LOCATION MAVCO TXEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, hyperthermic Calcidic Haplustalfs
TYPICAL PEDON: Mavco loam - rangeland (Colors are for dry soil unless otherwise stated.)
A1--0 to 1 inch, light brownish gray (10YR 6/2) loam, dark grayish brown (10YR 4/2) moist; weak platy and weak fine subangular blocky structure; slightly hard, very friable; few fine roots; few fine animal tunnels; few fragments of snail shell; strongly effervescent, moderately alkaline; abrupt smooth boundary. (1/4 to 2 inches thick)
A2--1 to 12 inches, grayish brown (10YR 5/2) loam, dark grayish brown (10YR 4/2) moist; moderate fine and medium subangular blocky granular structure; hard, friable; many fine roots; many fine pores and root channels; few fine animal tunnels; few wormcasts; few fragments of snail shell; few fine fragments of limestone about 1/4 inch in diameter; violently effervescent, about 22 percent calcium carbonate equivalent; moderately alkaline; gradual smooth boundary. (5 to 20 inches thick)
Btk1--12 to 29 inches, very pale brown (10YR 7/3) clay loam, brown (10YR 5/3) moist; moderate fine and medium subangular blocky structure; hard, friable; few faint clay films on faces of peds; many fine roots; many fine pores and root channels; few fine animal tunnels; few wormcasts; few fragments of snail shell; about 10 percent masses and concretions of calcium carbonate up to 1/2 inch in diameter; few siliceous pebbles; about 35 percent calcium carbonate equivalent; violently effervescent, moderately alkaline; clear irregular boundary. (10 to 24 inches thick)
Btk2--29 to 46 inches, very pale brown (10YR 7/3) clay loam, pale brown (10YR 6/3) moist; weak fine and medium subangular blocky structure; hard, friable; few faint clay films on faces of peds and in pores and root channels; very few fine roots; very few animal and root tunnels filled with slightly darker soil material; about 25 percent masses of calcium carbonate; about 50 percent calcium carbonate equivalent; violently effervescent, moderately alkaline; clear wavy boundary. (10 to 30 inches thick)
Bk--46 to 70 inches, very pale brown (10YR 7/4) clay loam, light yellowish brown (10YR 6/4) moist; weak fine and medium subangular blocky structure; hard, friable; few faint clay films on faces of peds, lining pores, and in root channels; very few roots; few krotovina; about 15 percent masses of calcium carbonate about 55 percent calcium carbonate equivalent; violently effervescent, moderately alkaline.
TYPE LOCATION: Maverick County, Texas; 9.9 miles northwest of high school in Eagle Pass on U. S. Highway 277 (this point is 1.1 miles southeast of junction of U. S. Highway 277 and Texas Highway 131); 0.6 mile east on old airport road; 0.3 mile south; 200 feet west in rangeland.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to more than 80 inches. The soil is calcareous in all horizons. Calcium carbonate equivalent averages 20 to 40 percent in the upper 20 inches of the Bt horizon.
The A horizon has hue of 10YR, value of 4 through 6, and chroma of 2 or 3. When values are less than 5.5 dry and 3.5 moist the A horizon is less than 6 inches thick. It is loam, silt loam, or clay loam.
The Btk horizon has hue of 2.5Y, 10YR or 7.5YR, value of 5 through 7 and chroma of 3 or 4. The 10- to 40-inch control section is clay loam, silty clay loam, or clay with a clay content of 35 to 45 percent. An estimated 10 to 25 percent of the clay is carbonate clay.
Color of the Bk horizon has hue of 2.5Y or 10YR, value of 6 through 8, and chroma of 3 or 4. Secondary calcium carbonate in the form of soft bodies or concretions ranges from about 5 to 50 percent by volume.
COMPETING SERIES: There are no other series in the same family. Similar soils include the Caid, Elindio, Garceno, Maverick, Uvalde, and Verick series. Caid, Elindio, and Uvalde soils have a mollic epipedon. Verick soils have sola less than 20 inches thick. Garceno and Maverick soils have more than 35 percent silicate clay in the 10- to 40-inch control section.
GEOGRAPHIC SETTING: Mavco soils occur on nearly level to gently sloping stream terraces and uplands. Slope gradients range from 0 to 3 percent but are mainly less than 1.5 percent. The soil formed in alluvium from limestone and is high in calcium carbonate. The climate is hot and semiarid. Average annual precipitation is 17 to 24 inches and mean annual temperature ranges from 70 to 74 degrees F. Frost free period is 270 to 290 days, and elevation ranges from 600 to 850 feet. The Thornthwaite P-E indices range from about 21 to 28.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the similar Caid, Elindio, Garceno, and Uvalde series and the Copita, Darl, and Zapata series. Copita soils lack argillic horizons. Darl and Zapata soils have petrocalcic horizons and are shallow
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.
USE AND VEGETATION: Used almost exclusively as rangeland. Native grasses are mainly red grama, threeawn, Texas bristlegrass, pink pappusgrass, sand dropseed, Hall's panicum, fall witchgrass and tobosa. Woody plants are small mesquite, paloverde, guayacan, cenizo, guajilla, twisted acacia, tasajillo, condalias, vine ephedra, pricklypear, and catclaw acacia. Ratear is a very common forb.
DISTRIBUTION AND EXTENT: The northwestern Rio Grande Plain of Texas and probably Mexico. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Maverick County, Texas; 1972.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 12 inches
Argillic horizon - 12 to 46 inches
Calcic horizon - 12 to 70 inches.