Cultivation on a high ridge bed did not increase the grain weight of Hokkaido-bred wheat [Triticum aestivum] cultivar "Haruyutaka" in a warm district of western Japan

Cultivation on a high Ridge Bed did not Increase the Grain Weight of Hokkaido-Bred Wheat Cultivar "Haruyuta-Ka" in a Warm Diltrict of Western Japan : Tadashi TAKAHASHI sup *, Kanae SHIMAUCHI, Ynko NAKAGAWA, Kaori SHIBATA and Takeshi IIYAMA (Fac. of Agriculture, ramaguda Univ., ramaguchi 753-85l5, Japan) Abstract : Wheat cultivars, Haruyutaka and Daichinominori, were planted on high and low ridge beds to investigate the influence of water logging on the grain weight. Grain yield, dry matter production, canopy structure, water soluble carbohydrate (WSC) content in culm, and the nitrogen content and photosynthesis rate of leaf blades were measured. The ridge height of high and low ridge beds was 35 cm and 5 cm, respectively. There was no difference in grain weight between the high and low ridge beds in either cultivar, although the grain yield was higher on the high ridge bed than on the low ridge bed. The crop growth rate (CGR) was lower after anthesis than before anthesis in both cultivars on both high and low ridge beds, and especially the CGR of Haruyutaka on the high ridge bed was extremely low. This is because the net assimilation rate (NAR) on the high ridge bed in Haruyutaka was extremely low although green area index (GAI) on the high ridge bed was more than two times higher than that on the low ridge bed. In Haruyutaka, the content of WSC in the culrn at the milk-ripe stage was as low as half of that on the low ridge bed, and was lower than that at anthesis. The nitrogen content of leaves and photosynthetic rate of upper two leaves in Haruyutaka were higher on the high ridge bed than on the low ridge bed, but these values were extremely lower than the values in Daichinominori. On the high ridge bed, dry matter production was high from the early growth stage, but the growth was too luxuriant and the GAI after anthesis was high, particularly in Haruyutaka, and the NAR after anthesis was extremely low. Thus, the grain weight on the high ridge bed was not heavier than on the low ridge bed, even though the grain yield was higher.