the effect of plant density and various levels of nitrogen on protein percent, yield and nitrate accumulation in potato tuber

in order to evaluate plant density and different nitrogen levels on protein percent, yield and nitrate accumulation in potato tuber cv. agria, a factorial experiment based on randomized complete block design with three replications was conducted in ardabil in 2006. factors included nitrogen levels: 0, 80, 160 and 200 kg ha-1 net nitrogen and plant densities: 5.5, 7.5 and 11 plant m-2. results showed that plant density of 11 plant m-2 caused the higher rates of tuber number, tuber dry weight, tuber yield and protein per unit area. the lowest mean tuber weight and protein percent was derived in this density, as well. with increasing nitrogen level up to 80 kg ha-1, number, yield, dry weight and protein content of tuber was increased. in plant density×nitrogen level interaction treatment, the most nitrate concentration in tuber dry weight was achieved using 200 kg ha-1 net nitrogen and density of 5.5 plant m-2. so, based on the results, application of 80 kg ha-1 net nitrogen and density of 11 plant m-2 to get the highest yield and protein and the lowest nitrate concentration in tuber under the ardabil conditions is recommended.