In the framework of the "Directive concerning the protection of waters against pollution caused by nitrate from agricultural resources (91/676/EEC)," losses of nitrate nitrogen to groundwater and surface water have to be limited. In the moderate climate regions of western Europe, drainage losses mainly occur during wintertime. The residual nitrate nitrogen in the soil profile after the harvest in autumn is considered as the main determinant of nitrate losses. In Flanders, a preliminary limit value of 90 kg NO 3 -N ha 21 up to a soil depth of 0.90 m between 1 October and 15 November is proposed. During this period in 2001, the Soil Service of Belgium sampled .18,000 fields. From these results, some interesting conclusions can be drawn. As expected, differences in residual nitrate after harvest are highly influenced by the crop, soil type, and carbon content of the soil. The percentage of fields with a residual nitrate nitrogen content below the target value of 90 kg N ha 21 differed from 39% to 86%, because of the influence of the crop grown on the parcel. On an average, a high nitrate value was found after early harvested crops (cereals, flax [Linum L.]) and after crops with high protein content due to plant residues remaining on the field after harvest (peas [Pisum sativum L.] and beans [Phaseolus vulgaris L.]). Soil type was also important because, only 42% of the fields with clay soils were below 90 kg NO 3 -N ha 21 , and in sandy soils this figure was 75%. This is

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