An Improved Woodruff Buffer for Estimation of Lime Requirements

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Abstract
The dominant quick‐test method of estimating soil lime requirements in the USA Corn Belt and adjacent area is the Shoemaker, McLean, Pratt (SMP) buffer method. This work was done to compare an improved Woodruff buffer with the SMP buffer to determine which most accurately estimated soil lime requirement. This study used a Ca(OH)2‐CaCl2 soil titration procedure and incubation of soils with finely ground, chemically pure CaCO3 to compare the accuracy of the original Woodruff procedure, the SMP single buffer procedure, and the new Woodruff procedure in estimating the lime requirements of 89 soil samples. The results supported 1961 findings by Ohio workers that the original Woodruff procedure drastically underestimated lime requirements. The results also supported the literature that the SMP procedure underestimates low lime requirements. The SMP tended to overestimate high lime requirements. Based upon the results of this study, the new Woodruff procedure was a better predictor of lime requirements than the SMP procedure.