The present investigation was carried out in the period 1977-1981 at the
Department of Soil Science and Plant Nutrition of the Agricultural
University Wageningen, Netherlands. This university supplied the major
financial sup- port through a research grant, with additional financial
support rendered by the Dutch Nitrogen Fertilizer Industry and Unilever
Research, Netherlands. This support is gratefully acknowledged. In the
present form this report is the author's doctoral dissertation submitted
to the Faculty of the Agricul- tural University. The author hereby
wishes to thank prof. dr. ir. A. van Diest for his criti- cal reading
and correction of the English text, and drjr. J. H. G. Slangen for his
valuable advices during the investigations and in the course of the
preparation of this report. The au thor also acknowledges the valuable
support received from several Agricultural Research Institutes and
University Depart- ments which made facilities and manpower available to
conduct the ex- periments and to transform the results obtained into the
present report. Contents Preface / v Abstract / 1 List of ab breviations
/ 2 Introduction / 3 2 Literature / 6 2. 1 Nitrogen transformations in
soil / 7 2. 2 Nitrate uptake / 7 Nitrate reduction in plants / 7 2. 3 2.
4 Nitrate contents in plants / 8 2. 5 Cultural measures / 9 2. 5. 1
Nitrogen dressing / 9 2. 5. 1. 1 Nitrogen amount / 9 2. 5 . 1.