Sources of potassium in the fertilization of Agata potato

The potato plant presents extraordinary productive capacity, being the fertilization one of the essential factors to optimize the cultivars potential. Potassium (K), the nutrient most absorbed and transported by the crop, interferes with the productivity and tubers quality. Despite many efforts to improve the general and nutritional management of the crop, information as K source and its parceling are still not well elucidated, generating doubts to the producers regarding the decision making. The aim of this study was to evaluate the development, productivity and potatoes quality in relation to sources and proportions of potassic fertilization and its subdivision. The field experiment were conducted with the Agate variety, in the municipalities of Ibicoara - BA and São Gotardo - MG. The design was in randomized blocks, in factorial 6X2, with four replications. The treatments consisted of the combination of potassium chloride and double sulfate of potassium and magnesium (100% KCl; 87.5% KCl + 12.5% K2SO4.2MgSO4; 75% KCl + 25% K2SO4.2MgSO4; 50% KCl + 50% K2SO4.2MgSO4; 25% KCl + 75% K2SO4.2MgSO4 and 100% K2SO4.2MgSO4) of the potassium recommended amount (100% at planting or 50% at planting and 50% at the beginning of tuberization). The proportion of potassium fertilizer sources in São Gotardo-MG does not affect the vegetative development at 60 days after planting (DAP) and potato productivity. In Ibicoara-BA, plants fertilized with 100% KCl reduced the amount of discarded tubers and presented aerial dry mass (MSA) accumulation 41% higher than the application of 50% KCl and 50% K2SO4.2MgSO4. The K subdivision is favorable to special tuber classes in São Gotardo-MG and reduces the class Discard in Ibicoara-BA. Most of the proportions between K2SO4.2MgSO4 and KCl did not differ from the exclusive use of KCl for the quantitative parameters. On the other hand, qualitative factors such as starch and soluble solids are related to the application of 100% of K via K2SO4.2MgSO4 in installments.