In the Paraiba Valley potatoes are planted moinly during the dry period, but with irrigation. As the situation of the Valley and the time of harvest permit securing better prices, eight experiments were conducted between 1954 and 1958 for determining whether, under such conditions, it would pay to increase the rotes of application of N, P, and K generally recommended by the Instituto Agronômico for the State of São Paulo. The experiments showed that substantially better yields were obtained when the rates of application were increased up to a certain level. Based an the cost for fertilizing and the value of the corresponding yield increases, the authors suggest, as a general orientation, the application of 120-180-120 kilograms of N-P2O5-K2O to the hectare, and indicate the cases where the dose of each nutrient might be increosed or reduced. They recommend, finally, to recalculate the doses whenever the prices change appreciably.