Tuber Quality Parameters of Potato Varieties Depend on Potassium Fertilizer Rate and Source

The influence of potassium fertilizer source (K2SO4 and KCl) and fertilizer rates on potato tuber quality parameters under pot and field experimental conditions were studied. The pot experiment included high rate of potassium fertilizers providing 600 mg K2O kg-1 soil from both sources, studded at four varieties.The field experiment included two fertilizer rates - 100 and 200 kg K2O ha-1. The dry matter content in tubers from the plants of the pot experiment was the highest for the controls of the three studied varieties - 19.78% for „Louisiana”; 17.16 for „Riviera” and 17.26% for „Hussar”. The highest dry matter content (20.98%) in field conditions was observed for variant K200 (K2SO4). For all variants from the pot trail fertilized with KCl the starch content was decreased approximately with 2.2 to 2.4% in comparison to controls. The highest tuber starch content was observed also for the control (15.24%) from the field study.The fertilization did not influence the reducing sugars content in tubers. The content was around 0.40% independently of the trail conditions and cultivars. The application of KCl decreased the content of vitamin C in tubers for all variants from the pot trail compared to the controls (from 46% at variety „Louisiana” to 61% to Agria). In the field experiment the high rate of K200 KCl reduced vitamin C content with approximately 54% (8.40 mg 100 g-1) in comparison to variant K100 K2SO4 (18.10 mg 100 g-1). Positive influence of KCl on crude protein content in tubers at all varieties from both trials was recorded.