Univrsity of Tehran Press Iranian Journal of Field Crop Science 2008-4811 51 2 2020 06 21 Changes in some growth and yield indices of Spinach (Spinacia oleracea L.) under nitrogen fertilization and plant density Changes in some growth and yield indices of Spinach (Spinacia oleracea L.) under nitrogen fertilization and plant density 183 198 78045 10.22059/ijfcs.2019.279354.654601 FA Farnaz Goodarzi Department of Horticulture University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, Mojtaba Delshad Department of Horticulture University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, Forouzandeh Soltani Department of Horticulture University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran, Hamed Mansouri Sugar Beet Research Department, Hamedan Agricultural and Natural Resources Research and Education Center, Hamedan, Journal Article 2019 04 16 The Identification of the factors affecting the yield and edible quality of spinach (<em>Spinach oleracea</em> L.) and their interaction with the environmental conditions are the most important issues in crop production management. In this experiment, the effect of three levels of plant density (71, 45 and 33 plant m^-2), six levels of nitrogen fertilizer (100, 200, 250, 300, 350 and 400 kg urea ha^-1) and control on yield, growth indices and quality of spinach was evaluated in the field condition. These experiments were carried in 2014-15 and 2015-16, in a randomized complete block design with three replicates. The results showed that interaction effects of nitrogen fertilizer and plant density and year only had Significant effcet on nitrate content (p < 0.001). Nitrogen fertilizer increased biomass, yield, growth parameters like leaf area index, crop growth rate, and qualitative parameters like nitrate content, potassium percentage, chlorophyll a,b and total traits while had not significant effect on net assimilation rate and relative growth rate. Interaction effects of plant density and year had a significant effect on all traits except potassium percentage (p < 0.001). The increase in plant density led to increase in the biomass, leaf area index and nitrate content but chlorophyll content was significantly decreased. It is suggested that in autumn cropping in Karaj region, and under high light and temperature conditions, 71 plants m^-2and 250kg urea ha^-1 could be better to estimate the aims of economic profitability for highest yield and maintaining a healthy level of nitrate in the plant tissue. The Identification of the factors affecting the yield and edible quality of spinach (<em>Spinach oleracea</em> L.) and their interaction with the environmental conditions are the most important issues in crop production management. In this experiment, the effect of three levels of plant density (71, 45 and 33 plant m^-2), six levels of nitrogen fertilizer (100, 200, 250, 300, 350 and 400 kg urea ha^-1) and control on yield, growth indices and quality of spinach was evaluated in the field condition. These experiments were carried in 2014-15 and 2015-16, in a randomized complete block design with three replicates. The results showed that interaction effects of nitrogen fertilizer and plant density and year only had Significant effcet on nitrate content (p < 0.001). Nitrogen fertilizer increased biomass, yield, growth parameters like leaf area index, crop growth rate, and qualitative parameters like nitrate content, potassium percentage, chlorophyll a,b and total traits while had not significant effect on net assimilation rate and relative growth rate. Interaction effects of plant density and year had a significant effect on all traits except potassium percentage (p < 0.001). The increase in plant density led to increase in the biomass, leaf area index and nitrate content but chlorophyll content was significantly decreased. It is suggested that in autumn cropping in Karaj region, and under high light and temperature conditions, 71 plants m^-2and 250kg urea ha^-1 could be better to estimate the aims of economic profitability for highest yield and maintaining a healthy level of nitrate in the plant tissue. https://ijfcs.ut.ac.ir/article_78045_4e8de789e08397c65646a8a0de7e906d.pdf