Evaluation of Soil Tests as a Measure of Phosphorus and Potassium Availability in Illinois Coal Waste1
- B. G. Lewis and
- M. Mc Kiernan2
The Mitscherlich-Bray relationship was applied to soil test-extractable P and K in coal waste, and yield of tall fescue (Festuca arundinacea Schreb.) grown in the waste at pH 6.5. The typical exponential function between yield and extractable P obtained with soil-grown plants was not exhibited by the waste-grown plants for dilute acid or acid ammonium fluoride extractants, partly because values > 15 mg/kg extractable P in the waste could not be obtained despite heavy P fertilization. Correlation coefficients (r2) for extractable P in the growth media vs. P concentrations in shoots were 0.45 for the waste, and 0.81 for Elliott silt loam. Results with extractable K and yield on the waste were inconclusive, due to the confounding effect of an apparent Ca interference with K uptake. It is concluded that results of “soil testing” for P and K in coal waste should be interpreted with caution; in some cases, the tests may be inappropriate as indices of available forms of these elements in the waste.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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