Buffer Methods for Determining Lime Requirement of Soils With Appreciable Amounts of Extractable Aluminum

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Abstract
Studies were conducted to determine why certain soil test methods fail to indicate the actual lime requirement in many Ohio soils. Samples of 14 soils from various areas of the State were collected for study. The soils were incubated with various rates of applied CaCO3 to determine actual lime requirement of each soil. Attempts were made to find laboratory methods that would accurately indicate the lime requirement of each. For these soils the Woodruff method had indicated only about half the amount of the actual lime requirement. The Mehlich triethanolamine method indicated accurately the amount of lime required for the unlimed acid soils. However, this method indicated too high a lime requirement on soils partially limed. Subtraction of the acidity measured above pH 6.8 by the triethanolamine method and then addition of the extractable Al, gave a very good indication of lime needs on all soils not limed above neutrality regardless of lime additions. Addition of extractable Al to total bases and triethanolamine‐measured acidity to pH 6.8 gave nearly constant cation‐exchange capacities of soils regardless of lime additions. These studies have led to development of an improved soil test buffer method for rapid routine laboratory analyses. It appears to be adequate for indicating lime needs of soils regardless of extractable (soluble) Al present.

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