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

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ABSTRACT WILLIAM Effects of Topsoil Thickness and Nitrogen Fertilizer on the Revegetation of Coal Mine Spoils' A field study was established at a coal mine site in northwest Colo- rado to measure the effects of 0 -, 10 -, 20 -, 30 -, and 46 -cm depths of topsoil (a fine, monlmorillonitic Typic Argiboroll) on establishment, percent stand, and species composition of a seeded stand. Percentage stand increased linearly from 16.4% on the 0 -cm topsoil treatment to 49.1 on the 46 -cm treatment by the second growing season. A green- house study using topsoil and spoil from the same area evaluated the same topsoil depths with respect to their effects on herbage and root production of Intermediate wheatgrass (Agropyron intermedium) and wheat (Triticum aestivum). Herbage and root production of both species increased linearly with increasing topsoil thickness. Herbage production of wheat was, on the average, 32% greater than that of intermediate wheatgrass; however, root production of intermediate wheatgrass was 78% greater than wheat when grown in topsoil and 145% greater when grown without topsoil in spoil alone. A 112 kg N /ha fertilizer treatment increased biomass (herbage and roots) of intermediate wheatgrass by 74% over similar unfertilized treatments. When 15 cm of topsoil was mixed with 15 cm of spoil (total thickness of the topsoil mixture was 30 cm) in the greenhouse, herbage and root production of intermediate wheatgrass were the same as when grown in 15 cm of topsoil alone. Additional Index Words: reclamation, disturbed lands, overburd- en, root growth, biomass production, northwest Colorado, strip mine. McGinnies, William J., and Paula J. Nicholas. 1980. Effects of top- soil thickness and nitrogen fertilizer on the revegetation of coal mine spoils. J. Environ. Qua1.9:681 -685. Reclamation programs for coal strip mines strive to stabilize the disturbed site, discourage weedy species, and encourage establishment of beneficial perennial plant species. Rapid establishment of perennial plant species on disturbed sites will normally remedy potential problems of site stabilization and competition by weedy species. In some cases, annual small -grain species can rapidly provide the plant cover necessary to prevent ero- sion and runoff and later provide a stubble -mulch in which to seed perennial grasses, forbs, and shrubs (Schuman et al., 1980). Currently, strip mine reclama- tion programs in the West return disturbed sites to either croplands, primarily for dryland production of small grains, or to rangeland, for use by wild and domestic ungulates. Site- specific edaphic conditions will dictate the methods by which any desired plant cover can most successfully be established. One of the most important management practices for establishing any type of vegetation on mine spoils is replacement of the topsoil. ' Cooperative investigations of USDA, SEA -AR, Fort Collins, Colo., and the Colorado Agric. Exp. Stn., Fort Collins, Colo. Pub- lished with the approval of the Director of the Colorado Agric. Exp. Stn. as Sci. Ser. Paper no. 2423. The EPA, the Bureau of Land Manage., and Energy Fuels Corp. also provided funding or other sup- port for this research. Received 24 March 1980. ' Range Scientist, USDA, SEA -AR, and Graduate Research As- sistant, respectively, Crops Res. Lab., Colorado State Univ., Fort Collins, CO 80523. J. MC GINNIES AND PAULA J. NICHOLAS' The replacement of suitable topsoil over reshaped spoil material has increased the success of vegetation establishment on disturbed sites (Dusek, 1975; Farmer et al., 1974; Hodder, 1973; Richardson et al., 1975). Topsoiling usually enhances infiltration because of the organic constituents found in topsoil and its friable, relatively coarse aggregated texture (Power et al., 1974; Hodder, 1977). Topsoil can also serve as a buffer zone when covering sodic spoil materials from which there is an upward migration of salt (Bauer et al., 1978; Power et al., 1976; Power et al., 1978; Ries et al., 1977). In northwest Colorado, replacement of topsoil over spoil did not benefit stand composition and production for several grass species and alfalfa (Berg and Barrau, 1973). When grown in spoil alone, stands were dominated by alfalfa, which was able to produce above- ground biomass comparable to that produced on top- soil, presumably because of its ability to fix N and de- velop a deep root system which can utilize water that in- filtrates deeply into spoils. However, studies in North Dakota (Power et a1.,1976; Power et al., 1978; Ries et al., 1977), Montana (Dusek, 1975; Farmer et al., 1974; Hodder, 1973; Richardson et al., 1975; and Dollhopf et al., 1977), and Wyoming (Schuman and Taylor, 1978) have shown that topsoiling increased grass production over similar nontopsoiled treatments. Current Federal Coal Mine Regulations require that topsoil be removed, stored, redistributed, and adequate nutrient levels main- tained in order to meet postmining revegetation require- ments. Nitrogen deficiency is believed to be a major limiting factor in achieving productivity comparable to that of premining plant communities and in obtaining adequate erosion control on some disturbed sites (Woodmansee et al., 1979). Nitrogen deficiency on disturbed sites may result from insufficient or unsuitable topsoil, acceler- ated soil erosion, the limited success of N- fixing species, prolonged storage of the topsoil, and the mixing of sub- soil materials into the topsoil. On leveled mine spoil covered with various topsoil depths in North Dakota, wheat grain yields increased with increasing topsoil thickness, but were not increased by N fertilization, be- cause adequate N was already present in the soil ma- terials used (Bauer et al., 1978). While several studies have shown that aboveground grass production increases with increased topsoil thick- ness over spoil, little has been reported on the effects of topsoil thickness on rooting patterns. Schafer et al. (1977) found that 3 -4 years were required before root systems of plants grown in mine spoils resemble those in natural soils in weight and distribution. Root growth into spoil materials should contribute to the stabiliza- tion of disturbed sites, enhance soil development pro- cesses, and increase chances of plant survival during periods of drought. Our studies evaluated the benefits of using topsoil on reshaped mine spoils in northwest Colorado. A green- house experiment was designed to (i) determine the ef- fect of topsoil thickness on the herbage and root growth J. Environ. Qual., Vol. 9, no. 4, 1980 681