Nitrate leaching to groundwater at experimental farm 'De Marke' and other Dutch sandy soils

This study focuses on nitrate leaching to the groundwater as a result of the land use system of experimental farm 'De Marke', translated to other sandy soils in the Netherlands. The land use was extrapolated to five major sandy soil map units, selected from the 1: 50 000 Soil Map of the Netherlands, using simulation models. To allow extrapolation to other conditions, the land use system was described in terms of decision rules for fertilization, grassland management, sowing and harvesting of silage maize, and supplementary irrigation. The decision rules were used as input to simulation models that were calibrated and validated using data from 'De Marke'. Then, simulations were performed for 30 consecutive years. For 'De Marke' the calculated annual average nitrate concentration at 1 m depth was 67 mg l(-1). The nitrate concentration for the soil map unit covering the largest area of sandy soils in the Netherlands Cambic Podzol, Hn21-VI) would be higher than for 'De Marke', but for the four other soil map units the calculated nitrate concentrations would be lower. It was concluded that the land use system of 'De Marke' would result in annual average nitrate concentrations lower than 50 mg l(-1) at several locations in the Dutch sandy areas.