Abstract
Appropriate expression on the maturity is necessary for the right combination among varieties of silage corns. Current expressions like early and "very late" as well as the relative maturity scale in current use are not accurate enough for this purpose. I propose here "Hokkaido Relative Maturity" (HRM) Scale, which takes characteristics local dependence of corn growth rate on temperature. HRM is calculated by the equation: Σ(SHU)/HU=HRM (Days), where Σ(SHU) is simple sum of heat units accumulate between seeding and the best cutting stage for silage materials, that is untile the DM value reach 30% of the whole crop, and HU is an average of daily mean temperature above 0.1℃ over twelve locations. HU is equal to 17.5℃. The HRM values of "Wase-homare" and "Hokuyu" are 130 and 147 days, respectively.
