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Use of Triethanolamine Acetate-Barium Hydroxide Buffer for the Determination of Some Base Exchange Properties and Lime Requirement of Soil¹

ABSTRACT

The use of a triethanolamine acetatebarium hydroxide buffer has been proposed for the determination of base exchange capacity, base and hydrogen saturation, and lime requirements of soil. A 0.2 N solution buffered at approximately pH 8.15 has the advantages of barium hydroxide for the efficient neutralization of soil acids, and the efficient replacement of soil bases, but it has not all the disadvantages of barium hydroxide notably in its reaction with soil components other than base exchange materials, and in its ready formation of insoluble carbonate with carbon dioxide, provided this buffer solution is not raised above pH 8.2 by basic constituents present in the soil or added to the soil. Under these conditions sulfate ions are quantitatively precipitated by the barium and they must be removed from the soil or corrected for.

A procedure is described for the application of triethanolamine acetate-barium hydroxide to the estimation of lime requirement of soil, and involves the determination of barium adsorbed by the soil (base or lime adsorptive capacity at approximately pH 8.15), titratable acidity, and replaceable magnesium.

The barium adsorbed by the soil is determined by the difference in concentration of the test solution before and after treatment of the soil. This is accomplished rapidly and fairly accurately titrametrically using tetrahydroxyquinone (T.H.Q.) as the indicator. This method is considered particularly useful where lime applications based on pH data alone are likely to cause injury (overliming) and where it is essential to consider the nature of the liming material to be added with reference to magnesium deficiencies of the soil.

¹ Contribution from the North Carolina Agricultural Experiment Station, Raleigh, N. C.

² Associate Soil Chemist.