LOCATION WILSON TX+OKEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Oxyaquic Vertic Haplustalfs
TYPICAL PEDON: Wilson silt loam--cropland. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; very dark gray (10YR 3/1) silt loam, gray (10YR 5/1) dry; weak fine granular structure; massive when dry; very hard, firm, sticky and plastic; common fine roots; moderately acid; abrupt wavy boundary. (3 to 10 inches thick)
Bt--5 to 20 inches; very dark gray (10YR 3/1) silty clay, gray (10YR 5/1) dry; moderate medium angular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots; few fine pores; thin continuous clay films 1/2 unit of value darker than interior of peds; vertical cracks 1/2 inch wide are filled with material from the Ap horizon; slightly acid; gradual wavy boundary. (10 to 20 inches thick)
Btssg1--20 to 32 inches; grayish brown (2.5Y 5/2) silty clay, light brownish gray (2.5Y 6/2) dry; moderate medium angular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots; few fine pores; few slickensides; few medium pressure faces; thin continuous clay films on surface of peds; vertical cracks 1/4 inch wide partly filled with material from above; few fine crystals of gypsum; few fine calcium carbonate concretions; slightly alkaline; diffuse wavy boundary.
Btssg2--32 to 65 inches; grayish brown (2.5Y 5/2) silty clay, light brownish gray (2.5Y 6/2) dry; weak coarse angular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots; few fine pores; few slickensides; patchy clay films on surface of peds; common fine crystals of gypsum; few fine masses of calcium carbonate; slightly alkaline; gradual smooth boundary. (combined Btss subhorizons are 25 to 60 inches thick)
BCkss--65 to 80 inches; olive gray (5Y 5/2) silty clay, light gray (5Y 7/2) dry; weak coarse angular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots; few fine pores; few slickensides;
few coarse masses of calcium carbonate; few small fragments of clay; very slightly effervescent; moderately alkaline.
TYPE LOCATION: Kaufman County, Texas; 4 miles southeast of the intersection of Texas Highway 34 and U. S. Highway 175 in Kaufman, 0.15 mile northeast and 0.2 mile southeast of intersection of county road and U. S. Highway 175, 150 feet southwest in field.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to more than 80 inches. The weighted average clay content of the upper 20 inches of the argillic horizon ranges from 35 to 50 percent. When dry, cracks at least 1/4 inch wide extend from the top of the argillic horizon through a thickness of 12 inches or more within the upper 50 inches of the soil. Slickensides and/or wedged-shaped aggregates and pressure faces range from few to common and begin at a depth of 14 to 26 inches. Linear extensibility is greater than 2.5 inches (6 cm) within 40 inches (100 cm) of the soil surface. COLE ranges from 0.07 to 0.10 in the upper 50 inches of the argillic horizon. The surface layer is variable in thickness with a series of micro crests and troughs in the Bt horizon that range from 4 to about 20 feet apart. Redoximorphic features are contemporary in the upper Bt1 horizon and are mainly relic in the lower part of the Bt horizon. The soil does not have aquic soil conditions in the upper 20 inches in most years.
The A horizon is less than 10 inches thick in more than 50 percent of the pedon, but it is as much as 15 inches thick in some subsoil troughs. It has hue of 10YR or 2.5Y, value of 3 to 5, and chroma of 1 or 2. Texture is loam, silt loam, silty clay loam, clay loam or their gravelly counterparts. Siliceous pebbles and small cobbles range from 0 to 35 percent. It is massive and hard or very hard when dry but is soft or friable with structure when moist. Some pedons have a thin E horizon in subsoil troughs. Reaction ranges from moderately acid to neutral.
The Bt horizon has hue of 10YR or 2.5Y, value of 2 to 4, and chroma of 1 or less. Texture is clay loam, silty clay loam, silty clay, or clay. Some pedons have iron concentrations in shades of brown or yellow that range from few to common. Siliceous pebbles range from 0 to about 15 percent by
volume. Reaction ranges from slightly acid to slightly alkaline.
The Btss horizon has hue of 10YR to 5Y, value of 3 to 7, and chroma of 2 or less. Iron concentrations in shades of yellow, brown or olive range from none to common. Texture is commonly silty clay or clay and less commonly silty clay loam or clay loam. Reaction ranges from moderately acid to slightly alkaline and is typically noncalcareous.
The BCk or BC horizon has colors in shades of gray or brown. Redoximorphic features of these colors and in other shades of yellow, red or olive range from few to many. Texture is clay loam, silty clay loam, silty clay, or clay. Some pedons have fragments or thin strata of shale or marl. These materials make up less than 35 percent of the matrix. Reaction ranges from neutral to moderately alkaline. Concretions and masses of calcium carbonate range from none to common.
The C horizon, where encountered, is shale or marl or stratified layers of shale, marl and clay.
COMPETING SERIES: There are no competing series. Similar soils are the Dacosta, Herty, Lufkin, Mabank, and Steedham series. Dacosta soils have a mollic epipedon and are members of the hyperthermic family. Herty, Lufkin and Mabank soils have an abrupt texture change between the A and Bt horizon. In addition, Herty soils are in the udic moisture regime. Steedham soils have sola from 20 to 40 inches thick, and are well drained.
GEOGRAPHIC SETTING: Wilson soils are on nearly level to gently sloping terraces or remnants of terraces. Slope gradients are 0 to 5 percent but dominantly less than 1 percent. The soil formed in alkaline clayey alluvium. Mean annual temperature ranges from 64 to 70 degrees F., and mean
annual precipitation ranges from 32 to 45 inches. Frost free days range from 220 to 270 days and elevation ranges from 250 to 700 feet. Thornthwaite P-E indices from 50 to 70.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Bonham,
Burleson,
Crockett,
Houston Black,
Lufkin,
Mabank, and
Normangee series. Bonham soils have mollic epipedons. Burleson soils are on similar positions. Burleson and
Houston Black soils are clayey to the surface and have slickensides (Vertisols). Crockett and Normangee soils have Bt horizons with chroma of more than 2. Bonham, Houston Black, Crockett and Normangee soils are on slightly higher positions above Wilson. Lufkin soils are on similar or
slightly lower concave positions. Mabank soils are on similar positions.
DRAINAGE AND PERMEABILITY: Moderately well drained. Permeability is very slow. Runoff is low on 0 to 1 percent slopes, medium on 1 to 3 percent slopes, and high on 3 to 5 percent slopes. Very slow internal drainage. The soil is seasonally wet and is saturated in the surface layer and upper part of the Bt horizon during the winter and spring seasons for periods of 10 to 30 days.
USE AND VEGETATION: Wilson soils are cropped to cotton, sorghums, small grain, and corn. Many areas are now idle or are used for unimproved pasture. Original vegetation was tall prairie grasses, mainly andropogon species, and widely spaced motts of elm and oak trees. Most areas that are not cropped have few to many mesquite trees.
DISTRIBUTION AND EXTENT: Mainly in the Blackland Prairies of Texas, with small areas in Oklahoma. The soil is extensive, probably exceeding 1,000,000 acres.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Wilson County, Texas; 1907.
REMARKS: Classification change from Udertic Haplustalfs to Oxyaquic Vertic Haplustalfs based on knowledge that these soils are saturated for 2 to 4 weeks in most years. This period of time is within the definition of saturation for one month or more if rules of rounding are applied, i.e., 2 to 6 weeks saturation is considered inclusive.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 5 inches. (A horizon; very hard and massive when dry).
Argillic horizon - 5 to 65 inches. (Bt horizons)
Vertic feature - Cracks in the upper part of the argillic horizon (5 to 32 inches), few slickensides between 20 and 77 inches, and linear extensibility greater than 6.0 cm.
ADDITIONAL DATA: Type location pedon NSSL S62TX-(129)257-2 Kaufman County, Texas. Texas Ag. Exp. Station Lab. S63TX-145-1; S82TX-289-32