LOCATION MATAMOROS TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, calcareous, hyperthermic Vertic Ustifluvents
TYPICAL PEDON: Matamoros silty clay--cropland. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 8 inches; light brownish gray (10YR 6/2) silty clay, dark grayish brown (10YR 4/2) moist; massive; very hard, firm; sticky; common fine roots; calcareous; moderately alkaline; abrupt smooth boundary. (5 to 12 inches thick)
C1--8 to 24 inches; light brownish gray (10YR 6/2) clay, dark grayish brown (10YR 4/2) moist; massive; clay consists of fragments about 2 inches across the axis; the interfaces of the fragments are dull and not shiny; very hard, very firm, sticky; common fine roots; few fine pores; distinct bedding planes are evident; calcareous; moderately alkaline; abrupt smooth boundary. (6 to 20 inches thick)
C2--24 to 27 inches; brown (10YR 5/3) silt loam, dark brown (10YR 4/3) moist; few fine faint very dark brown mottles; few lenses of silty clay; massive; bedding planes are evident; hard, friable, slightly sticky in the matrix of silt loam; few fine roots; remnants of leaves in various stages of decomposition are along the fractures of the lenses of silty clay; calcareous; moderately alkaline; abrupt smooth boundary. (0 to 4 inches thick)
2Ab--27 to 31 inches; grayish brown (10YR 5/2) silty clay, dark grayish brown (10YR 4/2) moist; weak coarse blocky structure; hard, firm; sticky; few black charcoal spots about 1 to 2 cm in diameter; calcareous; moderately alkaline; abrupt smooth boundary. (0 to 8 inches thick)
2Cb--31 to 50 inches; light brownish gray (10YR 6/2) silty clay, grayish brown (10YR 5/2) moist; few fine distinct dark brown mottles consisting of decomposing organic material on few of the interfaces; massive; silty clay consists of angular fragments having dull faces and no definite pattern of cleavage or size, varying from about 1/2 inch to 3 inches across the axis; very hard, very firm, sticky; calcareous; moderately alkaline.
TYPE LOCATION: Cameron County, Texas; 8.0 miles south; 20 degrees west of San Benito; 0.1 mile east of the intersection of Farm Road 2250 and U.S. Highway 281; 0.2 mile south on unpaved road and 50 feet east into field.
RANGE IN CHARACTERISTICS: Average texture of the 10- to 40-inch control section is silty clay loam, silty clay, or clay with clay content of 35 to 55 percent.
Texture of individual stratum ranges from very fine sandy loam to clay. Thickness of loamy layers ranges from 1 to about 4 inches and their combined thickness ranges from about 2 to 10 inches.
The soils, when dry, have cracks, 1 to 10 cm wide that reach to a depth of at least 50 cm, and have a COLE of 0.07 to 0.13. One or more Ab horizons occur at depths of 20 to 50 inches in some pedons.
The A and C horizons to a depth of 40 inches are grayish brown (10YR 5/2), light brownish gray (10YR 6/2; 2.5Y 6/2), brown (10YR 5/3), or pale brown (10YR 6/3). Moist value of the A horizon is more than 3.5, or if less than 3.5, the horizon is less than 10 inches thick. The grayish colors with chromas of 2 or less are due to the alluvial sediments and not due to wetness. Mottling ranges from none to a few faint yellowish brown mottles in the lower part. Conductivity is 0.8 to 4.0 mmhos/cm at 25 degrees C.
COMPETING SERIES: There are no series in the same family. Similar soils include Camargo, Chargo, Grulla, and Mangum series. Camargo soils have fine-silty control sections. Chargo soils lack evident stratification in the 10- to 40-inch control section and have B horizons. Grulla soils are saturated for several weeks during most years and have grayish coloration due to wetness. Mangum soils have mean annual soil temperatures less than 72 degrees F.
GEOGRAPHIC SETTING: Matamoros soils occur on nearly level active flood plains of the Rio Grande and its tributaries. These soils flood about once every 5 to 10 years. The soil formed in clayey sediments that are slightly altered and several feet thick. Slope gradients are less than 1 percent. The climate is semiarid to dry subhumid. Mean annual precipitation ranges from 17 to 27 inches, mean annual temperature of 71 to 74 degrees F., and Thornthwaite annual P-E indices of 24 to 32.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Camargo and Grulla series and Rio Grande series. Camargo soils occur on similar surfaces and Grulla soils occur in depressions. Rio Grande soils have coarse-silty control sections and occur at lower elevations on younger terraces.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; slow permeability.
USE AND VEGETATION: Used mostly for irrigated cropland.
Principal crops grown are cotton, grain sorghum, sugarcane, and a wide variety of cool season vegetables. Native vegetationconsists of fourflower trichloris grass, sacaton grass, cottontop grass, plains bristlegrass, common bermudagrass, hackberry, Rio Grande ash, and mesquite trees.
DISTRIBUTION AND EXTENT: Known areas are in the Rio Grande Plain of Texas and probably in Mexico. Series is of moderate extent, about 50,000 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Cameron County, Texas; 1970.