LOCATION ORSA               CO
Established Series
GB
09/2006

ORSA SERIES


The Orsa series consists of deep well to somewhat excessively drained soils that formed in thick coarse textured materials weathered and locally transported from arkosic materials. Orsa soils are on alluvial fans, high dissected terraces and valley sideslopes and have slopes of 1 to 15 percent. Mean annual precipitation is about 43 centimeters (17 inches) and mean annual temperature is about 9 degrees C. (48 degrees F.) at the type location.

TAXONOMIC CLASS: Sandy, mixed, mesic Torriorthentic Haplustolls

TYPICAL PEDON: Orsa coarse sandy loam in grassland (Colors are for dry soil unless otherwise noted.)

A1--0 to 20 centimeters (0 to 8 inches); dark grayish brown (10YR 4/2) coarse sandy loam, very dark brown (10YR 2/2) moist; moderate very fine granular structure; soft, very friable; 5 percent fine and very fine angular granitic pebbles; slightly acid; gradual smooth boundary. (15 to 25 centimeters (6 to 10 inches) thick)

A2--20 to 51 centimeters (8 to 20 inches); dark grayish brown (10YR 4/2) loamy coarse sand, very dark brown (10YR 2/2) moist; weak very coarse subangular blocky structure parting to medium subangular blocks; slightly hard, very friable; 10 percent fine and very fine angular granitic pebbles; neutral; gradual smooth boundary. (0 to 25 centimeters (0 to 10 inches) thick)

A3--51 to 69 centimeters (20 to 27 inches); brown (10YR 5/3) gravelly loamy coarse sand, dark brown (10YR 3/3) moist; weak medium angular blocky structure; loose; 20 percent fine and very fine angular granitic pebbles; neutral; gradual wavy boundary. (36 to 51 centimeters (14 to 20 inches) thick)

C--69 to 152 centimeters (27 to 60 inches); light yellowish brown (10YR 6/4) gravelly loamy coarse sand, dark yellowish brown (10YR 4/4) moist; massive; loose; 20 percent fine and angular granitic pebbles; neutral. (Several feet thick)

TYPE LOCATION: Douglas County, Colorado; 1,300 feet north and 500 feet west of the SE corner of sec. 12, T. 8 S., R. 68 W.

RANGE IN CHARACTERISTICS:
Mollic epipedon: 51 to 102 centimeters (20 to 40 inches) thick
Texture: loamy fine sand or coarser
Chemical response: typically are noncalcareous to more than 152 centimeters (60 inches), uniformly calcareous material depth from 102 to 152 centimeters (40 to 60 inches or more.
The particle size control section: gravelly loamy coarse sand or coarse sand and may have minor amounts of gravelly coarse sandy loam with a large proportion of medium, coarse and very coarse angular sand which has a high percentage of flat bearing surfaces between sand grains
Rock fragments: 15 to 35 percent by volume in a major part of the control section and are predominantly fine angular granitic pebbles
Consistence of peds: harder than textures indicated due to an arkosic influence
The solum and C horizon: slightly acid to moderately alkaline
Mean annual soil temperature: 8 to 11 degrees C. (47 to 52 degrees F.)
Mean summer soil temperature: 17 to 19 degrees C. (62 to 66 degrees F.)

A horizion:
Hue: 2.5Y to 7.5YR
Value: 4 or 5, 2 or 3 moist
Chroma: 1 to 3
Organic matter: less than one percent in the upper 20 inches

C horizon:
Hue: 2.5Y to 7.5YR
Value: 5 or 6

COMPETING SERIES: These are the Blakeland and Dailey series.
Blakeland and Dailey soils have less than 15 percent rock fragments and have mollic epipedons less than 51 centimeters (20 inches) thick.
Dailey soils have little or no coarse and very coarse angular sand.

GEOGRAPHIC SETTING:
Landform: alluvial fans, high dissected terraces and valley sideslopes
Slope: 1 to 15 percent
Parent material: thick coarse textured weathered and locally transported from arkose deposits of Dawson and Arapahoe formations
Mean annual precipitation: 43 centimeters (17 inches), with peak periods of precipitation in the spring and summer
Mean annual temperature: 8 to 11 degrees C. (46 to 51 degrees F.)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Blakeland soils and Bresser soils.
Bresser soils have sandy clay loam Bt horizons.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage: well to somewhat excessively drained
Runoff: low or very low
Saturated Hydraulic Conductivity: high or very high

USE AND VEGETATION: These soils are used principally as native pastureland. Some small areas are tilled.
Native vegetation is mainly big and little bluestem, sandreed grass, sand dropseed, and blue grama.

DISTRIBUTION AND EXTENT: The foothill and Black Forest of east central Colorado. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado

SERIES ESTABLISHED: Douglas County, Colorado, 1974.

REMARKS: Diagnostic horizon and features recognized in this pedon are:

Modified format by LRM in 7/2006 to include metric conversion and change permeability to saturated hydraulic conductivity.


National Cooperative Soil Survey
U.S.A.