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Chemical Properties and Natural Fenilin~ -These soils are moderately weathered and maturely <br />• dc~cloped. having distinct genetic horizonation including horizons of secondary carbonate accumulation. <br />The soil exchange complex is dominated by calcium; however, not enough free carbonate from magnesium <br />and calcium is present to tie up plant nutrients. As a result, the soils are neutral to alkaline. <br />Natural fertility levels are above average with the. exception of phosphorus which showed some deficiencies <br />by analysis (see Exhibit 26). Tillage operations that may destroy or mix the soil horizons should be <br />supplemented with a fertilization program consisting of nitrogen and phosphorus to provide vigorous <br />stands of grass during reclamation. <br />Mannino Unit Number ]7 - Moderately deep (20 to 40 inches to bedrock) and deep (more than 40 <br />inches to bedrock), light colored, foe textured (more than 35 percent clay), well developed soils having <br />mautrc soil horizonation including horizons of silicate clay accumulation (BZt horizons) and horizons of <br />secondary carbonate and which occur in parts of the study area where the mean summer soil temperature <br />(June, July, and August mean temperature measured at 20 inches) is 59°F or warmer. <br />ClassifiG~tion of Alaior Components - The components listed below comprise the major part of the <br />mapping unit: <br />A. Ustollic Haplargids (Brown Soils). <br />1. Fine, montmorillonitic, mesic family. <br />(Renohill Series) <br />(Ulm Series) <br />(Aqua Fria Series) <br />B. Borollic Haplargids (Brown Soils) <br />• 1. Fine, montmorillonitic family. <br />(Boctcher Series) <br />Extent and 1\laior Areas of Occurrence -Mapping unit number 17 occurs in small acreage in the West <br />Elk stud}• area and is found principally on the terraces and valley filling sideslopes east and north of <br />1,1innesota Creek. <br />Characteristic Tonoeranhv -Soils of this mapping unit occupy gently to moderately sloping alluvial fans <br />and valley filling side-slopes. Slopes are uniform ranging from about two to 20 percent. <br />Physical Propenies -The soils of mapping unit number 17 are mature soils having distinct genetic <br />horizonation and well developed, stable, natural soil structure. This soil structure is essential to free <br />movement of air and water. The texture of the soil is fine (more than 35 percent clay), and therefore <br />subject to puddling if handled wet and packing if traversed with heave equipment. <br />Careful management techniques should be used during disturbance of these soils. There is a narrow range <br />of moisture content in which they can be handled without suffering loss of physical properties. For this <br />reason this unit is classified as moderately good for seedbed material use. <br />The soils of this unit also have wide shrink/ssvell ratios. Coefficients of linear extensibility (ratio of volume <br />o(dn' to moist soil) ranges from 0.05 to 0.15 with an average of about 0.1. Total potential extensibility of <br />a 40 inch section ranges from 2.0 to 6.0 inches. In addition, the soils of this unit are very sticky and <br />slippery when wet. <br />Normally, the soils of this unit are not subject to serious food hazards although a few of the lower <br />footslopes may food occasionally. Soil erosion is not usually accelerated unless native vegetation is <br />destroyed or depleted. When disturbed they become moderately susceptible to wind and water erosion and <br />control measures should be used. <br />