The effect of plant density and sowing date on grain yield and yield components of Early promising corn hybrids.

An experiment was conducted during 2004-2005 in Nyshabour Agricultural and Natural Resource Research Stations for evaluating the grain yield responses of two promising early corn hybrids (Sc 5oo and Sc 400), under different sowing dates and plant density. Sc 301(old) and Sc 302 (promising), were used as check for two consequent years. Hybrids planted at 15 May,31 May and 15 June with plant densities 75000, 85000 and 95000 plant/ha. A RCBD with split plot –factorial arrangement and four replications was used. Sowing date were in main plot and the factorial of hybrids x densities were in sub plot. Based on statistical analysis of variances for 2004, Delaying planting and increasing plant density decreased grain yield non- significantly. Grain yield for Sowing in 31 May (14.45 t/ha ), Sc 400(14.86 t/ha) and density 85000( 13.68t/ha ) were the best treatments for 2004. There was not any significant difference between sowing dates and plant densities levels for 2005 too. Grain yield of 31 May (13.78 t/ha ), Sc 400(14.19 t/ha) and density 95000( 13.45t/ha ) were the best treatments for 2005. Sc 500 yielded 5.4 and 6.6 % higher than tow checks but mean differences were not significant. T-test analysis showed that there was no statistical difference between checks for grain yield. Based on combine analysis there were significant differences among sowing dates and hybrids (p= 0.01) and year x sowing dates x hybrids interactions (p= 0.05). Delaying planting decreased grain yield by 2.9%. but all densities could be suitable depending on management level and sowing date. In general, hybrid Sc 400 with 14.52 t/ha grain yield which planted at 31 May with 85000 plant/ha could be recommended for Nyshabour.