[Effects of rice-duck farming on paddy field's methane emission]

By using closed-chamber technique, the characteristics of CH4 emission from an integrated rice-duck ecosystem were studied in 2006 and 2007. The results showed that comparing with conventional flooded rice ecosystem (CK), integrated rice-duck system (RD) was distinguished in its high dissolved oxygen (DO) in field surface water and significantly lower CH4 emission, due to the activities of duck. In 2006, the average CH4 emission flux and the total CH4 emission during the whole rice growth period of RD were 6.84 +/- 1.49 mg +/- m(-2) x h(-1) and 19.34 +/- 1.15 g x m(-2), being 32.7% and 26.3% lower than those of CK (10.17 +/- 1.25 mg x m(-2) x h(-1) and 26.25 +/- 2.17 g respectively; while in 2007, the values of the two test items of RD were 7.68 +/- 0.74 mg x m(-2) x h(-1) and 18.41 +/- 1.05 g x m(-2), being 19.0% and 19.3% lower than those of CK (9.53 +/- 0.40 mg x m(-2) x h(-1) and 22.81 +/- 0.75 g +/- m(-2)), respectively. The emission flux of CH4 had two peaks, being appeared at tillering and heading stages, respectively. The seasonal fluctuations of CH4 emission flux had significant positive correlations with soil temperature and soil dissolved organic carbon content (DOC), but no obvious correlation with soil total organic carbon.