Effect of Cultivars, Harvesting Time and Level of Nitrogen Fertilizer on Nitrate and Nitrite Content, Yield in Romaine Lettuce

In order to evaluate the effect of nitrogen fertilizer levels (0, 60, 120, 180), cultivars (Pich Ahwazi, Pich Varamini) and harvesting time (morning, evening) on yield, nitrate and nitrite accumulation in edible parts of lettuce, a research was conducted in Shahid Chamran University of Ahwaz, Iran. This study was arranged in spilt plot experiment on randomized complete block design base, in three replications. Results indicated that effects of nitrogen fertilizer amount on yield were significant at 1% levels. Highest yield was accomplished when the Pich Ahwazi cultivar received 120 kg N ha-1. There was appositive relation ship between amount of nitrogen fertilizer and level of nitrate and nitrite accumulation in edible parts of lettuce. In two cultivars nitrate and nitrite is stem and of outer leaves were higher than inner leaves. The effect of harvest time on nitrate and nitrite content was significant at 1% level and nitrate and nitrite amount were lower in evening in comparison to morning harvesting. There had significant different in the nitrate content between cultivar and nitrite accumulation in Pich Varamini was higher than Pich Ahwazi but significant different was not seen among cultivars in nitrite accumulation. Therefore, nitrogen fertilizer and harvesting time are major factors on nitrate and nitrite accumulation in lettuce.