Rice-duck and rice-fish co-culture systems are a major production systems in rice paddy fields in Southern China. Studying methane and nitrous oxide emissions and their economic value from those ecosystems can provide a theoretical and practical basis for further development and utilization of such traditional techniques.

Methane and nitrous oxide emissions from rice-duck (RD) and rice-fish (RF) systems were measured in situ using static chambers technique. Results shown that the peak of methane emission fluxes appeared at full tillering stage and complete heading stage. Average emission fluxes from RD and RF were significant lower than that from CK. Nitrous oxide fluxes remained low in flooding irrigation and high in draining of water. Compared with CK, the total amount of nitrous oxide emissions from RD significantly higher and RF lower. In 2006 and 2007, the total greenhouse effects of methane and nitrous oxide were 4,728.3 kg CO₂·ha^-1 and 4,611.0 kg CO₂·ha^-1; and 4,545.0 kg CO₂·ha^-1 and 4,754.3 kg CO₂·ha^-1, respectively. The estimated cost was 970.89 yuan/ha and 946.81 yuan/ha, 933.25 yuan/ha and 976.23 yuan/ha, respectively. Those values were significantly lower than CK (5,997.6 yuan/ha and 5,391.5 yuan/ha).

Rice-duck and rice-fish co-cultures can effectively decrease and control methane and nitrous oxide emissions, and they are effective strategies to reduce greenhouse gas from rice paddy fields. This, as well as the economic advantages from those systems, can be an incentive for wider adoption by farmers.