Water management and nitrogen (N) fertilizers are the two main driving factors of greenhouse gas emissions. In this paper, two irrigation modes, controlled irrigation (CI) and flood irrigation (FI), and four nitrogen fertilizer levels (N0: 0, N1:,85, N2:,110, and N3:,135 kg·hm-2) were set to study the effect of different irrigation modes and N fertilizer amount on greenhouse-gas emissions of paddy fields in cold region by using the static chamber-gas chromatograph method; yield and water consumption were also analyzed. The results showed that, compared with FI, CI significantly reduced CH4 emissions by 19.42~46.94%, but increased N2O emissions by 5.66~11.85%. Under the two irrigation modes, N fertilizers could significantly increase N2O emissions, but the CH4 emissions of each N treatment showed few differences. Compared with FI, appropriate N application under CI could significantly increase grain number per spike, seed-setting rate, and 1000-grain weight, thus increasing yield. Under the two irrigation modes, water consumption increased with the increase of N application rate, and the total water consumption of CI was significantly lower than that of FI. The global warming potential (GWP) of CI was significantly smaller than that of FI. The trend of GWP in each treatment was similar to that of CH4. Through comprehensive comparison and analysis of water productivity (WP), gas emission intensity (GHGI), and the yield of each treatment, we found that CI+N2 treatment had the highest WP (2.05 kg·m-3) and lowest GHGI (0.37 kg CO2-eq·kg-1), while maintaining high yield (10224.4 kg·hm-2). The results of this study provide an important basis for guiding high yield, water-savings, and emission reduction of paddy fields in cold regions.
Keywords: comprehensive assessment; greenhouse gas; irrigation mode; paddy fields; water productivity; yield.