Potential acidity is of great importance for the base saturation determination and for the recommendation of liming. The objective of this study was to evaluate the relationship between pH SMP and H + Al contents, in order to establish an equation for the potential acidity estimation of soils from Northern Minas Gerais, Brazil. The H + Al concentration (0.5 mol L-1 calcium acetate pH 7.0) and pH SMP were analysed at EPAMIG/CTNM soil fertility laboratory, in 50 soil samples. The pH in water of the soil samples ranged from 4.6 to 7.8, organic carbon contents varied from 3 to 45 g kg-1 and clay contents from 80 to 610 g kg-1. The potential acidity, expressed in cmol c dm-3, can be estimated by measuring the pH SMP using the following equation: H + Al = 0.00359 + 1556.5806 e- pH SMP (R² = 0.96**)
soil pH; buffer solution; hidrogen; exchangeable aluminum