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• 1985). Often, the quality of spoil material to be covered by topsoil is <br />the major controlling factor (Schuman and Puwer, 1980; Garth and Martin, <br />1982). Together, the ultimate topsoil replacement depth and resultant <br />spoil quality can greatly influence productivity and longevity of the <br />vegetation established on reclaimed lands (Schuman et al., 1985). <br />Poor quality spoil material niay require more than 60 inches of topsoil <br />and/or subsoil replacement whereas good quality spoil may nut need any. <br />Doll et al. (1984) and Barth and Martin (1982) demonstrated that from 36 <br />to 60 inches of topsoil and/or subsoil was necessary for optinwm <br />production on sodic or acidic spoil. Barth (1984) found that production <br />of perennial grasses on bare spoil with no adverse properties was as <br />great as when spoil was covered with soil of any thickness. <br />In the northern Great Plains, maximum production is generally achieved <br />on suitable spoil when topsoil replacement depths range from 10 to 24 <br />inches. Schuman et al. (1980) showed that 15 inches of topsoil provided <br />• the maximum native forage production, highest infiltration and greatest <br />water holding capacity on reclaimed spoil in Wyoming. Pinchak et al. <br />(1985) also found 15 inches of topsoil to be optimum in Wyoming in terms <br />of seeded species production and limited infestation of non-seeded <br />species. Barth and Martin (1981) showed fine sandy loans topsoil depths <br />to be 10 inches for optimum perennial grass production on nonsaline, <br />nonsodic silt loam spoil in southeastern Montana. In northwestern <br />Colorado, McGinnies and Nicholas (1982) demonstrated with field and <br />greenhouse studies that vegetation stands, herbage yield and root <br />production all increased linearly as topsoil depths increased from 0 to <br />18 inches. <br />DePuit (1984) points out that optimum plant community composition and <br />diversity is often reached at shallower topsoil depths than what is <br />required for maximum production. This phenomenon apparently exists at <br />the Seneca and Trapper Mines. Pfannenstiel (1983) revealed that 6 to 8 <br />inches of topsoil applied to Wedge spoil at Seneca Hine in 1976 has <br />. produced a native looking sagebrush grassland community with a shrub <br />density of 1,450 stems per acre. P.edente and Hargis (1985) demonstrated <br />at Trapper Mine that with the compromise of some aboveground production, <br />9-39 Revised 10/01/86 <br />