ESTIMATING DENITRIFICATION IN AGRICULTURA LLY USED SOILS .2. RESULTS AND EVALUATION

This is the second of two papers describing a denitrification model. W hereas in the first paper the model approach was described, the second paper deals with results obtained with the model. To evaluate the mod el's performance, 14 profiles in the catchment area of a water-work we re studied in detail. For each site the potential and the actual annua l denitrification rater were estimated. It was found that the least fa vorable conditions for denitrification occurred in the sandy soils of the study area. Consequently, estimated denitrification rates were low est (< 10 kg N ha(-1) a(-1)) in these soils. Estimated denitrification rates were highest (50 kg N ha(-1) a(-1)) in peat and river plain soi ls, with either a high amount of organic matter and/or a high groundwa ter table. In silty loess soils, denitrification losses were estimated to be 20 to 35 kg N ha(-1) a(-1). With use of the anion concentration s in the surface layer of the groundwater, a plausibility study was co nducted to evaluate the estimated denitrification losses. Its results show that the values obtained are realistic. However, a true calibrati on of the model is still necessary.