2002-07-08_GENERAL DOCUMENTS - M2002004 (4)

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1 1 1 1 1 1 1 1 1 i 1 1 1 ' ABSTRACT 1 1 COLORADO SCHOOL OF MINES RESEARCH INSTITUTE Fourteen field plots were established at active coal mines in the Northern Great Plains. A wedge was cut into spoil and backfilled with soil; soil depth ranged from 0 to 152 cm over a linear distance of 15 m. Perennial grasses were planted in each plot, and production was measured from 1978 to 1981. Based on spoil traits and biomass response patterns, plots were grouped into four types. Spoil for Type I plots was near neutral, slightly saline, nonsodic, and clay loam in texture. Perennial grasses reached maximum production with approximately 50 cm of soil depth. Spoil for Type II plots was characterized as sodic and fine textured; soil -depth requirements averaged 83 cm for maximum pro- duction. Spoil for Type III plots was characterized as strongly acid, and pro- duction increased throughout the soil -depth range tested. Spoil for the Type IV plots was similar to soil in chemical and physical traits; there was no produc- tion response to soil depth. Soil -depth requirements were also dependent upon precipitation and species. In general, soil -depth requirements decreased in dry years and with use of intro- duced species. An appendix contains data evaluations on an individual plot basis.