This paper deals with two experiments on potato fertilization carried out in a sandy soil of Alta Sorocabana region, São Paulo State, Brazil. Five NPK fertilizers (6-16-12, 3-11-9, 5-10-10, 6-15-6 and 5-13-9) were compared for two periods in a year, applying 1,650 kg per hectare of each one. The results showed that the 5-10-10 mixture yielded more than other fertilizers, and it was economically best.