Evaluation of the corn heat unit for South Western Manitoba

Abstract

The effectiveness of the Corn Heat Unit as an agrometerological index for corn (Zea mays L.) was studied at eight locations in South-Western Manitoba in 1971 and 1972. Corn development(as measured by leaf stage, tasseling, silking, and kernel moisture) was related to corn heat unit accumulation. It was found that there were significant statistical differences between locations and years in the number of heat units required for tasseling and silking for each hybrid. There was a range of approximately 400 heat units in the number of corn heat units necessary for the attainment of physiological maturity(40 per cent kernel moisture) between the eight locations for individual hybrids. Therefore it was concluded that the corn heat unit is not a satisfactory parameter for predicting corn development in South Western Manitoba. Kernel moisture levels during the harvest period (early October) were found to be near the level (30 per cent) required for mechanical harvesting of grain. This was the case for the majority of the eight locations for the early maturing hybrids in both years. Analysis of the soil temperature measurements at the 20 and 50 cm depths at the eight locations indicated that soil temperature was an important factor in corn emergence and development.