Der Einfluß gesteigerter Stickstoffgaben auf die Entwicklung der Wurzelknöllchen,auf die symbiontische Stickstoffassimilation sowie auf das Wachstum und den Ertrag von Ackerbohnen (Vicia faba L.)

The effect of increasing nitrogen fertilizer rates on the development of root nodules, on the symbiotic N₂ assimilation, and on growth and yield of broad beans (Vicia faba L.) In pot experiments with broad beans (Vicia faba minor) the effect of increasing N fertilizer rates (0–800 mg N/pot) on nodulation, symbiotic N assimilation, plant growth, and yield has been studied. The plants were harvested at the beginning and at the end of flowering and at maturity. The following results were obtained: 1. No significant yield differences between treatments were found at the 1st and 2nd harvest, with exception of the 800 mg N/pot treatment which gave higher root yields at the first harvest. 2. At the 1st harvest (beginning of flowering) root nodule yield of the N-zero treatment was higher than the root nodule yield of the N treated plants. At later stages, however, no major differences in root nodule yield between the treatments N₁₀₀ and N₂₀₀ and the N-zero treatment were obtained. 3. Highest grain yields were obtained in the treatment with the lowest N-rate (100 mg N/pot) and in the treatment with the highest N rate (800 mg N/pot). The absolute highest amount of symbiotically fixed N was produced in the low N treatment (100 mg N/pot). Provided that the soil is low in available N a low fertilizer rate is required in order to exploit the full N₂ assimilation potential. 4. The total soil N remained fairly constant throughout the growing period.