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

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Greenhouse study: Topsoil Spoil Field study: Topsoil Spoil Table 1 Chemical and physical analyses of topsoil and spoil materiel used in the greenhouse and the field studies. Total pHt SAR EC N 6.9 0.04 0.32 2,824 7.0 0.24 0.88 1,826 6.1 0.36 1.40 1,808 7.3 1.27 1.30 998 t Saturation paste. $ Ca, Mg, and Na from saturation paste extract. of winter wheat (Triticum aestivum) and intermediate wheatgrass (Agropyron intermedium); (ii) evaluate the effect of mixing equal parts of topsoil and spoil on the growth of both wheat and intermediate wheatgrass; and (iii) evaluate the effect of N fertilizer on the herbage and root growth of intermediate wheatgrass. The field study was designed to determine the effect of topsoil thickness on the establishment and growth of a diverse mixture of grass, forb, and shrub species. METHODS mmhos/cm ppm The field study was conducted at the Energy Fuels Mine no. 1 lo- cated 32 km southwest of Steamboat Springs, Colo. Soil and spoil ma- terials were obtained from the same area for the greenhouse study. Elevation is 2,135 m, and average annual precipitation is 41 cm. The soil is a Routt loam, which is a fine, montmorillonitic Type Argi- boroll. Topsoil (A horizon) was obtained from an undisturbed sage- brush area. The spoils are from the Williams Fork Formation of the Upper Cretaceous Mesa Verde Group; this formation consists of mixed beds of shale and sandstone. The spoils used in these studies were a heterogeneous mixture of material from the various strata; mixing occurred during mining when the overburden was stripped by a dragline and when the spoil piles were leveled by a bulldozer. Samples of the topsoil and spoil materials used in both the green- house and the field studies were collected for chemical and physical characterization. Percent total N was determined by a modified Kjeldahl procedure (Bremner, 1965), and phosphorus (P) levels were determined by bicarbonate extraction methods (Olsen et al., 1954). Electrical conductivity (EC), Na, Ca, and Mg levels were determined on the saturation paste extract. Partical size distribution was de- termined by the hydrometer method. Greenhouse Study Cans were made of galvanized metal (stove) pipes, 15 cm in diam- eter by 61 cm in length, and were closed on the bottom with a wood plug equipped to allow drainage. The cans were filled with a total of 53 cm of either spoil alone or with a topsoil treatment. Spoil material was passed through a 1.3 -cm mesh screen beforehand in order to elim- inate very large rock materials common to spoil. Topsoil thickness treatments were 0, 10, 20, 30, and 46 cm of top- soil placed on top of 53, 43, 33, 23, and 7 cm of spoil, respectively. To simulate mixing topsoil with spoil, 30 cm of a mixture of 50 topsoil and 50% spoil were placed over 23 cm of spoil. Six replications were made of each of the above treatments. An additional five replications of the 0 -, 10 -, 20 -, and 30-cm topsoil depth treatments received a 112 kg /ha N fertilizer application in the form of ammonium nitrate. Each can was planted with 10 seeds of either winter wheat or inter- mediate wheatgrass on 7 Dec. 1976, and rapid germination followed. Topsoil thickness treatments receiving a N fertilizer treatment were planted with only intermediate wheatgrass. The cans were watered three times a week to above field capacity and allowed to drain; this practice maintained the soil moisture well above the permanent wilting point. The plants were thinned out 28 days after planting to leave the three most vigorous seedlings. 682 J. Environ. Qual., Vol. 9, no. 4, 1980 NaHCO,- extractable P Cat Mg Na Sand Silt Clay meq /liter 40 5.2 3.0 0.1 53 19 28 4 23.2 26.2 1.2 42 30 28 10 5.5 3.4 0.9 66 24 20 5 21.2 7.4 1.4 23 54 23 The greenhouse temperature averaged 22 °C. Sunlight was aug- mented with sodium -vapor lights, and light intensity ranged from a maximum PAR of 1,000 µEinsteins m - ' sec' to a minimum of 100 µEinsteins m sec Daylength was maintained at 14 hours. The first harvest of wheat and intermediate wheatgrass herbage was made on 1 March 1977. At the second harvest, 25 May 1977, the cans were split lengthwise and the soil and spoil washed from the roots. The herbage was separated from the roots, and roots were divided into those growing in the topsoil and those growing in the spoil. All root and herbage material was ovendried at 70 °C for 24 hours and weighed. Data were analyzed by standard analysis of variance and correlation techniques. Tukey's procedure was used where needed to evaluate dif- ferences between means. Field Study The field study was established at the Energy Fuels Mine No. 1 in the fall of 1976. The area had previously been mined, and the spoil material had been reshaped. Topsoil thickness treatments were 0, 10, 20, 30, and 46 cm of topsoil placed over spoil. There were two replica- tions. The plots were drilled- seeded with a seed mixture containing 17 grasses, 8 forbs, and 11 shrubs. Each plot was sampled by locating five permanent points across each plot and sampling within a 60 -cm by 91 -cm area centered at each point. Ratings of percent stand were based on a scale of 0 to 100 (0 indicated no seeded plants were present, and 100 indicated the maxi- mum possible stand existed within the rectangular frame used), and composition by species were determined on 21 June 1978, during the second growing season. RESULTS Chemical and physical analyses of the soil and spoil materials used in both studies indicated that these ma- terials have a relatively high potential for revegetation purposes (Table 1). Salt and sodium levels were low (as indicated by EC and sodium adsorption ratio (SAR) values) and pH values were neutral to slightly acidic. Previous analyses showed that the strata making up the overburden were neither saline nor sodic, nor did they contain any mineral or metal in quantities approaching a phytotoxic level.' P levels, and N levels to a lesser extent, were low in spoil materials. Topsoil materials had a sandy clay loam texture and the spoils had a clay loam texture. Greenhouse Experiment Total herbage production (combined weights of the two harvests) of both species increased linearly with top- soil thickness (r = 0.95). Power et al. (1978) reported similar increases in herbage yields with increased thick- ' Kent A. Crofts, Energy Fuels Corp., personal communication.