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

Abstracts

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.