Simulation of drainage process and nitrogen loss in paddy field using DrainMOD

Excessive nitrogen loss in drainage of paddy field is a main contributor of agricultural non-point source pollution (NPS). DrainMOD and DrainMOD-N are well-performed models to simulate farm drainage and nitrogen loss at a field scale. By applying this model in humid rice-growing areas, drainage process and nitrogen loss in experimental areas of Zhanghe Irrigation District, Hubei Province were simulated. Results showed that there was a good agreement between simulated and observed values of total drainage, nitrate nitrogen loss and ammonium nitrogen loss, with the relative errors of 4.6%, 16% and 2.8% (relative error of nitrate nitrogen was a little bigger), respectively. However, in terms of the different growing stages of paddy rice, there was large deviation between simulated and observed values. Preliminary analysis indicated that the parameters used in the model were not calibrated well due to limited observed data. On the whole, DrainMOD model can efficiently describe and predict drainage and nitrogen loss processes in paddy field, which plays an important role in improving efficiency of water and nitrogen use in farmland as well as reducing agricultural pollution.