LOCATION SPECK TXEstablished Series
TAXONOMIC CLASS: Clayey, mixed, superactive, thermic Lithic Argiustolls
TYPICAL PEDON: Speck clay loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 8 inches; brown (7.5YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate fine subangular blocky and granular structure; hard, firm; few fine roots; few chert pebbles; slightly acid; clear smooth boundary. (4 to 9 inches thick)
Bt--8 to 18 inches; reddish brown (5YR 4/4) clay, dark reddish brown (5YR 3/4) moist; moderate fine angular blocky structure; very hard, very firm; few fine roots; few fine pores; common clay films on faces of peds; few fine calcium carbonate concretions in the lower 2 inches; neutral; abrupt wavy boundary. (7 to 14 inches thick)
R--18 to 22 inches; indurated limestone bedrock that is fractured with few calcium carbonate coatings in fractures; hardness of 3 or more on Moh's scale.
TYPE LOCATION: Coleman County, Texas; 14 miles S 37 degrees E of Coleman County Courthouse; in rangeland 225 feet east of a point on a ranch trail, which is 600 feet north of a fork in the trail and 1.6 miles east of intersection of private ranch trail and county road which intersection is 0.1 mile north and 1.5 miles east of intersection Farm Road 2633 and U. S. Highway 283.
RANGE IN CHARACTERISTICS: Solum thickness and depth to limestone bedrock or limestone conglomerate ranges from 14 to 20 inches. Coarse fragments range from a few to 25 percent on the surface and in the soil. Cobbles and stones are mostly limestone, and pebbles are mostly angular fragments of chert. Thickness of the mollic epipedon ranges from 7 to 19 inches.
The A horizons has hue of 5YR to 10YR, value of 2 to 4, and chroma of 2 or 3. Texture is clay loam, silty clay loam, or clay or their gravelly counterparts. Reaction ranges from slightly acid to mildly alkaline.
The Bt horizon has hue of 2.5YR to 7.5YR, value of 3 to 5, and chroma of 2 to 4. Texture is clay loam, clay, or silty clay. Clay content ranges from 35 to 60 percent. Secondary calcium carbonate is within the Bt horizon of some pedons as concretions just above the limestone bedrock or as coatings on the surface of fragments and in fractures. Reaction ranges from neutral to moderately alkaline and is typically noncalcareous.
The R layer is limestone bedrock or limestone conglomerate with a hardness of more than 3 on Moh's scale. In some pedons it is fractured. When fractured, soil or small amounts of secondary calcium carbonate accumulations occur as coatings on the surface of fragments and in fractures.
COMPETING SERIES: These include the Ledru (NM) series. Similar soils are the Bexar, Claremore, Graham, Hensley, Lindy, Lula, Rowden, Rumple, Scullin, and Tarpley series. Ledru soils are drier in the soil moisture control section for longer periods and are over conglomerate of sand, gravel, and cobbles. Bexar and Hensley soils do not have a mollic epipedon. Claremore and Lula soils have Bt horizons with less than 35 percent clay. Bexar, Lindy, Rowden, Rumple, and Scullin soils have sola 20 to 40 inches thick. Graham soils have Bt horizons dominated by smectitic clays. Tarpley soils have more than 60 percent clay in the Bt horizons and smectitic mineralogy.
GEOGRAPHIC SETTING: Speck soils are on nearly level to moderately sloping uplands. Slopes range from 0 to about 8 percent. The soil formed in reddish residuum and colluvium derived from indurated limestone. Mean annual precipitation ranges from 20 to 30 inches, and mean annual air temperature ranges from 63 to 68 degrees F. Frost free days range from 210 to 240 days, and elevation ranges from 1,250 to 2,250 feet. Thornthwaite P-E index ranges from 31 to 46.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Bexar, Lindy, Rowden, and Scullin series as well as the Kavett, Lueders, Oplin, and Tarrant series. Bexar, Lindy, Rowden, and Scullin soils occur in similar positions. Kavett, Lueders, Oplin, and Tarrant soils do not have Bt horizons and occur on similar positions.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is slow. Runoff is low on slopes less than 1 percent, medium on 1 to 5 percent slopes, and high on 5 to 8 percent slopes.
USE AND VEGETATION: Used mainly for rangeland. Some areas are used for small grain and grain sorghums. Native vegetation consists of little bluestem, sideoats grama, Texas wintergrass, threeawn, and a few post oak and live oak trees.
DISTRIBUTION AND EXTENT: Mostly in the limestone areas of the Central Rolling Red Plains, Central Rolling Red Prairies and to a lesser extent in the Edwards Plateau and Grand Prairie.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Travis County, Texas; 1969.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 8 inches. (A horizon)
Argillic horizon - 8 to 18 inches. (Bt horizon)
Lithic contact - indurated limestone bedrock is at 18 inches.