Sources of potassic fertilizers in the quality of potato tubers

The potato response to fertilization requires relevant attention, especially when supplementing with potassium (K) because this element affects the composition of tubers. The high concentration of Chlorinein the main source of K for plants (KCl)may have a negative effect on tuber quality andthis can be a critical problem,especially tocultivars destined for processing. The objective of this study was to evaluate the influence of potassium chloride and double sulfate of potassium and magnesium (KCl and K2SO4.2MgSO4) and combinations between them in order to verify the effect of chlorine in the composition of potato tubers, cv. Asterix, suitable for industry. The amount of N, P and K used was determined by soil analysis and crop requirements.The determination of the reducing sugars was carried out according tothe spectrophotometric method (Somogyi-Nelson), as well as the total glycides and starch by the Lane Eyno method (titulometric). The higher dry matter and starch in the Asterix cultivaris related to the application of the combination: 26.3% of KCl and 73.7% of K2SO4.2MgSO4and 41.9% of KCl and 58.1% of K2SO4.2MgSO4, respectively. So, the combination of the two sources is indicated to promote higher content of these tuber qualities. Onthe other hand, sources and proportions of potassiumfertilizers do not interfere in the composition of sugars. The rate used in this study (180 kg ha-1) was probably not enough to reflect the deleterious effect of chlorine on the sugar tubers constituents