Abstract
In this experiment, in order to harvest buckwheat (Fagopyrum esculentum Moench) early in summer and use the paddy field more intensively in the warm southwestern region of Japan, the effects of different sowing times on the growth and seed yield of buckwheat were investigated. Seeds were sown every 10 days from mid-March to early June. The later the sowing time, the more flowers produced per plant and the lower the seed setting ratio and 1000 seed weight. In particular, seed setting ratio decreased markedly when the average minimum temperature exceeded 17.5°C during the period from the onset of flowering to maturing. As a result, the later the sowing time, the lower the seed yield per plant. Therefore, an early sowing time is recommended. In the region of Inland Sea of Japan (Setouchi), considering the late frost, the beginning of rainy season and the critical temperature mentioned above, seeding time is limited to the period between late-March and mid-April. If seeds are sown before mid-April, buckwheat can be harvested before transplanting of the rice seedlings, and after the harvest of buckwheat, summer crops such as rice, soybean and forage crops can be cultivated in the same paddy field.
