| ABSTRACT Proposing sufficiency ranges and critical levels is an important technique for correct evaluation of leaf nutrient diagnosis. In this study, the objective was to propose critical levels and sufficiency ranges of macro- and micronutrients for the diagnostic leaf of cowpea, collected at flowering, with the results of macro- and micronutrients and productivity in the Northeast of Brazil. The critical level was calculated by the reduced normal distribution and by the boundary line method, which was also used to generate sufficiency ranges. For the critical level by reduced normal distribution, the relationship of the nutrients with 90% of maximum productivity was adopted. For the boundary line, the relationship of the nutrients that are in the upper... |
