Effect of planting date and plant density on grain yield and yield components of two maize hybrids as second crop in Khorram Abad

To study the effect of planting date and density on yield, yield components and morphological characteristics of two grain maize hybrids, a field experiment was conducted as a split-plot factorial in randomized complete block design with three replications in Sarab Changaee Research Field Station, Khorram Abad, in 2005 cropping season. Three planting dates of 11 June, 26 June, and 11 July (corresponded with 24, 25.5 and 30 ºC) were assigned to main plots, and three plant densities of 40000, 80000, and 120000 plants ha-1 and two maize hybrids of SC260 and SC302 as factorial were randomized in subplots. Results indicated that the highest grain yield of 6167.2 kg ha-1, yield components (except 1000 kernel weight), biological yield of 13989.44 kg ha-1 and harvest index of 44.12% were obtained in second planting date (26 June). Significant differences were observed between plant density levels for grain yield, biological yield and harvest index. However, there was no significant differences between plant density levels for the number of kernel rows. ear-1, 1000 kernel weight and ear length. SC302 produced the highest grain yield of 7010 kg ha-1 in second planting date and 80000 plant ha-1.