Nitrogen Uptake and Utilization in Winter Wheat under Different Fertilization Regimes, with Particular Reference to Main Stems and Tillers

Two-year field trials with winter wheat under nine nitrogen (N) fertilizer treatments were conducted at TU Munich's research station in Southern Bavaria. The study investigated N uptake and N utilization of wheat stands for varying N fertilizer strategies, with emphasis on N application during stem elongation. N use was analysed in individual plants, separated into main stems and tillers to estimate the effect on the tiller category. While grain N uptake showed only slight differences, substantial differences were recorded for N uptake of straw, leading to significant variation in N harvest index as affected by N fertilizer treatment. Individual plant analysis indicated that N harvest indices of tillers were lower than those of main stems due to high N uptake into the straw of tillers. This was not modified by any of the N fertilization strategies. It is presumed that for tillers the translocation of nitrogen from straw into kernels is less effective than for main stems since ears of tillers produce a lower sink size. N fertilization with emphasis on stem elongation led to a below-average number of tillers and above-average N harvest indices for main stems as well as tillers. This was confirmed by a negative correlation between plant density and N harvest index. High N content in straw was not found to be necessary for achieving high N content in kernels. In addition to economical benefits, a N fertilization strategy with emphasis on application during stem elongation has environmental benefits in intensive wheat production systems.