Aluminum species and activity in sandy soil solution with long history of pig slurry addition

Abstract

The application of slurry may reducing the bioavailability the aluminum (Al), by increasing the concentration of soluble ligands. The study aimed to assess how the long-term use of pig slurry is able to modify the exchangeable Al content, activity, and distribution of chemical species of Al in soil solution. Soil samples of Typic Hapludalf were obtained from an experiment conducted for eight years with 19 pig slurry applications of 0, 20, 40 and 80 m³ ha^-1 at the Federal University of Santa Maria, in Santa Maria, Rio Grande do Sul (RS), Brazil. The soil samples was collected stratified in layers, to determine exchangeable Al content and extract the solution. The soil solution concentrations of the main cations, anions, dissolved organic carbon and pH were assessed. The distribution of the chemical species of Al and the activity of the Al³⁺ species was obtained through Visual Minteq software. The history of pig slurry applications did not modify the exchangeable Al content and had little impact on Al³⁺ activity in soil solution. Pig slurry applications reduce the phytotoxic potential of Al by increasing the concentration of soluble inorganic ligands, thus increasing the proportion of AlHPO₄⁺ and AlSO₄⁺ in soil solution