Add to ORKGThe investigation showed that the N-balance, applied minus removed, for N-rates of normal size was lower in winter wheat following ley for grass production or fallow than wheat following cereals or oil seed. In barley the N-balance was the lowest after sugar beets and the highest after spring cereals. It was also shown that the N-balance was lower on soils with clay contents of 15-25% than on soils with more or with less clay. Regional comparisons of the N-balance showed increasing values from south to north. Calculations of the N-balance at economic optimum N-rates showed N excess values from 10 to 27 kg ha-1 depending on region, clay content or preceding crop. For barley similar calculations gave values between 1 and 14 kg ha-1