Economic valuation associated with nitrogen losses from wetland rice-duck and rice- fish ecological system

To evaluate the potential effect of stocking ducks and fish on nitrogen (N) losses and economic value from paddy fields, an experiment was conducted on the experimental farm of Huazhong Agricultural University in Wuhan, China. The experimental field was equally divided into nine plots for three different treatments: (1) rice-duck ecosystem (RD), (2) rice-fish ecosystem (RF) and (3) rice only (R). N losses via N 2 O emission, NH 3 volatilization and N leaching were investigated during rice growth stage. N 2 O emissions were measured by a static chambers technique, NH 3 volatilization by a closed acid trap method, and N leaching by a field lysimeter. Compared with R and RF, RD significantly (p<0.05) increased N 2 O emissions during ducks and fish introduced into the paddy fields. The economic value of N losses via N 2 O emissions from RD, RF and R were 139.74, 121.19 and 123.77 yuan·ha -1 (Chinese currency; 1 euro = 8.28 yuan, April 19, 2012), respectively. N losses via NH 3 volatilization from RD were 43.09 kg·ha -1 , significantly lower than 44.89 and 46.30 kg·ha -1 in RF and R, with the economic value of 2808.71, 2926.04 and 3017.94 yuan·ha -1 , respectively. The economic value of N losses via total N leaching from RD and RF were 473.70 and 463.64 yuan·ha -1 , respectively, which were lower than that from R (503.40 yuan·ha -1 ). Besides the output value and input cost, the economic value from RD and RF were 9495.21 and 7211.54 yuan·ha -1 , respectively, which were higher than that from R (4297.69 yuan·ha -1 ). These results suggest the presence of ducks and fish in paddy fields could decrease N losses and contribute to the development of economy and environmental sustainability.