This study develops a methodology through a statistical method, for the determination of critical level in foliar analysis. The obtaining of the critical level with the continuous distribution of probability is a new proposal for foliar analysis interpretation, based on the reduced normal distribution. For this purpose it is necessary to have data of productivity (P) and of Q, defined as the relationship between P and n i (Q = P/n i), where n i is the content of the nutrient for which critical level is to be found. Initially Pr which represents 90% of the maxim, is calculated with the equation P(90%) = 1.281552s1 + x1 and for the calculation of Q 90% of the maximum value with the equation Q = 1.281552s2 + x2 where x1 and s1 are the arithmetic average and the standard deviation of P and x2 and s2 the average and the standard deviation of Q. The critical level is obtained by NCi = (1.281552s1 + x1)/(1.281552s2 + x2). The critical level methodology of the continuous distribution of probability allowed the calculation, for the coffee crop, of critical values within range of those recommended in the literature.
foliar analysis interpretation; critical level; normal distribution