Ridge Tillage Cultivation Reduced Greenhouse Gas Emissions in Cold-Region Paddy Fields

Ridge tillage (RC) has been proposed as a water-saving irrigation technique to mitigate greenhouse gas (GHG) emissions from paddy fields. To evaluate its effectiveness under cold-region climatic conditions, a two-year field experiment (2023–2024) was conducted in Northeast China. The study assessed the effects of RC on rice yield, methane (CH4), nitrous oxide (N2O), and total GHG emissions (expressed as CO2e). A no-puddling treatment (NP) was additionally included in 2024. The results showed that compared to conventional cultivation (CK), RC significantly increased the number of effective panicles in 2023 (p < 0.05) but did not significantly affect yield in either year. CH4 emissions exhibited a double-peak pattern, with peaks at the heading and grain-filling stages; the heading stage contributed the largest part (53.1–69.0%). N2O emissions showed no distinct seasonal pattern, although N fertilization events stimulated N2O peak. RC consistently reduced CH4 emissions, with reductions of 50.8% in 2023 and 71.0% in 2024. NP in 2024 reduced CH4 emissions by 27.0%. N2O emissions showed no significant differences among treatments; however, their contribution from fertilization events varied with treatment and year. Total GHG was dominated by CH4 (>99%). RC significantly lowered GHG and GHGI by 50.7–70.1% and 57.9–73.2% compared to CK, respectively. In conclusion, ridge tillage is an effective practice to reduce CH4 and GHG emissions while maintaining rice yield in cold-region paddy fields. The large inter-annual variability strongly affects baseline emissions and underscores the needs for multi-year assessments.