Simulating nitrate leaching in bare fallow soils: a model comparison

In Western Europe, agriculture is one of the major contributors to the pollution of ground- and surface waters. Environmental concern has created the need for protection of these waters against eutrophication, caused by nutrient losses from e.g. agricultural sources. Leaching models may be used to predict nitrate-N losses to the environment and a plethora of such leaching models already exist. Four nitrate leaching models (Burns model, SLIM, SACFARM and ANIMO), with varying degree of complexity and parameter requirements, were used to simulate leaching in a bare fallow soil on a number of fields in the Wijlegem catchment in Flanders, Belgium. The models' performance was evaluated both statistically and graphically. Although all models predicted nitrate content in the soil profile within acceptable limits, the slightly adjusted Burns model appeared to simulate both the nitrate nitrogen and the water content best for the calibration field. Similar results were obtained for the evaluation field experiments: the Burns–α model simulated the moisture and nitrate content fairly well, while SLIM performed well in simulating the nitrate content. In conditions with limited data availability, simple (management) models, needing only a limited number of parameters to be measured or calibrated, may yield better simulation results than complex mechanistic models.