Seven experiments were conducted in the State of São Paulo to compare the usual method of fertilizing potatoes, which consists in the addition of the NPK-mixture to the furrows, with the application of the total dose of nitrogen as top-dressing, and with treatments in which only one or two thirds of that dose were topdressed, the remaining being applied in the furrows. In some treatments one third of the dose was split and sprayed six times throughout the growing period. The total dose, of nitrogen, which was used as urea, corresponded to 80 kilograms to the hectare. The average response to nitrogen, of only + 7% where it was applied by the usual method, increased to +30 and +32% in the treatments where the whole or part of its dose was top-dressed. The highest response, corresponding to +39%, was obtained with the application of one third each in the furrows, as top-dressing, and in solution; however, this treatment comprised eight operations and seems to be suitable only to particularly intensive farming. Based on the observations made during the experiments, the authors believe that, even without the help of liquid applications, the average effect of nitrogen would have been appreciably higher if the initial parcel had not been applied in contact with the seedpieces and top-dressing had not been so delayed as it was.; in some experiments.