عنوان مقاله [English]
Under salinity stress nitrogen and other plant nutrients uptake is reduced. In order to study the effect of nitrogen on growth and nutrient concentrations of Valencia orange grafted on lemon seedlings, a factorial experiment was carried out. The first factor was irrigation water salinity at four levels (0.86, 2, 4 and 6 dS m-1) and the second factor was nitrogen at five levels (50, 80, 120, 160 and 200 mg N kg-1 soil as ammonium sulfate). Salinity increased sodium and chloride ions concentration in plant leaf and roots to toxic levels and reduced the plant leaf and root dry weight. The highest level of salinity increased the sodium content in leaves and roots and also chlorine in leaves by 9, 5 and 20 times compared to salinity of 0.86, respectively. Although nitrogen had no significant effect on sodium concentration in plant leaves, at salinity levels of 2, 4 and 6 dS m-1, increasing the application of nitrogen from 50 to 200 mg kg-1 soil reduced 19, 16 and 18% of leaf chlorine and increased the corresponding dry weight of leaves by 117, 39 and 42%, respectively. Salinity decreased nitrogen, phosphorus, potassium, and micro nutrients concentration in plant leaf and in some cases reached them to sub optimal levels. In contrast, nitrogen alleviated this adverse effect by increasing the concentration of these elements in plant tissues. Based on the results, by taking into account of environmental considerations, nitrogen levels above the optimum limits can be used to reduce the adverse effects of salinity in saline conditions.