The SMP buffer contains p-nitrophenol and potassium chromate, both hazardous substances. A solution without toxic substances, the so-called Santa Maria buffer (TSM) was developed to reproduce performance of the SMP buffer used to estimate potential acidity of soils in Rio Grande do Sul and Santa Catarina (SMP-RS/SC). Acid titrations of the SMP- RS/SC buffer and various mixtures of the components of the new buffer were performed, using multiparametric regression analysis to obtain the optimal TSM composition. The efficiency of TSM in reproducing SMP-RS/SC was tested in 21 soils from Rio Grande do Sul and the Cerrado. The potential acidity was measured by wet incubation with calcium carbonate. The soil-buffer pH obtained with TSM and the SMP-RS/SC pH values were similar, and consequently the values of potential acidity and lime recommendations were similar as well. The TSM can be used instead of SMP-RS/SC, without the need to change laboratory interpretations to estimate the potential acidity or lime requirement of soils.
TSM solution; chromium; p-nitrophenol; hazardous wastes
