Effects of Straw Incorporation Years and Water-Saving Irrigation on Greenhouse Gas Emissions from Paddy Fields in Cold Region of Northeast China

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 N2O, CO2, and CH4 were measured by the static chamber&ndash:gas chromatography method, and their global warming potential (GWP) and greenhouse gas intensity (GHGI) in units of CO2-equivalent at the 100-year scale were calculated. The results showed that the 5-year straw incorporation reduced N2O emissions but increased CH4 emissions. Compared with C1 and F1, C5 and F5 reduced N2O emissions by 73.1% and 44.9%, respectively, while increasing the CH4 emissions by 101.7 and 195.8%, respectively. Under different irrigation regimes, CI reduced CH4 emissions by 50.4&ndash:79.7% while increasing CO2 emissions by 8.2&ndash:44.9% compared with FI. The contribution of N2O and CO2 emissions were relatively high at the mature and milk stages, respectively, with a range of 16&ndash:54% and 41&ndash:52% for the treatments. In contrast, CH4 emissions were mainly manifested at the tillering stage, with a contribution of 36&ndash:58% for the treatments. Affected by higher CH4 emissions in FI, the GWP of CI was 1.4&ndash:47.6% lower than FI. In addition, the yield of CI was 10.0&ndash:11.5% higher than FI, which resulted in a GHGI of 11.5&ndash: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.