ABSTRACT
ABSTRACT: In order to reduce the nitrogen runoff loss from paddy fields, a paddy-pond system with water cycling was constructed based on the existing drainage-irrigation system in rice cropping region in plain polder of China. According to the characteristic of the paddypond system, we established a paddy-pond-external environment waters nitrogen runoff loss simulation model (PPE). The model was developed to estimate nitrogen runoff loss from paddy-pond system in rice cropping region. According to the conventional planting technique of rice in Nanjing, we analyzed the characteristics of the runoff water and runoff nitrogen from pond to external environment, irrigation water and irrigation nitrogen from external environment to pond during the whole rice-growth period based on the daily rainfall data of Nanjing from 1951 to 2010. The simulation results indicated that the irrigation and drainage unit of the paddy-pond system would improve nitrogen cycling rate, reduce runoff nitrogen loss from paddy fields.
