Tuesday, 8 November 2005
5

Challenges of Mehlich 3 Extraction for B and Comparison with Other Methods in Boron-Treated Soils.

Sara K. Allen1, Von D. Jolley1, Bruce L. Webb1, Amanda K. Shiffler1, and Vincent Haby2. (1) Brigham Young University Department of Plant and Animal Sciences, Brigham Young University, 253 WIDB, PO Box 5131, Provo, UT 84602-5131, (2) Texas A&M University, Texas Agricultural Expt. Stn., PO Box 200, Overton, TX 75684-0200

The hot water extraction procedure for estimating soil boron (B) availability to plants embodies several potential sources of error, and consequently pressurized hot water and DTPA-Sorbitol are proposed replacements. Recently, Mehlich 3 has been strongly promoted as a "universal" extractant in a wide variety of soils. Thus, this research will compare estimates of plant available B extracted by Mehlich 3 to pressurized hot water, DTPA-Sorbitol and conventional hot water extractions. These comparisons will be accomplished on samples from three experiments on limed, acid loamy fine sand treated with various levels of B: an incubation experiment, an alfalfa greenhouse experiment and an alfalfa field study. We will report correlations observed between extractable B with all extraction methods and rate of applied B for each experiment and report relationships between extractable B and alfalfa B concentration, uptake and yield. However, ICP analysis of B following extraction with Mehlich 3 chemicals has proven difficult because of B contamination within the ICP unit. No such problem was observed with ICP analysis of B with hot water, pressurized hot water or DTPA-Sorbitol extractions. We will report the effects of distilled water, nitric acid and sorbitol solutions used between samples for correcting B contamination. Sorbitol solution is the most effective solution found to alleviate the contamination problem. This contamination problem unique to Mehlich 3 may limit the development of Mehlich 3 as the "universal" extractant.

Handout (.pdf format, 2337.0 kb)

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