Abstract

MAIA, Celsemy E.; MORAIS, Elís R. C. de  and  OLIVEIRA, Maurício de. Critical level through the reduced normal distribution approach: a new proposal for interpretation of foliar analysis. Rev. bras. eng. agríc. ambient. [online]. 2001, vol.5, n.2, pp. 235-238. ISSN 1807-1929.  http://dx.doi.org/10.1590/S1415-43662001000200010.

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 P_r 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.

Keywords : foliar analysis interpretation; critical level; normal distribution.