LOCATION CONEJOS CO
Established Series
Rev. JPP/TWH/KLS
04/2018
CONEJOS SERIES
The Conejos series consists of very deep, well drained soils that formed in slope alluvium or colluvium derived from tuff and breccia. Conejos soils are on mountain slopes. Slopes range from 5 to 70 percent. Mean annual precipitation is about 810 mm and the mean annual temperature is about 1.7 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, isotic Vitrandic Haplocryalfs
TYPICAL PEDON: Conejos very cobbly ashy silt loam, on a north-facing, 35 percent slope in coniferous forest at an elevation of 3,110 meters. (Colors are for dry soil unless otherwise noted.) When described on July 19, 1983 the soil was moist throughout. Texture, gravel content and pH are from NSSL data.
Oa--0 to 5 cm; highly decomposed forest litter.
E--5 to 38 cm; pale brown (10YR 6/3) very cobbly ashy silt loam, brown (10YR 5/3) moist; weak fine subangular blocky structure; friable, slightly hard, slightly sticky, slightly plastic; 25 percent gravel, 15 percent cobble; very strongly acid (pH 4.9); clear smooth boundary. (20 to 40 cm thick)
E/B--38 to 51 cm; 55 percent pale brown (10YR 6/3) extremely gravelly ashy silt loam (E), brown (10YR 5/3), moist; 45 percent brown (7.5YR 5/4) extremely gravelly ashy sandy clay loam (Bt), brown (7.5YR 4/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; 60 percent gravel, 15 percent cobble; moderately acid (pH 5.6); gradual wavy boundary. (0 to 25 cm thick)
Bt1--51 to 122 cm; brown (7.5YR 5/4) very cobbly ashy sandy clay loam, brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; firm, very hard, moderately sticky and moderately plastic; 30 percent gravel, 25 percent cobble; moderately acid (pH 5.7); gradual wavy boundary.
Bt2--122 to 160 cm; light brown (7.5YR 6/4) very gravelly ashy sandy clay loam, brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; moderately sticky and slightly plastic; 35 percent gravel, 10 percent cobble; slightly acid (pH 6.1). (combined thickness of Bt1, Bt2 horizons is more than 36 cm)
TYPE LOCATION: Rio Grande County, Colorado; about 16 miles south of Del Norte; in the SW 1/4 of the SE 1/4 of sec. 13, T. 37 N., R. 5 E.; Greenie Mountain USGS quad; Lat. 37 degrees 26 minutes 50 seconds N. and Long. 106 degrees 22 minutes 25 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 1.1 to 3.3 degrees C.
Mean summer soil temperature: 4.4 to 7.2 degrees C.
Depth to argillic horizon: 20 to 46 cm
Lithology of rock fragments: tuff, breccia
Particle-size control section (weighted average):
Clay content: 24 to 30 percent
Rock fragment content: 35 to 60 percent
E horizon (albic horizon in some pedons)
Hue: 7.5YR or 10YR
Value: 4 or 5 moist
Chroma: 2 or 3, dry or moist
Texture: ashy silt loam or ashy loam, with cobbly, very cobbly or stony modifiers
Clay content: 10 to 20 percent
Rock fragment content: 25 to 45 percent total; 10 to 30 percent gravel, 10 to 20 percent cobble, 0 to 20 percent stones
Acid oxalate extractable Al + 1/2 Fe: 0.20 to 0.60 percent
Glass content: 5 to 25 percent
Reaction (pH): 4.5 to 6.5
E/B horizon (not in all pedons)
E part
Hue: 7.5YR or 10YR
Value: 4 or 5 moist
Chroma: 2 or 3, dry or moist
Texture: ashy silt loam or ashy loam, with very cobbly, very gravelly, or extremely gravelly modifiers
Clay content: 10 to 20 percent
Bt part
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4, dry or moist
Texture: ashy clay loam, ashy sandy clay loam, or ashy loam; with very gravelly, very cobbly, or extremely gravelly modifiers
Clay content: 22 to 32 percent
Rock fragment content: 35 to 80 percent total; 20 to 65 percent gravel, 10 to 20 percent cobble, 0 to 5 percent stones
Acid oxalate extractable Al + 1/2 Fe: 0.10 to 0.50 percent
Glass content: 5 to 25 percent
Base saturation: 80 to 100 percent
Reaction (pH): 5.1 to 7.3
Bt1, Bt2 horizon(s)
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4, dry or moist
Texture: ashy clay loam, ashy sandy clay loam, or ashy loam; with very gravelly or very cobbly modifiers
Clay content: 22 to 32 percent
Sand content (fine sand and coarser sand): 35 to 60 percent
Rock fragment content: 35 to 60 percent total; 20 to 45 percent gravel, 10 to 25 percent cobble; 0 to 5 percent stones
Acid oxalate extractable Al + 1/2 Fe: 0.10 to 0.40 percent
Glass content: 5 to 20 percent
Base saturation: 80 to 100 percent
Reaction (pH): 5.6 to 7.3
COMPETING SERIES:
Weberg (OR) - have redoximorphic features and a seasonal water table
GEOGRAPHIC SETTING:
Landform - mountain slopes
Elevation - 2,500 to 3,600 meters
Slopes - 5 to 50 percent
Parent material - slope alluvium or colluvium derived from tuff and breccia
Mean annual temperature - 0.6 to 3.9 degrees C.
Mean annual precipitation - 630 to 1,020 mm
Frost-free period - 30 to 65 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained, medium runoff, moderate permeability.
USE AND VEGETATION: Used mainly for forestland. Potential natural vegetation is subalpine fir, Engelmann spruce, Rocky Mountain whortleberry, common juniper, senecio, silvery lupine, heartleaf arnica, and fringed brome.
DISTRIBUTION AND EXTENT: Southwestern Colorado, San Juan Mountains; LRR E, MLRA 48A; moderately extensive.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Rio Grande County, Rio Grande National Forest, West Part soil survey area, 2006. The name Conejos is taken from a nearby river and county. Pronunciation is Con-ay-hohs.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: 8 to 152 cm
Particle-size control section: 38 to 88 cm (Upper 50 cm of the Bt horizon)
Argillic horizon: 38 to 160 cm (E/B, Bt1, and Bt2 horizons)
Vitrandic feature: 5 to 51 cm (E and E/B horizons)
Clay contents are calculated from 1500 kPa water and organic carbon.
Conejos soils have a cryic temperature regime and an udic soil moisture regime.
ADDITIONAL DATA: NSSL sample S84CO105-001 (sampled as Granile).
National Cooperative Soil Survey
U.S.A.