Nitrogen losses from integrated rice–duck and rice–fish ecosystems in southern China

Abstract

Nitrogen (N) losses via nitrous oxide (N2O) emission, ammonia (NH3) volatilization and N leaching were investigated from N fertilizer applied to integrated rice–duck and rice–fish ecosystems in southern China. N2O emissions was measured by a static chambers technique, NH3 volatilization by a closed acid trap method, and N leaching by a field lysimeter. The experimental field was equally divided into nine plots for three different treatments: (1) conventional rice field (CK), (2) rice–duck ecosystem (RD) and (3) rice–fish ecosystem (RF). N2O emissions from fertilizer was affected by fertilization and drainage of paddy fields. RD significantly increased N2O emissions while RF decreased N2O emissions. N losses via N2O emissions in CK, RD and RF were 1.94, 2.19 and 1.91 kg N/ha, respectively. N losses via NH3 volatilization in CK, RD and RF were 46.30, 43.09 and 44.89 kg N/ha, respectively. Due to the presence of ducks and fish, RD and RF decreased N losses via NH3 volatilization and leakage of $${\text{NO}}_{\text{3}}^ - $$ and total N. N losses via $${\text{NO}}_{\text{3}}^ - $$ leaching in CK, RD and RF were 2.83, 2.57 and 2.45 kg N/ha, respectively, and N losses via total N leaching were 6.73, 6.11 and 5.81 kg N/ha, respectively. Analysis of total N losses via N2O emission, NH3 volatilization and N leaching indicated that total N losses in RD and RF were 51.39 and 52.60 kg N/ha, respectively, which were lower than that (54.97 kg N/ha) in CK, suggesting that the presence of ducks and fish could decrease N fertilizer loss rates, and thus promote N fertilizer use efficiency.