LOCATION CHO                     TX

Established Series


The Cho series consists of soils that are very shallow and shallow to a petrocalcic horizon. These well drained soils formed in loamy calcareous gravelly alluvium. These nearly level to moderately sloping soils are on stream terraces, alluvial fans and knolls on alluvial plain remnants on dissected plateaus. Slope ranges from 0 to 8 percent. Mean annual air temperature is about 19 degrees C (66 degrees F), and mean annual precipitation is about 635 mm (25 in).

TAXONOMIC CLASS: Loamy, carbonatic, thermic, shallow Petrocalcic Calciustolls

TYPICAL PEDON: Cho loam--in rangeland. (Colors are for dry soil unless otherwise stated.)

A--0 to 25 cm (0 to 10 in); brown (10YR 4/3) loam, dark brown (10YR 3/3) moist; weak fine granular and weak medium subangular blocky structure; slightly hard, friable; many fine roots; common fine pores; 5 percent indurated caliche fragments on surface; 10 percent indurated caliche fragments; violently effervescent; moderately alkaline; abrupt wavy boundary. (Thickness of the A horizon is 18 to 51 cm [7 to 20 in])

Bkkm--25 to 36 cm (10 to 14 in); pinkish white (7.5YR 8/2) indurated caliche laminar petrocalcic; fractured at intervals of 150 to 460 mm (6 to 18 in) across by 25 to 51 mm (1 in to 2 in) thick; 5 percent brown (10YR 4/3) loam between plates and in solution channels; violently effervescent; moderately alkaline; clear wavy boundary. (Thickness of the Bkkm horizon is 5 to 30 cm [2 to 12 in])

Bkk--36 to 152 cm (14 to 60 in); pink (7.5YR 8/4) loam; massive; slightly hard, friable; 20 percent finely disseminated calcium carbonate; 20 to 30 percent weakly cemented to strongly cemented concretions and caliche fragments; violently effervescent; moderately alkaline.

TYPE LOCATION: McCulloch County, Texas; From the intersection U.S. Highway 87 and U.S. Highway 377 in Brady, 17.3 miles west-northwest on U.S. Highway 87, 15.9 miles north on Farm Road 503, (approximately 3.7 miles north of Doole), 0.4 mile northeast on ranch trail, and 200 feet northwest in rangeland. (Doole USGS topographic quadrangle; Latitude: 31 degrees, 26 minutes, 56.4 seconds N; Longitude: 99 degrees, 35 minutes, 34.8 seconds W; NAD83)

Depth to petrocalcic contact: 18 to 50 cm (7 to 20 in)

Particle-size control section (weighted average):
Clay content: 15 to 35 percent total clay

A horizon
Hue: 7.5YR or 10YR
Value: 3 to 5 dry
Chroma: 2 or 3 dry
Texture: Loam or clay loam, or their gravelly phases
Clay content: 15 to 35 percent total clay
Effervescence: Violently
Reaction: Slightly alkaline or moderately alkaline
Calcium carbonate equivalent: 40 to 65 percent by weight in the fine-earth fraction
Rock fragments: Amount-0 to 34 percent, size-2 to 75 mm, kind-caliche; and/or amount-0 to 5 percent, size-76 to 250 mm, kind-limestone

Bkkm horizon
Hue: 5YR to 10YR
Value: 7 or 8 dry
Chroma: 1 to 4 dry
Cementation: Strongly cemented to indurated, laminar in upper 4 to 5 cm
Effervescence: Violently
Reaction: Slightly alkaline or moderately alkaline

Bkk horizon
Hue: 5YR to 10YR
Value: 7 or 8 dry
Chroma: 1 to 4 dry
Texture: Loam, clay loam or silty clay loam; and their gravelly and very gravelly phases
Effervescence: Violently
Reaction: Slightly alkaline or moderately alkaline
Calcium carbonate equivalent: 40 to 85 percent by weight
Rock fragments: Amount-0 to 50 percent by volume, size-2 to 75 mm, kind- caliche, siliceous, and limestone

COMPETING SERIES: There are no other series in this family. Similar series are Eola (TX), Kavett (TX), Mailtrail (TX), Mereta (TX), Noelke (TX), Ozona (TX), Pitzer (TX), Valco (TX), and Valera (TX).
Eola and Mailtrail soils: Have more than 35 percent coarse fragments in the control section.
Kavett and Valera soils: Have a petrocalcic horizon that is underlain by hard limestone and Valera soils are moderately deep to a petrocalcic.
Mereta soils: Are clayey and the mineralogy is mixed.
Noelke soils: Have a lithic contact within 50 cm of the surface.
Ozona and Pitzer soils: Have less than 40 percent by weight calcium carbonate equivalent in the control section.
Valco soils: Mean annual soil temperatures is 22 degrees C (72 degrees F) or higher.

Parent material: Loamy calcareous gravelly alluvium several feet thick or ancient alluvium derived from limestone and sandstone.
Landscape: Dissected plateaus
Landform: Stream terraces, alluvial fans and/or knolls on alluvial plain remnants
Slope: 0 to 8 percent
Climate: Dry subhumid
Soil moisture: Typic ustic moisture regime
Precipitation Pattern: The majority of the yearly amount occurs during the fall and spring months. The winter and summer months are normally drier.
Mean annual precipitation: 508 to 686 mm (20 to 27 in)
Mean annual air temperature: 18 to 20 degrees C (64 to 68 degrees F)
Frost free days: 210 to 240
Elevation: 366 to 610 m (1,200 to 2,000 ft)
Thornthwaite P-E index: 25 to 50

GEOGRAPHICALLY ASSOCIATED SOILS: These are Kavett (TX), Mereta (TX), Nuvalde (TX), Rowena (TX) and Valera (TX) series.
Kavett and Valera soils: Occur on backslope and footslope positions.
Mereta soils: Occur on similar positions
Nuvalde and Rowena soils: Occur on lower positions on footslopes and are formed from more recent alluvial sediments.

DRAINAGE AND PERMEABILITY: Well drained. Permeability in the petrocalcic horizon is slow to very slow. Runoff is negligible on 0 to 1 percent slopes, very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, and medium on 5 to 8 percent slopes.

USE AND VEGETATION: Mainly used as rangeland. Some areas are used for growing small grains. The climax plant community is a mid grass prairie. The dominant grass is sideoats grama. Other grasses include little bluestem, Texas wintergrass, silver bluestem, Arizona cottontop, dropseeds, white tridens, hairy grama, little bluestem, slim tridens, buffalograss, Wright's threeawn, and curly mesquite. The woody plant is live oak. Forbs include bushsunflower, orange zexmenia, and gayfeather. With heavy stocking rates, the site could potentially deteriorate to a plant population of lotebush, prickly pear, Texas persimmon, tasajillo, agarito, threeawns, red grama, Texas grama, hairy tridens, prairie coneflower, and broomweed.

DISTRIBUTION AND EXTENT: West-Central Texas. Central Great Plains Winter Wheat and Range Region, LRR-H: MLRA 78A-Rolling Limestone Prairie; MLRA 78B-Central Rolling Red Plains, Western Part; and MLRA 80B-Texas North-Central Prairies. Southwest Plateaus and Plains Range and Cotton Region, LLR-I: MLRA 81A-Edwards Plateau, Western Part; MLRA 81B-Edwards Plateau, Central Part; and MLRA 82A-Texas Central Basin. Southwestern Prairies Cotton and Forage Region, LRR-J: MLRA 85-Grand Prairie. The series is extensive with over 500,000 acres.


SERIES ESTABLISHED: McCulloch County, Texas; 1970.

REMARKS: These soils were formerly included in the Kimbrough and Mereta series.

Although the series is classified as typic ustic at the series type location, the moisture subclass is aridic ustic in the western portion of the correlated range. A new series should be established for the the aridic ustic moisture regime.

Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: 0 to 25 cm (0 to 10 in). (A horizon)
Petrocalcic horizon: 25 to 36 cm (10 to 14 in) (Bkkm horizon)
Calcic horizon: 36 to 152 cm (14 to 60 in) (Bkk horizon)


TAXONOMIC VERSION: Keys to Soil Taxonomy, 11th Edition, 2010.

National Cooperative Soil Survey