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

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6 With exception of the Cordero and Big Sky plots, one plot was constructed at each mine. Replicated plots were constructed at the Cordero mine, and two plots, one using overburden spoil and a second using interburden spoil, were constructed at the Big Sky mine. Replicated plots were also constructed at the Belle Ayr mine in the fall of 1980, but at the time of writing this report, there were essentially no data available from these plots. SEEDBED PREPARATION Prior to cultural operations, a sample of spoil and one of soil were taken from each plot, placed in a cloth bag, and air dried. In the laboratory, these samples were sieved to remove particles larger than 2 mm in diameter, and, for certain laboratory analyses, portions were ground to a nominal 150 mesh (0.105 mm). The samples were then analyzed using standard agronomic methods as described in Appendix A. Each plot was fertilized with N and P immediately preceding seeding; reclam- ation research has demonstrated that N and P fertilizer increase both aboveground and belowground biomass (Holechek et al., 1981). For those plots located north of Gillette, Wyoming, 3 kg of superphosphate (equivalent to 130 lb P /acre) and '3 kg of ammonium nitrate (equivalent to 95 lb N /acre) were applied to each plot. Due to the possibility of increasing the osmotic stress to an undesirable level, the rate of N fertilizer application was reduced to 1.5 kg per plot (equivalent to 47 lb N /acre) for those plots south of Gillette. The rate of P application was not changed for these plots. The fertilizer was broadcast on the surface and rototilled into the surface 15 cm of soil or spoil. However, when soil depth was less than 15 cm, the fer- tilizer was raked into the soil to a depth of 3 to 8 cm. Each plot was then raked and large clods and rocks that would interfere with planting were removed. A roller weighing approximately 40 kg was pulled across the plot to produce a firm seedbed. SEEDING The five different species of perennial grasses used in this experiment are as follows: Common Name Crested Wheatgrass Pubescent Wheatgrass Thickspike Wheatgrass Western Wheatgrass Green Needlegrass COLORADO SCHOOL OF MINES RESEARCH INSTITUTE Variety Nordan Luna Critana Rosanna Lodorm Scientific Name Source Agropyron cristatum Agropyron trichophorum Agropyron dasystachyum Agropyron smithii Stipa viridula W. Kansas E. Montana E. Montana E. Montana E. Montana Prior to seeding the green needlegrass, the seeds were stratified by soaking in water for 12 hr followed by storage in the dark at 4 °C for 10 days. To establish a vegetative constant, crested wheatgrass was planted in all plots. This species appeared best suited, in the authors' opinion, to tolerate the range of edaphic and climatic conditions present in the NGP. In the central portion of each plot, seven rows of crested wheatgrass were planted; row spacing was 30 cm. Based on ecological conditions, such as soil type, climate, etc., two other grass species were selected for each plot, and six rows of each of these species were planted.