Abstract
Silking stages of three corn varieties (Wasehomare, Hokuyu and P3715) were estimated according to the concept of DVI (Horie et all), using the Nonparametric method recently proposed (Takezawa and Tamura). The Growth data obtained at Tokachi Agricultural Experiment Station at 5 seeding times in each year through 1979 to 1985 were used. The results are: 1) Curves showing the relationships between Developmental rate (DVR) and air temperature were similar to sigmoid. We termed the curve as DVR-T curve. The shape of DVR-T curve differed among varieties. At low air temperature regimes, the curve was more linear in Wasehomare than in other two varieties. On the other hand, the rate of decrease in DVR at high air temperature regimes was higher in the order Wasehomare<Hokuyu<P3715. Especially in P3715, the curve gradually declined as the temperature reached higher than about 23°C. 2) Although ranges of the silking stage observed in the experiment were very wide (33∼40 days), differences in days between observed and estimated silking stages were less than three days in Wasehomare and Hokuyu. Estimation in those varieties was accurate. In P37l5, the differences are somewhat larger than those of the two varieties. 3) The length of the silking stages were more accurately estimated using the Nonparametric method than by the Accumulative temperature method. This was probably because a more correct evaluation of temperature response is possible by useing the Nonparametric method.
