LOCATION GRAYCO COEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Ustic Haplargids
TYPICAL PEDON: Grayco sandy loam, 0 to 2 percent slope in rangeland at an elevation of 7,714 feet. (Colors are for dry soil unless otherwise noted.) When described on July 19, 2004 the soil was dry throughout. The surface is covered by about 25 percent gravel derived from granite, gneiss, and mica schist.
A--0 to 10 centimeters; brown (7.5YR 4/3) sandy loam, dark brown (7.5YR 3/3) moist; 18 percent clay; weak fine granular structure; friable, soft, slightly sticky, slightly plastic; common very fine and fine roots throughout; common very fine irregular pores; 10 percent gravel; noneffervescent; neutral (pH 7.0); clear smooth boundary.
Bt--10 to 36 centimeters; brown (7.5YR 5/4) loam, brown (7.5YR 4/4) moist; 26 percent clay; moderate fine subangular blocky structure, and moderate medium subangular blocky structure; friable, hard, moderately sticky, moderately plastic; common very fine and fine roots throughout; common very fine dendritic tubular pores; common continuous faint clay films on faces of peds; 10 percent gravel; noneffervescent; slightly alkaline (pH 7.4); clear wavy boundary.
Bk--36 to 46 centimeters; brown (7.5YR 5/3) very gravelly sandy loam, brown (7.5YR 4/3) moist; 20 percent clay; weak medium subangular blocky structure, and weak fine subangular blocky structure; friable, slightly hard, slightly sticky, slightly plastic; common very fine and fine roots throughout; common very fine dendritic tubular pores; common fine irregular carbonate masses around rock fragments; 35 percent gravel and 5 percent cobbles; slightly effervescent; 1 percent calcium carbonate equivalent; slightly alkaline (pH 7.6); abrupt wavy boundary.
2Bk1--46 to 61 centimeters; brown (7.5YR 5/3) extremely gravelly loamy sand, brown (7.5YR 4/3) moist; 5 percent clay; massive; loose, loose, nonsticky, nonplastic; common very fine roots throughout; common very fine irregular pores; many fine irregular carbonate masses around rock fragments; 60 percent gravel and 10 percent cobbles; strongly effervescent; 3 percent calcium carbonate equivalent; moderately alkaline (pH 8.0); gradual wavy boundary.
2Bk2--61 to 109 centimeters; brown (7.5YR 5/3) extremely gravelly sand, brown (7.5YR 4/3) moist; 2 percent clay; massive; loose, loose, nonsticky, nonplastic; common very fine roots throughout; common very fine irregular pores; common fine irregular carbonate masses around rock fragments; 60 percent gravel and 5 percent cobbles; slightly effervescent; 1 percent calcium carbonate equivalent; slightly alkaline (pH 7.8); gradual wavy boundary.
2C--109 to 203 centimeters; brown (7.5YR 5/3) extremely gravelly sand, brown (7.5YR 4/3) moist; 2 percent clay; single grain; loose, loose, nonsticky, nonplastic; common very fine roots throughout; common very fine irregular pores; 60 percent gravel and 5 percent cobbles; slightly effervescent; 1 percent calcium carbonate equivalent; slightly alkaline (pH 7.8).
TYPE LOCATION: Costilla County, Colorado; Grayco sandy loam; Gracia USGS topographic quadrangle, NAD83; 37 degrees 0 minutes 3.17 seconds north latitude and 105 degrees 34 minutes 24.91 seconds west longitude; UTM 448,965 meters E, 4095,124 meters N, zone 13.
RANGE IN CHARACTERISTICS:
Soil moisture: aridic bordering on ustic.
Mean annual soil temperature: 41 to 46 degrees F (5.0 to 7.8 degrees C)
Mean summer soil temperature: 63 to 66 degrees F (17.2 to 18.9 degrees C)
Thickness of argillic horizon: 5 to 20 inches (13 centimeters to 51 centimeters)
Depth to argillic horizon: 2 to 6 inches (5 to 15 centimeters)
Depth to secondary carbonates: 10 to 20 inches (25 to 51 centimeters)
Depth to lithologic discontinuity: 10 to 40 inches (25 to 102 centimeters)
Depth to strongly contrasting particle size class: 10 to 60 inches (25 to 152 centimeters)
Particle-size control section (weighted average):
Clay content: 18 to 27 percent
Sand content: 35 to 60 percent
Silt content: 13 to 47 percent
Rock fragment content: 15 to 60 percent gravel and cobbles
A horizon(s)
Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: sandy loam
Clay content: 12 to 20 percent
Carbonate clay content: 0 to 2 percent
Sand content: 50 to 80 percent
Silt content: 10 to 40 percent
Fragment content, total: 0 to 15 percent
Fragment size and content: 0 to 15 percent indurated gravel derived from granite, gneiss, and mica schist
Calcium carbonate equivalent: 0 to 1 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 6.1 to 7.3
Organic matter content: 1.0 to 2.0 percent
Bt horizon(s)
Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: loam, gravelly sandy clay loam
Clay content: 12 to 27 percent
Carbonate clay content: 0 to 4 percent
Sand content: 35 to 65 percent
Silt content: 15 to 40 percent
Fragment content, total: 0 to 35 percent
Fragment size and content: 0 to 30 percent indurated gravel
0 to 5 percent indurated cobbles derived from granite, gneiss, and mica schist
Calcium carbonate equivalent: 0 to 1 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 6.6 to 7.3
Organic matter content: 0.5 to 1.0 percent
Bk horizon(s)
Hue: 7.5YR or 10YR
Value: 4 to 6 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: very gravelly sandy loam, very gravelly sandy clay loam, gravelly loam
Clay content: 10 to 27 percent
Carbonate clay content: 2 to 6 percent
Sand content: 35 to 65 percent
Silt content: 15 to 40 percent
Fragment content, total: 15 to 60 percent
Fragment size and content: 15 to 50 percent indurated gravel
0 to 10 percent indurated cobbles derived from granite, gneiss, and mica schist
Calcium carbonate equivalent: 0 to 2 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 7.4 to 8.4
Organic matter content: 0.2 to 1.0 percent
2Bk horizon(s)
Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: extremely gravelly sand, extremely gravelly loamy sand
Clay content: 0 to 8 percent
Carbonate clay content: 0 to 2 percent
Sand content: 60 to 100 percent
Silt content: 0 to 37 percent
Fragment content, total: 60 to 85 percent
Fragment size and content: 55 to 70 percent indurated gravel
5 to 15 percent indurated cobbles derived from granite, gneiss, and mica schist
Calcium carbonate equivalent: 1 to 10 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 7.9 to 9.0
Organic matter content: 0.0 to 0.5 percent
2C horizon(s)
Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: extremely gravelly loamy sand, extremely gravelly sand
Clay content: 0 to 5 percent
Sand content: 87 to 100 percent
Silt content: 0 to 13 percent
Fragment content, total: 60 to 85 percent
Fragment size and content: 55 to 70 percent indurated gravel
5 to 15 percent indurated cobbles derived from granite, gneiss, and mica schist
Calcium carbonate equivalent: 0 to 2 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 7.9 to 8.4
Organic matter content: 0.0 to 0.5 percent
COMPETING SERIES:
These are the
Gretdivid,
Platoro, and
Relsob series
Gretdivid soils: have 25 percent or less coarse fragments in the 2C horizon.
Platoro soils: rock fragments are derived from basalt and are less than 60 percent in the 2C horizon.
Relsob soils: have less than 60 percent rock fragments in the 2C horizon.
GEOGRAPHIC SETTING:
Parent material: outwash derived from granite, gneiss, and mica schist.
Landform: outwash plain, outwash terrace
Slopes: 0 to 6 percent
Elevation: 7,500 to 8,500 feet (2,286 to 2,591 meters)
Mean annual air temperature: 39 to 43 degrees F (3.9 to 7.8 degrees C)
Mean annual precipitation: 8 to 12 inches (20 to 30 centimeters)
Precipitation pattern: Precipitation peaks in July and August. Summer precipitation occurs during intense summer thunderstorms.
Frost-free period: 85 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS:
Kibin soils: are fine-loamy and pachic
Trinchera soils: are fine-loamy and do not have lithologic discontinuity in the profile.
Fuertes soils: are somewhat poorly drained.
DRAINAGE AND PERMEABILITY: well drained, moderate permeability, Ksat class: moderately high, low runoff
USE AND VEGETATION: These soils are used for livestock grazing and irrigated cropland. Native plants commonly are Wyoming big sage, blue grama, ring muhly, rubber rabbitbrush, and sand dropseed
DISTRIBUTION AND EXTENT: San Luis Valley Area of south-central Colorado; LRR E; MLRA 51. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Costilla County, Colorado, Costilla County Soil Survey Area, 2009. The name Grayco is coined.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 4 to 14 inches.
Argillic horizon: 4 to 14 inches (10 to 36 centimeters) Bt horizon
Depth to lithologic discontinuity: 18 inches (46 centimenters)
Taxonomic version: Tenth Edition, 2006.