Abstract：On the basis of water-nitrogen coupling balance theory and field observation results, a simple but comprehensive model was developed to predict nitrogen losses from a urea applied rice paddy field, considering all the important hydrological pathways such as surface runoff, lateral seepage, and vertical leaching. Predicted results show that the model could accurately reflect the characteristics of nitrogen exports by above three pathways in a urea applied rice field after the identifications of various nitrogen transformation rate constants. The predicting accuracy of nitrogen loss by surface runoff is lower than lateral seepage and vertical leaching because of disturbance of nature rainfall. However, the errors of nitrogen losses between predicted and observed results are all less than 20% in three hydrological pathways, especially in vertical leaching and lateral seepage which are less than 10%.
2008, Vol. 29 
