Alteration of Microbial Populations in Surface Mine Revegetation and Their Effects on Nitrogen Cycling

Surface mining in the arid west results in soil disruption by alterning structure, water-holding capacity and nutrient availability. Intensive revegetation efforts may end in marginal rehabilitation due to adverse chamical and physical properties of the distrubed soil. Monitoring microbial activitiy and soil chemistry of revegetated and undisturbed areas of a surface mine in Southeastern Montana enabled delineation of major factors participating in soil fertility were determined. In the undisturbed site, the upper few centimeters of the soil profile contained most of the nutrients and the microbial populations. In the revegetated sites, due to mixing of various soil horizons, the concentration of nutirents in the surface soil was absent and microbial activity was consequently low. Laboratory studies indicated the segregation and replacement of A horizon soils restored native soil nitrogen to the upper few centimeters and reduced the need for heavy applications of inorganic nitrogen fertilizer. Also, the addition of manure to the soils increased gross yields and microbial activity. This may be due, in part, to increased availability of phosphorus in manure and to improved physical conditions of the soil with the manure applications