LOCATION CRAWFORD TXEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Leptic Udic Haplusterts
TYPICAL PEDON: Crawford clay--cropland. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 5 inches; brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; weak very fine angular blocky structure; very hard, firm, few fine pebbles of quartz and few fragments of limestone; neutral; abrupt smooth boundary. (4 to 8 inches thick)
A--5 to 12 inches; brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; moderate medium angular blocky structure parting to very fine blocky structure; extremely hard, very firm, very sticky, plastic; common pressure faces; few fine pebbles of quartz and fragments of limestone; neutral; gradual irregular boundary. (5 to 12 inches thick)
Bss1--12 to 21 inches; brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; moderate medium angular blocky and weak very fine blocky structure; extremely hard, very firm, very sticky, plastic; few slickensides tilted 20 degrees to 40 degrees from horizontal; many pressure faces; few fine pebbles of quartz and fragments of limestone; neutral; gradual wavy boundary. (6 to 12 inches thick)
Bss2--21 to 28 inches; dark reddish brown (5YR 3/2) silty clay, dark reddish brown (5YR 3/2) moist; crushed peds are (5YR 3/3) moist; strong medium blocky structure; extremely hard, very firm, very sticky, plastic; common slickensides about 1-1/2 inches across the long axis; many pressure faces; few pebbles of quartz and limestone; neutral; abrupt irregular boundary. (5 to 15 inches thick)
R--28 to 38 inches; indurated fractured limestone; fractures are about 10 to 20 inches apart; dark reddish brown clay in the fine crevices.
TYPE LOCATION: Coryell County, Texas; from the intersection of Texas Highway 36 and Farm Road 107 in Fort Gates, 17.1 miles east on Farm Road 107, 2.2 miles north on county road, and 200 feet east in cropland, on Bluebonnet Experiment Station.
RANGE IN CHARACTERISTICS: Solum thickness and depth to limestone bedrock is 20 to 40 inches. The weighted average clay content of the particle-size control section ranges from 40 to 60 percent. When dry, cracks 1/2 to more than 2 inch wide extended from the surface to a depth of more than 12 inches. Cracks remain open from 90 to 150 cumulative days in most years. Slickensides and wedge-shaped peds begin at a depth of 8 to 18 inches. Siliceous pebbles and limestone pebbles and cobbles range from none to 5 percent by volume. However, some pedons have a thin layer in the lower part containing 18 to 35 percent limestone fragments. It is clay or silty clay throughout. The reaction ranges from slightly acid to moderately alkaline and is mainly effervescent. Microknolls are effervescent throughout in some pedons and the matrix immediately above the bedrock is effervescent in some pedons.
The A horizon has colors with hue of 5YR or 7.5YR, value of 2 to 4, and chroma of 2 or 3. Some pedons have hue of 10YR with these value and chroma in the upper part. Also, near the center of some microdepressions the chroma is less than 2.
The Bss horizons have hue of 5YR or 7.5YR, value of 2 to 5, and chroma of 2 to 4. Also, near the center of some microdepressions the chroma is less than 2.
The R layer is indurated limestone bedrock.that is coarsely fractured. It is continuous or is interbedded with marl, or shaly clay at vertical intervals of 6 to 18 inches. In most pedons the bedrock cannot be excavated with conventional digging equipment such as a backhoe machine.
COMPETING SERIES: These include the Dalco, Greenvine and San Saba series in the same family and the similar Anhalt and vertel series. Dalco and Greenvine soils have a paralithic contact at a depth of 20 to 40 inches. San Saba soils have hue of 10YR to 5Y. Anhalt and vertel soils are in a very-fine family.
GEOGRAPHIC SETTING: Crawford soils are on nearly level or gently sloping uplands. Slope gradients are mainly less than 2 percent and range from 0 to 5 percent. The soil formed in clayey sediments underlain by limestone at depths of 20 to 40 inches. It occurs mainly on the Main Street Limestone and Georgetown Formation of the Lower Cretaceous system. The mean annual precipitation ranges from 26 to 34 inches. The mean annual temperature is 65 degrees to 68 degrees F.,and frost free days range from 230 to 250. Elevation ranges from 400 to 1100 feet above seal level. Thornthwaite annual P-E index from 36 to 56.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing San Saba series, and the Bexar, Denton, Hensley, Lindy, Speck, and Yates series. Bexar, Hensley, Lindy, and Speck soils have B2t horizons. In addition, Hensley and Speck soils have sola less than 20 inches thick. Denton soils lack intersecting slickensides. Yates soils have more than 35 percent coarse fragments, and limestone bedrock is within 14 inches of the surface.
DRAINAGE AND PERMEABILITY: This soil is well drained. Permeability is very slow when the soil is saturated and rapid when it is dry and cracked. Runoff is low on slopes less than 1 percent, medium on 1 to 3 percent slopes, and high on 3 to 5 percent slopes.
USE AND VEGETATION: Used for cropland, pasture, and range. Crops grown are small grains, grain sorghums, and cotton. Native vegetation is little bluestem, sideoats grama, blue grama, and buffalograss. Trees are live oak, Spanish oak, post oak, juniper, and elm.
DISTRIBUTION AND EXTENT: The Grand Prairie and Edwards Plateau of central Texas. The series is extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: McLennan County (Waco area), Texas; 1905.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 38 inches.
Deep, wide cracks that remain open 90 to 150 cumulative days in most years.
Vertical features: Slickensides.at depth of 12 to 28 inches
Epipedon color-chroma, moist of 1.5 or more to 12 inch depths.
Lithic contact - occurs at 28 inches.
ADDITIONAL DATA: TAES data - SSIR 30 - Texas page 293.
SIR number: TX0623