2007 Volume 76 Issue 2 Pages 279-287
To evaluate the incidence of cool summer damage as early as possible, we made a model to estimate the sterility percentage from the cool degree days in the consecutive developmental stages of young panicles. For estimation of the sterility percentage, we used nonparametric regression with, the limitation that the values of the adjoined partial regression coefficient β are not greatly different. The parameter for water temperature was decided from the relation between the water temperature and sterility percentage in the deep flooding experiments with cv. Akitakomachi. The contribution rate of the model using this parameter for estimation of sterile percentage was 77.2%. This parameter may be applied to other cultivars by assuming the difference of cool summer tolerance as the difference in the base temperatures of cool degree days. The base temperatures for cv. Sasanishiki, Akitakomachi and Hitomebore were 21.0°C, 20.5°C and 19.5°C, respectively. The parameter for air temperature was decided using several varieties with different cool summer tolerances the damage from cool summer in 2003 at Tohoku areas. The parameter of air temperature was useful for the evaluation of cool summer damage in the fields though the accuracy was lower than the parameter for water temperature. In conclusion, we can estimate the sterility percentage caused by cool summer in real time by running this model.
