LOCATION BACA CO+SDEstablished Series
The Baca series consists of very deep, well drained soils that formed in mixed material from Tertiary pedisediments modified by wind. Baca soils are on plains and uplands. Slopes range from 0 to 15 percent. Mean annual precipitation is about 15 inches and mean annual air temperature is about 50 degrees F.
TAXONOMIC CLASS: Fine, smectitic, mesic Aridic Haplustalfs
TYPICAL PEDON: Baca silt loam, rangeland. (Colors are for dry soil unless otherwise noted).
A--0 to 5 inches; light brownish gray (10YR 6/2) silt loam; dark grayish brown (10YR 4/2) moist; moderate very fine granular structure; soft, very friable; neutral (pH 6.6 - 7.3); clear smooth boundary. (3 to 6 inches thick)
BA--5 to 8 inches; pale brown (10YR 6/3) light clay loam; brown (10YR 4/3) moist; weak medium and fine prismatic structure parting to moderate fine subangular blocks; slightly hard, very friable; few faint clay films on horizontal and vertical faces of peds; slightly alkaline (pH 7.4 - 7.8); clear smooth boundary.
Bt--8 to 20 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; moderate and strong prismatic structure parting to moderate and strong fine and very fine angular blocks; very hard, friable; few distinct clay films; slightly alkaline (pH 7.4 - 7.8); gradual smooth boundary. (Combined thickness of the Bt horizons is 7 to 19 inches)
Btk--20 to 24 inches; pale brown (10YR 6/3) silty clay loam; brown (10YR 5/3) moist; weak medium prismatic structure parting to weak and moderate medium subangular blocks; hard, friable; some visible calcium carbonate as concretions; few distinct clay films on horizontal and vertical faces of peds; strongly effervescent; moderately alkaline (pH 7.9 - 8.4); gradual smooth boundary. (3 to 6 inches thick)
Bk1--24 to 44 inches; pale brown (10YR 6/3) clay loam; brown (10YR 5/3) moist; hard, very friable; massive; visible secondary calcium carbonate in finely divided forms as thin seams and streaks, and as small concretions; strongly effervescent; moderately alkaline (pH 7.9 - 8.4); gradual smooth boundary. (15 to 24 inches thick)
Bk2--44 to 60 inches; pale brown (10YR 6/3) loam; brown (10YR 5/3) moist; massive; slightly hard, friable; some calcium carbonate mostly as concretions and in thin seams and streaks inherent in the parent material; moderately alkaline (pH 7.9 - 8.4). (Several feet thick)
TYPE LOCATION: Baca County, Colorado; 230 feet east of the northwest corner of Sec. 5, T. 33 S., R. 48 W.
RANGE IN CHARACTERISTICS:
Soil moisture: moist intermittently April through August; ustic moisture regime bordering on aridic
The mean annual soil temperature is 50 to 57 degrees F.
Mean summer soil temperature is 68 to 75 degrees F.
Depth to calcareous material: 8 to 20 inches with at least 1/4 of the Bt horizon being noncalcareous in the upper part.
The depth to the base of the argillic horizon ranges from 15 to 31 inches thick.
Particle size control section: (weighted average)
Clay content: 35 to 50 percent
Sand content: 5 to 25 percent with less than 15 percent fine or coarser sand
Rock fragment content: 0 to 5 percent
A horizon:
Hue: 10YR or 2.5Y
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 1 through 3
Reaction: neutral through moderately alkaline
Surface horizons having value as dark as 5 dry and 3 moist do not exceed 4 inches in thickness.
Bt horizon:
Hue: 7.5YR to 2.5Y
Value: 5 to 7 dry, 4 or 5 moist
Chroma: 2 to 4
Texture: silty clay loam, clay loam, silty clay, or clay
Clay content: 35 to 50 percent
Silt content: 25 to 60 percent
Sand content: 5 to 40 percent with less than 15 percent fine sand or coarser.
Reaction: neutral through moderately alkaline
Btk horizon:
Hue: 2.5Y to 7.5YR
Value: 5 to 7 dry, 4 or 5 moist
Chroma: 2 to 4
Texture: silty clay loam, clay loam, silty clay, or clay
Clay content: 35 to 50 percent
Silt content: 25 to 60 percent
Sand content: 5 to 40 percent with less than 15 percent fine sand or coarser.
Reaction: slightly alkaline through moderately alkaline
The Bk or C horizons:
Hue: 7.5YR to 2.5Y
Reaction: slightly alkaline through strongly alkaline
Calcium carbonate equivalent: 5 to 15 percent
COMPETING SERIES: These are the
Hesper(MT),
Leiter(WY),
Manzanst(CO), Moorehead(WY),
Natank(AZ),
Norrest(SD), and
Ulmet(CO) series.
Hesper soils: are noncalcareous in the argillic horizon and lack Btk horizons.
Leiter soils: have a paralithic contact at depths of 20 to 40 inches.
Manzanst soils: are calcareous throughout and average more than 15 percent fine and coarser sand.
Moorehead soils: have a mean annual temperature of 44 to 50 degrees F., average more than 15 percent fine or coarser sand, and have wettest moisture period from March through June.
Natank soils: have a lithic contact at depths of 20 to 40 inches.
Norrest soils: have a paralithic contact at depths of 20 to 40 inches.
Ulmet soils: average more than 15 percent fine and coarser sand.
GEOGRAPHIC SETTING:
Landform: plains and uplands
Elevation: 4,000 to 6,500 feet.
Slope: 0 to 15 percent
Parent material: mixed material derived from Tertiary pedisediments modified by wind.
Mean annual precipitation: 14 to 18 inches
Wettest period: April through August
Driest period: November through February
Mean annual temperature ranges from 49 to 55 degrees F.
Frost free period: 120 to 165 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Campo,
Richfield,
Wiley, and
Stoneham soils.
Campo soils have an abrupt textural boundary between A and B horizons.
Richfield soils have a mollic epipedon.
Stoneham and Wiley soils have less than 35 percent clay in the argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: These soils are used both as rangeland and as irrigated cropland. Native vegetation is mainly blue grama, buffalograss, western wheatgrass, broom snakeweed, and cactus.
DISTRIBUTION AND EXTENT: Southeastern and eastern Colorado. LRR E,G; MLRA 67, 49; The soil is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: The Southern Great Plains Wind Erosion Area, 1937.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Particle size control section: the zone from 8 to 24 inches. (Bt and Btk horizons)
Ochric epipedon: the zone from 0 to 5 inches. (A horizon)
Argillic horizon: the zone from 8 to 24 inches. (Bt and Btk horizons)
Class is changed from Ustollic Haplargids to Aridic Haplustalfs due to additional moisture in the moisture control section. Last updated by the state 3/94.
The assignment of the cation exchange activity class is supported by laboratory sample #S87CO071-005.
Modified by Lee Neve in 1/2002 to include RIC for the Btk horizon and major re-format of the OSD.
Taxonomic Version: Second Edition, 1999
ADDITIONAL DATA: Laboratory sample #S87CO071-005