LOCATION PALAFOX TXEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, hyperthermic Ustic Haplocalcids
TYPICAL PEDON: Palafox clay loam--rangeland on broad plain.
(Colors are for dry soil unless otherwise stated.)
A--0 to 12 inches; brown (10YR 5/3) clay loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky and weak
fine granular structure; hard, firm; common fine roots; many fine
and very fine pores; few small waterworn siliceous pebbles; few
peds at 4 to 5 inches are noncalcareous; 6 percent calcium
carbonate equivalent; calcareous matrix; moderately alkaline;
gradual wavy boundary. (7 to 16 inches thick)
Bk1--12 to 28 inches; brown (10YR 5/3) clay loam, dark brown (10YR 4/3) moist; moderate medium angular blocky structure; hard, firm; common fine roots; many fine pores; few small waterworn siliceous pebbles; few threads and films of calcium carbonate; 17 percent calcium carbonate equivalent; calcareous; moderately alkaline; gradual wavy boundary. (6 to 17 inches thick)
Bk2--28 to 34 inches; yellowish brown (10YR 5/4) clay loam,
dark yellowish brown (10YR 4/4) moist; moderate fine and medium angular blocky structure; very hard, firm; few fine roots; about 2 percent by volume of threads, films, and soft masses of calcium carbonate; 22 percent calcium carbonate equivalent; calcareous; moderately alkaline; gradual wavy boundary. (6 to 26 inches
thick)
Bkz--34 to 45 inches; light yellowish brown (10YR 6/4) clay loam, yellowish brown (10YR 5/4) moist; weak fine angular blocky structure; very hard, firm; few fine roots in upper part; few
films and soft masses of calcium carbonate; 19 percent calcium carbonate equivalent; saline; calcareous; moderately alkaline; gradual wavy boundary. (6 to 70 inches thick)
Ckyz--45 to 72 inches; light yellowish brown (10YR 6/4) clay loam, yellowish brown (10YR 5/4) moist; massive; hard, firm; about
10 percent by volume threads, films, soft masses, and crystals of calcium sulfate; few threads and films of calcium carbonate; 12 percent calcium carbonate equivalent; saline; calcareous;
moderately alkaline.
TYPE LOCATION: Webb County, Texas; from intersection of
Interstate Highway 35 and F.M. 1472 in Laredo, 27.9 miles
northwest on F.M. 1472, 50 feet north of fence in rangeland.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 30 to 60 inches. Total clay in the 10- to 40- inch control section ranges from 25 to 40 percent, and silicate clay ranges from 20 to 35 percent. Calcium carbonate equivalent of the 10- to 40- inch
control section averages from 10 to 25 percent. The calcic
horizon occurs at depths of 10 to 39 inches and has a calcium carbonate equivalent of 5 to 15 percent more than the C horizon. Coarse fragments comprise 0 to about 10 percent by volume and may
be concentrated in individual horizons. Electrical conductivity
is 0 to 2 mmhos/cm at 25 degrees C. in the upper 30 inches and
ranges from 2 to 16 mmhos/cm below 30 inches. The exchangeable sodium percentage is 0 to 10 percent in the upper 30 inches and increases with depth. Reaction is moderately alkaline or strongly alkaline throughout.
The A horizon is grayish brown (10YR 5/2), pale brown (10YR 6/3), brown (10YR 5/3), or light brownish gray (10YR 6/2). Texture is
clay loam, loam, or sandy clay loam. Moist values are greater
than 3.5.
The B horizons are pale brown, light yellowish brown, yellowish brown, brown, or very pale brown in hue of 10YR, 7.5YR, or 2.5Y, value of 5 to 7, and chroma of 3 to 6. It is clay loam or silty
clay loam with 20 to 35 percent silicate clay.
The C horizons are very pale brown, light yellowish brown, pale brown, pink, or pale yellow in hue of 10YR, 7.5YR, or 2.5Y, value
of 6 or 7, and chroma of 3 to 4. Crystalline gypsum and other
salts range from 1 to 15 percent by volume. It is clay loam,
silty clay loam, or loam.
COMPETING SERIES: There are no competing series in the same
family. Series in similar families are
Aguilares,
Coahuila,
Copita,
Garceno,
Moglia, and
Pryor. Aguilares soils have more
sand coarser than very fine sand. Coahuila soils have more than
40 percent calcium carbonate equivalent in the control section. Copita soils have more than 15 percent sand coarser than very fine sand, and also have sandstone at 20 to 40 inches. Garceno and
Pryor soils have more than 35 percent silicate clay in the control section, and Garceno soils also lack a calcic horizon. Moglia
soils are more saline and have a different plant community.
GEOGRAPHIC SETTING: Palafox soils occur on nearly level uplands
of the Western Rio Grande Plain. Surfaces are plain to convex. Slopes range from 0 to 3 percent but are typically less than 2 percent. They formed in calcareous sediments of the Tertiary age. The average annual precipitation range is 16 to 20 inches and the Thornthwaite P-E index range is 23 to 26. The mean annual air temperature range is 71 to 74 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These include
Brundage,
Catarina,
Jimenez,
Maverick, and
Quemado series and
Copita of the competing series. Brundage soils have fine-loamy control sections and are at lower elevations parallel to drainageways. Catarina
soils have intersecting slickensides and are on broad, nearly
level to gently sloping valleys at lower elevations. Copita soils are on higher or lower elevations adjacent to the Palafox soils. Jimenez and Quemado soils have loamy-skeletal control sections and are on small hills or ridges at higher elevations. Maverick soils are more clayey and are at lower elevations on the more sloping erosional surfaces.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: This soil is used primarily for rangeland and wildlife habitat. Some of the larger areas would be suitable for irrigated cropland if irrigation water was available. The native vegetation in excellent condition is composed of 90 percent
grasses, 5 percent woody plants, and 5 percent forbs. In
excellent condition mid grasses dominate. Blackbrush, mesquite,
and lotebush are dominant woody plants. The major forbs are
velvet bundleflower, orange zexmenia, and bushsunflower. As retrogression occurs, woody plants, especially blackbrush, and mesquite increase in density. Grasses which increase or invade,
are red grama, Hall's panicum, threeawn, and Texas bristlegrass.
DISTRIBUTION AND EXTENT: Western Rio Grande Plain of Texas. The series is of large extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Webb County, Texas 1982.
ADDITIONAL DATA: Partial analyses of two pedons were determined
by the Soil Survey Laboratory, Lincoln, Nebraska, Lab Sample Nos. 80-891 to 80-896.