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<br /> <br />-34- <br />Potted ponderosa pine were also planted on a graded area of the <br />spoils. These were put out late in the season and made Little growth. <br />Future Work <br />The factor mos[ limiting to plant growth on the gray spoils ap- <br />pears to be a severe deficiency of plan[ available P. Fertillzacion <br />has not helped the sitctation, probably because of three Factors: <br />I) the steep banks and coarse nature of the spoils make it difFicult <br />to mix the P fertilizer into the spoils; 2) the added P may be rapidly <br />transformed in the highly calcareous spoils to chemical fotzns not <br />available Co seedlings; 3) the spoils are coarse and have a poor <br />moisture environment Eor herbaceous seedlings. <br />Intensive treatments such as mulching, sprinkling, and manure <br />c.•ould undoubtedly help in establishing herbaceous species. However, <br />coarse-textured gray spoils may be better adapted to woody species, <br />so additional work and observations are suggested on these species <br />before 1nCensive work on herbaceous species establishcuenC is begun. <br />URANIUM MINING SPOILS - MAYBELLB <br />Background and Observations <br />These spoils are sandy overburden removed in open-pit mining <br />for uranium in the Brown's Park geological formation in northwestern <br />Colorado. The spoils are unconsolidated sands in piles up to 100 <br />feet high with some nearly level areas of 2-20 acres on the top:>. <br />The tops of the piles are wind stripped, and the re .are accumulations <br />of wind blown sand nn the east and south side of the piles. 'Iln~ <br />spoils covering an area of several hundred acres are located about <br />four miles east of Maybelle, north of U. S. Highway 40. 17ie average <br />annual precipitation in the area is abaut 12 inches; the elevat~.on <br />is about 6000 feet. <br />toning ceased in the early 1960's, and crested wheatgrass was <br />seeded on the spoils in Chose areas where farm machinery could be <br />used. In some places a Fair stand of crested wheatgrass has been <br />established, but individual plants are small wiL-h poor vigor. 7'he <br />native vegetation on the deep sandy soils in the area is dominated <br />by big sagebrush, Grasses in the understory arc western wheatgrass, <br />Indian ricegrass, and needle and thread. There are some stands of <br />bittcrbrush near the west end of the disturbed area. Big rabbit- <br />brush is a major shrub along roadsides. In the sununer of 1969 there ~, <br />was a thick stand vP Russian thistle almost everywhere on [lie spoils, <br />but the thistle grew only a few centimeters in height because of the i <br />low fertility conditions. Rabbitbrush and big sagebrush have seeded <br />Ln on the spoils in places, and on north slopes have established i <br />fair stands. Once established these species have made good growth <br />despite the low fertility of the spoils. , <br /> <br />