LOCATION PERNITAS                TX

Established Series
MLG-JLS-JAG
02/2018

PERNITAS SERIES

The Pernitas series consists of very deep, well drained, moderately permeable soils that formed in calcareous loamy alluvium derived from sandstone of Pleistocene and Pliocene ages. These nearly level to moderately sloping soils are on summits, backslopes, and footslopes of ridges. Slopes range from 0 to 8 percent. Mean annual precipitation is about 711 mm (28 in) and mean annual air temperature is about 22.2 degrees C (72 degrees F).

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, hyperthermic Typic Argiustolls

TYPICAL PEDON: Pernitas sandy clay loam--rangeland. (Colors are for dry soil unless otherwise stated.)

A--0 to 28 cm (0 to 11 in); dark gray (10YR 4/1) sandy clay loam, very dark gray(10YR 3/1) moist; weak medium prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky; common fine and medium roots; common fine pores; few wormcasts and insect tunnels; few snail shells; few fine threads of calcium carbonate; very slightly effervescent; moderately alkaline; clear smooth boundary. (18 to 36 cm [7 to 14 in] thick)

Bt1--28 to 43 cm (11 to 17 in); grayish brown (10YR 5/2) clay loam, dark brown(10YR 3/3) moist; weak medium prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky; few fine and medium roots; common fine pores; common distinct clay films on surfaces of peds; few fragments of snail shell; few threads and very fine nodules of calcium carbonate; very slightly effervescent; moderately alkaline; gradual smooth boundary.

Bt2--43 to 76 cm (17 to 30 in); brown (7.5YR 5/4) clay loam, brown (7.5YR 4/4) moist; weak medium prismatic structure parting to moderate medium subangular blocky; very hard, friable, sticky; few fine roots mostly between peds; few fine pores; common distinct clay films on surfaces of peds; few fine threads and nodules of calcium carbonate; very slightly effervescent; moderately alkaline; clear wavy boundary. (combined thickness of the Bt horizon is 28 to 102 cm [11 to 40 in])

Bk1--76 to 91 cm (30 to 36 in); light brown (7.5YR 6/4) clay loam, brown (7.5YR 5/4) moist; massive; hard, friable, slightly sticky; estimated 20 to 25 percent by volume masses and nodules of calcium carbonate; strongly effervescent; moderately alkaline; gradual wavy boundary. (combined thickness of the Bk horizon is 0 to 38 cm [0 to 15 in])

Bk2--91 to 203 cm (36 to 80 in); pinkish gray (7.5YR 7/2) clay loam, light brown (7.5YR 6/4) moist; massive; hard, friable, slightly sticky; an estimated 15 to 20 percent calcium carbonate mostly in the form of irregular shaped masses; strongly effervescent; moderately alkaline.

TYPE LOCATION: Jim Wells County, Texas; from the intersection of U.S. Highway 281 and Texas Highway 359 in Alice; 3 miles west on Texas Highway 359; 10 miles north and 2.7 miles northwest on County Road 236; 4.2 miles west on County Road 237 and 0.3 mile southwest into native range. Shaeffer Ranch USGS Quad; Latitude: 27 degrees, 55 minutes, 24.9 seconds N; Longitude: 98 degrees, 13 minutes, 32.1 seconds W, NAD 83.

RANGE IN CHARACTERISTICS:
Soil Moisture: A typic ustic moisture regime. The soil moisture control section is dry in some or all parts for more than 90 days but less than 180 cumulative days in normal years. These soils are intermittently moist in September through November and March through May.
Mean annual soil temperature: 22.2 to 23.3 degrees C (72 to 74 degrees F)
Calcic horizon: 51 to 102 cm (20 to 40 in)

Particle-size control section: (weighted average)
Total Clay content: 24 to 40 percent
Silicate Clay content: 24 to 35 percent

A horizon
Hue: 10YR
Value: 3 or 4
Chroma: 1 to 3
Texture: fine sandy loam, sandy clay loam
Clay content: 12 to 32 percent
Fragments: 0 to 1 percent, indurated chert gravel and/or snail shells
Calcium carbonate equivalent: 1 to 10 percent
Effervescence: very slight or slight
Electrical Conductivity: 0 to 2 mmhos/cm
Reaction: slightly alkaline or moderately alkaline

Bt horizon
Hue: 7.5YR, 10YR
Value: 4 to 7
Chroma: 2 to 4
Texture: sandy clay loam, clay loam, sandy clay
Clay content: 21 to 40 percent
Fragments: 0 to 3 percent, subangular to subrounded, moderately to very strongly cemented calcrete gravel and/or snail shells
Calcium carbonate equivalent: 8 to 20 percent
Effervescence: slight to violent
Electrical Conductivity: 0 to 2 mmhos/cm
Reaction: slightly alkaline or moderately alkaline

Btk (where present) horizon
Hue: 7.5YR, 10YR
Value: 6 to 8
Chroma: 2 to 4
Texture: clay loam, sandy clay loam, sandy clay
Clay content: 22 to 40
Fragments: 0 to 10 percent, subangular to subrounded, moderately to very strongly cemented calcrete gravel
Identifiable secondary carbonates: 10 to 40 percent, fine to medium, masses and nodules
Calcium carbonate equivalent: 10 to 20 percent
Effervescence: strong to violent
Electrical Conductivity: 0 to 2 mmhos/cm
Reaction: slightly alkaline or moderately alkaline

Bk Horizon
Hue: 7.5YR, 10YR
Value: 6 to 8
Chroma: 2 to 4
Texture: clay loam, sandy clay loam, loam
Clay content: 18 to 35
Fragments: 0 to 15 percent, subangular to subrounded, moderately to very strongly cemented calcrete gravel
Identifiable secondary carbonates: 10 to 40 percent, fine to medium, masses and nodules
Calcium carbonate equivalent: 10 to 50 percent and decreases with depth
Effervescence: strong to violent
Electrical Conductivity: 0 to 2 mmhos/cm
Reaction: moderately alkaline

COMPETING SERIES: These are the Alet(TX), Colmena(TX), Orelia(TX), Pharr(TX), Runge(TX) and Weesatche(TX) series of the same family.
Alet soils: do not have calcic horizons and occur in drainageways.
Colmena, Orelia, Runge, and Weesatche soils: are noncalcareous in the upper part of the sola.
Pharr soils: have a calcic horizon at a depth of more than 102 cm (40 in) and have a semiactive activity class.

GEOGRAPHIC SETTING:
Parent Material: calcareous loamy alluvium derived from sandstone of Pleistocene and Pliocene age; mainly from the Oakville, Fleming, and Goliad formations.
Landform: Shoulders, backslopes, and footslopes of low ridges
Slope: 0 to 8 percent
Mean annual air temperature: 21.1 to 23.3 degrees C (70 to 74 degrees F)
Mean annual precipitation: 610 to 914 (24 to 36 in)
Precipitation Pattern: Precipitation falls mainly during the spring and fall months. June through August and December through March are the driest months.
Frost free period: 275 to 295 days
Elevation: 45.7 to 243.9 m (150 to 800 ft)
Thornthwaite annual P-E indices: 25 to 44

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Annarose, Olmedo, Pettus, Pharr, Runge, Sarnosa, and Weesatche series.
Annarose, Pettus, and Sarnosa soils: are on slightly higher positions; do not have an argillic horizon
Olmedo soils: are on summits of ridges; are shallow to a petrocalcic horizon
Pettus soils: have a loamy-skeletal particle-size control section
Pharr and Runge soils: are on similar positions; have a calcic horizon at a depth of more than 100 cm (40 in).
Weesatche soils: are on similar positions; are noneffervescent in the surface horizon.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate. Runoff low on 1 to 5 percent slopes, and medium on 5 to 8 percent slopes.

USE AND VEGETATION: Used mostly for livestock grazing and wildlife habitat. Some areas are crop production, mostly for grain sorghum. Present vegetation includes pink pappusgrass, lovegrass tridens, fall witchgrass, hooded windmillgrass, and plains bristlegrass. Woody vegetation includes mesquite, catclaw, spiny hackberry, and blackbrush, and guallijo. The ecological site is Gray Sandy Loam, 20-35"PZ (R083CY456TX).

DISTRIBUTION AND EXTENT: Central portion of the Rio Grande Plain of Texas (MLRA 83A, 83C). The series is of large extent.

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

SERIES ESTABLISHED: Jim Wells County, Texas; 1976.

REMARKS: This is a benchmark series.
Pernitas soils were previously included with the Hildago series.

Diagnostic horizons and features recognized in this pedon are:

Particle-size control section: 28 to 76 cm (11 to 30 in)
Mollic epipedon: 0 to 43 cm (0 to 17 in) (A and Bt1 horizon).
Argillic horizon: 28 to 76 cm (11 to 30 in) (Bt1 and Bt2 horizon).
Calcic horizon: 76 to 203 cm (30 to 72 in) (Bk1 and Bk2 horizon).

ADDITIONAL DATA: NSSL data from Live Oak County, TX (S91TX-297-002), and Texas A&M characterization from Duval County, TX (S81-131-001).

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

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National Cooperative Soil Survey
U.S.A.