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.
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