Aluminum in Soils: I. Extraction Methods and Magnitudes in Clays and Ohio Soils

Abstract

Abstract Various procedures were used for extraction of Al from Ohio soils representing a wide range in extractable Al. One normal NH 4 OAc at pH 4.8 was selected as an extracting solution because of its superiority over Ba(OAc) 2 and BaCl 2 . One normal NH 4 OAc plus 0.2 N BaCl 2 was no better than NH 4 OAc alone. At this pH it extracts enough Al from most soils for accurate measurement with little possibility of damage to the clay crystal. Eight Ohio soils were electrodialyzed and resaturated to various levels with K and/or Ca. Extractable Al was determined in these soils after equilibration. At the zero‐base added level, the extracted Al ranged from 4.7 me. per 100 g. of soil in the Wooster to 19.8 in the Hoytville. Increased saturation with K and/or Ca decreased the amount of Al extracted. Somewhat more Al was obtained from K‐soils than from Ca‐soils even though the pH values of the former were higher. Comparable studies with illite, bentonite, kaolinite, Putnam subsoil clay, vermiculite, and chlorite were also made. The importance of Al at the magnitudes found in the field and laboratory soils is discussed. The general failure of existing soil tests for lime requirement to adequately account for the Al in acid soils was considered. The possibility of Al interfering in various chemical and biological studies is mentioned.