The most important published and unpublished experimental results of the EUF research team in Germany and Austria on the calculation of nitrogen recommendations for cereals are reviewed. Electro Ultrafiltration is a multipurpose testing method also usable for estimating two forms of soil nitrogen, nitrate (NO₃) and easily mineralizable organic nitrogen (N_org). The latter can also be expressed as a quotient, the ratio between the N_org extracted at 80°C to that extracted at 20°C (N_org-Q). The EUF N_org contents in the top soils (0 - 30 cm) of more than 32,000 sites in 1990 ranged between 40 and 160 kg N/ha, with a mean of 75 kg/ha, while the EUF EUF NO₃ -N contents of these soils varied considerably less, with a Mean of 59 kg N/ha. The mean EUF N_org quotients  were 0.5, ranging from 0.3  to 0.9. A close positive correlation was found between the quotient and the calcium status of the soils  (r=0.96). Humus content and the EUF N_org quotient were also positively correlated. A highly significant positive correlation was found between EUF N_org quotients and EUF nitrate contents (r=0.97), because of the higher nitrate supply potential (mineralization capacity) of soils rich in humus and lime. Field trials of winter wheat on more than 100 sites showed that all three measures are necessary to calculate N fertilizer requirements: EUF NO₃-N, EUF N_org and EUF N_org 80°C/20°C quotient. Multiple regression equations are presented for the determination of spring and total N requirements of winter wheat in Germany and Austria. In part 2 of the publication, the calculation of the N fertilizer requirements of sugar beet on the basis of the EUF N fractions and the experience with the EUF procedure in German and Austrian agriculture will be discussed.