Grain yield and yield components of corn (Zea mays L.) hybrids in response to planting dates in semi-arid region in Isfahan

Recognition of heat requirement for different hybrids causes understanding the suitable planting date on the basis of their natural characteristics. So, to evaluate the effects of different planting dates on corns hybrids, an experiment was conducted in 2008 at Cultural Experimental and Research Center, Kaboutar Abad, Isfahan, Iran. A split plot layout within randomized complete block design with three replications was used. Main plots were three planting dates (June 5th, June 20th and July 5th), and subplots were six hybrids, namely, O. K. S. C. 250, K. S. C. 320 (Early maturity hybrids), K. S. C. 400, O. S. S. K. 552 (Mid maturity hybrids) and O. S. S. K. 713, K. S. C. 704 (Late maturity hybrids). Delay in cropping, caused significant increase in the number of days and GDD from planting to germination, seed yield and harvest index, and also, caused significant decrease in the number of days and ODD from planting to tassel stage, physiological maturity, seed number per row and protein percentage. The effect of planting date on ear seed row number and 1000-seed weight was not significant. The effect of hybrid on developmental stages and all traits was significant. Maximum ODD was related to K. S. C. 704 (Late maturity hybrid). The maximum seed number per row, 1000-seed weight, seed yield and harvest index were related to K. S. C. 400 and O. S. S. K. 713 (Mid maturity hybrids). The O. S. S. K. 713 hybrid had maximum protein percentage. Results showed that plantation of mid maturity hybrids, namely, K. S. C. 400 and O. S. S. K. 552 in July 5th is the best choice to achieve the maximum seed yield.