LOCATION STEPHEN                 TX

Established Series


The Stephen series consists of shallow, well drained, moderately slowly permeable soils formed in residuum weathered from chalk. These soils are on gently sloping to sloping uplands. Slopes are mainly 1 to 5 percent but range from 1 to 8 percent. Mean annual precipitation is about 964 mm (38 in) and the mean annual air temperature is about 18.75 degrees C (65.7 degrees F).

TAXONOMIC CLASS: Clayey, mixed, active, thermic, shallow Udorthentic Haplustolls

TYPICAL PEDON: Stephen silty clay--cropland. (Colors are for dry soil unless otherwise stated.)

Ap--0 to 20 cm (0 to 8 in); brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; moderate fine subangular blocky and granular structure parting to very fine subangular blocky; hard, firm, sticky, plastic; many fine roots; few fine chalk fragments; calcareous, moderately alkaline; abrupt wavy boundary. (18 to 51 cm [7 to 20 in] thick)

A--20 to 30 cm (8 to 12 in); about 65 percent platy chalk fragments and platy chalk in place and about 35 percent dark brown (7.5YR 3/3) moist silty clay in the horizontal and vertical crevices and between the loose chalk fragments; few to strongly cemented cobblestones and limestone; few fine roots; few fine pores; calcareous, moderately alkaline; abrupt irregular boundary. (0 to 15 cm [0 to 6 in] thick)

Cr---30 to 71 cm (12 to 28 in); pink (5YR 8/3) and very pale brown (10YR 8/2) platy chalk this is less hard than 3, Mohs scale; moderately alkaline; few thin tongues of dark brown calcareous silty clay in crevices between some chalk plates.

TYPE LOCATION: McLennan County, Texas; from the intersection of Farm Road 1695 and Farm Road 2837 in Lorena, 0.6 mile northwest on Farm Road 2837 to intersection with county road, 300 ft west and 100 ft north of intersection in cropland;
USGS topographic quadrangle: Lorena, TX;
Latitude 31 degrees, 23 minutes, 36.20 seconds North;
Longitude 97 degrees, 13 minutes, 21.40 seconds West
Datum: WGS 84.

Solum depth: ranges from 18 to 51 cm (7 to 20 in) thick.
Soil Moisture: An ustic soil moisture regime. The soil moisture control section is dry in some or all parts for 90 or more cumulative days per year in normal years.
Mean annual soil temperature: 17 to 21 degrees C (63 to 70 degrees F)
Depth to paralithic contact: 18 to 51 cm (7 to 20 in)
Thickness of mollic epipedon: 18 to 51 cm (7 to 20 in)
Thickness of free carbonates: 18 to 51 cm (7 to 20 in)

Particle-size control section (weighted average)
Clay content: 35 to 55 percent
Silicate clay content: 35 to 61 percent
Calcium carbonate equivalent: 40 to 80 percent in the layer below the A horizon
The chalky limestone, when moist, can be cut with a spade.

A or Ap horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5
Chroma: 1 to 3
Texture: clay, silty clay, silty clay loam, or clay loam with 35 to 55 percent clay
Rock Fragments: amount-0 to 25 percent; size-gravel; kind-Chalk
Olive mottles or streaks range from none to common in the lower part to the A horizon. The lower boundary of the A horizon ranges from wavy to irregular.

A, C/A or A/C horizons (where present):
Hue: 7.5YR or 10YR
Value: 3 to 8
Chroma: 1 to 3
Texture: clay, silty clay, silty clay loam, or clay loam with 35 to 55 percent clay
Rock Fragments: amount-0 to 5 percent; size-fine gravel to cobbles; kind-chalk or limestone
Pararock Fragments: amount- 60 to 80 percent; size- medium gravel to stone; kind-chalk

Cr horizon:
Hue: 5YR to 10YR,
Value: 4 to 8
Chroma: 1 to 3
Pararock fragments: kind-chalk
Shades of pink, white, and gray interbedded chalk and limy earths or soft limestone and limy earths.

COMPETING SERIES: There are no series in the same family. Similar soils are Brackett, Castephen, Doss, Eckrant, Purves, Real, and Whitewright series.
Brackett, Castephen, Doss, Real, and Whitewright soils: have carbonatic mineralogy and contain less than 35 percent silicate clay. In addition, Brackett and Whitewright soils lack a mollic epipedon; and Real soils contain more than 35 percent fragments.
Eckrant and Purves soils: have a lithic contact with indurated limestone. In addition, Eckrant soils contain more than 35 percent coarse fragments.

Parent material: interbedded chalk, marl, or soft limestone rubble, mainly of the Austin Formation
Landscape: dissected plains
Landform: ridge
Slope: 1 to 8 percent, mainly less than 5 percent
Mean annual precipitation: 762 to 1,189 mm (30 to 47 in)
Mean annual air temperature: 16.9 to 20.7 degrees C (62.4 to 69.3 degrees F)
Frost-free period: 224 to 277 days
Elevation: 131.2 to 272.6 m (430.4 to 894.4 ft)
Thornthwaite P-E Index: 44 to 66

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Altoga, Austin, Brackett, Eddy, and Lott series.
All of these soils: have carbonatic minerology and less than 35 percent clay in the control section. In addition; Altoga, Brackett, and Eddy do not have mollic epipedons.

Drainage class: Well;
Permeability class: Moderately slow
Runoff: medium on slopes of 1 to less than 5 percent and high on slopes of 5 to 8 percent.
Medium internal drainage.

USE AND VEGETATION: Mainly in cultivation and used for growing small grains. A few areas are in native range. Native grasses are little bluestem, sideoats grama, hairy grama, and buffalograss. Some areas are used for urban land uses.

DISTRIBUTION AND EXTENT: The Blackland Prairie of Texas. MLRA 86A. The series is extensive.


SERIES ESTABLISHED: Ellis County, Texas; 1962.

REMARKS: Classification was changed 11/89 from clayey, mixed, thermic, shallow Entic Haplustolls to clayey, mixed, thermic, shallow Udorthentic Haplustolls.

Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon: 0 to 20 cm (0 to 8 in) (Ap horizon).
Paralithic contact: chalk at a depth of 30 cm (12 in).
Free carbonates: 0 to 71 cm (Ap, A, and Cr horizons)


Taxonomic Version: Keys to Soil Taxonomy, Twelfth Edition, 2014.

National Cooperative Soil Survey