Abstract
To elucidate a suitable fertilizer application method for early sowing of winter type wheat Iwainodaichi, we investigated the effect of late topdressing on growth and grain yield over a 4-year period. Late top dressing decreased the total dry weight at the flowering stage, but did not affect the morphological characters of leaf and stem, leaf area index (LAI) at flowering stage and sink size. The grain yield was increased by late topdressing in 2 of the 4 years as compared with early or standard topdressing. In those 2 years, late topdressing did not affect the number of flts per spike but increased the number of grains per spike and SPAD value during ripening. In the plant with late topdressing, sink size and grain yield were larger in Iwainodaichi than in Chikugoizumi in 3 of the 4 years. This seems to be attributed to the larger potential sink size of Iwainodaichi. These results suggest that in order to get a high grain yield of wheat sown early, large sink size and high SPAD value during ripening are required, and in this respect, late topdressing is advantageous for Iwainodaichi.
