الفهرس | Only 14 pages are availabe for public view |
Abstract In modern agriculture, the nitrate accumulation in vegetables has become a serious threat to human health. That caused by an imbalance between nitrate absorption and assimilation in plants. Nitrogen fertilization and light intensity are the main factors affected nitrate accumulation. Therefore, a pot experiment was conducted during two successive summer and winter seasons of 2019 at the greenhouse of Fac. Agric., Cairo Univ., Giza, Egypt, on lettuce (Lactuca sativa L. var. longifolia Lam) plants to investigate the effect of growth seasons (summer and winter), different rates (0, 60, 90 and 120 Kg N fed-1 ) and sources CO (NH2)2, NH4NO3 and (NH4)2SO4 of nitrogen fertilizers on lettuce growth and nitrate concentrations. The results showed that fresh and dry weight, yield and nutrient contents of lettuce plants gradually increased according to increasing dose of nitrogen, up to 90 Kg N fed-1 and the magnitude of increase, according to different N fertilizers used , was in the following order: CO (NH2)2 > NH4NO3 > (NH4)2SO4. The accumulation of nitrate was higher in winter compared to summer season for both inner and outer leaves. The highest values for both seasons were recorded in the outer leaves, which significantly increased with increasing N fertilizer dose and the magnitude of increase, according to N sources used, was in the following order: NH4NO3 > CO(NH2)2 > (NH4)2SO4. This study recommend the combined use of urea rate at 90 Kg N fed-1 in summer season to achieve the highest yield with acceptable nitrate content |