LOCATION VELASCO TXEstablished Series
TAXONOMIC CLASS: Very-fine, mixed, superactive, calcareous, hyperthermic Cumulic Endoaquolls
TYPICAL PEDON: Velasco clay on 0.1 percent slope--in rangeland.
(Colors are for moist soils unless otherwise stated.)
Ag1--0 to 8 inches; dark reddish brown (5YR 3/3) clay, reddish brown (5YR 4/3) dry; moderate coarse angular blocky structure; very hard, very firm; few fine roots; common fine and medium distinct gray (7.5YR 6/1) and few fine distinct very dark gray iron depletions; few calcium carbonate concretions; slightly effervescent; moderately saline; moderately alkaline; clear smooth boundary. (0 to 15 inches thick)
Ag2--8 to 30 inches; dark brown (7.5YR 3/2) clay, dark brown (7.5YR 4/2) dry; weak medium and coarse angular blocky structure; very firm, very sticky and plastic; common fine roots; many medium and coarse distinct dark gray (N 4/0) and light gray (N 5/0) iron depletions; strongly effervescent; strongly saline; moderately alkaline; clear smooth boundary. (20 to 50 inches thick)
Bg--30 to 65 inches; mottled reddish brown (2.5YR 4/4), yellowish red (5YR 4/6), and dark gray (10YR 4/1) clay; moderate coarse angular blocky structure; very firm, very sticky and plastic; few fine roots; few calcium carbonate concretions; strongly effervescent; strongly saline; strongly alkaline.
TYPE LOCATION: Brazoria County, Texas; from the intersection of the Brazos River and the Intracoastal Waterway about 3 miles south of Freeport, 1.2 miles west along Intracoastal Waterway, 200 feet north from bank in rangeland.
RANGE IN CHARACTERISTICS: Solum thickness is 60 to more than 80 inches. The soil is calcareous throughout. The 10- to 40-inch control section averages between 60 and 70 percent clay. The soil is saturated to the surface for periods of 4 to 8 months and seldom dries to below field capacity. Soil salinity ranges from moderate through strong. Some pedons have an organic surface horizon less than 4 inches thick. Some pedons have buried horizons below 40 inches.
The A horizons have hue of 5YR to 10YR, value of 2 or 3, and chroma of 1 to 3. Combined thickness of A horizons range from 24 to more than 40 inches. Most pedons have few to many distinct or prominent iron depletions. Texture is mainly clay, but a thin layer of silty clay is on the surface of some pedons. Reaction ranges from neutral to strongly alkaline. Salinity ranges from moderate to strong.
The B horizon has hue of 2.5YR to 7.5YR, value of 3 to 5, and chroma of 2 to 8. Reaction is slightly alkaline or moderately alkaline. Some pedons have thin buried horizons. The buried horizons have lower chroma and hue.
In some pedons, a 2C horizon, that is stratified loamy or sandy materials, is encountered at 60 inches or more below the surface.
COMPETING SERIES: There are no competing series in the same family. Similar soils include the Beaumont, Brazoria, Harris, Iberia, Lomalta, Surfside, and Tracosa series. Beaumont, Brazoria, Iberia, Lomalta, and Surfside soils have vertic properties. In addition, Beaumont, Brazoria, and Iberia soils are non-saline. Harris soils have gray colors throughout, are noncalcareous. Tracosa soils have a peraquic moisture regime and are flooded daily by tidal action.
GEOGRAPHIC SETTING: Velasco soils are on nearly level flood plains of the Gulf Coast Marsh. Slopes are less than 1 percent. The soils formed in calcareous clayey recent alluvium, at elevation of less than 5 feet above sea level. Average annual precipitation ranges from 40 to 50 inches. Average annual temperature is more than 72 degrees F. Frost-free days range from 230 to 270. The Thornthwaite P-E indices exceed 48.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the similar Beaumont, Harris, and Tracosa series and the Francitas, Galveston, Ijam, Mustang, Narta, and Veston series. Beaumont, Francitas, Ijam, and Narta soils are on slightly higher areas. Harris soils are in similar positions. Francitas and Narta soils are on slightly higher areas. They are gray and noncalcareous. Tracosa soils are on slightly lower elevations. Veston soils are loamy and Galveston and Mustang soils are sandy.
DRAINAGE AND PERMEABILITY: Velasco soils are very poorly drained. Runoff is high, and permeability is very slow. A water table fluctuates from the soil surface to a depth of about 30 inches. These soils are occasionally flooded by both fresh and salt water during Gulf storms. In a few places very high tides cover the soil.
USE AND VEGETATION: Used for rangeland and wildlife habitat. Native vegetation is water loving and salt tolerant grasses and sedges such as marshhay cordgrass, common reed, and seashore saltgrass.
DISTRIBUTION AND EXTENT: Gulf Coast Saline Prairie (MLRA 150B) and Gulf Coast Marsh (MLRA 151) areas of Texas and possibly Louisiana. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Brazoria County, Texas; 1978.
REMARKS: Velasco soils were previously considered as a saline phase of the Roebuck series. The high chromas in the lower horizons are related to the red parent materials. The requirements for low chroma is waived on the assumption that the saturated zone is devoid of oxygen and the red colors remain after citrate dithionate extraction.
Classification changed from Cumulic Haplaquolls to Cumulic Endoaquolls 11/2000 based on typifying pedon description. Further study and characterization data of the series is needed to verify hydrology and classification.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 30 inches (A1g and A2g horizons).
Aquic features - low chroma redox features and reduction.
ADDITIONAL DATA: National Soil Survey Laboratory samples 76PO759, 76PO760. THD data from a pedon in Brazoria County, Texas (S76TX-039-011).
TAXONOMIC VERSION: Soil Taxonomy, Second Edition, 1999.