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450

Lime Requirement

Physio Chem: LiR

Summary

Buffer pH is the measure of a soil’s active and reserve acidity (i.e., buffer capacity) and is used to estimate lime recommendations.  The method is based on the Shoemaker, McLean and Pratt (SMP) method using the reaction of soil buffered acidity with a chemical buffer resulting in a change in the pH of the buffer.  This method is used for estimating exchange acidity including that associated with exchangeable aluminum.  Standard calibration curves exist for liming based on a SMP value to a desired pH for soil groups.  The lime requirement reported for this test is based on a desired pH of 7.0.  The result is reported in T/A/8in (tons per acre of 100% CaCO3 required based on an 8 inch furrow slice weighing 2.4 million pounds).  The table used is from Soil, Plant and Water Reference Methods for the Western Region, 2003.

Sample amount requested:  15 g
Questions concerning limited sample size can be answered by the UC Davis Analytical Laboratory.

Shoemaker, H. E., McLean, E. O. and Pratt, P. F. 1961. Buffer methods for determining lime requirement of soils with appreciable amounts of extractable aluminum. Soil Sci. Soc. Am. Proc. 25:274-277.