LOCATION CHARGO TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, hyperthermic Vertic Haplustepts
TYPICAL PEDON: Chargo silty clay--cultivated. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 5 inches; gray (10YR 5/1) silty clay, very dark
grayish brown (10YR 3/2) moist; massive, crusty and cloddy in the upper 2 inches; very hard, very firm, sticky and plastic; few
threads of salt; saline; strongly effervescent; moderately alkaline; abrupt smooth boundary. (3 to 9 inches thick)
Az1--5 to 12 inches; dark grayish brown (10YR 4/2) silty
clay, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; very hard, very firm, sticky and plastic; few fine pores; common threads of salt; saline; strongly effervescent, moderately alkaline; gradual smooth boundary. (5 to 10 inches thick)
Az2--12 to 17 inches; grayish brown (10YR 5/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure, few wedge-shaped aggregates; very hard, very firm; sticky and plastic; few fine pores; common threads of salt; saline; strongly effervescent; moderately alkaline; gradual wavy boundary. (10 to 16 inches thick)
Bz--17 to 36 inches; brown (10YR 5/3) silty clay, dark brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure, few wedge shaped peds; very hard, very firm, sticky and plastic; few fine pores; few dark streaks in old partially filled cracks; common threads of salt and bodies; saline; strongly effervescent; moderately alkaline; gradual wavy boundary. (5 to 19 inches thick)
Bkz--36 to 41 inches; light brownish gray (10YR 6/2) silty clay, dark brown (10YR 4/3) moist; weak fine angular blocky structure, few fine shiny peds; very hard, very firm, sticky and plastic; common medium (3 percent) masses and concretions of calcium carbonate; saline; violently effervescent; moderately alkaline; clear wavy boundary. (3 to 12 inches thick)
2Cz--41 to 47 inches; very pale brown (10YR 7/3) silt loam; ; massive; hard, friable; few fine distinct brownish yellow masses of iron accumulation, brown moist; saline; violently effervescent; moderately alkaline; clear wavy boundary. (4 to 20 inches thick)
3Ckz--47 to 63 inches; light brown (7.5YR 6/4) silty clay, brown (7.5YR 5/4) moist; massive; very hard, very firm, sticky and plastic; common medium (3 percent) masses and concretions of calcium carbonate; saline; violently effervescent, moderately alkaline.
TYPE LOCATION: Cameron County, Texas; about 1.1 miles east of Bayview; 1.4miles on FM 2480 from intersection of FM 2480 and FM 510 in Bayview to junction with county road, 2.0 miles northeast on county road, 100 feet north of road.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 30 to 50 inches. Depth to contrasting strata of silt loam or very fine sandy loam ranges from 40 to 80 inches. Cracks ranging from 0.4 to 1.0 inch wide extend to depths of 30 inches or more. COLE ranges from .09 to .14.
The 10- to 40-inch control section is silty clay loam or silty clay, with clay content ranging from 35 to 55 percent, and silt content in excess of 40 percent. Soil salinity ranges from slightly affected to strongly affected and increases with depth and ranges from 4 up to 20 or more dS/m within the root zone. These soils contain more than one percent organic matter in the epipedon, but the surfaces are very hard when dry.
The A horizon has hue of 10YR, value of 4 or 5, and chroma of 1 to 3. Texture is silty clay or clay.
The B horizon has hue of 10YR, value of 4 to 6, and chroma of 2 or 3. Texture is silty clay loam or silty clay. It is weak to moderate subangular blocky and blocky. A few pressure faces or small slickensides occur in the B horizon and 2C horizon.
The 2C and 3C horizons have hue of 10YR, value of 6 or 7, and chroma of 3 or 4. Texture is silt loam, very fine sandy loam, silty clay loam, or silty clay somewhat stratified in most pedons.
Accumulation of calcium carbonate in the B, 2C, and 3C horizons ranges from a few masses or concretions to 3 percent of weakly cemented and strongly cemented concretions.
COMPETING SERIES: This is the Runn series. Similar soils are the Cameron, Harlingen, Knippa, Laredo, McAllen, Olmito, Runn, and Raymondville series. Runn soils have epipedons that are not hard setting and do not have mollic colors. Cameron soils have contrasting clayey over loamy textures in the 10- to 40-inch control sections. Harlingen soils have intersecting slickensides and have epipedons with moist values of more than 3.5. Knippa soils have a calcic horizon within 40 inches of the surface. Laredo and McAllen soils have less than 35 percent clay in the 10- to 40-inch control section. Olmito and Raymondville soils have mollic epipedons and in addition, Raymondville soils contain 20 to 40 percent sand in the 10- to 40-inch control section.
GEOGRAPHIC SETTING: Chargo soils occupy nearly level terraces and deltas above overflow. Surfaces are plane to concave with gradients of less than 1 percent. The soil formed in alluvial silty clays or silty clay loams over stratified silty sediments many feet thick. The climate is dry subhumid. The mean annual precipitation ranges from 25 to 30 inches, and the mean annual air temperature ranges from 74 to 76 degrees F. Thornthwaite P-E indices range from 26 to about 36.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Cameron, Harlingen, Laredo, and Olmito series and Benito series. Benito soils have slickensides and epipedons with moist values of more than 3.5.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; slow permeability. A seasonal water table occurs in some irrigated areas during the cool seasons of the year. A seasonal water table occurs below 12 inches in some irrigated areas and in areas where cultural features restrict surface drainage.
USE AND VEGETATION: Mostly cultivated. Main crop grown is
cotton. A few areas are improved pastures. Native vegetation
was mid-grasses and thorny shrubs.
DISTRIBUTION AND EXTENT: Occurs principally on old stream
terraces and deltas in the lower reaches of the Rio Grande and
its major tributaries in southern Texas and probably in Mexico.
The soil is of moderate extent, about 12,000 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Cameron County, Texas; 1970.
REMARKS: Diagnostic horizons and features recognized in the pedon are:
Ochric epipedon: 0 to 17 inches. (A horizons)
Cambic horizon: 17 to 41 inches. (B horizons)