2020 Volume 89 Issue 4 Pages 299-306
The variable-rate fertilization (VRF) based on a diagnosis of crop growth would be effective for the enhancement of yield and quality of wheat. In this study, we hypothesized that control of the tiller number would be important for VRF in wheat grown through intensive nitrogen fertilization during stem elongation (INFDSE) and determined whether yield losses due to poor seedling establishment could be compensated by control of the amount of N top-dressed at tillering (GS14). The poor seedling establishment was reproduced by lowering the sowing density. At the lower sowing density, seedling density was approximately 80 stands per m2 which was significantly lower than that at the normal sowing density which had approximately 120 stands per m2. In GS14, the tiller number at the lower sowing density was also lower than that at the normal sowing density. Increase in the amount of N top-dressed at tillering, however, did not increase the tiller number; the tiller number at the initiation of stem elongation was approximately 400 per m2 in all treatments. Even in plants grown by INFDSE, a ear number of more than 350 per m2 could be obtained at the lower sowing density because more than 85% of the tillers formed an ear. As a result, yields of plants grown at the lower sowing density were identical to those of plants grown at the normal sowing density under INFDSE. This study confirmed that under INFDSE, although the tiller number could not be controlled by N top-dressing at tillering, a high yield can be derived at seedling density of more than 80 per m2.
