عنوان مقاله [English]
Nitrogen is the most important element in plant growth and yield. There are several sources for supplying nitrogen needed by the plant, including the use of chemical fertilizers. But excessive use of chemical fertilizers in addition to contamination of water and soil has also caused health risks to the community. Therefore, optimizing the use of chemical fertilizers and replacing them with organic sources can be a step forward in increasing the health of the community. For this purpose, a field experiment with different levels of urea fertilizer and various nitrogen sources were carried out in a factorial arrangement in a randomized complete block design with three replications on strawberry in 2016 at Someh-Sara, Gilan, Iran. The experimental factors included urea (0, 75 and 150 kg.ha-1) and various sources of nitrogen (Azospirilum, Azotobacter, Nano-nitrogen and Control). The results showed that in levels of nitrogen source, the application of urea fertilizer increased the shoot weight and shoot length, but decreased total antioxidant capacity, total flavonoid compounds and vitamin C. The highest fresh weight of shoot and fruit number were obtained from nano-nitrogen treatment + 75 kg.ha-1. While the highest amounts of vitamin C, total antioxidant capacity and total flavonoid compounds were obtained from Azotobacter and Azospirilum inoculated plants, Azotobacter was superior to Azospirilum in most of the traits and with increasing the application of urea fertilizer, maintained its efficiency compared to control. The highest fruit yield was obtained from nano-nitrogen + 75 kg.ha-1, but there was no statistically significant difference with Azotobacter + 75 kg.ha-1. Therefore, since the aim of the experiment was to increase the yield and quality of the fruit, Azotobacter + 75 kg.ha-1 is recommendable compared to other treatments.