A study of methods of measuring exchangeable aluminum and their correlation with root damage from aluminum toxicity

Although it is known that aluminum ions are toxic to plants, very little is known about the quantity of exchangeable aluminum needed to produce damage. The purpose of this study was to evaluate three common measures of exchangeable aluminum and to correlate the amounts measured with plant root damage. Exchangeable aluminum was measured by titration of the whole soil, fluoride titration and colorimetric determination. All three determinations were found adequate for pre-diction of aluminum damage. There is a correlation between pH and exchangeable aluminum, but it is not adequate for prediction purposes. It was found that root damage was likely if more than two meq/100g of exchangeable aluminum were present and the pH was less than five. The existence of organic matter-aluminum complexes in the soils studied was not shown.