Lime Requirement Method Comparison for Use In Mississippi.

Lime is expensive in Mississippi because calcitic and dolomitic materials must be imported. This leads to reluctance to lime soils, yet soil acidity issues plague producers every year through reduced yields due to inefficient nutrient availability in the soil and reduced root growth.  Thus, it is imperative that lime recommendation methods provide accurate results.  The objective of this study was to compare a number of different methods for determining the lime requirement using a variety of Mississippi soils.  Ten soils with initial pH values of 4.33 to 5.26 were collected from the Delta, the Pontotoc Ridge Experiment Station, the Leveck Animal Research Center, and the Beaumont Horticulture Unit. Preliminary Lime Requirements (LR) were determined to a target pH of 6.8 using an average of current methods used by the University of Georgia, the University of Kentucky, and Auburn University. Incubations of six weeks with alternating wetting and drying cycles were conducted with regent grade CaCO₃ added at the rates of 0, 0.25xLR,  0.5xLR, 0.75xLR, and LR to each soil.  Subsamples of the incubated soil were then sent to Mississippi State University, Auburn University, University of Kentucky, University of Georgia, North Carolina State University, University of Florida, and Clemson University public soil testing laboratories for analysis of pH and LR using the routine methods of the respective laboratories. Data from each laboratory was returned to MSU for analysis of LR versus buffer pH. The regression analysis shows that the Sikora II method LR was more highly correlated with buffer than the other methods, including the Modified Woodruff currently used by the MSU ES Soil Testing Laboratory.