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Nitrogen and Potassium Fertilization Responses of Potato (Solanum tuberosum) cv. Spunta

Kavvadias, V., Paschalidis, C., Akrivos, G., Petropoulos, D.
Communications in soil science and plant analysis 2012 v.43 no.1-2 pp. 176-189
Solanum tuberosum, correlation, field experimentation, harvest index, nitrogen, nitrogen fertilizers, potassium, potatoes, tubers
A potato field experiment was conducted for 2 consecutive years to determine the effects of nitrogen (N) and potassium (K) fertilization rates on the yield and quality of potato cv. Spunta cultivated on soil low in N and K. A 3 × 4 complete factorial experiment was used with three rates of nitrogen (330, 495, and 660 kg N ha–¹) and four rates of potassium (112, 225, 450, and 675 kg K₂Ο ha–¹). An additional treatment without fertilization was used as the control. On soils low in N and K, potatoes showed low yield response to K fertilizer. The greatest tuber yields for both years were achieved at 495 kg N ha–¹ and 112 kg K₂O ha–¹ (29.81 t ha–¹) and 225 kg ha–¹ (27.13 t ha–¹), respectively. Differences in mean fresh weight due to treatment application were not significant. Application of 495 kg N ha–¹ significantly reduced harvest index (the ratio of tuber dry weight to the total dry weight at harvest) compared to 330 kg N ha–¹, but at 660 kg N ha–¹ harvest index achieved the greatest significant value. Potassium fertilization had no significant influence on harvest index. Nitrogen rates positively influenced the number of tubers. The addition of 450 kg K₂O ha–¹ significantly enhanced the number of tubers compared to the lower K rates, and the number was significantly decreased by the application of 675 kg K₂O ha–¹. Tuber dry-matter concentration was significantly promoted by N fertilization in both cultivation years, but it was negatively affected by K fertilization in the first year of cultivation. There was no change in tuber N with N application, but N application strongly increased nitrate (NO₃) concentration, which fluctuated between 360 and 1382 mg kg–¹ wet mass. Tuber NO₃ was negatively correlated with tuber yield, indicating that high levels of NO₃ in tubers can adversely affect yield. Tuber response to K fertilization was not in accordance with the rate of applied nutrient.