Comparison of water drainage and nitrate leaching calculated by soil water balance model and dynamic process model

Based on the field data from the three plots of one hectare in Quzhou County on North China Plain,water drainage and nitrate leaching are calculated with a soil water balance model (SWB) and the dynamic process model (DPM).Quantities of water drainage and nitrate leaching calculated by the SWB method range from 191～202 mm and 38～63 kg·N/hm² in 1998/1999 respectively.When the DPM method is used,they range from 168～234 mm and 27～53 kg·N/hm² respectively.The cause for the difference is that the upword and unsaturated water flow is taken into account by the DPM method,but not by the SWB method.The DPM method needs lot of field data,mainly to study nitrogen cycle in field,assess water and nitrogen usage efficiency and optimize management soil water and nitrogen fertilizer.But the SWB needs few field data to calculate the quantities of water drainage and nitrate leaching.The SWB is a good method for management soil water and nitrogen fertilizer in fields without high precision.