Radiation use efficiency and phenological and physiological characteristics in hybrids of maize (Zea may L.) on response to different densities

In order to determine radiation use efficiency and phenological and physiological characteristics of three maize hybrids on seven plant densities, an experiment was conducted during 2006 growing season in Mashhad, Iran. Three maize hybrids including late-rippening maize (704), medium-rippening (504) and early-rippening maize (260) and seven plant densities including D1=3, D2=5, D3=7, D4=9, D5=11, D6=13 and D7=15 plants m² were compared in a strip plots design with three replications. There was significant difference on plant growth period and there were difference effects on dry matter, leaf area index, crop growth rate, net assimilation rate, and leaf area duration. Optimum indices were obtained in third plant density (D3) for late-rippening hybrid (704), in fourth plant density (D4) for medium-rippening hybrid (504) and in fifth plant density for early-rippening hybrid (260). When increasing plant density more than optimum rang of density, the time interval between pollination and silking increased while plant growth period decreased. When the plant density increased, leaf area index, dry matter and light use efficiency were increase too.