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• The soils of this unit have moderate shrink/swell ratios. Total potential extensibility fora 40-inch section <br />ranges Uom U.8 to 2.0 inches. <br />In their natural state, these soils are not subject to accelerated erosion by either wind or water unless <br />natural vegetation has been destroyed or depleted. It cleared and disturbed, they are moderately <br />susceptible to mass movement especially when very wet. <br />Chemical Properties and Natural Fertility -These soils are moderately weathered, maturely developed <br />units having genetic soil horizons of silicate clay accumulation (B2t horizons) but normally lacking <br />horizons of secondary carbonate accumulation. The soil solum (A and B horizons) is neutral to mildly <br />alkaline in reaction while the C horizon is neutral to moderately alkaline and may contain some free <br />carbonate. Under such conditions, the cation exchange complex (portion of the soil having an ability to <br />hold and exchange cations) is base saturated with the calcium cation, but there is not enough free calcium <br />and magnesium carbonate to seriously depress the availability of other plant nutrients. Natural fertility <br />levels arc high in the upper horizons of the soil, gradually decreasing with depth as organic content <br />decreases. Nitrogen supplies and availability arc closely related with the amount and decomposition of soil <br />organic matter. Any practice that alters the amount of soil organic matter or causes more rapid <br />decomposition oforganic matter will directly affect nitrogen levels in the soil. <br />Nn evidence of deficiencies of essential plant nutrienu or trace elements is noted, but evidence of <br />borderline phosphorus deficiency is indicated by the soil anah5is (see Exhibit 26). Temporary fertilization <br />programs (or disturbed areas that arc being revegetated should include supplemental additions of nitrogen <br />and phosphorus to insure the best possible seedling growth and vigor. <br />MappinC Unit Number X30 -This mapping unit has the same description as mapping unit number 30 <br />• Classification of Maior Components -The components listed below comprise the major part of the <br />mapping unit: <br />A. Argic Cryoborolls (Chernozem). <br />1. Fine-loamy, mixed family. <br />(Kimmons Series) <br />(Inchauspic Series) <br />(Gclkie Series) <br />B. Arctic Pachic Cryoborolls (Chernozem). <br />1. Fine-loamy. mixed tamily. <br />(Bathos Series) <br />(Bondurant Series) <br />Extent and Alaior Areas of Occurrence Mapping unit number X_'t0 has a large total acreage and occurs <br />throughout the mine area at elevations greater than 7,800 feet. I,are_st areas occur in the southern, <br />central, and eastern parts of the mine area. <br />Characteristic Tonprranhv -These soils are considered the normal soils of the colder parts of the mine <br />area and occur on moderately to steeply sloping hill and valley topography. Typically they occupy side hill <br />locations, but unless bedrock is close to the surface, they occur on hill and ridge crests as well. <br />Slopes range from about 3 to 6U percent. <br />Physical Pro t~Crties -The soils of mapping unit number X_'i0 have for the most part the same physical <br />• propcnics of the soils in mapping unit number 30. <br />