Effects of nitrogen fertilizer and plant density on N-P-K uptake by potato tuber

In order to evaluate nitrogen fertilizer and plant density effects on N-P-K uptake by potato tuber cultivar Agria, a factorial experiment based on randomized complete block design was conducted with three replications in 2006, Ardabil, Iran. Factors were 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 the highest nitrogen percent of tuber and mean tuber weight was achieved using 80 kg ha⁻¹ along with 5.5 plant m⁻². The highest phosphorus and copper uptake by tuber was observed at 80 kg ha⁻¹ nitrogen and density of 7.5 plant m⁻². With increasing nitrogen application up to 200 kg ha⁻¹ and densities of 7.5 and 11 plant m⁻², the highest uptake of calcium and potassium was done, respectively. With increasing nitrogen level up to 80 kg ha⁻¹, and increase in density, number and yield of tuber per unit area was increased and at 80 kg ha⁻¹ nitrogen level (equal to 160 kg ha⁻¹ nitrogen) and 11 plant m⁻², the highest number and yield of tuber was achieved. So, treatment of 80 kg ha⁻¹ nitrogen and 11 plant m⁻² in order to gain tubers having high edible quality and high yield along with the lowest nitrate pollution (in the soil and under–ground water) is recommended.