Selection of chemical extractors for the evaluation of availability of zinc in soils in the state of São Paulo, Brazil

Abstract

The purpose of this study was to evaluate methods for predicting availability of Zn in soils. Surface soil samples representing "Podzolized soils from Lins and Marília var. "Marília" and var. "Lins", medium texture Dark-Red Latosol, Dusky-Red Latosol and "Terra Roxa Estruturada", were gathered from fields in Jaboticabal, SP, Brazil. Corn was used as indicator plant in a greenhouse experiment. Availability of Zn was determined with: 0.5 M CaCl₂, 2.0 N MgCl₂, N CH₃COONH₄ (pH 6.0 and 4.8), 0.05 and 0.1 N HCl, 0.05 N H₂SO₄, 0.005 M DTPA (pH 7.3 and 6.0), 1.0% Na₂-EDTA, 0.01 M EDTA + 1.0 M (NH₄)₂CO₃ (pH 8.6) and 0.02 M EDTA + 0.5 M CH₃COOH + 0.5 M CH₃COONH₄. By using the simple correlation coefficients (Zn extracted from soils x absorbed by plants) it can be concluded that the complexant agents and acid solutions showed to be efficient. The salt solutions showed low extraction capacity, low correlation coefficients and less accuracy. By considering aspects as accuracy and easy management DTPA pH 7,3 and Na₂-EDTA can be indicated as the most apropriate (r values, respectively, 0.873** and 0.868** and V.C. 7.52% and 7.98%).