EFFECT OF VARIED N-FERTILIZATION ON YIELD FORMATION OF WINTER-WHEAT UNDER PARTICULAR CONSIDERATION OF MAINSTEMS AND TILLERS

Two-year field trials with winter wheat in nine N-fertilizer treatment s were conducted in southern Bavaria to investigate the basis of yield stability and yield superiority of N-fertilization strategies with em phasis on N-application during stem elongation. In measurements of ind ividual plants the contribution of mainstems and tillers to yield form ation was examined. While grain yield showed only slight differences, significant differences between harvest indices were observed among th e fertilizer treatments. High harvest indices were regularly recorded in low stand densities. Individual plant analysis proved that early N- application led to high stand densities which intensified reduction pr ocesses during ear development. N-fertilization with emphasis on stem elongation lessened reduction processes. Low yield of tillers was main ly attributed to a low grain number per ear. Differences in grain yiel d between mainstems and tillers could not be modified by means of N-fe rtilizer treatment. Highest yields on mainstems as well as on tillers were recorded in N-fertilizer treatment with emphasis on stem elongati on. This study demonstrates that an excessive initiation of yield comp onents causes an unproductive consumption of resources which is detrim ental to yield formation. It is concluded that optimum N-fertilizer tr eatment should aim at plant stands with strong individual plants which can be achieved by emphasis of N-fertilization during stem elongation . The stimulation of the initiation of yield organs is of minor import ance as compared to a decrease of reduction process.