Sistema integrado de diagnose e recomendação (DRIS) na cana-de-açúcar

Abstract

Diagnosis and Recommendation Integrated System (DRIS) is one of the various methods used for interpreting leaf analysis, developed by Beaufils (1973), in which direct and inversely comparisons are made between binary ratio of nutrients in samples evaluated and ratio of nutrients in a high productivity population. DRIS indices determination allows the diagnosis of plant nutrient status, whether it is deficient, balanced or excessive, independently of its critical concentration. Thus, this study aimed to establish DRIS indices to sugarcane for the following elements: N, P, K, Ca, Mg, S, Fe, Zn, Cu, Mn, B. Samples were collected from a commercial farming located in Santa Rita, PB. It was collected leaf +3, according to Kuijper system. Then samples were treated and determinate their nutrient content. DRIS norms used were developed for Alagoas to sugarcane. DRIS indices calculated provided a prediction of response to additional fertilizer. For most nutrients it was verified balanced ratios. Ca and Fe were the most unbalanced elements, where the first was classified as excessive and the second, deficient. That may happen because of the mutual effect of both elements, inhibiting uptake. For example, Fe has higher concentration with less Ca in solution, which acts in transportation of molecules and in cell membrane integrity. With Ca deficiency, cell membrane has more permeability, increasing Fe content in plant. Therefore, it is important to identify the most accurate criterion for DRIS norms determination, being preferred the use of specific DRIS norms instead of universal ones. Also the method used to calculate DRIS indices can interfere in the results.