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<br />16' • SOIL SURVEY
<br />cent. Leaps and Riorop soils make uP about 10 percent
<br />of some mapped areas.
<br />This soil is used mostly for grazing. Small areas are
<br />used for irrigated hay and pasture. Runoff is medium
<br />to rapid, and the erosion hazard is slight to moderate.
<br />Capability units VIe-1 irrigated, VIIe-1 nonit•rigated;
<br />Deep Clay Loam range site.
<br />Duffson Series
<br />The Duffson sel•ies consists of moderately deep, well-
<br />drained, calcareous soils on hills, ridges, and benches.
<br />Slopes are 5 to 40 percent. These soils formed in locally
<br />transported alluvium that was derived from calcareous,
<br />interbedded sandstone and shale.
<br />In a representative profile. the sw•face layer is gray-
<br />ish-brown loam about 5 inches thick. The subsoil is
<br />brown and light yellowish-brown loam and clay loam
<br />about 15 inches thick. 1t is calcareous in the lower part.
<br />The substratum is about 10 inches of strongly calcar-
<br />eous, white loam. Below this is sandstone bedrock.
<br />Duffson soils are at elevations of 7,500 to 9,500 feet.
<br />The average annual soil temperature is 95" F. The aver-
<br />age soil temperature in summer is 02°. The average
<br />annual precipitation is 17 inches. The vegetation is
<br />commonly big sagebrush, Arizona fescue, wheatgrass,
<br />and native bluegrass.
<br />Permeability is moderately slow. The root zone is
<br />only 20 to 90 inches deep, and available water capacity
<br />is low.
<br />Most of the acreage i, used for grazing.
<br />The Duffson soils in the Gunnison Area are mapped
<br />only with Corpening and Spring Creek suits.
<br />Representative profile of Duffson loam, 5 to 35 per-
<br />cent slopes; NWlj4 sec. 35, T. 48 iv.. R. 2 E., Saguache
<br />County:
<br />Al-0 to 5 inches, grayish-brown (lOYR 5/2) light loam,
<br />very dark grayish brown (lOYR 3/2) moist; mod-
<br />erate, very fine, granular structure; soft, very
<br />friable; ]0 percent fine sandstone gravel; pH 0.8;
<br />clear, smooth boundary.
<br />Hlt-5 to 9 inches, brown (7.5YR 5/3) clay loam, dark
<br />brown (7.6YR 3/3) moist; weak, medium, sub-
<br />angular blocky structure parting to moderate, very
<br />fine, subangular blocky; slightly hard, very friable;
<br />thin patchy clay films on ped Faces; about 10 per-
<br />cent fine sandstone gravel; pH 6.6; clear, smooth
<br />boundary.
<br />B2t-B to 16 inches, brown (7.6YR 5/3) clay loam, dark
<br />brown (7.5YR 9/3) moist; weak, medium, pris-
<br />matic structure parting to moderate, medium, sub-
<br />angular blocky; hard, friable; thin nearly con-
<br />tinuous clay films on ped faces; about 10 percent
<br />angular sandstone gravel; pH 7.0; clear, wavy
<br />boundary.
<br />H3tca-16 to 20 inches, light yellowish-brown (lOYR 6/4)
<br />heavy loam, yellowish brown (10YR 6/4) moist;
<br />weak, medium, subangular blocky structure; hard,
<br />friable; few, thin, patchy clay films on ped faces;
<br />10 percent angular sandstone gravel; lime in fine
<br />seams and small concretions; pH 8.0; gradual, wavy
<br />boundary.
<br />Cca-20 to 30 inches, white (lOYR 8/2) loam, light gray
<br />(lOYR 7/2) moist; massive; hard, friable; about
<br />10 percent sandstone gravel; calcareous; marl-like
<br />lime coatings on stone fragments; pH 8.2; clear,
<br />smooth boundary.
<br />R~0 inches, sandstone.
<br />The A horizon is typically loam, but in places is fine sandy
<br />loam. It is 4 to 9 inches thick end is grayish brown or brown.
<br />Depth to bedrock ranges from 20 to 40 inches. The content
<br />of gravel ranges from 6 to 15 percent.
<br />Duffson-Corpening looms, 5 to 35 percent slopes (DrEI.
<br />-This mapping unit is mainly in the central part of the
<br />survey area. The largest acreage is between Razor and
<br />Cochetopa Creeks. The unit is about 50 percent Duffson
<br />loam and 30 percent Corpening loam. The Duffson soil
<br />is generally on northern and eastern exposures. The
<br />Corpening soil is commonly on windswept, southern and
<br />western exposures. In some eroded areas of these soils,
<br />the surface la}•er is thinner and stonier than that in
<br />the profiles described as representative of the series.
<br />Included with these soils in mapping are small areas
<br />of Lucky and Partin soils, areas of severely eroded Duff-
<br />son and Corpening soils, and areas of Rock outcrop :uxl
<br />Stony rock land. Also included are areas of Alluvial
<br />land and Alluvial land, wet, commonly along small drain-
<br />agewaysand tce slopes. Included soils make up less than
<br />20 percent of the total acreage.
<br />This unit is almost entirely in range. Runoff is me-
<br />dium. The erosion hazard is moderate unless a good
<br />plant cover is maintained. Capability unit VIe-5 non-
<br />irrigated; Duffson soil in Mountain Loam range site,
<br />Corpening soil in Dry Mountain Loam range site.
<br />Uuffson-Spring Creek stony looms, 5 to 40 percent
<br />slopes (DsE).-This mapping unit is mainly in the north-
<br />central part of the survey area. It is about G5 percent
<br />Duffson stony loam and 20 percent Spring Creek stony
<br />loam. The Duffson soil is mainly on northern exposures.
<br />At the higher elevations it has a surface layer 10 to 20
<br />inches thick. The Spring Creek soil is on windswept,
<br />southern and western exposures. It has the profile de-
<br />scribed as representative of the Spring Creek series.
<br />Slopes are complex.
<br />Included with these soils in mapping are small areas
<br />of blond and Partin soils and areas of Alluvial land and
<br />Alluvial land, wet. along minor drainageways in nar-
<br />row, winding valleys. Also included are areas of Rock
<br />outcrop and Stony rock land on the steeper slopes and
<br />a few small sandy areas of wind-deposited material nn
<br />north-facing slopes near Gunnison. Included soils make
<br />tlp 15 percent of the total acreage.
<br />Nearly all the acreage is in native vegetation and is
<br />used for range, recreation, and wildlife. Runoff is me-
<br />dium to rapid, and the erosion hazard is moderate to
<br />high. About half the acreage, particularly where vege-
<br />tation is sparse, has been eroded by wind and water.
<br />In these areas the surface layer is thinner and stonier
<br />than is typical. In some areas up to 3 acres in size, the
<br />Spring Creek soil has been so severely eroded that hed-
<br />rock is exposed. Capability unit VIIs-1 nonirrigated;
<br />Duffson soil in Mountain Loam range site. Spring Creek
<br />soil in Dry Mountain I.nam range site.
<br />Evanston Series
<br />The Evanston series consists of deep, well-drained
<br />soils oll alluvial fans and valley-fill slopes. Slopes are
<br />1 to 20 percent. These soils formed in alluvium that was
<br />derived from sandstone, rhyolite, and tuff.
<br />In a representative profile the surface layer is dark-
<br />brown loam about 6 inches thick. The subsoil is brown
<br />clay loam and loam about 12 inches thick. It is calcare-
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