LOCATION SEGUIN TXEstablished Series
TAXONOMIC CLASS: Fine-silty, carbonatic, thermic Fluventic Haplustolls
TYPICAL PEDON: Seguin silty clay loam - pecan orchard and park.
(Colors are for dry soil unless otherwise stated.)
A--0 to 13 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular and very fine subangular blocky structure; hard, friable; common fine roots; few fine pores; common worm casts; few medium fragments of snail shell; calcium carbonate equivalent about 40 percent; calcareous; moderate alkaline; gradual smooth boundary. (8 to 18 inches thick)
Bw--13 to 26 inches; grayish brown (10YR 5/2) silty clay loam, dark grayish brown (10YR 4/2) moist; moderate medium granular structure; slightly hard, friable; few fine roots; few fine pores; few worm casts; few fine fragments of snail shells; few films and threads of calcium carbonate; few discontinuous very fine sandy loam strata in lower part; calcium carbonate equivalent about 45 percent; calcareous; moderately alkaline; gradual smooth boundary. (5 to 24 inches thick)
C--26 to 62 inches; light brownish gray (10YR 6/2) silty clay loam, grayish brown (10YR 5/2) moist; massive; slightly hard, very friable; few fine roots in upper part; few films and threads of calcium carbonate; common strata of very fine sandy loam, silt loam, and silty clay loam from 1/8 to 4 inches thick; calcium carbonate equivalent about 45 percent; calcareous; moderately alkaline.
TYPE LOCATION: Guadalupe County, Texas; in the flood plain of the Guadalupe River 0.3 mile northeast of the Texas Highway 123 river bridge in Seguin, Texas; 300 feet north of the river channel.
RANGE IN CHARACTERISTICS: Average texture of the 10- to 40-inch control section is silt loam, loam, silty clay loam, or clay loam. Silicate clay ranges from 18 to 30 percent. Calcium carbonate equivalent ranges from 40 to 60 percent.
The A horizon is dark grayish brown (10YR 4/2; 2.5Y 4/2), dark brown (10YR 4/3), grayish brown (10YR 5/2; 2.5Y 5/2), or brown (10YR 5/3).
The Bw horizon is grayish brown (10YR 5/2), brown (10YR 5/3), or pale brown (10YR 6/3).
The C horizon is light brownish gray (10YR 6/2), pale brown (10YR 6/3), or very pale brown (10YR 7/3, 7/4). The texture of individual stratum in the C horizon varies from loamy very fine sand to silty clay and a few strata have up to 15 percent limestone pebbles. Some pedons have buried A horizons 5 to 10 inches thick.
COMPETING SERIES: There are no other series in the same family. Similar soils include the Asa, Bergstrom, Bosque, Frio, Gowen, Grigston, Laredo, Spur, and Toyah series. All these soils have less than 40 percent calcium carbonate equivalent in the control section. In addition, Bergstrom, Bosque, Frio, and Gowen soils have mollic epipedons more than 20 inches thick; Grigston soils have mean annual soil temperatures less than 59 degrees F.; Laredo soils have mean annual soil temperature more than 72 degrees F.; and Spur and Toyah soils have fine-loamy control sections.
GEOGRAPHIC SETTING: These soils occur in flood plains of streams and rivers that carry sediments from Cretaceous limestone and shale in the subhumid and semiarid regions of Texas. Flooding occurs at intervals of about once each year to once every 5 years in areas not protected by dams. Slope gradients are mainly less than 1 percent but range up to 3 percent. The climate is dry subhumid with a mean average rainfall of 28 to 35 inches. The Thornthwaite P-E indices are 38 to 48. Mean average temperature is 64 to 70 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the similar Bosque and Frio soils.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability.
USE AND VEGETATION: Mostly used for pasture and pecan orchards. Some areas are used for recreation and a few areas are cropped to cotton, corn, grain sorghum, and oats. Native vegetation is pecan and elm trees with an understory of grasses such as big bluestem, little bluestem, switchgrass, indiangrass, Texas wintergrass, and Virginia wildrye.
DISTRIBUTION AND EXTENT: Mainly along the Guadalupe and San Marcos Rivers in south Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Caldwell County, Texas; 1972.
REMARKS: The soils were formerly included in the Frio series.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 13 inches.
Cambic horizon - 13 to 26 inches.
Fluventic feature - stratification below 26 inches.