Established Series


The Fort Collins series consists of very deep, well drained soils that formed in mixed eolian sediments and alluvium. Fort Collins soils are on terraces, hills, plains, and alluvial fans and have slopes of 0 to 10 percent. The mean annual precipitation is about 38 centimeters (5 inches) and the mean annual temperature is about 8 degrees C. (47 degrees F.)

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Aridic Haplustalfs

TYPICAL PEDON: Fort Collins loam - grassland. (Colors are for dry soil unless otherwise noted).

A--0 to 13 centimeters (0 to 5 inches); light brownish gray (10YR 6/2) loam, dark grayish brown (10YR 4/2) moist; moderate fine granular structure; soft, very friable; neutral (pH 7.2); clear smooth boundary. (8 to 15 centimeters (3 to 6 inches) thick)

BA--13 to 20 centimeters (5 to 8 inches); light brownish gray (10YR 6/2) loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky structure parting to fine granular; hard, very friable; few faint clay films on faces of peds; neutral (pH 7.2); clear smooth boundary. (8 to 10 centimeters (3 to 4 inches) thick)

Bt--20 to 46 centimeters (8 to 18 inches); brown (10YR 5/3) heavy loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate fine subangular blocks; very hard, very friable; common distinct clay films on faces of peds, and as coatings in root channels and pores; slightly alkaline (pH 7.6); gradual smooth boundary. (13 to 30 centimeters (5 to 12 inches) thick)

BCk--46 to 61 centimeters (18 to 24 inches); pale brown (10YR 6/3) loam, brown (10YR 5/3) moist; weak medium subangular blocky structure; hard, very friable; few faint clay films on faces of peds; few faint clay films in some root channels; some visible secondary calcium carbonate occurring mostly as concretions; strongly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (10 to 25 centimeters (4 to 10 inches) thick)

Ck--61 to 152 centimeters (24 to 60 inches); pale brown (10YR 6/3) loam, brown (10YR 5/3) moist; massive; hard, very friable; visible calcium carbonate occurring as concretions and in thin seams and streaks; violently effervescent; moderately alkaline (pH 8.2); gradual smooth boundary.

TYPE LOCATION: Larimer County, Colorado; approximately 1 block north of LaPorte Avenue on North Shields Street, and 152 meters (500 feet) west of North Shields Street in Sec. 11, T. 7 N., R. 69 W.


Mean annual soil temperature: 8 to 13 degrees C. (47 to 55 degrees F.)
Mean summer soil temperature: 15 to 22 degrees C. (59 to 72 degrees F.)
Depth to the base of the Bt: 28 to 76 centimeters (11 to 30 inches)
Depth to calcareous material: 20 to 51 centimeters (8 to 20 inches)
Organic carbon upper 38 centimeters (15 inches): ranges from .6 to 2 percent (weighted average .8 percent)
Average sand/clay ratio: 1 to 3
Base saturation: 90 to 100 percent
Rock fragments: 0 to 15 percent, (typically less than 5 percent)
Moisture control section: not dry in all part for more than 1/2 of the time that the soil temperature is above 5 degrees C. (41 degrees F.) (moist in some or all parts during May and June)
Moisture control section: not dry for 45 consecutive days following July 15.

A horizon:
Hue: 10YR or 2.5Y
Value: 5 to 7, 3 to 5 moist
Chroma: 2 or 3
When the value of the surface horizon is as dark as 5 dry and 3 moist the horizon must be thin enough so that if the soil is mixed to 7 inches it will have an ochric epipedon or it must contain less than 1 percent organic matter. Structure: usually granular but may be weak subangular blocky
Firmness: soft or slightly hard
Reaction: neutral to slightly alkaline.

Bt horizon:
Hue: 2.5Y to 7.5YR
Value: 5 to 7, 4 or 5 moist
Chroma: 2 to 4
Texture: loam or clay loam
Clay content: 18 to 35 percent
Silt content: 20 to 50 percent
Sand content: 20 to 50 percent (more than 15 percent but less than 35 percent being fine sand or coarser)
Structure: prismatic but subangular blocky in some pedons
Reaction: neutral or slightly alkaline.

Bk or C horizon:
Hue: 2.5Y or 10YR
Value: 6 or 7, 5 or 6 moist
Chroma: 2 to 6
Reaction: moderately alkaline or strongly alkaline
Calcium carbonate equivalent: 5 to 15 percent
Textures: loam or clay loam and less commonly sandy clay loam.

COMPETING SERIES: These are the Arnor, Arwite, Augustine, Bigbow, Bosonoak, Carri, Celacy, Celavar, Dalhart, Deekay, Dermala, Elwop, Evpark, Flugle, Gateson, Goesling, Iwela, Lykorly, Navajita, Nyjack, Oldwolf, Olnest, Orlie, Parkelei, Pinitos, Rauzi, Ribera, Rockybutte, Stoneham, Toluca and Wagonhound series.
Arnor and Rauzi soils are redder hues and Arnor soils contain 15 to 30 percent rock fragments.
Augustine, Dalhart, Goesling, & Pinitos soils have thicker argillic layers with the base of the Bt in excess of 56 centimeters (22 inches).
Augustine soils may have a calcic horizon below 102 centimeters (40 inches).
Arwite, Deekay and Wagonhound soils are dry for 45 consecutive days in July through September.
Bosonoak soils have secondary carbonates in the surface.
Carri, Celacy, Celavar, Elwop, Evpark, Gateson, Nyjack, Oldwolf, and Ribera soils have a lithic or paralithic contact above 102 centimeters (40 inches).
Flugle soils have greater than 35 percent fine sand and coarser in the particle size control section.
Iwela soils have a lithologic discontinuity of stones at 66 centimeters (26 inches) and the moisture control section is dry in may and June.
Lykorly soils have up to 25 centimeters (10 inches) of overburden over a lithologic discontinuity with additional clay content and have a moisture control section that is dry in May and June.
Navajita soils have a 5 to 10 percent pararock fragments.
Orlie and Parkelei soils are dry in most parts of the moisture control section in May and June when the soil temperature at 51 centimeters (20 inches) is greater than 5 degrees C. (41 degrees F.)
Pinitos and Ribera soils have moisture control sections that are dry in May and June.
Olnest and Rockybutte soils may have rock fragments through out the profile.
Stoneham soils have less than 15 percent fine sand or coarser.
Toluca soils are noncalcareous above 25 centimeters (10 inches).

Parent materials: alluvium (may be modified by a thin mantle of eolian deposits)
Landscape: terraces, hills, plains, or alluvial fans
Slopes: 0 to 10 percent
Mean annual precipitation: 33 to 43 centimeters (13 to 17 inches)
Mean annual temperature: 7 to 12 degree C. (45 to 53 degrees F.)
Mean summer temperature: 14 to 21 degrees C. (57 to 70 degrees F.)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Stoneham and Olnest soils.

Drainage: well drained
Runoff: medium
Saturated Hydraulic Conductivity: moderately high

USE AND VEGETATION: These soils are used as native pastureland and as dry and irrigated cropland.
Principal irrigated crops are small grains, alfalfa, corn, sorghums, and sugar beets.
Dryland crops are limited primarily to winter wheat.
Native vegetation is blue grama grass, wheatgrass and some buffalo grass.

DISTRIBUTION AND EXTENT: Eastern Colorado, Montana, and Wyoming. The series is of large extent. MLRA 67


SERIES ESTABLISHED: The Greeley Area, Colorado, 1904.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Argillic horizon: 20 to 46 centimeters (8 to 18 inches)

This series is changed in class from Ustollic Haplargids to Aridic Haplustalfs due to update and revision of higher moisture levels in the moisture control section.
Last updated by the state 3/94.

10/2005 JCR LM Changed to semitab format, added metric conversion and changed permeability to saturated hydraulic conductivity.

National Cooperative Soil Survey