Abstract
“Minaminokaori”, a wheat cultivar for bread making in western Japan, produces protein-rich grains although its yield is moderately low. The objective of this study was to examine the effects of intensive nitrogen fertilization during stem elongation (INFSE), but no nitrogen fertilization during vegetative stages, on grain protein content (GPC) and grain yield in 2014/15 and 2015/16 in Kumamoto prefecture. In both years, spike number per unit area in INFSE-treated plants was 5–20% larger than that in conventionally fertilized plants (control). In 2014/15, grain yield of INFSE was 15% higher than in the control while GPC was not reduced. In 2015/16, although the grain yield in INFSE was identical (607 g m–2) to the control, GPC was significantly high (13.8%) compared with the control (12.5%). The number of grains per spike and 1000 grain weight were not influenced by INFSE in both years. The increase in spike number was attributed to the increased number of spike-bearing tillers at higher nodes of the main stem. For instance, 62.2% of the third nodes on the main stem bore productive spikes in INFSE-treated plants, but only 19.1% in the control. The mean dry weight of tillers from the third nodes was 2.28 g in INFSE-treated plants and 1.67 g in the control. The aboveground part of the INFSE-treated plants accumulated more nitrogen (5.3 g m–2) than the control (3.6 g m–2) during full heading to maturity. Therefore, total nitrogen accumulation was significantly higher in the INFSE-treated plants (18.8 g m–2) than in the control (15.6 g m–2). INFSE can increase yield and GPC by increasing the uptake of nitrogen, and thus this fertilization system is suitable for cultivation of bread wheat cultivars.
