Rev. Bras. Ciênc. Solo.2022;46:e0220125.

ISSUE Cover

Base saturation is an inadequate term for Soil Science

Tales Tiecher , Luke Gatiboni , Danilo Rheinheimer dos Santos , Carlos Alberto Bissani , Amanda Posselt Martins , Clesio Gianello , Deborah Pinheiro Dick , Edson Campanhola Bortoluzzi , Pedro Alexandre Varella Escosteguy , Leandro Souza da Silva , Gustavo Brunetto , Fábio Joel Kochem Mallmann , Volnei Pauletti , Cledimar Rogério Lourenzi , Rogério Oliveira de Sousa, Filipe Selau Carlos , Antônio Carlos Azevedo

12/Dec/2022

DOI: 10.36783/18069657rbcs20220125

ABSTRACT

Bases are chemical species that donate electrons, accept protons, or release hydroxyls (OH^–) in aqueous solution. In Soil Science, “base saturation”, “exchangeable bases” or “basic cations” has been widely used to distinguish Ca²⁺, Mg²⁺, Na⁺, and K⁺ from H⁺ and Al³⁺ cations. This terminology is confusing since none of these cations are truly a base in chemistry sense. However, in the absence of the proposition of a correct term, the term “base saturation” remains in use nowadays, causing confusion among students, professionals, and even among professors and researchers in Soil Science, as it leads to the erroneous interpretation that the soil acidity can be corrected by adding these cations to the soil. Here, we present the historical background of this nomenclature and a theoretical foundation that justifies the abolition of the use of these terms in Soil Science. We consider that the most correct is to call it “Ca-Mg-K-Na saturation”, which, despite being long, would refer directly and without any misinterpretation of the terminology. In Soil Fertility, the “base saturation” is often calculated only as a function of the sum of Ca, Mg, and K, since the Na content is negligible in most tropical and subtropical soils. Thus, one could use the term “Ca-Mg-K saturation”. Likewise, it is also suggested to abolish the use of the term “sum of bases” and use the term “sum of Ca-Mg-K” or “sum of Ca-Mg-K-Na” instead when necessary.