Ear formation and grain yield of winter wheat as affected by time of nitrogen supply.

Abstract

Winter wheat cv. Caribo (1979) or Arminda and Okapi (1980) was provided with an additional N dressing at different stages between tillering and ear emergence after a basal N dose applied at the onset of tillering. The effect of N on ear formation depended greatly on the growth stage at the time of N application. Max. effects on tiller formation and spikelet initiation were achieved when additional N was supplied at the beginning of tillering; on ear number when N was supplied at the onset of stem elongation; on the numbers of fertile spikelets, grains/fertile spikelet and grains/ear when N was applied during stem elongation until flag leaf emergence and on single grain wt. when N was applied at ear emergence. Variations in 1000-grain wt. were small, therefore grain yield/ear as well as yield/unit area was largely determined by grain number. Main shoots outyielded ear-bearing tillers because of a higher grain number. In ear-bearing tillers, grain yield largely depended on grain number, being highest in the older tillers. Grain formation of ear-bearing tillers was more strongly affected by the time of additional N application than that of main shoots. Top-dressings of N applied during stem elongation increased the grain number of ear-bearing tillers considerably, because both the number of fertile spikelets and the grain number/fertile spikelet were higher. In the young late-appeared tillers, the opt. time to apply additional N for grain set shifted to later stages of development. (Abstract retrieved from CAB Abstracts by CABI’s permission)