ﺗﺄثیر سطوح مختلف نیتروژن بر عملکرد و شاخص‌های رشد گیاه گوجه‌فرنگی

To evaluate the effects of different levels of nitrogen (N) and salinity on yield and growth indices of tomato, a factorial experiment with a completely randomized design and three replications was performed in greenhouse conditions. Treatments included four levels of salinity (0.5, 2.5, 4.5 and 6.5 dS/m as NaCl) and four levels of N (0, 60, 120 and 240 kg/ha). The results showed that fruit yield, plant height, shoot dry weight and leaf surface area were decreased with an increase in salinity level. The highest and the lowest values for these traits were measured in treatments with 0.5 and 6.5 dS/m salinity level, respectively. But, root dry weight increased with an increase in salinity level. The highest fruit yield and plant height were obtained from the application of 120 kg N /ha, which were not significantly different from those obtained from the application of 240 kg N/ha. The lowest fruit yield and growth indices were measured in treatments not receiving N. The highest fruit yield and plant height were measured in the treatment with salinity level of 0.5 dS/m, receiving 120 kg N/ha. The highest shoot dry weight and leaf surface area were obtained from the treatment with salinity level of 0.5 dS/m, receiving 240 kg N/ha. The lowest plant growth indices were observed in the treatment with salinity level of 6.5 dS/m, not receiving any N. The highest root dry weight was measured in the treatment with salinity level of 6.5 dS/m, receiving 120 kg N/ha. The least root dry weight was obtained in the treatment with salinity level of 0.5 dS/m but not receiving any N. The results of this research showed that in areas with saline irrigation water, application of proper amount of N can alleviate the negative effect of salinity on yield and growth indices of tomato plant. The amount of required N to obtain maximum yield decreases as the level of salinity increases.