LOCATION PLACK              TX+OK NM

PLACK SERIES

TAXONOMIC CLASS: Loamy, mixed, superactive, mesic, shallow Petrocalcic Calciustolls

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

A--0 to 20 cm (0 to 8 inches); grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak fine granular and subangular blocky structure; slightly hard, friable; many fine roots; few fine calcium carbonate nodules to 5 mm; strongly effervescent, moderately alkaline; abrupt smooth boundary. (10 to 50 cm [4 to 20 inches] thick)

Bkkm--20 to 66 cm (8 to 26 inches); white (10YR 8/1) indurated platy caliche; laminar in the upper 2 cm; strongly cemented throughout; plates are 2 to 15 cm thick; hardness about 4 Moh's scale; violently effervescent, moderately alkaline. (15 to 120 cm [6 to 48 inches] thick)

Bkk1--66 to 122 cm (26 to 48 inches); very pale brown (10YR 8/4) loam; very pale brown (10YR 7/4) moist; weak fine subangular blocky structure; hard, very friable; about 40 percent fragments of indurated caliche up to 4 cm across; about 60 percent by volume of calcium carbonate as masses, nodules, and finely disseminated carbonates; violently effervescent, moderately alkaline; clear wavy boundary. (25 to 120 cm [10 to 48 inches] thick)

Bkk2--122 to 203 cm (48 to 80 inches); very pale brown (10YR 7/4) loam; light yellowish brown (10YR 6/4) moist; weak fine subangular blocky structure; hard, very friable; about 10 percent fragments of indurated caliche up to 2 cm across; about 50 percent by volume of calcium carbonate as masses, nodules and finely disseminated carbonates; violently effervescent, moderately alkaline.

TYPE LOCATION: Dallam County, Texas; 0.4 kilometer (0.25 mile) south and 183 meters (600 feet) west from NE corner Section 14, Block 7 of the FDW Survey, about 20.9 kilometers (13.0 miles) east of Texline on Farm Road 296, then 9.7 kilometers (6.0 miles) east of the intersection of Farm Roads 296 and 1879 on county dirt road and 2.4 kilometers (1.5 miles) north into pasture on the Panhandle National Grasslands; Latitude: 36 degrees, 24 minutes, 7 seconds N; Longitude: 102 degrees, 41 minutes, 23 seconds, Coldwater West, Texas USGS quad; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: An ustic moisture regime bordering on aridic. The soil moisture control section is dry in some or all parts for more than 180 but less than 220 days, cumulative, in normal years. July through August and December through February are the driest months. These soils are intermittently moist in September through November and March through June.
Mean annual soil temperature: 13 to 15 degrees C (55 to 59 degrees F)
Depth to petrocalcic horizon: 10 to 50 cm (4 to 20 inches)
Particle-size control section: 18 to 35 percent silicate clay

A horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5, 2 to 4 moist
Chroma: 2 or 3
Texture: fine sandy loam, loam, clay loam, or gravelly loam with clay content of 14 to 32 percent
Effervescence: Strong or violent
Reaction: Moderately alkaline

Bkkm horizon:
This horizon ranges from fractured, indurated, and thin to thickly laminar to continuously indurated, thickly laminar. Some pedons have indurated to moderately cemented pea-shaped, calcite structures below the laminar caps (pisolitic structure).

Bkk horizons:
Hue: 7.5YR or 10YR
Value: 7 or 8, 6 or 7 moist
Chroma: 1 to 4
Texture: fine sandy loam, loam
Coarse fragments: 10 to 45 percent petrocalcic fragments
Secondary calcium carbonate: 50 to 80 percent calcium carbonate by volume in the form of masses, nodules, and finely disseminated carbonates.
Effervescence: violent
Reaction: moderately alkaline or strongly alkaline

COMPETING SERIES: This is the Pidineen series. Similar soils also include the Kerrick, Kimberson, Kimbrough, Lea, and Pastura series.
Kimberson, Kimbrough, and Lea soils: have an average annual soil temperature more than 15 degrees C.
Kerrick soils: have a petrocalcic horizon that ranges from 50 to 100 cm deep.
Pastura soils: have an ochric epipedon.
Pidineen series: have a mean annual soil temperature less than 13 degrees C.

GEOGRAPHIC SETTING:
Parent material: loamy eolian sediments of Pleistocene age over indurated caliche of Pliocene age.
Landform: eolian plain
Slopes: 0 to 5 percent with dominant slope gradients ranging from 0 to 3 percent.
Elevation: 916 to 1,448 meters (3,000 to 4,750 feet).
Mean annual air temperature: 12 to 14 degrees C (54 to 57 degrees F).
Mean annual precipitation: 432 to 559 mm (17 to 22 inches).
Frost-free period: 170 to 200 days (4,080 to 4,800 hours)
Thornthwaite annual P-E Index Values: 25 to 36.

GEOGRAPHICALLY ASSOCIATED SOILS:
These are the similar Kerrick soils and the Conlen, Potter, Sunray, and Texline soils.
Kerrick soils: are on similar landscape positions.
Sunray and Texline soils: are on similar landscape positions and have an argillic horizon.
Conlen soils: are on similar landscape positions and have carbonatic mineralogy.
Kerrick soils: are on similar landscape positions.
Potter soils: are on lower landscape positions and have average annual soil temperatures of more than 15 degrees C (59 degrees F).

DRAINAGE AND PERMEABILITY: Well drained and moderate permeability. Surface runoff is low on 0 to 1 percent slopes and medium on 1 to 5 percent slopes.

USE AND VEGETATION: These soils are used nearly exclusively for livestock grazing. Climax vegetation includes sideoats grama, little bluestem, buffalograss, hairy grama, slim tridens, purple and wright threeawns, bushsunflower, gray goldaster, daleas, gayfeather, plains blackfoot, sundrops, catclaw, ephedra, hackberry, and javelinabrush. This soil has been correlated to the Very Shallow (R-077AY013TX) ecological site in MLRA-77A.

DISTRIBUTION AND EXTENT: Southern High Plains, Northern Part (MLRA 77A in LRR H) north of the Canadian River in Texas, Oklahoma, and New Mexico. The series is of minor extent.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Dallam County, Texas; 1970.

REMARKS: Series revised during the MLRA-77 Update Soil Survey; Hansford County, Texas; 2006.
Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon - 0 to 20 cm (A horizon)
Petrocalcic horizon 20 to 66 cm (Bkkm horizon)
Calcic horizon - 66 to 203 cm (Bkk1, Bkk2 horizons)

ADDITIONAL DATA: NSSL data on sample number: S99OK-139-001 (Texas County, Oklahoma).

TAXONOMIC VERSION: Keys to Soil Taxonomy, Tenth Edition, 2006.