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~~'hcn disturbed or cleared, their susceptibility to both wind and water erosion increases, although their <br />• natural coarse cloudiness tends to moderate wind erosion. <br />Some tendenry toward mass movement is seen in the soils of this mapping unit, particularly in the <br />southwestern part of the mine plan area. The potential for such movement is considered moderate under <br />normal conditions and could become greater iF additional moisture is incurred, particularly if natural <br />vegetative cover is destroyed or reduced. <br />Chemical Properties and Natural Fertilirv -These soils are only moderately weathered and, with the <br />exception of a few places, they are calcareous throughout. Accumulation of secondary carbonate in <br />definite genetic horizons has not occurred except under a few of the more strongly developed soils having <br />weak B horizons. Although they have free carbonate throughout the root zone, excess calcium or <br />maencsium carbonates arc not a problem to soil fertility. <br />Sodium or other soluble salts were not observed to have concentrated in detrimental amounts except <br />+ahcrc these soils were associated with seepage. (See ranges of soil properties used in mapping). The <br />occurrence of some evidence oC detrimental salinity in areas of these soils does occur and makes them <br />somewhat suspect. <br />Natural fertility levels for the soils of this unit are considered moderate. Total vegetative production is <br />lo+vcr than for some of the darker soils of comparable texture occurring at higher elevations, but this is a <br />function of soil moisture supply rather than nutrient level. With the exception of nitrogen, no critical <br />deficiencies of plant nutrients were noted in the field, but the soil analysis indicates some evidence of <br />phosphorus deficiency (Exhibit 26). In their natural start, nitrogen supplies seem to be adequate but if <br />any operation involving the loss of the surface horizon (A horizon) is planned, a temporary fertilization <br />program including nitrogen and phosphorus would assist in revegetation procedures. <br />• t\4apninc Unit Number 6 - Shallow (less than 20 inches to bedrock), dark to light colored, loamy to <br />clavcy, undeveloped to moderately developed soils ranging in degree of soil horizonation from soils with <br />only slightly darkened surface horizons to soils with dark surface horizons and thin but moderately well <br />developed subsurface horizons of silicate clay accumulation. This complex group occurs in pare of the <br />study area having a mean summer soil temperature (June, July, and August averages measured at 20 inches <br />or at bedrock) of 59°F or warmer. <br />Classification of Major Comnonents -The components listed below comprise the major part of the <br />mapping unit: <br />A. Torriorthentic Haplustolls (Chestnut Regosols). <br />1. Loamy, mixed, mesic, shallow family. <br />(Trelona Series) <br />2. Clayey, montmorillonitic, mesic, shallow family. <br />(Series unknown) <br />Aridic Haplustolls (Chesnut Regosols). <br />1. Loamy, mixed, mesic, shallow family. <br />(Series unknown) <br />2. Clayey, montmorillonitic, mesic, shallow family. <br />(Series unknown) <br />C. Lithic Haplustolls (Chesnut Lithosol). <br />1. Loamy, mixed, mesic family. <br />(Santana Series) <br />• 2. Loamy-skeletal, mixed, mesic family. <br />(Boller Series) <br />