Effect of urea fertilizer application rate on nitrogen uptake and allocation and protein content in of potato

In order to investigate the effect of different levels of nitrogen fertilizer on nitrogen uptake and allocation to different organs of the plant, especially the tubers, nitrate accumulation and protein yield in potato tuber, during the four-year an experiment implemented in Agricultural Research Station of Mohaghegh Ardabil University in randomized complete block design with three replications. Factor studied in this experiment was different levels of nitrogen included 0, 80, 160 and 200 kg N ha from urea source. The results showed that application of 160 kg nitrogen per hectare had the highest rates for fresh tuber yield, percentage and yield protein. With increasing of levels of fertilizer from zero to 200 kg per hectare were observed increasing in the characteristics of tuber and shoot nitrogen percentage, nitrogen uptake in tubers, shoots and total plant and nitrate accumulation in dry and fresh matter, so that the characters was lowest in non-fertilizer and application of 200 kg fertilizer was highest value and the highest group statistically. The highest tuber yields (31.49 ton.ha-1) and protein yield (467.95 kg.ha-1) were achived in the first and fourth year, respectively. In general, excessive increase of more than optimal nitrogen in the soil cause reduces the yield of potatoes and also by reducing the amount of protein increases the accumulation of nitrates in tuber and is caused a drop in product quality.