LOCATION ACUNA              TX

ACUNA SERIES

TAXONOMIC CLASS: Fine-silty, carbonatic, hyperthermic Aridic Calciustolls

TYPICAL PEDON: Acuna silty clay--rangeland. (Colors are for dry soil unless otherwise stated.)

A1--0 to 18 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; the upper 2 inches is grayish brown (10YR 5/2); moderate medium subangular blocky structure parting to moderate medium granular; slightly hard, friable; common fine and medium roots; common fine pores; few fine threads and films of calcium carbonate; few fine calcium carbonate concretions less than 2 mm across; calcareous; moderately alkaline; clear wavy boundary. (10 to 20 inches thick)

B21--18 to 30 inches; brown (7.5YR 5/4) clay, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure parting to moderate medium granular; hard, friable; few fine roots; common very fine pores; few films and threads of calcium carbonate; few thin discontinuous clay films on vertical ped surfaces; calcareous; moderately alkaline; abrupt wavy boundary. (6 to 28 inches thick)

B22ca--30 to 38 inches; pink (7.5R 7/4) silty clay, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; slightly hard; friable; many very fine pores; 15 percent by volume of threads, films, and concretions 2 mm to 2 cm across of calcium carbonate; calcareous; moderately alkaline; clear wavy boundary. (8 to 28 inches thick)

B23ca--38 to 60 inches; pink (7.5YR 8/4) silty clay, reddish yellow (7.5YR 7/6) moist; weak fine subangular blocky structure; slightly hard, friable; common very fine pores; 8 percent by volume of threads, films and soft masses of 2 mm to 2 cm across of calcium carbonate, calcareous; moderately alkaline; gradual wavy boundary. (10 to 25 inches thick)

B24ca--60 to 72 inches; reddish yellow (7.5YR 6/6) silty clay, strong brown (7.5YR 5/6) moist; weak fine subangular blocky structure; slightly hard, friable; about 5 percent by volume of soft masses and concretions 2 mm to 2 cm across of calcium carbonate; calcareous; moderately alkaline. (9 to 20 inches thick)

TYPE LOCATION: Val Verde County, Texas; from the intersection of U. S. Highway 90 and U. S. Highway 277 in Del Rio; 3.3 miles east on U. S. Highway 90 to Ranch Road 2523; 8.3 miles generally northeast on Ranch Road 2523 to ranch entrance; 0.3 mile west on private road; 75 feet north in range.

RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to more than 60 inches. The depth to distinct accumulations of calcium carbonate is about 16 to 40 inches with 5 to 30 percent visible secondary forms. Total calcium carbonate content in the 10 to 40 inch control section is about 40 to 55 percent. Depth to limestone or gravel ranges from 6 to 20 feet. Limestone fragments of pebble size range from 0 to 15 percent. COLE ranges from 0.03 to 0.05. Total clay of the 10 to 40 inch control section ranges from 35 to 50 percent and silicate clay ranges from 20 to 35 percent.

The A horizon is very dark grayish brown, dark grayish brown, grayish brown, dark brown, or brown in hue 10YR, chromas of 2 through 3 and values of 3 through 5. Moist values and chromas are less than 3.5. Texture of the A horizon is silty clay loam, silty clay or clay.

The B21t horizon is brown, light brown, or pale brown in hues of 10YR and 7.5Y, chromas of 3 through 4, and values of 5 through 6. It is silty clay loam, silty clay, or clay. Structure ranges from weak to moderate subangular blocky.

The B2ca horizons are brown, light brown, pale brown, very pale brown, light yellowish brown, or pink in hues of 10YR and 7.5YR, chromas of 3 through 4 and values of 5 through 8. It is silty clay loam, silty clay, or clay. Some pedons have Cca horizons below 40 inches with colors the same as the B2ca horizons.

COMPETING SERIES: There are no soils in the same family. Similar soils are the Angelo, Castroville, Dant, Elindio, Knippa, Lewisville, Nuvalde, and Uvalde series. All of these soils have less than 40 percent calcium carbonate equivalent in the 10 to 40 inch control section. Angelo and Knippa soils crack when dry and have mean annual soil temperatures less than 72 degrees F. Castroville, Lewisville, and Nuvalde soils are most in the control section for longer periods of time. Dant soils lack a calcic horizon within a depth of 40 inches and have a fine-loamy control section.

GEOGRAPHIC SETTING: Acuna soils are on nearly level to gently sloping filled valleys and ancient stream terraces. Slope gradients range from 0 to 3 percent but are mainly less than 1 percent. The soil formed in alluvium high in calcium carbonate from limestone areas. The climate is semiarid. Mean annual precipitation ranges from 16 to 21 inches and mean annual air temperature ranges from 69 degrees to 73 degrees F. The Thornthwaite P-E indices are 25 to 34.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the Darl, Langtry, Mavco, Olmos, Valverde, Zapata, and Zorra series. Darl, Olmos, and Zapata soils have a petrocalcic horizon within 20 inches of the surface. Langtry and Zorra soils are shallow to limestone. Mavco and Valverde soils have ochric epipedons and in addition, Valverde soils have bedrock at depths of 40 to 60 inches.

DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.

USE AND VEGETATION: Used mainly as rangeland. In good and excellent range condition it is dominated by sideoats grama, slim tridens, plains bristlegrass, and silver bluestem. As retrogression occurs red grama, perennial threeawn, fall witchgrass, and Hall's panicum increase along with woody shrubs. As deterioration continues a large percent of the plants consists of woody shrubs such as mesquite, whitebrush, agarita, yuccas, and cacti with an understory of red grama, hairy tridens, and perennial treeawn. Some areas are irrigated and seeded to improved forage grasses. Oats are grown for forage in some areas.

DISTRIBUTION AND EXTENT: The northwestern Rio Grande Plain and southern Edwards Plateau of Texas and probably Mexico. The series is of moderate extent.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Val Verde County, Texas; 1979. REMARKS: The Acuna series would have been classified in the Calcisol great soil group. It was formerly included with the Elindio series.

ADDITIONAL DATA: Acuna soil samples: Texas Highway Department Lab Nos. E78640039, E78640040, E78640041.

National Cooperative Soil Survey U. S. A.

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ELINDIO SERIES

LOCATION ELINDIO            TX

TAXONOMIC CLASS: Fine-silty, mixed, hyperthermic Aridic Calciustolls

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

A--0 to 15 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky and granular structure; hard, friable; many fine roots, common fine pores and root channels; few worm casts; few small fragments of shell; calcareous; moderately alkaline; gradual smooth boundary. (9 to 20 inches thick)

Bw--15 to 26 inches; brown (10YR 5/3) clay loam, dark brown (10YR 4/3) moist; moderate fine subangular blocky structure; very hard, firm; common fine roots; few fine pores and root channels; few worm casts; few fragments of snail shell; few films and threads of calcium carbonate; calcareous; moderately alkaline; gradual wavy boundary. (9 to 22 inches thick)

Bk1--26 to 39 inches; very pale brown (10YR 7/3) clay loam, pale brown (10YR 6/3) moist; moderate fine and medium subangular blocky structure; very hard, firm; few fine roots; few fine pores and root channels; few worm casts; contains about 5 percent by volume of soft masses and films and threads of secondary calcium carbonate; calcareous; moderately alkaline; gradual wavy boundary. (7 to 18 inches thick)

Bk2--39 to 72 inches; very pale brown (10YR 7/4) clay loam, light yellowish brown (10YR 6/4) moist; weak fine subangular blocky structure; very hard, firm; many fine and medium pores; few krotovina, contains about 25 percent by volume of soft masses of secondary calcium carbonate; calcareous; 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); 0.4 mile east on old airport road; 100 feet north in rangeland.

RANGE IN CHARACTERISTICS: Solum thickness is 40 to more than 60 inches. Calcium carbonate equivalent ranges from about 10 to 25 percent in the A horizon and from about 20 to 40 percent in the B and C horizons. Salinity is typically less than 2.0 mmho/cm, but in irrigated areas salinity ranges from 4 to 16 mmho/cm due to poor water management.

The A horizon is very dark grayish brown and has hue of 10YR, value of 4 and 5, and chroma of 2 or 3. Texture is silty clay loam or clay loam. The 10 to 40 inch control section is clay loam or clay with a clay content of 30 to 45 percent. An estimated 10 to 20 percent of the clay is carbonate clay.

The Bw horizon has hue of 2.5Y or 10YR, value of 5 or 6 and chroma of 2 through 4. Texture is clay loam or clay.

The Bk horizon has hue of 2.5y or 10YR, value of 5 through 8 , and chroma of 2 through 4. Visible secondary calcium carbonate in the form of soft masses and concretions ranges from about 2 to 35 percent by volume in the lower part of the Bk horizon. Some pedons have Ck horizons below 40 inches with colors the same as the Bk horizons.

COMPETING SERIES: These are the Uvalde series of the same family and the similar Acuna, Angelo, Castroville, Dant, Knippa, Lewisville, Nuvalde, and Quanah series. Uvalde soils are dry in the moisture control section for shorter periods. Acuna soils have carbonatic mineralogy. Angelo and Knippa soils crack when dry and have mean annual soil temperatures less than 72 degrees F. Castroville, Lewisville, Nuvalde and Quanah soils are moist in the control section for longer periods of time. Dant soils lack a calcic horizon within a depth of 40 inches and have a fine-loamy control section.

GEOGRAPHIC SETTING: Elindio 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 that is high in calcium carbonate and is derived from limestone areas. The climate is hot and semiarid. Average annual precipitation is 18 to 22 inches and the annual temperature is 70 to 74 degrees F. Frost free period is 275 to 290 days and elevation ranges from 550 to 700 feet. The Thornthwaite P-E indices are about 21 to 27.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dant, Darl, Mavco, and Zapata series. Dant soils have a COLE greater than 0.07 and lack calcic horizons at depths of less than 40 inches. The Darl and Zapata soils have petrocalcic horizons and, in addition, Darl, Mavco and Zapata soils ochric epipedons; Mavco soils also have Bt horizons. These soils occur on similar surfaces.

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, bristlegrass, pink pappusgrass, Hall's panicum, fall witchgrass, tobosa, and curlymesquitegrass. Woody plants are mesquite, guayacan, spiny hackberry, condalias, whitebrush, guajillo, and pricklypear cactus.

DISTRIBUTION AND EXTENT: The northwestern Rio Grande Plain of Texas and probably Mexico. The series is of moderate extent.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Maverick County, Texas; 1972.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon - 0 to 15 inches. (A-horizon)

Cambic horizon - 15 to 26 inches. (Bw horizon)

Calcic horizon - 26 to 72 inches. (Bk horizon)

Soft powdery lime - 26 to 72 inches. (Bk horizon)

National Cooperative Soil Survey U.S.A.

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LOCATION JIMENEZ            TX

JIMENEZ SERIES

TAXONOMIC CLASS: Loamy-skeletal, mixed, hyperthermic, shallow Petrocalcic Calciustolls

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

A--0 to 9 inches; dark grayish brown (10YR 4/2) very gravelly loam, very dark grayish brown (10YR 3/2) moist; weak granular structure; slightly hard, friable; 70 percent by volume of water-worn quartzite, chert, limestone, sandstone, and basalt pebbles mostly less than 6 cm in diameter; calcareous; moderately alkaline abrupt wavy boundary. (7 to 20 inches thick)

Bkm--9 to 18 inches; white (10YR 8/2) strongly cemented caliche with about 40 percent of the mass consisting of embedded gravel; smooth and finely etched on the upper surface, upper 1/2 inch is finely laminated, and has a hardness of 3 (Moh's scale) when dry; diffuse irregular boundary. (2 to 20 inches thick)

Bk--18 to 60 inches; white (10YR 8/2) weakly cemented, massive caliche with about 50 percent embedded gravel.

TYPE LOCATION: Maverick County, Texas; in pasture 100 feet east of U.S. Highway 277 and 5.5 miles north; 12 degrees west of post office in Quemado via U.S. Highway 277.

RANGE IN CHARACTERISTICS: The A horizon is brown (10YR 5/3; 7.5YR 5/2), grayish brown (10YR 5/2), dark brown (10YR 4/3; 7.5YR 4/2), or dark grayish brown (10YR 4/2). It is very gravelly loam, very gravelly sandy loam, or very gravelly sandy clay loam; the fraction less than 2 mm ranges from 12 to 27 percent clay. Gravel content is 35 to 80 percent. The pebbles are rounded and are mostly siliceous but include lesser amounts of limestone, basalts, and sandstone. In some pedons the pebbles have coatings of calcium carbonate 1 to 5 mm thick. The pebbles on the surface are uncoated. Calcium carbonate equivalent is 1 to 40 percent.

The Bkm horizon is laminar or massive; estimated hardness is 2.5 to 3.0 on the Moh's scale; and it may be fractured and platy-like in the upper part.

COMPETING SERIES: There are no series in this family. Similar soils are Amistad, Boracho, Ector, Kimbrough, Langtry, Olmos, Quemado, Real, Valco, Zapata, and Zorra series. Amistad, Boracho, Ector, Kimbrough, and Real soils have mean annual soil temperatures less than 72 degrees F. In addition, Amistad, Ector, Langtry, and Real soils, as well as, Olmos, Zapata, and Zorra soils have carbonatic mineralogy. Quemado soils have an ochric epipedon and argillic horizon. Valco soils contain less than 35 percent coarse fragments.

GEOGRAPHIC SETTING: These soils are on old high terraces, generally paralleling the Rio Grande in an undulating to hilly landscape, the result of much dissection. Slope gradients range from 1 to 30 percent, but the average is about 10 percent. The soil formed in beds of gravelly caliche mostly 3 to 20 feet thick which rests on limestone, calcareous clays, or shales. At the type location, the climate is semiarid with an annual precipitation of 18 inches, a mean annual temperature of 74 degrees F., and a Thornthwaite P-E index of 26.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Quemado, and Zapata series. Quemado soils occur at higher elevations and have less slope gradient. Zapata soils occur at lower elevations.

DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderate permeability.

USE AND VEGETATION: Used as native range for sheep, goats, and cattle. Native vegetation consists of mid grasses, a few short grasses, about 25 percent woody shrubs and 5 percent perennial forbs. With retrogression, woody plants, dominated by guajillo and blackbrush, form a dense canopy. Other increasers and invaders are threeawn, hairy tridens, and red grama.

DISTRIBUTION AND EXTENT: South Texas in the western part of Rio Grande Plain, generally within 10 miles of the Rio Grande. Probably occurs in Mexico. The series is extensive, about 250,000 acres.

MLRA OFFICE RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Kinney County, Texas; 1970.

National Cooperative Soil Survey U. S. A.

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LOCATION MAVCO              TX

MAVCO 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 OFFICE 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.

National Cooperative Soil Survey U.S.A.

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LOCATION TONIO              TX

TONIO SERIES

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, hyperthermic Ustic Calciargids

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

A1--0 to 10 inches; brown (10YR 5/3) fine sandy loam, dark brown (10YR 4/3) moist; weak fine and medium subangular blocky structure; slightly hard, very friable; few fine roots; many fine pores; few threads and films of calcium carbonate; slight effervescence moderately alkaline; gradual smooth boundary. (7 to 18 inches thick)

Bt1--10 to 30 inches; brown (7.5YR 5/4) sandy clay loam, dark brown (7.5YR 4/4) moist; weak fine and medium subangular blocky structure; slightly hard, very friable; few patchy clay films on faces of peds; few fine roots; many fine pores; few threads and films of calcium carbonate strong effervescence; moderately alkaline; gradual smooth boundary. (6 to 24 inches thick)

Bt2--30 to 40 inches; light brown (7.5YR 6/4) sandy clay loam, brown (7.5YR 5/4) moist; moderate fine and medium subangular blocky structure; hard, friable, few patchy clay films on faces of peds; few fine roots; many fine pores; common threads and films of calcium carbonate; strong effervescence; moderately alkaline; gradual wavy boundary. (6 to 16 inches thick)

Btk--40 to 54 inches; very pale brown (10YR 7/4) sandy clay loam, light yellowish brown (10YR 6/4) moist; weak fine and medium subangular blocky structure; hard, friable; few fine pores; contains about 10 percent by volume of soft bodies of calcium carbonate up to 1/2 inch diameter; strong effervescence; moderately alkaline; abrupt wavy boundary. (10 to 24 inches thick)

Cr--54 to 74 inches; pink (7.5YR 7/4) sandstone, reddish yellow (7.5YR 6/6) moist; few yellowish red (5YR 5/6) streaks; weakly cemented; brittle; strong effervescence; moderately alkaline.

TYPE LOCATION: Dimmit County, Texas; 15.1 miles southeast of Garrizo Spring on Farm Road 186, then 2.7 miles west on private road to Hamilton Ranch Headquarters, then 3.4 miles north to corrals, continue 0.8 mile north to pipeline, then northwest 1.1 miles across pond dam to metal gate, then 0.7 mile northwest across pond dam, then 50 feet east in rangeland.

RANGE IN CHARACTERISTICS: Solum thickness ranges from 40 to 60 inches over weakly to strongly cemented sandstone. Conductivity of the saturation extract is about 1 to 4 millimhos.

The A horizon is dark brown (10YR 4/3), brown (10YR 5/3), pale brown (10YR 6/3), dark grayish brown (10YR 4/2), grayish brown (10YR 5/2; 2.5Y 5/2), yellowish brown (10YR 5/4), and light yellowish brown (10YR 6/4). Mollic colors are less than 6 inches thick in the A horizon. It is fine sandy loam, loam, or sandy clay loam. Calcium carbonate equivalent is 1 to about 10 percent.

The B horizon is brown (10YR 5/3; 7.5YR 5/4), yellowish brown (10YR 5/4), light olive brown (2.5Y 5/4), pale brown (10YR 6/3), light brown (7.5YR 6/4), light yellowish brown (10YR 6/4), very pale brown (10YR 7/3, 7/4, 8/4), reddish yellow (7.5YR 7/6), yellow (10YR 7/6; 2.5Y 7/6). The lower parts of the B horizon are usually of lighter color than the upper parts. It is fine sandy loam, loam, sandy clay loam, or clay loam with clay content of the upper 20 inches of the B horizon ranging from 19 to 34 percent. Calcium carbonate equivalent is 10 to 30 percent. Visible calcium carbonate is threads, films, lumps, or concretions which range from a few to as much as 25 percent by volume in some part of the B horizon.

The Cr horizon is weakly to strongly cemented calcareous sandstone. The sandstone is interbedded with shale, calcium carbonate or gypsum layers in some pedons.

COMPETING SERIES: There are no other known series in the same family. Similar series include Copita, Dilley, Faskin, Mavco, Triomas, and Verick series. Copita soils have sola 20 to 40 inches thick and lack argillic horizons. Dilley and Verick soils have sola less than 20 inches thick. Faskin and Triomas soils have mean annual soil temperature less than 72 degrees F. Mavco soils have fine-silty control sections with carbonatic mineralogy.

GEOGRAPHIC SETTING: Tonio soils occur on an nearly level to gently undulating landscape with slope gradients ranging from 0 to 5 percent. Surfaces are plane to convex. These soils formed in calcareous sandstone. The climate is semiarid; average annual precipitation ranges from about 17 to 26 inches. Thornthwaite annual P-E indices range from 20 to 31; mean annual temperature at the type location is 72 degrees F.

GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Copita, Mavco, and Verick series and Brystal, Caid, Pryor, Uvalde, and Zavco series. Brystal and Zavco soils are noncalcareous in the upper sola and have redder hues throughout. Caid and Uvalde soils have mollic epipedons. Copita and Brystal soils occur on similar surfaces. Mavco, Caid, Pryor, and Uvalde soils occur on broad outwash plains at slightly lower elevations. Pryor soils have more than 35 percent clay in the control section. Verick soils occur in more sloping areas at higher elevations. Zavco soils occur in more areas at lower elevations.

DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.

USE AND VEGETATION: Primarily rangeland. Small areas are culitivated to such crops as small grain, grain sorghum, introduced grasses and a few vegetables. Native grasses presently consist of red grama, threeawn, bristlegrass, Hall's panicum, hooded windmillgrass, pink pappusgrass, cottontop, and fall witchgrass. Woody plants include mesquite, black brush, white brush, guayacan, twisted acacia, lotebush, allthorn, goatbush, Texas persimmon, wolfberry, guajillo, leatherstem, and pricklypear. Forbes, such as rat ear and Russian thistle are common.

MLRA OFFICE RESPONSIBLE: Temple, Texas

DISTRIBUTION AND EXTENT: Western Rio Grande Plain; probably in Mexico. The series is of moderate extent. SERIES ESTABLISHED: Dimmit County, Texas; 1982.

REMARKS: These soils were formerly classified in the Calcisol great soil group. These soils have been included with Copita soils in past surveys.

National Cooperative Soil Survey U. S. A.

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