Effect of Plant Density on Radiation Use Efficiency, Extinction Coefficient and Grain Yield of Two Sunflower Cultivars in Northern Khuzestan

Plant density is one of the important factors influencing the amount of light reaching to plants. An experiment was carried out at agricultural research farm of Azad university of Dezfol (Sanjer region) in 2013 and 2014. The experiment design was factorial in a randomized complete block with three replications. Plant densities of (4.5, 5.5, 6.5 and 7.5 plant/m2). Two sunflower cultivars of Shahroodi and Domsefid were cultivated. The results showed that the effect of plant density was significant on leaf area index (LAI), Radiation use efficiency (RUE), Grain yield, extinction coefficient (K) and light interception (LI). The highest LAI and RUE were 4.24 and 1.92(MJ/M2/S) for Shahroodi cultivar, respectively. The highest K and LI in Domsefid cultivar were 0.137 and 43.4% respectively. The increase in plant density of both cultivars resulted in increasing the RUE. The highest grain yield for Domsefid cultivar (6.5 plant/m2) was 5249.9 kg/ha. The highest grain yield for Domsefid cultivar (6.5 plant/m2) was 5249.9 kg/ha. The highest grain yield for Domsefid cultivar (6.5 plant/m2) was 5249.9 kg/ha.