Abstract :
In order to determine the effects of different levels of nitrogen on yield and nitrate content of four spring onion genotypes in semi arid condition of Iran, an experiment was coducted in 2010, at Research Farm, Faculty of Agriculture, Islamic Azad University, Khorasgan Branch (Esfahan) (Latitude 32o40/ N, lonitude 51o58/, and 1570 m elevation). A split plot design within randomized complete block design with three replications was used. The main plots were nitrogen fertilizer (0, 100, 200 and 300 kg N/ha), and subplots were four cultivars (Cisakht, Dorche, Esfahan and Swit Spanish). Nitrogen had significant influence on bulb diameter, bulb height, weight average of bulb, total yield, favorite yield and nitrate content of bulb, but nitrogen had no significant effect on total percentage of dry matter and specific weight. Bulb diameter, bulb height, weight average of bulb, total yield, favorite yield, total percentage of dry matter and nitrate contetn of bulb was significantly influenced by cultivar. Specific weight was not significantly affected by cultivar. On the basis of the results, the maximum bulb diameter, bulb height, weight average of bulb, total yield, favorite yield was related to application on 200 kg N/ha, and there were no significant differences between 200 and 300 kg N/ha. The highest nitrate content also related to application of 300 kg N/ha, but the amount of nitrate content of bulb in application of 200 kg N/ha was appropraite. The use of more chemical fertilizers may increase the nitrate content in crop, and decrese onion quality. The maximum bulb diameter, bulb height, weight average of bulb, total yield, favorite yield and total percentage of dry matter was obtained in cultivation of Cisakht. So, it seems that application of 200 kg N/ha and Cisakht cultivar is appropraite for the similar condition like this experiment.
