Effect of gamma irradiation before seed germination and different levels of nitrogen on growth and yield of German chamomile

To evaluate the effect of gamma rays on the seeds and amounts of nitrogen on growth and yield of chamomile (Chamomilla recutita synonym Matricaria chamomilla)، a factorial experiment was conducted based on randomized complete block design with three replications at the Research Farm of Agriculture College of Shahid-Beheshti. -Urmia in 2010. Treatments were gamma rays from cobalt-60 on chamomile seeds cv. ‘Bodegold’ (zero، four، eight، 12، 16، and 20 Gray) and different levels of nitrogen (zero، 50، 100، and 150 kg/ha، urea after appearance of the 4th leaf). The highest leaf dry weight per plant (12. 5 g) and per hectare (4194 kg/ha)، stem dry weight per plant (49 g) and biomass (19995 kg/ha) were obtained at 8 gray and 100، 100، 150، and 150 kg/ha of nitrogen. The highest dried flower yield at the second harvest (104 kg/ha) were obtained from 20 gray by 100 kg/ha nitrogen، and the yield of the third harvest (122 kg/ha) was from 20 gray of gamma irradiation. While، the highest flower yield at the first harvest (419 kg/ha) and total yield (533 kg/ha) were produced from 0 gray and 150 kg/ha nitrogen. Essential oil percent did not affected by treatments، but despite the significant interaction effect of gamma irradiation and nitrogen on the yield of essential oil، means comparison showed no significant differences among treatments. Yield of dried flower in the first harvest، had the greatest impact on the harvest index.