The determination of soil potential acidity (H + Al) extracted by the 0.5 mol L-1 calcium acetate solution is a routine analysis in Brazilian soil laboratories. However, due to analytical facilities, it is becoming a regular procedure to estimate the values of potential acidity using the equilibrium pH of the soil suspension with the SMP solution. The aim of this study was to look at the relationship between pH SMP and H + Al in soils of Pernambuco, in order to obtain an equation to estimate the potential acidity. The work was carried out at the UFRPE soil fertility laboratory using 145 soil samples from several regions of the state. The results indicated that the equation H + Al = 0.4837 SMP² - 8.4855 SMP + 38.448 (R² = 0.90), expressing the H + Al values in cmol c dm-3, can be used to estimate the potential acidity using the pH SMP methodology.
soil pH; aluminum; hydrogen; soil testing