprehensive effect of “CH 4 reduction, N 2 O promotion, and minor CO 2 mitigation” (log response ratios, ln RR=-0.48, 0.28, and -0.09, respectively). Specifically, intermittent irrigation exerted the most pronounced impact, with both CH 4 mitigation (ln RR=-0.51) and N 2 O promotion (ln RR = 0.52) reaching their peak intensities. Driven by spatial hydrothermal heterogeneity, the Southeast Coastal region exhibited the highest sensitivity in gas flux responses. Conversely, North China showed the lowest risk of N 2 O promotion (ln RR = 0.12) while maintaining robust mitigation capacity. RF modeling and meta-regression identified geographical region, soil pH, and soil organic matter (SOM) as the core predictors for the variances in CH 4 ( R 2 = 55.2%), N 2 O ( R 2 = 59.4%), and CO 2 ( R 2 = 48.1%) effects, respectively. Crucially, regression models pinpointed neutral-to-alkaline conditions (pH 7.0-7.2) as the critical threshold for N 2 O responses, beyond which alkaline soil conditions were associated with a transition from N 2 O promotion to mitigation. Path analysis further confirmed that irrigation modes exerted the strongest direct negative effect on CH 4 . Soil pH showed a highly significant direct inhibition on N 2 O, whereas precipitation introduced a notable indirect positive effect on N 2 O by driving soil acidification; meanwhile, SOM showed a dominant direct contribution to CO 2 mitigation. In conclusion, the environmental feedback of water-saving irrigation is a product of deep coupling between technical interventions and natural backgrounds. Future mitigation policies must integrate a “smart-adaptation” framework tailored to regional precipitation, soil pH, and SOM matrices, thereby orchestrating a synergy between watershed-scale green agricultural development and carbon neutrality goals.