Phosphorus and Potassium Relationships in Southwestern Virginia Coal‐Mine Spoils

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AbstractNutrient deficiencies are commonly reported as a major limiting factor in reclaiming Appalachian surface‐mine spoils. Our objective was to intensively study the P and K relationships of representative mine spoils and contiguous natural soils derived from the Wise Formation in southwestern Virginia. Quantity/intensity (Q/I) relationships for P and K were developed for the major occurring spoils and representative natural soil materials. Sandstones (sublitharenites) and siltstones dominate the Wise Formation and show three phases of cementation—an initial carbonate phase, a second goethite phase, and a third silica overgrowth phase. Total P ranged from 255 to 530 mg/kg in the dominant sandstone and siltstone spoil types, and the majority of P was associated with complex carbonates. Phosphorus in the weathered natural soil materials was dominantly associated with Fe oxides. Phosphorus Q/I analyses coupled with P fractionation data indicate that fixation by Fe oxides is the most likely cause of P deficiencies in rock spoils derived from the Wise Formation and may be a widespread problem limiting revegetation and reclamation success in the Appalachian region. This problem is difficult to rectify by fertilization; hence, Fe oxide‐rich strata, and spoils derived from them, should be avoided during regrading to optimize surface mine reclamation. Micas and traces of feldspars are the dominant sources of K in the mine spoils. Potassium fixation by weathered mica occurs in natural soils derived from the Wise Formation, but not in unweathered spoils. Nonferruginous rock substitutes for topsoil are therefore superior as a plant growth medium in regard to P and K availability.