Soil Biological Properties Before and After Revegetation of An Acid Mine Drainage Kill Zone Using Minimal Inputs of Lime and Compost.

Hundreds of thousands of acres in Pennsylvania and other coal producing states are wastelands due to damage from acid mine drainage (AMD).  AMD is created when previously buried iron and sulfur minerals are exposed to air during the coal mining process, generating a highly acidic, iron-rich solution that eventually ends up in our water supplies and degrades our soils.  The AMD kill zone in this study is located in Clearfield County, PA and has been barren for at least 100 years.  The severe acidity of precipitated “iron crusts” at this site provides very unfavorable conditions for plants to grow and survive.  Severe erosion by overland flow of water from the old mine shaft has resulted in formation of deep channels in an irregular terrain.

 Replicated plots in three zones were established by incorporating lime and three different treatments of compost. Then, a grass mixture was broadcasted and rolled in.  The plots were then mulched with straw to enhance germination and preserve soil moisture.  For two growing seasons the following properties of unplanted and planted soils were measured: culturable microbial populations (R2A plates), microbial biomass carbon (chloroform fumigation extraction), respired CO₂ (soil incubation), and soil pH and EC.  Vegetative measurements included:  total biomass, percent ground coverage, and species composition.  A bench scale column study of plant growth in materials from each of the three zones was also conducted in the greenhouse.

 Our findings showed significant differences for the three different zones in plant and microbial responses to lime and compost additions. The best plant response was observed in yellowish-grey zones which had higher pH, indicating that removal of iron crusts prior to planting facilitates plant growth. This study provides evidence that minimal additions of organic matter and lime are effective in starting the revegetation process in AMD kill zones.