| Summary: | Straw incorporation has a variety of impacts on greenhouse gas (GHG) emissions. However, few studies have focused on the effects of multi-year straw incorporation. In this study, a field experiment was established to study the effects of straw incorporation and water-saving irrigation on GHG emissions in the cold region of Northeast China. The following four treatments were included: (i) controlled irrigation (CI) with 1-year straw incorporation (C1), (ii) controlled irrigation with 5-year straw incorporation (C5), (iii) flooded irrigation (FI) with 1-year straw incorporation (F1), and (iv) flooded irrigation with 5-year straw incorporation (F5). The fluxes of N<sub>2</sub>O, CO<sub>2</sub>, and CH<sub>4</sub> were measured by the static chamber–gas chromatography method, and their global warming potential (<i>GWP</i>) and greenhouse gas intensity (<i>GHGI</i>) in units of CO<sub>2</sub>-equivalent at the 100-year scale were calculated. The results showed that the 5-year straw incorporation reduced N<sub>2</sub>O emissions but increased CH<sub>4</sub> emissions. Compared with C1 and F1, C5 and F5 reduced N<sub>2</sub>O emissions by 73.1% and 44.9%, respectively, while increasing the CH<sub>4</sub> emissions by 101.7 and 195.8%, respectively. Under different irrigation regimes, CI reduced CH<sub>4</sub> emissions by 50.4–79.7% while increasing CO<sub>2</sub> emissions by 8.2–44.9% compared with FI. The contribution of N<sub>2</sub>O and CO<sub>2</sub> emissions were relatively high at the mature and milk stages, respectively, with a range of 16–54% and 41–52% for the treatments. In contrast, CH<sub>4</sub> emissions were mainly manifested at the tillering stage, with a contribution of 36–58% for the treatments. Affected by higher CH<sub>4</sub> emissions in FI, the <i>GWP</i> of CI was 1.4–47.6% lower than FI. In addition, the yield of CI was 10.0–11.5% higher than FI, which resulted in a <i>GHGI</i> of 11.5–52.4% lower than FI, with C5 being the lowest. The irrigation regime of CI combined with 5-year straw incorporation was an effective agronomic measure to increase yield and reduce GHG emissions from paddy fields in the cold region of Northeast China.
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