Effect of growth seasons and nitrogen fertilization on the growth, yield and nitrate accumulation of lettuce (Lactuca sativa L.) plants

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 2019/20 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 increased gradually 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.