evaluation of maximum light absorption and light extinction coefficient in different levels of nitrogen and wheat cultivars

the experimental was split plot in a randomized complete block design with three replications. in this experiment, different levels of nitrogen in the main plots included four levels (0, 50, 100 and 150 n) kg.ha-1 urea and wheat varieties, including cultivars, sepahan and sw were placed in the subplots. results showed that nitrogen fertilizer and cultivar were significant effects on maximum light absorption. fertilizer treatment of 150 kg.ha-1 nitrogen resulted in maximum light absorption compare to other treatments. maximum light absorption was related to pishtaz cultivar. the interaction between nitrogen and cultivar on maximum light absorption was significant at 5% probability level. treatment of 150 kg.ha-1 nitrogen with pishtaz cultivar had the highest average of light absorption. as well as the calculated extinction coefficient of light during the growing season to control treatment, 50, 100 and 150 kg.ha-1 nitrogen was respectively equal to -0.4675,  -0.4794, -0.4858 and -0.495 and for pishtaz, sepahan and sw cultivars was -0.488, -0.4618 and -0.4504 respectively. results indicate that in order to achievement to maximum light absorption, 150 kg.ha-1 nitrogen fertilizers together with pishtaz cultivar at the condition similar to this study seems to be appropriate