LOCATION PLACEDO TX+LAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, nonacid, hyperthermic Typic Fluvaquents
TYPICAL PEDON: Placedo silty clay--rangeland. (Colors are for moist soil unless otherwise stated.)
Ag1--0 to 8 inches; dark gray (10YR 4/1) silty clay, gray (10YR 5/1) dry; weak medium angular blocky structure; firm; very sticky and plastic; many fine roots; strongly saline; slightly alkaline; gradual smooth boundary. (4 to 18 inches thick)
Ag2--8 to 25 inches; dark gray (10YR 4/1) clay, gray (10YR 5/1) dry; weak medium angular blocky structure; very firm, extremely sticky and plastic; common fine roots; strongly saline; slightly alkaline; gradual smooth boundary. (12 to 24 inches thick)
Ag3--25 to 36 inches; dark gray (10YR 4/1) clay, light gray (10YR 6/1) dry; few fine faint olive brown mottles; weak coarse angular blocky structure; very firm, very sticky and plastic; few fine roots; strongly saline; slightly alkaline; clear smooth boundary. (10 to 20 inches thick)
Cg1--36 to 50 inches; dark gray (10YR 4/1) clay loam, light gray (10YR 6/1) dry; massive; very hard, firm, sticky and plastic; few fine roots; few thin strata of fine sandy loam; strongly saline; slightly alkaline; clear smooth boundary. (0 to 15 inches thick)
Cg2--50 to 62 inches; gray (10YR 5/1) loam, light gray (10YR 6/1) dry; massive; slightly hard, friable; few thin strata of fine sandy loam and clay; strongly saline; slightly alkaline.
TYPE LOCATION: Calhoun County, Texas; 3.6 miles southwest of intersection of Highways U. S. 87 and State 238 in Port Lavaca; 100 feet west of State Highway 238 and between two channels of Big Chocolate Bayou.
RANGE IN CHARACTERISTICS: Clayey and loamy alluvium is more than 80 inches thick. The clay content of the 10 to 40 inch control section ranges from 35 to 50 percent. Reaction throughout the soil is slightly or moderately alkaline, and calcareous to noncalcareous. Salinity as expressed in mmhos/cm ranges from 16 to 40 in the control section.
The Ag1 horizon is dark gray (N 4/ ; 10YR 4/1; 5Y 4/1) or gray (N 5/ ; 10YR 5/1; 5Y 5/1). It is clay, silty clay, clay loam, or silty clay loam. In some pedons the A horizon is overlain by a mucky peat Oe horizon 1 to 3 inches thick.
The Ag2 and Ag3 horizons has hue of 10YR to 5GY, value of 4 to 7 and chroma of 0 to 2. Fine and medium, faint to distinct, yellowish and brownish mottles are in some pedons. They are clay, silty clay, or silty clay loam.
The C or 2C horizon has the same color range as the A horizon but individual strata are reddish, brownish or yellowish. It ranges from loam to clay and is stratified with more clayey and more sandy layers.
COMPETING SERIES: There are no competing series in the same family. Similar soils are the Aransas, Austwell, Barrada, Harris, Ijam, Surfside, Swan, Tracosa and Veston series. Aransas soils have vertic properties. Austwell soils have a cambic horizon and the water table is below 24 inches for extended periods. Barrada soils have a salic horizon. Harris, Surfside, and Swan soils have mollic epipedons. Ijam soils are dryer in the control section and crack when dry. Trascosa soils lack stratification and are subject to daily tidal flooding. Veston soils are in a fine-silty family.
GEOGRAPHIC SETTING: Placedo soils are in nearly level flood plains of rivers and streams at or near sea level. They formed in saline, alkaline, recent alluvium high in montmorillonitic clays. Mean annual precipitation is 30 to 45 inches and average annual temperatures range from 70 degrees to 73 degrees F. Thornthwaite P-E index ranges from 40 to 64.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Aransas, Follet, Ijam, Swan, Tracosa and Veston series. Aransas, Ijam, and Veston are on slightly higher positions. Follet, Tracosa, and Swan soils are on similar positions.
DRAINAGE AND PERMEABILITY: Very poorly drained; runoff is negligible or the soil is ponded; very slow permeability. A water table fluctuates from above the soil surface to about 12 inches below the surface most of the time. Following rains the soils are flooded by fresh water. Tides frequently flood the soils with sea water.
USE AND VEGETATION: Used for rangeland and wildlife. Native vegetation includes marshhay cordgrass, smooth cordgrass, gulf cordgrass, bushy sea-oxeye, seashore saltgrass, spiny aster, shoregrass, sedges, and rushes.
DISTRIBUTION AND EXTENT: Flood plains of rivers and small streams near sea level in the central part of the gulf coast of Texas. It is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Calhoun County, Texas; 1972.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon 0 to 36 inches
N-value of less than 0.7
Irregular distribution of organic carbon
Aquic conditions.
ADDITIONAL DATA: Sampled for SDHPT from Jackson County, TX (THD84TX-239-002).