LOCATION MORAPOS COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Typic Argiustolls
TYPICAL PEDON: Morapos clay loam - on southwest-facing convex 7 percent slope in rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 5 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; soft, friable, moderately sticky and moderately plastic; neutral (pH 7.2); clear wavy boundary. (4 to 8 inches thick)
Bt1--5 to 9 inches; brown (10YR 5/3) clay loam, dark brown (10YR 3/3) moist; moderate fine and medium angular blocky structure; very hard, firm, very sticky and moderately plastic; common distinct clay films on ped faces; neutral (pH 7.2); clear wavy boundary. (3 to 10 inches thick)
Bt2--9 to 23 inches; yellowish brown (10YR 5/4) clay, dark yellowish brown (10YR 4/4) moist; strong fine prismatic structure parting to strong medium and coarse angular blocky; very hard, firm, very sticky and very plastic; common distinct clay films on ped faces; neutral (pH 7.2); clear wavy boundary. (5 to 15 inches thick)
Bk1--23 to 31 inches; brown (10YR 5/3) clay loam; brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate coarse subangular; very hard, firm, very sticky and moderately plastic; calcium carbonate; segregated as common white (10YR 8/1) threads; strongly effervescent, moderately alkaline (pH 8.2); clear wavy boundary. (5 to 8 inches thick)
Bk2--31 to 40 inches; pale brown (10YR 6/3) clay loam; brown (10YR 5/3) moist; moderate medium prismatic structure parting to weak coarse subangular blocky; hard, firm, moderately sticky and moderately plastic; calcium carbonate segregated as many white (10YR 8/1) threads; strongly effervescent, moderately alkaline (pH 8.2); gradual wavy boundary. (5 to 18 inches thick)
Bk3--40 to 53 inches; light gray (2.5Y 7/2) clay loam; light yellowish brown (2.5Y 6/3) moist; weak coarse prismatic structure; slightly hard, firm, moderately sticky and moderately plastic; calcium carbonate segregated as many white (10YR 8/1) threads; 11 percent calcium carbonate equivalent; strongly effervescent; moderately alkaline (pH 8.2); diffuse wavy boundary (8 to 13 inches thick)
Bk4--53 to 60 inches; light gray (2.5Y 7/2) clay loam; light yellowish brown (2.5Y 6/3) moist; massive; slightly hard, firm, moderately sticky and moderately plastic; lime is somewhat inherent in the parent material and visible as many white (10YR 8/1) threads of calcium carbonate; 7 percent calcium carbonate equivalent; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Moffat County, Colorado; seven miles south of Hamilton, Colorado; 3,850 feet east and 250 feet north of the southwest corner of Sec. 32, T. 4 N., R. 91 W. Longitude: 107 degrees, 37 minutes, 47 seconds west. Latitude: 40 degrees, 16 minutes, 7 seconds north.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 41 to 44 degrees F.
Mean summer soil temperature: 59 to 65 degrees F.
The soil temperature at a depth of 20 inches is above 41 degrees for 170 to 190 days.
Soil moisture: Ustic moisture regime (typic ustic subclass). The moisture control section in most years is moist in all parts for 30 to 45 consecutive days in May and June, and dry in all parts for 45 consecutive days immediately after July 15, and moist in some but not all parts for most of the period from September 1 through March 30. It is not dry in all parts for more than half the time that the soil temperature is higher than 41 degrees F. at a depth of 20 inches.
Thickness of the mollic epipedon: 7 to 15 inches
Depth to calcareous material: 14 to 40 inches
Linear extensibility: 5.0 to 6.0 (estimated)
A horizon
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 1 to 3
Texture: clay loam, loam, silt loam
Reaction: neutral or slightly alkaline
Bt horizon
Hue: 7.5YR or 10YR
Value: 4 to 6, 3 to 5 moist
Chroma: 2 to 4
Texture: clay loam, silty clay loam, silty clay, or clay
Clay content: 35 to 45 percent
Reaction: neutral or slightly alkaline.
Btk horizon (present in some pedons)
Hue: 10YR
Value: 5 dry, 4 moist
Chroma: 2 to 4, dry or moist
Texture: clay loam, clay
Clay content: 35 to 45 percent
Gravel content: 0 to 5 percent
Calcium carbonate equivalent: 1 to 7 percent
Reaction slightly alkaline or moderately alkaline
Bk horizon
Hue: 2.5Y to 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 or 3, dry or moist
Texture: clay loam, silty clay loam, or clay
Gravel content: 0 to 10 percent
Calcium carbonate equivalent: 1 to 14 percent
COMPETING SERIES: These are Absarokee, Acree, Barela, Capillo, Delson, Ekah, Herm, Moreno, Nortez, Pramiss, Ricot, Tamaneen, Tukuhnik, Work, and Zau series
Absarokee,
Nortez,
Pramiss, and
Zau soils have bedrock at depths of 20 to 40 inches.
Acree soils have hues of 5YR or redder in the lower Bt horizon.
Barela,
Capillo, and
Tukuhnik soils have bedrock at depths of 40 to 60 inches
Delson,
Herm, and
Moreno soils are noncalcareous.
Ekah soils have a calcic horizon.
Ricot soils have a lithologic discontinuity in the lower part of the profile.
Tamaneen soils have a lithologic discontinuity in the lower part that is loamy with greater than 50 percent rock fragments.
Work soils are moist in some or all parts during June and July and parts of August.
GEOGRAPHIC SETTING: Morapos soils are on structural benches, hills, plateaus, and mountain slopes. Slopes are 2 to 50 percent. The soil formed in slope alluvium and residuum from shale and siltstone, with admixture of loess in some pedons. Elevation ranges from 6,300 to 7,600 feet. The mean annual precipitation ranges from 16 to 20 inches and is evenly distributed throughout the year except for a slight decline in July. Over half of the precipitation is received as snow. Mean annual temperature ranges from 40 to 43 degrees F., and the mean summer temperature ranges from 59 to 67 degrees F. The frost free season is 65 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Pagoda, Hesperus, Herm, Iles, and Campspass series. Pagoda and Hesperus soils have mollic epipedons which are 16 or more inches thick. Herm soils are noncalcareous. Iles and Campspass soils do not have mollic epipedons.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used mainly for rangeland. Some are used for dryland wheat and alfalfa. Principal native vegetation is mountain big sagebrush, Saskatoon serviceberry, Letterman's needlegrass, slender wheatgrass, and western wheatgrass.
DISTRIBUTION AND EXTENT: Northwestern Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Moffat County (Moffat County Area), Colorado, 1991. The name is taken from Morapos Creek which is near the type location.
REMARKS: Climatic conditions are close to fitting that of the xeric moisture regime. Snow cover occurs in October before the moisture control section becomes moistened in all parts; hence it has no opportunity to be moist in all parts for 3 of the 4 months after the winter solstice. Snow melt occurs in mid-April to mid-May and moistens the control section and below. Increased evapotranspiration dries out the control section by mid-July. Summer precipitation comes as irregular showers which are not sufficient to moisten the soil down to the top of the control section. As evapotranspiration decreases in late September, the showers moisten the soil down into the top part of the moisture control section.
The 10/2002 revision restricts the series characteristics to northwestern Colorado, where it was proposed and established. It will not be correlated in southwestern Colorado in the future. This change mainly affected the climatic setting and the vegetation.
Diagnostic horizons recognized in this pedon are:
Mollic epipedon - from 0 to 9 inches.
Argillic horizon - from 5 to 23 inches.
Particle-size control section: The zone from 5 to 23 inches (the entire argillic horizon).