Evaluation of Modified Mehlich and Sikora Buffer Methods as an Alternative to Modified Woodruff Buffer in Determining Lime Requirement for Missouri Soils

• Published in: Communications in Soil Science and Plant Analysis 2012, Vol.43 (1-2), p.496-505
• Main Authors: Nathan, Manjula V, Sun, Yichang, Scharf, Peter C
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alkalies; Biological and medical sciences; buffers; calcium carbonate; calcium chloride; Environmental Protection Agency; Fundamental and applied biological sciences. Psychology; Lime requirement; Mehlich buffer; Methods; Sikora buffer; soil; Soil science; Soil testing; wastes; Woodruff buffer
• ISSN: 1532-2416; 0010-3624; 1532-2416; 1532-4133
• DOI: 10.1080/00103624.2012.641843

The modified Woodruff buffer (MWB) test is used to determine lime requirement (LR) for Missouri soils. Though this method is proven to work for Missouri soils, it uses p-nitrophenol, which is a hazardous substance. Soil-testing laboratories are under increasing pressure to reduce hazardous wastes, which must be collected and disposed of following U.S. Environmental Protection Agency protocols. The goal of this study was to evaluate the modified Mehlich buffer (MMB) and the Sikora buffer (SB) as alternatives to the MWB in determining the LR for Missouri soils. Thirty soils were collected from major agricultural areas in Missouri, treated with calcium carbonate (CaCO₃), and incubated for 90 days. Soil pHₛ [0.01 M calcium chloride (CaCl₂) 1:1] was regressed against CaCO₃ rate, and the actual LR was estimated for each soil to raise the soil pHₛ to target levels of 5.8, 6.3, and 6.8. The MWB, MMB, and SB pHs were regressed against the actual LR for all 30 soils to evaluate the effectiveness of each test for estimating the LR. The MMB and SBs were found to be as good as or better than MWB in predicting LR in Missouri soils. Both buffers (MMB and SB) were found to be equally effective in generating accurate estimates of the LR to raise soils to pHS 5.8, 6.3, and 6.8 (for pH values 5.8: R² = 0.76, 0.82, 0.81; for pH values 6.3: R² = 0.80, 0.88, 0.86; and pH values 6.8: R² = 0.77, 0.89, 0.87 for MWB, MMB, and SB, respectively). A test to evaluate the stability of the buffers over time indicated that MMB had the shortest bench life (about 21 days) when compared to the MWB and SB, thus making it less feasible for use by soil test laboratories. Based on performance and stability, SB is a better alternative than MWB for Missouri soils.