Abstract
This study was conducted in the autumn season 2013 at AL-Hawija district 60 km west Kirkuk city to investigate effect of two plant densities (66667 and 88889 plant/ha) and three nitrogen fertilizer (300, 350 and 400 kg urea/ha) on yield and it's components for three maize hybrids (DKC 6842, DKC 6610 and Tietar). The experiment was conducted by using RCB desing in split-split plot with three replications, the main plots represented by the plant density, sub plots represented by nitrogen fertilizer levels and sub-sub plots were represented by the hybrids. The results illustrated that there were no a significant differences between two plant densities for all traits were studied. 400 kg urea/ha gave highst rate in ear length and diameter, 1000 grain weight and grain yield compared with 300 kg urea/ha. The hybrids significantly differe in all traits were studied, the Tietar hybrid was significantly superior in ear length and diameter, no. of row/ear and no. of grain / row, while the DKC 6610 hybrid significantly superior in 1000 grain weight, grain weight/ear and grain yield. The second order interaction effect of some traits were studied, the DKC 6610 hybrid ander high plant density and high nitrogen fertilizer rate gave highest grain yield. grain yield had a positive correlation with 1000 grain weight and grain weight/ear.