Characteristics of Coal Mine Overburden Important to Plant Growth

Abstract

AbstractThis investigation was conducted to determine physical and chemical properties of mineland overburden, to evaluate plant growth in these materials, and to identify properties of overburden materials before mining that may serve as predictors of potential plant growth.Eighteen overburden materials from five surface coal mines in the Illinois coal basin of southwestern Indiana were sampled and analyzed for 20 physical and chemical properties. Twelve were unconsolidated materials, including A and B horizons, lacustrine sediments, and glacial tills, and six were rock strata that break and weather easily. Growth potential for overburden materials, with and without sewage sludge and fertilizer amendments, was evaluated in greenhouse pot culture using alfalfa, wheat, and white pine. Oats yield, and survival and growth of Virginia pine and yellow‐poplar were evaluated for 10 materials in outdoor containers.Regression analysis of plant growth against chemical and physical properties of the overburden materials did not reveal properties that could be consistently used in a formula approach to predicting plant growth potential of the materials. Electrical conductivity of the material extract and water storage capacity were most frequently significantly related to growth. High plant tissue levels of B, Fe, Mn, and Al suggested toxicity problems on some materials. The general ranking of overburden materials evaluated for plant growth potential was lacustrine sedment ≥ A horizons > B horizons = glacial tills ≥ brown shale > sandstone > gray shale > black fissile shales; however, physical properties unfavorable to extraction and replacement of lacustrine material may limit its use under field conditions. Addition of sewage sludge resulted in vastly improved growth of wheat, and to a lesser extent, alfalfa, on most materials in the greenhouse. Fertilization with N‐P‐K was less effective than sludge but usually produced increased plant growth.