The high response of potato to the addition of nutrients to the soil, requires special attention to aspects related to fertility, especially nitrogen (N), because it is the nutrient that causes the greatest impact on productivity. In order to identify the critical content of N in potato in response to the nitrogen doses, we installed an experiment in Perdizes, Minas Gerais state, Brazil, from July to November 2010 using the cultivar Asterix. The experimental design was randomized blocks with five N levels (0, 70, 140, 210 and 280 kg ha-1) and four replications. The N doses were split, applying 20% at planting date and 80% on coverage, along with the operation of ridging thirty days after planting. The rest of fertilization consisted of 400 kg ha-1 P2O5 and 300 kg ha-1 K2O, combined with 30 kg ha-1 of a source of micronutrients. About fifty days after planting date we obtained one sample of leaves of the plots, which were subjected to analysis of N content in leaf tissue. At the end of the crop cycle harvested tubers were weighed and calculated the productivity of the floor area of the parcels being converted into kg ha-1. The critical level was determined as a function of the applied doses, the estimated yield and foliar N. The estimated N that provides the highest yield of potato tubers is 173 kg ha-1, the obtained yield corresponding to 21.8 t ha-1 of tubers. Considering the dose to obtain 90% of the yield (155.7 kg ha-1), the critical leaf N content is estimated to be 67.6 g kg-1.
