Response of Different Maturity Groups of Grain Maize Hybrids to Planting Date in Kermanshah

Twenty Iranian and exotic maize hybrids in five different maturity groups were studied in Kermanshah in 2007 and 2008 growing seasons. Four planting dates (20 April, 30 April, 14 May and 01 June) and hybrids were arranged as split plot in randomized complete block design with three replications. The planting dates were assisgned to main plots and hybrids were randomized in sub-plots. Results indicated that early May is the most suitable planting date for late maturing hybrids in temperate region of Kermanshah. Mid-May planting as well as late-May and early-June can cause harvesting with high grain moisture in late maturing hybrids, and delay planting of the following crops in autum. Commercial maize hybrid, KSC 704, was ready for harvest with proper moisture in 10-15 Sep., 23-30 Sep., mid-Oct. and late Oct., in planting dates of 20 April, 30 April, 14 May and 01 June, respectively. Late plantings limits the time for land preparation, therefore, delays planting of wheat as following crop. Mid-season hybrids with shorter crop life cycle become ready for harvest about 2-3 weeks earlier from 14 May and 01 June planting dates. These hybrids are identified as suitable for replacement of KSC 704, without significant reduction in grain yield.