LOCATION DURANGO CO
Established Series
Rev. JPP/TWH/KLS
03/2018
DURANGO SERIES
The Durango series consists of very deep, well drained soil formed in fine textured slope alluvium or colluvium derived from shale. Durango soils are on hillslopes, paleoterraces, and ridges. Slopes range from 1 to 30 percent. Mean annual precipitation is about 381 mm and mean annual temperature is about 9.4 degrees C.
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Aridic Haplustalfs
TYPICAL PEDON: Durango cobbly loam, on a northeast facing, simple, 10 percent slope in chained pinyon-juniper woodland at an elevation of 2,256 meters. (Colors are for dry soil unless otherwise noted.) When described on 6/12/79 the soil was moist from 0 to 107 cm.
A--0 to 8 cm; brown (7.5YR 4/2) cobbly loam, dark brown (7.5YR 3/2) moist; weak fine granular structure; soft, very friable, nonsticky and slightly plastic; many fine and medium roots; 20 percent cobble, 5 percent gravel; neutral (pH 7.2); clear smooth boundary. (5 to 20 cm thick)
BA--8 to 20 cm; brown (7.5YR 5/2) clay loam; brown (7.5YR 4/2) moist; moderate medium subangular blocky structure parting to moderate medium granular; hard, firm, moderately sticky and moderately plastic; many fine and medium roots; few distinct clay films on faces of peds; 5 percent gravel and 5 percent cobble; slightly alkaline (pH 7.4); clear smooth boundary. (8 to 20 cm thick)
Bt--20 to 64 cm; reddish brown (5YR 5/3) clay loam, reddish brown (5YR 4/3) moist; weak medium prismatic structure parting to moderate medium angular blocky; very hard, very firm, very sticky and plastic; many fine and medium roots; many distinct clay films on faces of peds; 2 percent cobble, 2 percent gravel; slightly alkaline (pH 7.4); clear smooth boundary. (25 to 76 cm thick)
Btk--64 to 79 cm; light reddish brown (5YR 6/3) clay loam, reddish brown (5YR 5/3) moist; weak medium subangular blocky structure parting to moderate fine subangular blocky; very hard, very firm, sticky and plastic; few distinct clay films on faces of peds; visible calcium carbonate in seams and masses; strongly effervescent; 2 percent cobble, 2 percent gravel; slightly alkaline (pH 7.6); clear smooth boundary. (10 to 40 cm thick)
Bk--79 to 107 cm; brown (7.5YR 5/4) clay loam, brown (7.5YR 5/2) moist; massive; very hard, very firm, moderately sticky and moderately plastic; visible calcium carbonate in seams and masses; strongly effervescent; 2 percent cobble, 2 percent gravel; slightly alkaline (pH 7.8); gradual wavy boundary. (0 to 76 cm thick)
2C--107 to 152 cm; gray (10YR 6/1) clay, gray (10YR 5/1) moist; massive; very hard, very firm, moderately sticky and moderately plastic; strongly effervescent; slightly alkaline (pH 7.6)
TYPE LOCATION: La Plata County, Colorado. Located about 18 kilometers southwest of Ignacio, Colorado. About 305 meters south and 274 meters east of the northwest corner of Sec. 28, T. 33 N., R. 8 W. Ignacio USGS quad.; Lat. 37 degrees, 04 minutes, 45 seconds N., and Long. 107 degrees, 43 minutes, 42 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 8.3 to 11.1 degrees C.
Mean summer soil temperature: 15.6 to 18.3 degrees C.
Depth to secondary calcium carbonate: 46 to 91 cm
Depth to 2C horizon (if present): 76 to 152 cm or more
Depth to the base of the argillic horizon: 66 to 117 cm
Particle size control section:
Clay content: 35 to 45 percent
Rock fragment content: 0 to 15 percent
A horizon
Hue: 5YR to 10YR
Value: 4 to 6 dry, 3 through 5 moist
Chroma: 2 to 4, dry or moist
Texture, fine earth fraction: loam, clay loam; may have cobbly and gravelly modifiers
Clay content: 15 to 35 percent
Rock fragment content: 0 to 50 percent, mostly cobble and gravel
Reaction (pH): 6.6 to 7.8
Bt horizon
Hue: 5YR or 7.5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 4, dry or moist
Texture: clay, clay loam
Clay content: 30 to 50 percent
Rock fragment content: 0 to 15 percent
Reaction (pH): 6.6 to 7.8
Btk horizon
Hue: 5YR or 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 4, dry or moist
Texture: clay loam, clay
Clay content: 30 to 50 percent
Rock fragment content: 0 to 15 percent
Calcium carbonate equivalent: 1 to 10 percent
Reaction (pH): 7.4 to 8.4
Bk horizon
Hue: 5YR or 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 1 to 4, dry or moist
Texture: clay loam, clay
Clay content: 30 to 50 percent
Rock fragment content: 0 to 15 percent
Calcium carbonate equivalent: 5 to 14 percent
Reaction (pH): 7.8 to 9.0
2C horizon, if present
Hue: 2.5YR to 10YR
Texture: clay loam, clay
Clay content: 30 to 50 percent
Rock fragment content: 0 to 15 percent
Calcium carbonate equivalent: 2 to 10
Reaction (pH): 7.8 to 9.0
COMPETING SERIES:
Cueva (NM) - are moderately deep to densic contact
Erramouspe (NM) - are moderately deep to lithic contact
Fikel (NM) - are deeper than 117 cm to the base of the argillic horizon
Hosta (NM) - have hues yellower than 7.5YR in the argillic horizon
Montecito (NM) - have calcic horizons
Nogal (NM) - are moderately deep to paralithic contact
Oritz (NM) - are deep or very deep to densic contact
Prater (CO) - have hues yellower than 7.5YR in the argillic horizon
Tinian (NM) - are moderately deep to lithic contact
Wilmac (NM) - are moderately deep to paralithic contact
GEOGRAPHIC SETTING:
Landform - hillslopes, paleoterraces, and ridges
Elevation - 1,850 to 2,300 meters
Slopes - 1 to 30 percent
Parent material - slope alluvium or colluvium derived from shale
Precipitation pattern - May and June are the driest months; July and August are the wettest months
Mean annual precipitation - typically 330 to 406 mm, but can range to 457 mm in some areas
Mean annual air temperature - 7.2 to 11.1 degrees C.
Mean summer air temperature - 15.6 to 18.9 degrees C.
Frost-free period - 100 to 140 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained, medium runoff; slow permeability.
USE AND VEGETATION: These soils are used principally for rangeland and wildlife habitat. Native vegetation is pinyon, juniper, Gambel's oak, big sagebrush, skunkbush, snowberry, Antelope bitterbrush, mountain mahogany, Indian ricegrass, western wheatgrass, Kentucky bluegrass, needleandthread, and Junegrass.
DISTRIBUTION AND EXTENT: Southwestern Colorado. LRR D; MLRA 36; moderately extensive.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: La Plata County Area, Colorado, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Argillic horizon: 20 to 79 cm (Bt and Btk horizons)
Secondary carbonate accumulation: 64 to 152 cm (Btk, Bk and 2C horizons)
Particle-size control section: 20 to 70 cm (Bt and part of Btk horizon)
Durango soils have a mesic temperature regime and an ustic moisture regime bordering on aridic.
National Cooperative Soil Survey
U.S.A.