Nitrogen has strong impact on potato yield and its effects on plants can be evaluated by specific nutritional diagnostic techniques. The objective of this work was to determine the optimum economical N rate for tuber yield and to estimate the critical value of plant N indices in leaf of two potatoes cultivars. The experiment had a 4×2 factorial in a completely randomized block design with four replications, with four N levels (0, 100, 200 e 400 kg ha-1 of N, pre-planting applied […]