The Effect of Nitrogen Rate on Extinction Coefficient and Radiation Use Efficiency in Wheat (Triticum aestivum L.) Genotypes

In order to investigate the effects of different levels of nitrogen rate on extinction coefficient and radiation use efficiency of genotypes wheat cultivars، an experiment was conducted on Araghi Mahalleh (Gorogan) research farm during 2009. The experiment was carried out using randomize complete block with four replications. Nitrogen rates were arranged in four levels (0، 90، 180، 270 kg ha-1) and wheat cultivars included; Tajan، Falat and N81-18. The result showed that nitrogen rate and cultivar do not effect on the extinction coefficient، but they effect on radiation use efficiency. In such a way that maximum amount of radiation use efficiency is for N81-18 cultivar on nitrogen rate of 90 kg ha-1. As increase in fertilization level، leaf area index and dry material increased too. But this increase was grater in fertilization level of 90 kg ha-1 compared with 180 kg ha-1.