Estimativa da acidez potencial dos solos do estado de Mato Grosso com base em métodos tampões

Abstract

The estimation of the H+Al values by buffer methods must be regionally calibrated. The state of Mato Grosso does not have an official method for this analysis, instead using equations from other regions, which can lead to mistaken recommendations for soil acidity correction. Therefore, the objective of this work was to calibrate and compare various buffer methods to estimate the contents of H+Al in the soil classes representative of the ecoregions of the state of Mato Grosso. For this purpose, the state was divided into nine ecoregions and soil samples were collected from the arable layer in each one. After chemical and granulometric characterization, the levels of H+Al of 196 samples were determined by the calcium acetate method and the equilibrium pH of the soil:CaCl2 suspension and buffer solution was measured by the SMP, TSM and Sikora methods. The pH values of the buffers and H+Al levels obtained by the calcium acetate method were submitted to regression analysis to choose a mathematical model able to estimate the H+Al values of the soil samples. The logarithmic nonlinear equation H+Al (cmolc dm-3 ) = 53.105 - 26.54 ln(pHSMP) (R2 = 0.91**) provided the best estimate of the H+Al values of the typical soils found in Mato Grosso. Besides this, when comparing the proposed equation with those of other Brazilian states, we found that using non-calibrated equations for the state leads to underestimation of the liming recommendation. The TSM method is more recommended than the Sikora to replace the SMP method in soil analysis laboratories in the state and has the added advantage of not generating polluting residues. Finally, we recommend conducting further experiments with soil samples from the state to validate the liming recommendations based on buffer methods.