Tillage effects on CH4 and N2O emission from double cropping paddy field

Greenhouse gas emission is becoming a very important issue with the continuous increasing in the global temperature. In order to evaluate carbon sequestration potential of paddy and reducing emission of greenhouse gas, tillage effects on CH4 and N2O emissions from paddy soil and the trade-off relationship between CH4 and N2O were explored. The closed chamber method was used to measure the CH4 and N2O emission from the paddy field with the treatments of conventional tillage (CT), rotary tillage (RT), no-tillage (NT) at Ningxiang County, Hunan Province. The results show as following. 1) CH4 emission mainly comes from the late rice paddy, which accounted for 69%, 67%, 73% of the studied period under CT, RT and NT, respectively; 2) CH4 emission of all treatments attributed to less than 1% in the winter-fallow season, while the differences of the emission among three treatments are significant with RT＞CT＞NT; 3) N2O emission shows highly temporal variability that N2O emission in early rice paddy is RT＞NT＞CT, while in late rice paddy is NT＞RT＞CT, and the N2O is absorbed in winter-fallow season; 4) CT is beneficial to decreasing N2O emission during the studied period, while NT is beneficial to decreasing CH4 emission; 5) During the studied period, correlation between CH4 and N2O shows negative significantly, but the correlation between CH4 and N2O in winter-fallow season is not significant. In general, though increasing N2O emission appreciably, NT is beneficial to decreasing CH4 emission, and the comprehensive greenhouse effect of N2O and CH4 is also decreased.