Effects of Different Sowing Dates on Grain Yield and Its Components of Summer Maize

[Objective] To study effects of different sowing dates on grain yield and components of maize,as well as the variation of 1000grain weight,grains per spike and spokes.[Method]With Zhengdan 958 and Denghai 605 as test material,effects of different sowing dates on grain yield and its components of summer maize were studied by sowing winter wheat at different dates.[Result] The results showed that the growth period of maize was delayed with the delaying of sowing date.Grain yield and 1000-grain weight of maize were decreased with the delaying of sowing date.Peak value of grain yield appeared on June 7.Grains per spike of maize were increased firstly and decreased with the delaying of sowing date then.The peak value of spokes appeared on June 14.The difference of the number of spokes was not significant.[Conclusion] Suitable sowing date of Zhengdan 958 and Denghai 605 was about June 7 under the ecological conditions of Huang-Huai region.