LOCATION IRAAN TX

Established Series
Rev. JLR-PHF-LEL
11/2013

IRAAN SERIES

The Iraan series consists of very deep, well drained, moderately slowly permeable soils formed in calcareous loamy alluvium derived from limestone. These nearly level soils occur on flood plains along streams on dissected plateaus and river valleys. Slope ranges from 0 to 2 percent. Mean annual precipitation is about 406 mm (16 in) and the mean annual air temperature is about 17.8 degrees C (64 degrees F).

TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Cumulic Haplustolls

TYPICAL PEDON: Iraan silty clay loam, on a flood plain - in rangeland.
(Colors are dry soil unless other stated.)

A1--0 to 18 cm (0 to 7 in); dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium granular and subangular blocky structure; hard, friable; common wormcasts, many fine roots, few fine rounded limestone gravel; slightly effervescent; moderately alkaline; gradual smooth boundary. Thickness is 10 to 61 cm (4 to 24 in)

A2--18 to 71 cm (7 to 28 in); dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; hard, firm; few wormcasts, common pores, few rounded limestone gravel less than 4 mm (1/8 in) in diameter; few films and threads of calcium carbonate; strongly effervescent; moderately alkaline; clear smooth boundary. Thickness is 20 to 81 cm (8 to 32 in)

Bk1--71 to 109 cm (28 to 43 in); brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, firm; few rounded gravel less than 4 mm (1/8 in) in diameter; few films and threads of calcium carbonate; strongly effervescent; moderately alkaline; diffuse wavy boundary. Combined thickness of the Bk horizon is 94 to 145 cm (37 to 57 in)

Bk2--109 to 203 cm (43 to 80 in); brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; hard, firm; common rounded gravel less than 4 mm (1/8 in) in diameter; few films and threads of calcium carbonate; strongly effervescent; moderately alkaline.

TYPE LOCATION: Pecos County, Texas; from the intersection of U.S. Highway 285 and U.S. Highway 290 in Fort Stockton, 11.3 miles southeast on U.S. Highway 285, then 3.1 miles south on county road, then 1.4 miles west on ranch road, and 50 feet north in pasture.
USGS topographic quadrangle: ?; Latitude: 30 degrees, 42 minutes, 53.59 seconds N; Longitude: 102 degrees, 49 minutes, 6.32 seconds W; Datum: ?.

RANGE IN CHARACTERISTICS:
Soil moisture: Ustic-aridic moisture regime
Solum thickness: 152 to more than 203 cm (60 to more than 80 inches)
Mollic epipedon: 51 to 102 cm (20 to 40 in)
Secondary carbonates: 0 to 5 percent
Some pedons have gravelly or cobbly strata below 102 cm (40 in)
Some pedons have buried horizons.

Particle-size control section (weighted average):
Total Clay content: 30 to 45 percent
Silicate Clay content: 27 to 35 percent
Rock fragments: 0 to 15 percent; limestone gravel

A1 horizon
Hue: 7.5 YR, 10YR
Value: 3 to 5, 2 or 3 moist
Chroma: 2 or 3 dry or moist
Texture: silt loam, silty clay loam, or clay loam
Total Clay content: 27 to 40 percent
Carbonate clay content: 0 to 5 percent
Rock fragments: 0 to 5 percent; limestone gravel
Calcium carbonate equivalent: 2 to 5 percent
Electrical conductivity (mmhos/cm): 0 to 2
Reaction: moderately alkaline

A2 horizon
Hue: 7.5 YR, 10YR
Value: 3 to 5, 2 or 3 moist
Chroma: 2 or 3 dry or moist
Texture: silt loam, silty clay loam, or clay loam
Total Clay content: 27 to 40 percent
Carbonate clay content: 0 to 5 percent
Rock fragments: 0 to 10 percent; limestone gravel
Calcium carbonate equivalent: 2 to 10 percent
Electrical conductivity (mmhos/cm): 0 to 2
Reaction: moderately alkaline

Bk or Bw horizons
Hue: 7.5 YR, or 10YR
Value: 4 to 6, 3 to 5 moist
Chroma: 2 to 4 dry or moist
Texture: clay loam, silty clay loam, or silty clay
Total Clay content: 30 to 45 percent
Carbonate clay content: 3 to 10 percent
Rock fragments: 0 to 15 percent; limestone; dominantly gravel, but may contain a few cobbles
Calcium carbonate equivalent: 5 to 30 percent
Electrical conductivity (mmhos/cm): 0 to 2
Reaction: moderately alkaline

C or Ck horizon (where present)
Texture: loam, clay loam, silty clay loam, or silty clay

COMPETING SERIES: These are the Bergstrom, Bigetty, and Port series in the same family. Similar soils are the Oakalla and Rioconcho series.
Bergstrom and Port: occur in areas that receive more rainfall and are moist for longer periods
Bigetty: these soils occur in drier areas that receive less rainfall
Oakalla: these sois have a fine-loamy particle-size control section and have greater amounts of calcium carbonate
Rioconcho: these soils have a fine particle-size control section and have vertic properties

GEOGRAPHIC SETTING:
Parent Material: calcareous loamy alluvium derived from limestone
Landscape: dissected plateaus and river valleys
Landform: flood plain
Slope: 0 to 2 percent
Mean annual precipitation: 356 to 533 mm (14 to 21 in)
Thornthwaite P.E. indices: 18 to 26
Mean annual air temperature: 16.1 to 20.6 degrees C (61 to 69 degrees F)
Frost-free period: 210 to 260 days
Elevation: 274.3 to 1394.5 meters (900 to 4575 ft)

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dalby, Dev, Ector, Hodgins, Lozier, Reagan, Sanderson, and Upton series.
Dalby: these soils have slickensides and a fine particle-size control section and occur on similar postions
Dev: these soils have a loamy-skeletal particle-size control section and occur on similar positions
Ector and Lozier: these soils are shallow to a lithic contact and occur on ridgetops and sideslopes
Hodgins and Reagan: these soils have an ochric epipedon and occur on broader alluvial flats
Sanderson: these soils have a loamy-skeletal particle-size control section and occur on higher fans and footslopes
Upton: these soils are shallow to a petrocalcic horizon and occur on slightly higher fans and footslopes

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is negligible on slopes less than 1 percent and very low on 1 to 2 percent slopes.

USE AND VEGETATION: Most areas are in native rangeland. A few areas are in irrigated cropland. Crops are mainly cotton, grain sorghum, small grain, alfalfa and vegetables. The native vegetation is sideoats grama, tobosa grass, plains bristlegrass, blue grama and vine-mesquite. Woody species include mesquite, black walnut, hackberry and western soapberry.

DISTRIBUTION AND EXTENT: The Western part of Texas; LRR I - Southwest Plateaus and Plains Range and Cotton Region; Edwards Plateau, Western Part (MLRA 81A). The series is of moderate extent.

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

SERIES ESTABLISHED: Pecos County, Texas; 1977.

REMARKS:
Edited 11/2013 (RFG-THW): Converted to tabular format and added metric measurements. Updated the competing series, geographic setting, and associated soils sections.

Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 71 cm (0 to 28 in) (A1 and A2 horizons)
Cambic horizon -- 71 to 203 cm (28 to 80 in) (Bw horizons)
Cumulic feature - a mollic epipedon greater than 50 cm (20 in) thick and an irregular decrease in organic carbon content with depth, and greater than 0.3 percent organic carbon within 125 cm (50 in) of the surface.

ADDITIONAL DATA:

Taxonomic Version: Keys to Soil Taxonomy, Eleventh Edition, 2010

National Cooperative Soil Survey
U.S.A.