LOCATION LAREDO TX

Established Series
Rev. EHT-HCD-CLG-RM
11/2016

LAREDO SERIES

The Laredo series consists of very deep, well drained, moderately permeable soils that formed in calcareous, silty alluvium derived from mixed sources. These nearly level to very gently sloping soils occur on rare flood plains or low Holocene stream terraces. Slope ranges from 0 to 3 percent. Mean annual temperature is about 23.3 degrees C (74 degrees F) and mean annual precipitation is about 686 mm (27 in).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, hyperthermic Fluventic Haplustolls

TYPICAL PEDON: Laredo silty clay loam on east-facing linear 0 to 1 percent slopes in cropland at an elevation of 12.2 m (40 ft).
(Colors are for dry soil unless otherwise stated.)

Ap--0 to 20 cm (0 to 8 in); dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky and moderate very fine granular structure; hard, friable, sticky and plastic; strongly effervescent; moderately alkaline; abrupt smooth boundary. (10 to 31 cm [4 to 12 in] thick)

A--20 to 46 cm (8 to 18 in); dark grayish brown (10YR 4/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular and fine subangular blocky structure; hard, friable, sticky and plastic; few fine pores, 4 percent earthworm casts; strongly effervescent; moderately alkaline; clear wavy boundary. (20 to 41 cm [8 to 16 in] thick)

Bk--46 to 104 cm (18 to 41 in); light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak fine and medium subangular blocky structure; slightly hard, friable, sticky and plastic; many fine pores; few insect tunnels and root channels filled with slightly darker material from above; 2 percent films and threads of calcium carbonate; violently effervescent; moderately alkaline; clear wavy boundary. (41 to 91 cm [16 to 36 in] thick)

Bk/Ck--104 to 125 cm (41 to 49 in); 80 percent light brownish gray (10YR 6/2) silty clay loam with thin strata of silt loam (20 percent); grayish brown (10YR 5/2) moist; massive; slightly hard; friable, sticky and plastic; many fine pores; 4 percent masses and concretions of calcium carbonate; violently effervescent; moderately alkaline; clear wavy boundary. (10 to 25 cm [4 to 10 in] thick)

C--125 to 203 cm (49 to 80 in); light gray (10YR 7/2) silt loam with thin strata of silty clay loam and very fine sandy loam; grayish brown (10YR 5/2) moist; massive; slightly hard; friable; violently effervescent; moderately alkaline.

TYPE LOCATION: Cameron County, Texas; from the intersection of Farm Road 1479 and Farm Road 675 in Rangerville; 0.9 mile south on Farm Road 1479; 200 feet west in a cultivated field.
USGS quadrangle: Santa Maria, TX.
Latitude: 26 degrees, 05 minutes, 13.203 seconds N;
Longitude: 97 degrees, 45 minutes, 3.308 seconds W;
Datum: WGS 84.

RANGE IN CHARACTERISTICS:
Soil Moisture: A Typic-ustic soil moisture regime.
Mean annual soil temperature: 21.1 to 23.3 degrees C (70 to 74 degrees F).
Solum thickness is 86 to 203 cm (34 to 80 in)
Depth to identifiable secondary carbonate: 46 to 86 cm (18 to 34 in)
Thickness of the mollic epipedon: 25 to 51 cm (10 to 20 in)

Particle-size control section (weighted average)
Total Clay content: 18 to 45 percent
Silicate clay content: 18 to 35 percent.
Coarse Fragments: 0 to 2 percent
CEC/clay ratio: 0.60 to 0.90

A horizon
Hue: 7.5YR or 10YR
Value: 3 or 4
Chroma: 2 or 3
Texture: silt loam or silty clay loam
Clay content: 12 to 38 percent
Coarse fragments: 0 to 2 percent
Base saturation: 100 percent
Calcium carbonate equivalent: 5 to 20 percent
Electrical Conductivity (dS/m): 0 to 2
Sodium Adsorption Ratio: 0 to 4
Exchangable Sodium Percentage: 0 to 5
Effervescence: very slight or slight
Reaction (pH): moderately alkaline to strongly alkaline (7.9 - 8.6)

Bk or Bw horizon
Hue: 7.5YR or 10YR
Value: 5 or 6
Chroma: 2 to 4
Texture: silt loam, silty clay loam, or silty clay
Total clay content: 18 to 45 percent
Silicate clay content: 18 to 35 percent
Coarse fragments: 0 to 5 percent
Base saturation: 100
Calcium carbonate equivalent: 10 to 25 percent
Identifiable secondary carbonate: 0 to 2 percent very fine and fine films, threads, and masses
Electrical Conductivity (dS/m): 0 to 4, ranges to 10 to 41 cm (4 to 16 in) some pedons
Gypsum: 0 to 2 percent
Sodium Adsorption Ratio: 0 to 4, ranges to 5 to 41 cm (2 to 16 in) some pedons
Exchangable Sodium Percentage: 0 to 5
Effervescence: strong or violent
Reaction (pH): moderately alkaline to strongly alkaline (7.9 - 8.8)

B/C and C horizons
Hue: 10YR
Value: 6 or 7
Chroma: 2 to 4
Texture: silt loam, silty clay loam, with 2 to 12 inches thick of silt loam, silty clay loam, very fine sandy loam, or silty clay
Total clay content: 18 to 45 percent
Silicate clay content: 18 to 35 percent
Coarse fragments: 0 to 5 percent
Base saturation: 100
Calcium carbonate equivalent: 10 to 25 percent
Identifiable secondary carbonate: 1 to 5 percent, very fine and fine films, threads, masses, and strongly cemented concretions
Electrical Conductivity (dS/m): 0 to 4, ranges to 4 to 32 percent in some pedons
Gypsum: 0 to 2 percent
Sodium Adsorption Ratio: 0 to 8 percent, ranges from 2 to 16 in some pedons
Exchangable Sodium Percentage: 0 to 10
Effervescence: violent
Reaction (pH): moderately alkaline to strongly alkaline (7.9 - 8.8)

COMPETING SERIES: This is the Meguin series in the same family. Similar soils are the Camargo, Cameron, Lagloria, Mentone, Olmito, Reynosa, Sprone, and Toyah series.
Meguin soils: do not have identifiable secondary carbonates within 102 cm (40 in) of the surface and occur in a more moist climate
Camargo, Lagloria, and Reynosa soils: do not have a mollic epipedon
Cameron soils: have contrasting textures within 40 inches of the surface
Mentone, Sprone, and Toyah soils: have a thermic soil temperature regime.
Olmito soils: are fine textured in the particle-size control section

GEOGRAPHIC SETTING:
Parent material: calcareous, silty alluvium derived from mixed sources.
Landscape: relict delta plains and/or river valleys
Landform: rarely flooded flood plains or low Holocene terraces.
Slope: 0 to 3 percent, on plain to convex slopes.
Precipitation pattern: The soils are driest during the months of June through August and December through February. These soils are intermittently moist in September through November and March through May.
Mean annual precipitation: 432 to 711 mm (17 to 28 in)
Thornthwaite annual P-E indices: 28 to 40.
Mean annual air temperature: 22.2 to 23.3 degrees C (72 to 74 degrees F).
Frost-free period: 285 to 365 days.
Elevation: 3.1 to 289.6 m (10 to 950 ft).

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cameron, Lagloria, Olmito, and Reynosa series. All of these soils occur on adjacent bottomland terraces in similar positions but formed in different alluvial events.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate. Runoff is negligible on slopes less than 1 percent and low on 1 to 3 percent slopes. Saline water tables may occur within 1 to 3 m (3 to 10 ft) below the surface where irrigated. Brief flooding occurs in some areas after high rainfall events.

USE AND VEGETATION: Mostly irrigated cropland of cotton, grain sorghum, sugarcane, a wide variety of cool season vegetables, and citrus. Some dryland farming of cotton and grain sorghum. A few areas are used for wildlife habitat. Native vegetation was midgrasses and some thorny shrubs.

DISTRIBUTION AND EXTENT: Lower Rio Grande Plain, Texas along the Rio Grande; LRR I; MLRA 83D; the series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Webb County, Texas, 1906; Laredo area soil survey, Texas.

REMARKS:

Edited 11/2016 (RFG-GWH): Updated competing series, geographic setting, and associated soils sections.

Diagnostic horizons and features recognized in this pedon are:
Particle size control section: 25 to 102 cm (10 to 40 in).
Mollic epipedon: 0 to 46 cm (0 to 18 in). (A horizons)
Fluventic feature: have an irregular decrease in organic carbon with increasing depth.

ADDITIONAL DATA: Particle-size distribution, mineralogy, and chemical data from ARS-SCS cooperative study available on following representative pedons, National Resources Conservation Service Laboratory, Lincoln, Nebraska sample numbers 12877-12833; 12933-12939; 12940-12946. The assignment of the cation-exchange activity class is supported by laboratory data number S83TX-061-001 from Cameron County, Texas.

Taxonomic Version: Keys to Soil Taxonomy, Twelfth Edition, 2014.

National Cooperative Soil Survey
U.S.A.