Evaluation of Rapid Methods for Determining Lime Requirement Using East Texas Soils.

Several methods have recently been developed for determining the lime requirement (LR) of the low buffering capacity soils in the southeastern region of the U.S.  These methods are replacing the original Adams-Evans method (A-E) because it contains para-nitrophenol, a hazardous material requiring expensive disposal measures.  The Modified Adams-Evans (M A-E) and Moore-Sikora methods are modifications of the original A-E method using non-hazardous buffers as replacements for the p-nitrophenol.  Both methods use the original A-E equations and relationships. The University of Georgia (UGA) uses a single addition calcium hydroxide titration in combination with a calcium chloride salt pH.  These four methods were compared using 51 soils from east Texas for which a standard lime requirement (SLR) based on both a calcium hydroxide titration and incubation had been determined.  Soil pH was determined using 1:1 and 1:2 soil to solution ratios of both deionized water or 0.025 M CaCl₂ (salt pH).  The original A-E method had an R² value of 0.87 when regressed on the SLR and over estimated LR by approximately 227 kg ha^-1. The Moore-Sikora had an R² value of 0.82 and over estimated LR approximately 309 kg ha^-1. The UGA had an R² value of 0.74 and under estimated LR approximately 83 kg ha^-1. The M A-E had an R² value of 0.67 and over estimated LR approximately 327 kg ha^-1.  Use of 1:2 ratio pH and salt pH tended to improve estimates of lime requirement.