LOCATION PLEDGER TX+OKEstablished Series
TAXONOMIC CLASS: Very-fine, smectitic, hyperthermic Typic Hapluderts
TYPICAL PEDON: Pledger clay--cropland. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; black (10YR 2/1) clay, very dark gray (10YR 3/1) dry; moderate fine granular and fine subangular blocky structure; very hard, firm; common fine roots; slightly alkaline; abrupt smooth boundary. (4 to 8 inches thick)
A--5 to 20 inches; black (10YR 2/1) clay, very dark gray (10YR 3/1) dry; moderate medium subangular and angular blocky structure; extremely hard, very firm; few fine roots; few fine pores; slightly alkaline; gradual wavy boundary. (combined thickness of the A horizons is 12 to 30 inches)
Bss1--20 to 30 inches; black (10YR 2/1) clay, very dark gray (10YR 3/1) dry; moderate medium angular blocky structure; extremely hard, very firm; few fine roots; few fine pores; common prominent slickensides; many pressure faces; slightly alkaline; gradual wavy boundary. (4 to 12 inches thick)
Bss2--30 to 50 inches; dark reddish brown (5YR 3/3) clay, reddish brown (5YR 4/3) dry; weak medium angular blocky structure; very hard, firm; few fine roots; common prominent slickensides; many pressure faces; few pitted concretions of calcium carbonate; strongly effervescent; moderately alkaline; clear wavy boundary. (7 to 30 inches thick)
BCss--50 to 80 inches; reddish brown (5YR 4/3) clay; weak coarse prismatic structure; very hard, firm; common distinct slickensides; few thin discontinious strata of silt loam and silty clay; few fine calcium carbonate concretions; strongly effervescent; moderately alkaline.
TYPE LOCATION: Fort Bend County, Texas; from the intersection of U.S. Highway 90A and Farm Road 723 in Rosenberg, 2.1 miles north on Farm Road 723 to intersection of county road, 75 feet west and 300 feet south in cropland. (Latitude 29N, 35, 28; Longitude 95W; 48, 42)
RANGE IN CHARACTERISTICS: Solum thickness is more than 80 inches. The particle size control section averages between 60 and 80 percent clay. Sand content ranges from 1 to 5 percent. When dry, cracks more than 0.4 inch wide extend from the surface to depths ranging from 20 to 50 inches. Depth to slickensides and wedge shaped aggregates ranges from 12 to 26 inches. Calcium carbonate concretions, 1 to 5 mm in size, range from less than 1 to 3 percent of some horizon within 40 inches of the surface. Undisturbed areas have gilgai, with microhighs 4 to 12 inches higher than microlows. Distance between microhighs and microlows ranges from 8 to 12 feet.
The A horizons have color in hue of 5YR to 10YR, value of 2 or 3, and chroma of 1 or less. Texture is clay but ranges to silty clay in the upper part. Reaction ranges from slightly acid to moderately alkaline and is commonly noneffervescent, but ranges to slightly effervescent.
The upper Bss horizons have hue of 5YR to 10YR, value of 2 or 3, and chroma of 2 or less. The lower Bss horizons have hue of 2.5YR to 7.5YR, value of 2 to 5, and chroma of 2 to 4. Darker colors extend from the A horizon into the B horizon as fillings in former cracks. Reaction is slightly alkaline or moderately alkaline and is slightly or strongly effervescent.
The BCss horizon has about the same colors as the lower Bss horizons. Texture is mainly clay with thin discontinious strata of silt loam, silty clay loam, and silty clay. Buried soils having dark A horizons are common below 40 inches. Reaction is slightly alkaline or moderately alkaline and strongly effervescent.
COMPETING SERIES: There are no other series in this family. Similiar soils are the Brazoria, Ganado, Laewest and Lake Charles series. Brazoria soils have chroma of 3 or more, or value of 4 or more, in the upper 12 inches of the solum. Ganado, Laewest and Lake Charles soils have hue of 10YR or yellower throughout and have a fine particle-size control section. In addition, Laewest and Lake Charles soils are on uplands.
GEOGRAPHIC SETTING: Pledger soils are on nearly level flood plains. Slopes are plane and mainly less than one percent. The soil formed in recent calcareous, reddish stratified clayey and silty alluvium. The mean annual precipitation ranges from 40 to 52 inches. The mean annual temperature ranges from 70 to 72 degrees F. Elevation is 10 to 150 feet. Frost free days range from 260 to 280. Thornthwaite P-E indices range from 60 to 66.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Brazoria and Lake Charles series, and the Asa, Norwood, Roebuck and Sumpf series. Brazoria soils are in similar positions. Lake Charles soils are on slightly higher level uplands. Asa and Norwood soils have fine-silty control sections and are slightly higher in the flood plain. Roebuck and Sumpf soils are in lower lying concave areas, and are wet for longer periods of time.
DRAINAGE AND PERMEABILITY: Moderately well drained. Permeability is very slow. Runoff is low. Water enters the soil rapidly when dry and cracked, and very slow when moist. The soil floods rarely to frequently, except where protected, for brief duration.
USE AND VEGETATION: Mainly used as cropland for corn, cotton, and sorghum. Some areas are used for improved pasture of bermudagrass and dallisgrass. Native vegetation is pecan, elm, oak, ash, and cottonwood trees and mid and tall grasses.
DISTRIBUTION AND EXTENT: Mainly along the lower reaches of the Brazos and Colorado Rivers in the Coast Prairie (MLRA 150A). The series is of large extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Reconnaissance soil survey of Central Gulf Coast Area of Texas; 1910.
REMARKS: Particle size and mineralogy data from TAMU on 10 pedons from Matagorda, Wharton, Brazoria and Ft. Bend Counties, Texas, indicate a very-fine, montmorillonitic family. Based on this data, classification changed from fine, mixed, thermic Vertic Hapludolls to very-fine, montmorillonitic, thermic Typic Pelluderts, 8/90. The classification is changed from thermic Typic Pelluderts to hyperthermic Typic Hapluderts based on Amendment 16 to Soil Taxonomy (2/94). The temperature regime change is based on study by TAMU and local data.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon -- Ap, A, Bss1, and Bss2 horizons from 0 to 50 inches.
Cambic horizon -- BC horizon from 50 to 80 inches.
Vertic features -- Slickensides in horizons between 20 and 80 inches. Deep, wide cracks open less than 90 cumulative days in most years.
ADDITIONAL DATA: Engineering test data by TDHPT (Sample No. S76TX039-009, Brazoria County, TX).
Soil Interpretation Record: TX0304.