Abstract
A hybrid corn, Tomorokoshi Ko No. 7, was planted on 7 different dates in 1964. To denote heat requirements for silking and maturity, the term "heat-unit accumulation in the effective degrees" as a modification of the degree-days calculation to take into account temperature above or below the effective degree range for growth of corn was used. The effective degree ranges for the heat requirements were evaluated by the coefficient of variations among planting date. The use of the effective degree range, 10∼25°C, gave the least coefficient of variation, 1.43%, and 95% confidence interval, 807±11°C, for silking. In the same way, the use of the range, 1∼23°C, gave the least coefficient of variation, 2.41%, and 95% confidence interval, 786±18°C, for maturity after silking. From the above facts, it may be concluded that the heat-unit accumulations in the effective degrees required for silking from planting and for maturity after silking were assumed to be constant regardless of planting dates.
