LOCATION CERRO CO

Established Series
Rev. AJC/CRP/JCK
01/2023

CERRO SERIES

The Cerro series consists of very deep, well drained soils that formed in alluvium, colluvium, outwash or slide deposits. Cerro soils are on alluvial fans, fan remnants, outwash fans, landslides, mountain slopes and stream terraces. Slopes are from 0 to 50 percent. Mean annual precipitation is about 457 mm, and mean annual air temperature is about 6 degrees C.

TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Argiustolls

TYPICAL PEDON: Cerro clay loam in grassland. (Colors are for dry soil unless otherwise noted.)

A--0 to 18 cm; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular structure; soft, very friable, slightly sticky and slightly plastic; 10 percent stones; neutral (pH 7.0); clear smooth boundary. (13 to 25 cm thick)

Bt1--18 to 28 cm; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak coarse prismatic structure parting to moderate medium and fine angular blocky; moderate cracks between peds when dry; hard, firm, sticky and plastic; few faint clay films on faces of peds and on surfaces along root channels; 10 percent stones; neutral (pH 7.0); clear smooth boundary. (10 to 15 cm thick)

Bt2--28 to 66 cm; brown (7.5YR 5/2) clay, brown (7.5YR 4/2) moist; moderate medium prismatic structure parting to moderate medium angular blocky; wedge shaped aggregates with wide cracks between peds when dry; extremely hard, very firm, sticky and plastic; few distinct clay films on faces of peds and on surfaces along root channels and pores; 10 percent stones; neutral (pH 7.2); clear wavy boundary. (13 to 104 cm thick)

Bk--66 to 76 cm; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; weak coarse and medium angular blocky structure; wide cracks between peds when dry; extremely hard, very firm, sticky and plastic; distinct carbonate coats on rock fragments; threadlike calcium carbonate masses in the matrix; strongly effervescent; 10 percent stones; moderately alkaline (pH 8.2); gradual smooth boundary. (8 to 25 cm thick)

BCk--76 to 152 cm; pale brown (10YR 6/3) stony clay loam, brown (10YR 5/3) moist; massive; irregular cracks develop when dry; extremely hard, very firm, sticky and plastic; distinct carbonate coats on rock fragments; threadlike calcium carbonate masses in the matrix; 20 percent stones; strongly effervescent; moderately alkaline (pH 8.4).

TYPE LOCATION: Montrose County, Colorado; approximately 442 meters south of the northwest corner of Sec. 2, T. 48 N., R. 8 W. Latitude: 38 degrees, 27 minutes, 20 seconds N; Longitude: 107 degrees, 43 minutes, 31 seconds W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 5 to 8 degrees C
Mollic epipedon thickness: 18 to 40 cm
Rock fragments - 0 to 35 percent, mainly stones; 0 to 15 percent in the particle-size control section

A horizon
Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1, 2 or 3
Texture: clay loam, silty clay loam or loam
Clay content: 24 to 38 percent
Rock fragments: 0 to 15 percent--0 to 15 percent gravel; 0 to 10 percent cobbles; 0 to 15 percent stones
Reaction: pH 6.8 to 7.8

Bt horizons
Hue: 5YR, 7.5YR or 10YR
Value: 5, 6 or 7 dry; 3 or 4 moist
Chroma: 2, 3 or 4
Texture: clay, clay loam or silty clay
Clay content: 35 to 60 percent
Rock fragments: 0 to 15 percent--0 to 15 percent gravel; 0 to 10 percent cobbles; 0 to 15 percent stones
Reaction: pH 6.8 to 7.8

Bk or BCk horizon
Hue: 7.5YR or 10YR
Value: 6, 7 or 8 dry; 4 or 5 moist
Chroma: 2, 3 or 4
Texture: clay loam, silty clay loam, silty clay, or clay
Clay content: 35 to 50 percent
Calcium carbonate equivalent: 5 to 15 percent
Sodium adsorption ratio: 0 to 8
Rock fragments: 0 to 35 percent--0 to 15 percent gravel; 0 to 10 percent cobbles; 0 to 30 percent stones
Reaction: pH 8.0 to 8.6

COMPETING SERIES:
Bearpaw (MT) - formed in dense till and have moist bulk density of 1.55 or more above 100 cm
Burnel (MT) - have a mollic epipedon that is more than 40 cm thick
Cedarsprings (NM) - do not have secondary calcium carbonate accumulation
Coben (MT) - have gypsum accumulation
Danvers (MT) - have a calcic horizon
Fergus (MT) - do not have rock fragments more than 75 mm in size
Friana (AZ) - do not have secondary calcium carbonate accumulation; have a lithologic discontinuity
Gerbana (MT) - have a paralithic contact at depths of 50 to 100 cm
Gerber (MT) - have a lithologic discontinuity
Mondamin (SD) - have gypsum accumulation; do not have hue redder than 10YR
Nunnston (WY) - do not have rock fragments more than 250 mm in size; do not have hue redder than 10YR
Pagoda (CO) - have a mollic epipedon that is more than 40 cm thick
Regent (ND) - have a paralithic contact at depths of 50 to 100 cm
Reget (WY) - have a paralithic contact at depths of 50 to 100 cm
Ridgeview (SD) - have gypsum accumulation; do not have hue redder than 10YR
Wyola (MT) - do not have rock fragments more than 250 mm in size
Suposo (NM) - do not have rock fragments; do not have hue redder than 10YR
Tomasaki (UT) - do not have secondary calcium carbonate accumulation; have a lithologic discontinuity
Tsoodzil (NM) - have a mollic epipedon that is more than 40 cm thick
Yankee (NM) - have a mollic epipedon that is more than 40 cm thick

GEOGRAPHIC SETTING:
Landform - alluvial fans, fan remnants, outwash fans, landslides, mountain slopes and stream terraces
Elevation - 1,890 to 2,590 meters
Slopes - 0 to 50 percent
Parent Material - alluvium, colluvium, outwash or slide deposits
Mean annual air temperature - 4.4 to 7.2 degrees C
Mean annual precipitation - 381 to 508 mm
Frost-free period - 80 to 110 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bostwick and Herm soils.

DRAINAGE AND PERMEABILITY: Well to moderately well drained; moderately slow to slow permeability.

USE AND VEGETATION: Cerro soils are used mainly for rangeland. Native vegetation consists of mountain big sagebrush, western wheatgrass, muttongrass, serviceberry, wild onion, and Letterman's needlegrass.

DISTRIBUTION AND EXTENT: Cerro soils are of moderate extent in western Colorado. MLRA 48A.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Delta-Montrose Area, Colorado, 1965.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 28 cm (A and Bt1 horizons)
Argillic horizon - 18 to 66 cm (Bt1 and Bt2 horizons)
Secondary calcium carbonate accumulation - from 66 to 150 cm (Bk and BCk horizons)
Reversible trans-horizon cracks - from 18 to 76 cm (Bt1, Bt2 and Bk horizons)
Particle-size control section - from 18 to 66 cm (Bt1 and Bt2 horizons)

Cerro soils have a frigid temperature regime and an ustic moisture regime.

National Cooperative Soil Survey
U.S.A.