Das optimale N-Angebot im Frühjahr bei unterschiedlicher Keimdichte von Winterweizen

The optimal N-supply in spring for different plant densities of winter wheat
The influence of plant density (plt./m²) on the optimal N-supply in spring (N_min-content + N-fertilization) has been tested at three sites. The different plant density was produced by different seed rates in autumn of about 150, 250, 350, 450 and 550 grains/m². The N-supply in spring was - apart from a non-fertilized field (N_min-content) 80, 100, 120, 140 and 160 kg N/ha. Additionally, 80 kg N/ha were applicated as N-topdressing. Moreover the optimal N-supply in spring has been tested on a winter wheat field thinned out due to winterkilling. In detail we got the following results:
1. The reduction of the N_min-content due to the N-uptake by the plants slowed down in accordance with minor plant density.
2. The same N-supply in the soil produced a higher N-supply per individual plant in accordance with decreasing plant density and lead to a considerable increase of N-nutrition.
3. Thin crops showed a higher tillering. The differences in plant density between 150 and 550 plt./m² in spring diminished to about 90 ears/m² at harvest.
4. Independently of plant density the maximum yield was obtained by a N-supply (N_min+ N-fertilization) in spring of about 120 kg/ha N. Due to the abundant N-nutrition of the individual plants and the minor increase of yield a higher N-supply is not necessary with a minor plant density.
5. Essentially the yield level was only diminished with the lowest plant density (100-140 plt./m²).