Effect of plant density on yield and yield components of corn hybrids ( Zea mays )

In order to study the effect of plant density on yield and yield components of grain corn hybrids, a field experiment was conducted in 2007-2008 in Firouz-Abad of Iran. The experiment was conducted in split plot base on randomized completely block design with three replications. Main plots were four levels of corn cultivars: Hybrid of late maturing 704 (V1), hybrid of mid maturing 604 (V2), hybrid of early maturing 370 (V3) and hybrid of mid maturing 647 (V4). Sub plots were four levels of plant density: 65000 plant ha-1 (D1), 75000 plant ha-1 (D2), 85000 plant ha-1 (D3) and 95000 plant ha-1 (D4). The result showed that, the most grain yield, 1000-grains weight, biologic yield, obtained from hybrid of late maturing 704; and the most harvest index achieved from hybrids of mid maturing 647 and early maturing 370. With density increasing, hybrids reaction were different for each one of factors; so that the highest grain yield of hybrid 704 obtained from 75000 plant ha-1, for hybrids 604 and 647 obtained from 85000 plant ha-1  and for hybrid 370 obtained from 95000 plant ha-1.   Key words: Corn hybrid, plant density, yield, yield component.