Die Ertragsentwicklung von Wintergetreide und Zuckerrüben bei dauerhafter Senkung des N‐Düngungsniveaus

Abstract

Abstract Effects of Long‐term Fertilizer N Reduction on Winter Grain and Sugar Beet Yields The results of recent field experiments concerning the effect of long‐term N‐reduction on the yield and quality of sugar beet, winter wheat and winter barley on plots which had previously had received ample amounts of N are studied in this paper.The yield and quality of crops harvested on plots where N‐dressings had been reduced for 6–8 years were similar to those of crops grown on plots where N‐application had been reduced for only 1 year. Grain yield of winter wheat and winter barley grown without any N‐application decreased to about 60 % of amounts normally harvested under local conditions with recommended N dressings, whereas the white sugar yield still remained at 90 %. The yields decreased slightly with an increase in the duration of the experiments. Yields of both cereals and beets remained constant within each level of fertilization, even 6 years after inition of trials with 50, 75 and 125 % of locally recommended N dressings.On plots that did not receive nitrogen fertilization, N‐contents of grain were between 1.5 and 1.7 % for winter wheat and 1.0 and 1.6 % N for winter barley. These contents remained constant over a trial period of 6 years. The amount of annual export of 55–91 kg N/ha also remained constant. Limited N availability causes a decrease in grain protein content rather than in grain yield.Compared to winter grain species, sugar beet (with 74–117 kg N/ha in the beet body) could realize the highest annual export of nitrogen from the plot. Differences in annual N export existing between the various locations of the plots cannot be explained by differences in soil quality. Continuous high yields that were found even without any N‐dressings may be explained by asymbiotic N‐fixation, deposition of atmospheric N and a progressive decrease in soil N with 17–56 kg N/ha removed from soil resources annually.