The potential acidity is important because it is used in the determination of base saturation and the estimation of lime requirement. The objective of this study was to establish a regression equation to estimate the potential acidity with the SMP-pH measured in water under agitation of the SMP equilibrium solution with soil samples from the Jequitinhonha Valley, Minas Gerais State, Brazil. The H + Al concentration measured by 0.5 mol L-1 calcium acetate pH 7.0 and SMP pH were determined in 50 soil samples at the soil fertility laboratory of the UFVJM (Federal University of the Jequitinhonha and Mucuri Valleys). Their pH in water ranged from 4.0 to 7.6, organic carbon concentration varied from 1 to 29 g kg-1 and the clay content ranged from 100 to 810 g kg-1. The potential acidity, expressed in cmol c dm-3, can be estimated by measuring the SMP pH using the equation: Ln (H + Al) = 8.26 - 1.124312 pH SMP (R² = 0.97).
soil pH; lime requirement; buffer solution; H + Al
