Effect of nitrogen and phosphorous levels on Agronomic Characteristics in spinach

This field research was conducted to determination of nitrogen and phosphorus levels effect on yield, relative yield, fertilizer and water use efficiency, agronomic efficiency and nitrate accumulation in spinach (Spinacea oleracea) at Agricultural and Natural Resources Research Center of Tehran Province in 2008. The experiment was conducted as split plot based on randomized complete block design with three replications. Nitrogen levels were 0, 100, 150, 200 and 250 kg ha-1 and phosphorous levels were 0, 37.5, 50, 62.5 and 75 kg P2O5 ha-1. Fresh yield and nitrate of leaf measured. The results showed yield increased up to 50 kg P2O5 and 250 kg N ha-1 significantly. The highest rate of increase in fertilizer and water use efficiency and agronomic efficiency were achieved in 250, 150 and 250 kg N ha-1 and phosphorus levels at 75 kg ha-1, respectively. Nitrate content was affected by nitrogen fertilizer levels but phosphorous and interaction of nitrogen and phosphorus was not significant on plant nitrate. Based on the results, it was recommended that 250 kg N ha-1 and 50 kg P2O5 ha-1 is suitable for optimum yield and legal level of nitrate in spinach.