Nitrous oxide emissions from wetland rice-duck cultivation systems in Southern China.

Nitrous oxide (N2O) emissions from a rice-duck cultivation system in the subtropical region of China and its regulating factors were investigated by using a static chambers technique during rice growth seasons in 2006 and 2007. The experimental field was equally divided into six plots for two different treatments: One was a conventional rice field (CK) and the other was a rice-duck ecosystem (RD). With the same amount of urea applied as basal fertilization, N2O emission fluxes from RD and CK followed a similar seasonal variation trend. During the flooding seasons, the N2O emission flux was not correlated with temperature, but it was significantly related to soil inorganic nitrogen (SIN) (p < 0.01) and soil pH (p < 0.01). After drainage, the N2O emission flux was not correlated with temperature, SIN, and soil pH. Our experimental data showed that peaks of N2O emission flux occurred both in 2 weeks after urea application and after drainage. Compared to CK, RD could significantly increase N2O emission. We evaluated the integrated global warming potentials (GWPs) of a rice-duck cultivation system based on methane (CH4) and N2O emission, which showed that RD could suppress the total amount of CH4 and N2O emissions from rice paddies. Moreover, because the decrease of CH4 emissions from RD compared to CK was far more than the increase of N2O emissions from RD compared to CK, RD greatly reduced integrated GWPs (CH4 + N2O) compared to CK. So, the rice-duck cultivation system is an effective strategy for reducing integrated GWPs of the rice-duck cultivation systems based on CH4 and N2O in southern China and will contribute to alleviating global warming.