2020 Volume 89 Issue 4 Pages 285-298
In order to obtain basic knowledge for constructing a prediction model of direct-seeding cultivation on well-drained paddy field, we compared developmental stages for direct-seeding and transplanting among eight cultivars differing in maturity type from very early to mid-late including newly bred ones by the cropping season test in Tsukuba-Mirai City. Although accumulated temperature from direct-seeding or transplanting to ripening tended to decrease the later the planting date in both methods, the effect was large for mid-late maturing cultivars and small for very early maturing cultivars. The temperature in direct-seeding cultivation was higher and with larger year-to-year variability than in transplanting cultivation. This was considered to reflect the temperature during the raising of seedling period and the cultivation was easily affected by environmental factors in the early developmental stage. In the ripening stage, the difference in accumulated temperature with different planting dates was small in plants headed together, while the effects of weather factors, such as rain, and temperature drop, were large in both methods. Introduction of heading data into an existing heading date prediction model of transplanting cultivation revealed a significant correlation between the observed date and the estimated date. By improving the existing prediction model, it may be possible to estimate and predict the heading dates for direct-seeding cultivation. The findings help provide basic knowledge for constructing a prediction model and support introduction of direct-seeding cultivation to the current cultivation system.
