Environmental balance of 15n‐labelled fertilizer nitrogen applied to winter wheat in spring

Abstract

Model field experiments were carried out on orthic Luvisols soil in the years 1987, 1988 and 1989, in which winter wheat was fertilized with 15N‐ammonium nitrate in spring. Nitrogen was applied three times at rates of 40 kg N per ha at the beginning of vegetative growth, shooting and heading. The distribution of labelled fertilizer to plants and soil was traced in two successive samplings. The 15N‐uptake by wheat tops reached 45–50% for each rate of application, but in the dry year it was retarded. The residual fertilizer N in the soil was found in the upper layer 0–15 cm as fresh immobilized organic N. The lower soil layer 15–60 cm contents traces only from the labelled nitrate. Leaching of spring‐applied low fertilizer rates for cereals within the growth season is of minor importance, except in springs with early high rainfalls.

Key words:

• Model field experiments
• winter wheat
• ammonium nitrate
• 15N
• leaching

Stichwörter:

• Modellfeldversuche
• Winterweizen
• Ammoniumnitrat
• 15N
• Auswaschung