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• Physical Properties -The soils of mapping unit number X31 have for the most part the same physical <br />properties as the soils of mapping unit number 31. <br />Chemical Properties and Natural Fertility -The soils of mapping unit number X31 have the same <br />chemical properties and natural fertility as the soils of mapping unit number 31, with the exception of <br />phosphorus deficiency and different laboratory analysis. <br />Mapping Unit Number X32 -Moderately deep (20 to 40 inches to bedrock) and deep (more than 40 <br />inches to bedrock), dark colored, fine to very find textured (35 percent to more than 60 percent clay), <br />immaturely to maturely developed soils usually having continuous horimns of silicate clay accumulation <br />(B2t horizons) but having only darkened surface horizons (A horiwns) over clay textured C horizons in <br />places and occurring in pare of the study area where the mean summer soil temperature (June, Jufy, and <br />August mean temperature measured at 20 inches) is less than 59°F. <br />Classification of Major ComQonents -The components listed below comprise the major part of the <br />mapping unit: <br />A. Argic Vertic Cryoborolls (Chernozem). <br />1. Fine, montmorillonitic family. <br />(Cimarron Series) <br />2. Very fine, montmorillonitic family. <br />(Series unidentified) <br />B. Vertic Cryoboroll (Chernozem). <br />1. Fine, montmorillonitic family. <br />(ICissick Series) <br />• 2. Very fine, montmorillonitic (amily. <br />(Castle Series) <br />Extent and Major Areas of Occurrence -This mapping unit has a small total atteage in the mine area <br />and occurs on the southern extensions of Lion Mesa (Sections 4, 5, and 9; T14S, R90V~. <br />Characteristic Topoeraphy -Mapping unit number X32 occurs on the gently to moderately sloping tops <br />of mesa-like landforms and interfluvial divides where the fine and very fine textured sedimentary bedrocks <br />lie moderately close to the surface. <br />Physical Properties -The soils of this unit are very fine textured and have very wide shrink/swell ratios. <br />These two properties outweigh most of their other physical properties in determining the ability to be used <br />for most purposes. These soils are subject to dense packing if traversed by heavy machinery when moist <br />and are easily puddled to a dense impermeable mass if manipulated when we[. If disturbed when dry they <br />are extremely hard to move and tend to form large extremely hard clods that are very difficult to work into <br />good seedbeds. They can be handled over only a very narrow range of soil moisture without loss of good <br />physical properties. <br />Total extensibility of a 40-inch section is estimated to range from about 3.2 to 8.0 inches. Under normal <br />conditions grumasolic types of genesis (vertical soil movement due to pressures created by expansion of <br />heavy clays against crack fillings) are not pronounced; however, this is only because of the infrequency of <br />wetting and drying. The potential for such movement exists. <br />Because of their large shrink/swell ratios and their extremely fine textures, the soils of this group are <br />considered poor materials for seedbeds. <br />• No evidence of mass movement is seen in these soils but their potential for such movement is great. The <br />present lack of evidence of movement is probably due to the low water intake characteristic of the unit. <br />