Abstract
The grain yield of winter type wheat Iwainodaichi in early sowing and its relationship with dry matter production and yield components were investigated. Iwainodaichi and spring type wheat Chikugoizumi were cultivated by early and standard sowing. In early sowing leaf expansion was suppressed by low temperatures, but leaf area index (LAI) was almost the same as that in standard sowing, since the longer growth duration in early sowing increased the top dry weight at the flowering stage. Yield components, that is, spike number, grain number per spike and thousand grain weight in early sowing were not different from those in standard sowing so that the grain yields in early and standard sowing were not different. The spike number of Iwainodaichi was slight larger than that of Chikugoizumi since the maximum shoot number of Iwainodaichi was larger. However, grain number per spike of Iwainodaichi was smaller than that of Chikugoizumi so that the grain yields of Iwainodaichi and Chikugoizumi were not different. The grain yield closely correlated with LAI at the flowering stage and sink size, but did not correlate with mean temperature or cumulative solar radiation during ripening. These results suggest that grain yield is mostly determined before the flowering stage and the grain yield of the two cultivars in early sowing is not smaller than that in standard sowing because of its longer growth duration to the flowering stage.
