COMPARISON OF ALUMINUM SPECIATION IN SOIL SOLUTIONS EXTRACTED BY BATCH AND COLUMN METHODS

Abstract

Soil solutions from an Orthic Ferro-Humic Podzol and a Typic Humisol were extracted using a soil to solution ratio of 1:10 by the batch and column procedures. The aluminum speciation in the extracts was determined by measuring three forms of dissolved aluminum (uncomplexed monomeric, total monomeric and total reactive). The two methods of extraction gave different results. For most of the mineral horizons and the moderately to well-decomposed organic horizons the batch method tended to extract more dissolved aluminum, particularly in uncomplexed monomeric form. The greatest differences between the two methods were for the lowest bulk density materials, the L and F horizons of the Podzol and the Of of the Humisol. The variations were due to channelling in the column and the inability of the shaker to assure good mixing between the soil and solution. It is concluded that the batch method is best suited for routine laboratory analyses. Key words: Soil solution chemistry, Podzols, Humisols