Determination of heat requirement and the condition of corn cultivars for different maturity groups in Darab

Heat indices in comparison with systems based on the number of days have a higher ability to accurately predict the rate of development of hybrid corn. The experimental was conducted in split plot randomized complete block design with 4 sowing dates (July 10, July 20, July 30 and August 10) and 20 domestic and foreign hybrid in 5 hybrids maturity group and 3 replications in Darab region in 2007. Mean Comparison showed the most required time for emergence was belonging to the maturation group 700 and the lowest belonging to the maturation group 200, 300. Maturation group of 700 showed the highest number of days to physiological reach. Also in this experiment was shown that grain yield decrease in later planting dates and the moisture grain increase. Hybrids of 600 maturation group had the highest yield. In order to create different environments and to estimate the heat requirement were used heat indices GDD, CHU and GTI for each hybrid. The based on heat indices and studied factors, cultivars of BC504, BC666, OSSK602, BC404, as the best cultivars and July 30 planting date, the best planting date was introduced in the region of Darab. Also according to the regression reviews each three heat index, CHU heat index introduced as a stable indicator.