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eood pcrmeabiliry and aeration after disturbance. They are subject to packing if traversed by hea~N <br />• machinery and irreversible puddling if handfed when too u•et. <br />The soils of this unit have moderate shrinkJswell potentials with coefficients of linear extensibility ranging <br />from about 0.02 to 0.05 in most areas, and total potential extensibility within a 40 inch thickness of about <br />0.4 to 2.0 inches. When wet they are moderately slippery and sticky. Disturbed deposits from these soils <br />c:tn generally be worked down into good erosion-resistant seedbeds with conventional machinery and <br />practices. <br />Thcsc soils arc slightly susceptible to water erosion, particularly gullying and rilling. Wind erosion is not a <br />major concern unless native cover is destroyed. No mass movement was noted with the exception of very <br />steep slopes, extremely wet years, and destroyed native vegetation. <br />Chemical Properties and Natural Fcrtilirv - The soils of mapping unit number 4 are only moderately <br />weathered soils and except for the surface few inches in a few localities, they are calcareous throughout. <br />Accumulation o[ free secondary calcium carbonate in particular horizons has not occurred except under a <br />few of the more strongly developed components (Camborthids). Even in those components the calcium <br />atrhonatc accumulation is inconsistent, and should not be a problem in soil fertility. <br />Sodium or other soluble salts were not observed to have concentrated in detrimental amounts. The clay <br />fractions arc dominated by two to one lattice types of clay. <br />Natural fertility levels for the soils of this unit arc about normal for the area. Total vegetative production <br />is lower than (or some o[ the higher lying soil units, but this is considered to be a [unction oC moisture <br />availability rather than fertility. <br />• With the exception o[ nitrogen, no critical deficiencies of plant nutrients are obsen•ed, but some evidence <br />o! deficiency of phosphorus was found in the soil analysis (sec Exhibit 26). In their natural state nitrogen <br />levels appear to be adequate, but if the loss o! surface horizons occurs, a temporary fertilization program <br />including both nitrogen and phosphorus supplements would aid the revegetation procedure. <br />A4anpine Unit Number 5 - Moderately deep (20 to 40 inches to bedrock) and deep (more than 40 inches <br />to bedrock), light colored, fine textured (more than 35 percent clay), undeveloped soils having no soil <br />horizonation other than a slightly darkened surface horizon and weak and inconsistent horizons of <br />secondary carbonate accumulation (Torriorthents) or weakly developed soils having slightly darkened <br />surface horizons, brighter colored sub-surface horizons of ~vcak to moderate structure, and weak horizons <br />of secondary carbonate accumulation (Camborthids) occurring in parts of the stud}' area where mean <br />summer soil temperature (June, July, and August averages measured at 20 inches) is 59°F or warmer. <br />Classification of Maior Components -The components listed below comprise the major part of the <br />mapping unit: <br />A. Ustic Torriorthents (Rceosols). <br />1. Fine, montmorillonitic, (calcareous), mesic family. <br />(Gaynor Series) <br />2. Fine, montmorillonitic, (calcareous), frigid family. <br />(Dollard Series) <br />B. Usteric Torriorthents (Regosols). <br />1. Fine, montmorillonitic, (calcareous), mesic family. <br />(Lemon Series) <br />2. Fine, montmorillonitic, (calcareous), frigid family. <br />. (EIkaI Series) <br />(Marian Scrics) <br />