LOCATION DELSON CO
Established Series
Rev. TJH-GB-KLS
06/2023
DELSON SERIES
The Delson series consists of very deep, well drained soils that formed in alluvial material derived from sedimentary rocks and from residuum and colluvium from sandstone and shale. Delson soils are on stony outwash fans, benches, mountain and mesa side slopes. Slopes are 0 to 65 percent. The mean annual precipitation is about 430 mm and the mean annual temperature is about 5 degrees C.
TAXONOMIC CLASS: Fine, smectitic, frigid Typic Argiustolls
TYPICAL PEDON: Delson stony loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 20 cm; brown (7.5YR 4/2) stony loam, very dark brown (7.5YR 2/2) moist; weak fine subangular blocky structure parting to moderate fine granular; soft, friable, slightly sticky and slightly plastic; many medium and fine roots; 5 percent stones; neutral; clear smooth boundary. (10 to 38 cm thick)
BA--20 to 30 cm; brown (7.5YR 4/2) clay loam, very dark brown (7.5YR 2/2) moist; weak medium subangular blocky structure parting to moderate coarse granular; slightly hard, friable, sticky and plastic; thin patchy clay films on faces of peds; many medium and fine roots; 5 percent stones; neutral; clear smooth boundary. (0 to 20 cm thick)
Bt--30 to 86 cm; reddish brown (5YR 4/4) light clay, dark reddish brown (5YR 3/4) moist; moderate medium prismatic structure parting to strong medium angular blocky; extremely hard, very firm, very sticky and plastic; moderately thick continuous clay films on faces of peds; few medium and coarse roots; 10 percent stones; neutral; gradual wavy boundary. (25 to 76 cm thick)
BC--86 to 107 cm; brown (7.5YR 5/4) stony clay loam, brown (7.5YR 4/4) moist; moderate medium hard, friable, sticky and plastic; few thin clay films on faces of peds; few coarse roots; 20 percent stones; neutral grading to slightly alkaline in lower part; gradual wavy boundary. (10 to 30 cm thick)
C--107 to 152 cm; pale brown (10YR 6/3) stony clay loam, brown (10YR 5/3) moist; massive; hard, sticky and slightly plastic; 30 percent stones; slightly alkaline.
TYPE LOCATION: Delta County, Colorado; the NW1/4 of Sec. 24, T. 13 S., R. 93 W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 4 to 7.8 degrees C
Mean summer soil temperature - 15 to 18 degrees C
Thickness of solum - 50 to 125 cm or more
These soils are noncalcareous to depths of 100 cm or more
Rock fragment content - 0 to 35 percent cobbles and stones of sedimentary lithology, with the amount typically increasing with increasing depth.
Particle-size control section:
Texture - clay loam or clay
Clay content - 35 to 55 percent
A horizon
Hue: 7.5YR or 10YR
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 0 through 3
Reaction: pH 6.6 to 8.4
Bt horizon
Hue: 7.5YR or 5YR
Value: 4 to 6 dry, 3 to 6 moist
Chroma: 2 through 4
Reaction: pH 6.6 to 8.4
BC or C horizons
Hue: 2.5YR through 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 through 4
Reaction: pH 6.6 to 8.4
COMPETING SERIES:
Absarokee (MT) - are moderately deep to lithic contact
Acree (CO) - have horizons with secondary calcium carbonate accumulation
Barela (NM) - are deep to lithic contact; have rock fragments of basalt lithology
Capillo (NM) - are deep to paralithic contact
Dandrea (AZ) - are moderately deep to paralithic contact
Ekah (MT) - have horizons with secondary calcium carbonate accumulation
Herm (CO) - have hue of 10YR or yellower in the Bt horizon
Morapos (CO) - have horizons with secondary calcium carbonate accumulation
Moreno (NM) - have rock fragments of acid igneous intrusive lithology
Nortez (CO) - are moderately deep to lithic contact
Pramiss (CO) - are moderately deep to paralithic contact
Ricot (CO) - have a lithologic discontinuity at depths of 25 to 50 cm
Tamaneen (MT) - have hue of 10YR or yellower in the Bt horizon
Tukuhnik (UT) - have a calcic horizon
Work (MT) - have horizons with secondary calcium carbonate accumulation
Zau (CO) - are moderately deep to paralithic contact
GEOGRAPHIC SETTING:
Landform - alluvial fans, benches and high mesas
Elevation - 2,075 meters in the northern part of Colorado to 2,825 meters in the southern part of Colorado
Slope - 0 to 65 percent
Parent material - noncalcareous, moderately fine to fine textured alluvial fan materials derived from sedimentary and basaltic cap rock
Mean annual air temperature - 4 to 6 degrees C
Mean annual precipitation - 380 to 560 mm
Precipitation pattern - peak periods of precipitation occur during the months of August through October
Frost-free period - 80 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used primarily for grazing. Native vegetation is mainly Gambel oak, serviceberry, big sagebrush, and western wheatgrass or bluebunch wheatgrass. Some areas are pinon-juniper woodland.
DISTRIBUTION AND EXTENT: Delson soils are of moderate extent in the mountainous areas of west-central and southwestern Colorado; MLRAs 35, 43B, 48A, and 51.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Paonia Area, Colorado, 1976.
REMARKS: Diagnostic horizons and features recognized in the pedon are:
Mollic epipedon: 0 to 30 cm (A and BA horizons)
Argillic horizon: 30 to 80 cm (part of the Bt horizon)
Particle-size control section: 30 to 86 cm (Bt horizon)
Delson soils have a frigid temperature regime and an ustic soil moisture regime.
Converted to metric, formatting updated to current standards, and competing series section updated. 01/2021
National Cooperative Soil Survey
U.S.A.