LOCATION MERCEDES TXEstablished Series
TAXONOMIC CLASS: Fine, smectitic, hyperthermic Sodic Haplusterts
TYPICAL PEDON: Mercedes clay in cropland at an elevation of 33 feet. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 10 inches; gray (10YR 5/1) clay, dark gray (10YR 4/1) moist; moderate fine granular and subangular blocky structure; hard, firm, very sticky and very plastic; few fine roots; common fine fragments of shell; SAR is about 2; strongly effervescent, moderately alkaline; abrupt smooth boundary. (7 to 12 inches thick)
A--10 to 18 inches; gray (10YR 5/1) clay, dark gray (10YR 4/1) moist; moderate fine angular blocky structure; hard, firm, very sticky and very plastic; few fine roots and pores; few dark yellowish brown masses; many fine fragments of shell; SAR is about 4; strongly effervescent, moderately alkaline; gradual wavy boundary. (6 to 10 inches thick)
Bss--18 to 29 inches; gray (10YR 5/1) clay, dark gray (10YR 4/1) moist; moderate fine angular blocky structure; wedge-shaped aggregates; many distinct slickensides; very hard, very firm; very sticky and very plastic; few very fine roots and pores; many fine fragments of shell; SAR is about 9; strongly effervescent, moderately alkaline; diffuse wavy boundary. (5 to 14 inches thick)
Bssn1--29 to 47 inches; light brownish gray (2.5Y 6/2) clay, grayish brown (2.5Y 5/2) moist with a few gray streaks along apparently filled cracks up to 2 inches across; moderate fine angular blocky wedge-shaped aggregates; very hard, very firm, very sticky and very plastic; few very fine pores; many distinct slickensides, 14 inches across with axes tilted about 45 degrees from the horizontal; SAR is about 19; strongly effervescent, moderately alkaline; diffuse wavy boundary. (14 to 24 inches thick)
Bssn2--47 to 63 inches; pale brown (10YR 6/3) clay, brown (10YR 5/3) moist; moderate fine angular blocky wedge-shaped aggregates; very hard, very firm, very sticky and very plastic; few very fine pores; common distinct slickensides: few streaks of grayish brown (10YR 5/2) moist clay that are in old filled cracks; few fragments of shell; SAR is about 20; strongly effervescent, moderately alkaline; diffuse wavy boundary. (10 to 22 inches thick)
Bn--63 to 80 inches; very pale brown (10YR 7/3) clay, pale brown (10YR 6/3); moist; moderate fine and medium subangular blocky structure; very hard, very firm, very sticky and very plastic; SAR is about 20; strongly effervescent, moderately alkaline.
TYPE LOCATION: Cameron County, Texas; From the intersection of Loop 448 and Farm Road 106 in Harlingen; about 3.0 miles east on Farm Road 106 to the intersection with Farm Road 1595; 1.6 miles north on Farm Road 1595; about 150 feet west of road in cultivated field. Harlingen, Texas USGS topographic quadrangle; Latitude: 26 degrees, 12 minutes, 51 seconds N., Longitude: 97 degrees, 37 minutes, 59 seconds W.; NAD 83.
RANGE IN CHARACTERISTICS:
Soil Moisture: An Ustic moisture regime. The soil moisture control section (SMCS) is dry in some or all parts for more than 90, but less than 150 cumulative days in normal years. The SMCS is also either moist in some or all parts for 180 cumulative days or more, or moist for 90 or more consecutive days in normal years. November through April are the driest months, with a second low in July, while September is the wettest.
Solum thickness: 60 to more than 80 inches.
Slickensides: 10 to 30 inches below the surface.
Sodium Adsorption Ratio (SAR); 13 or more within 25 inches of the surface.
Soil salinity: nonsaline to moderately saline and increases with depth; electrical conductivity is 1 to about 12 dS/m.
Clay content of the particle size control section: 45 to 60 percent.
Siliceous pebbles comprise 0 to about 10 percent of any horizon.
The amplitude or waviness in the boundary between the A and B horizons is about 4 to 12 inches.
A horizon
Hue: 10YR or is neutral
Value: 5 or 6; Moist value is 3.5 to 5
Chroma: 0 or 1; Moist chroma of less than 1.5 extends to depths of 18 to 36 inches in more than half of each pedon.
Soil reaction: moderately or strongly alkaline.
Texture: clay
Bss horizon
Hue: 10YR or 2.5Y
Value: 5 or 6
Chroma: 2 or 3
Soil reaction: moderately or strongly alkaline.
Texture: clay
Bssn horizon
Hue: 10YR or 2.5Y
Value: 5 or 6
Chroma: 2 or 3
Soil reaction: moderately or strongly alkaline.
Texture: clay
Bn horizon
Hue: 7.5YR or 10YR
Value: 5 to 7
Chroma: 2 to 4
Soil reaction: moderately or strongly alkaline.
Texture: clay throughout
Accumulations of crystalline neutral salts range from 0 to 10 percent.
Some pedons have a 2C horizon of silt loam or very fine sandy loam beginning at depths of about 60 to 70 inches.
COMPETING SERIES: These are the Arroyada (TX), Catarina (TX), Coquat (TX), Cotulla (TX), Duvert (TX), Lasalle (TX), Montell (TX), Victine (TX), and Victoria (TX) series in the same family.
Arroyada and
Coquat soils: are somewhat poorly drained, have an ochric epipedon, and formed in Holocene alluvium on flood plains.
Catarina soils: have an ochric epipedon, and formed in clayey alluvium and colluvium derived from sediments of Eocene age.
Cotulla soils: have an ochric epipedon, formed in thick beds of calcareous, saline, clayey sediments that are, in places, interbedded with shale and sandstone, and occur in areas with mean annual precipitation ranging from 19 to 26 inches.
Duvert soils: have an ochric epipedon and a paralithic contact within 20 to 40 inches of the soil surface.
Lasalle soils: have an ochric epipedon, and have hue of 7.5YR or redder in the B horizons.
Montell soils: have an ochric epipedon and a gypsic horizon.
Victoria and
Victine soils: Victoria soils are well drained and depth to SAR of more than 13 ranges from 28 to 39 inches. Victine soils are somewhat poorly drained and have higher SAR in the upper 20 inches.
GEOGRAPHIC SETTING:
Parent material: calcareous, clayey alluvium of late Pleistocene age
Landform: broad, nearly level deltaic plains
Slopes: 0 to 5 percent
Mean annual temperature: 73 or 74 degrees F
Mean annual precipitation: 24 to 28 inches
Frost-free period: 340 to 365 days
Elevation: 15 to 55 feet
Thornthwaite P-E Index: 30 to 36
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Harlingen, Hidalgo, Lozano, Lyford, Racombes, Raymondville, and Tiocano series.
Harlingen soils: have moist chromas of 1.5 or more in some part of the upper 12 inches in more than half of each pedon and are on a slightly higher landform.
Hidalgo soils: are in a fine-loamy particle size family, have a calcic horizon within 40 inches and are on a higher landform.
Lozano and
Lyford soils: are in a fine-loamy particle size family, have an ochric epipedon, and are on a higher landform.
Racombes soils: are in a fine-loamy particle size family, have a mollic epipedon more than 20 inches thick, and are on a higher landform.
Raymondville soils: have calcic horizons at depths of less than 40 inches and do not have gilgai microrelief.
Tiocano soils: are in depressions and have cracks that remain open less than 150 days in most years.
DRAINAGE AND PERMEABILITY: Moderately well drained. Permeability is very slow. Runoff is high on slopes less than 1 percent and very high on 1 to 5 percent slopes.
USE AND VEGETATION: Mostly irrigated cropland. Cotton and grain sorghum are the major crops. Few small areas are in rangeland and wildlife habitat.
DISTRIBUTION AND EXTENT: Lower Rio Grande Plain, Texas; Land Resource Region I-Southwest Plateaus and Plains; MLRA 83D; the series is moderate in extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Uvalde County, Texas; 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 18 inches. (A horizon)
Cambic horizon: 18 to 63 inches. (Bss horizon)
SAR more than 13 in upper 40 inches.
ADDITIONAL DATA: NSSL data from Cameron County, TX (S01TX-061-001) and (S01TX-061-002).
TAXONOMIC VERSION: Keys to Soil Taxonomy, Ninth Edition, 2003.