LOCATION DOURO TX+NM

Established Series
Rev. RM-TCB
09/2014

DOURO SERIES

The Douro series consists of well drained soils that are moderately deep to a petrocalcic horizon. The permeability is moderate above the very slowly permeable petrocalcic horizon. Douro soils formed in calcareous loamy eolian sediments of the Blackwater Draw Formation of Pleistocene age. These soils are on nearly level to very gently sloping plains. The mean annual precipitation is 406 mm (16 in) and the mean annual temperature is 16 degrees C (61 degrees F). Slopes range from 0 to 3 percent.

TAXONOMIC CLASS: Fine-loamy, siliceous, active, thermic Ustalfic Petrocalcids

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

A--0 to 10 cm (0 to 4 in); dark reddish brown (5YR 3/4) fine sandy loam, dark reddish brown (5YR 3/3) moist; weak fine and medium subangular blocky structure parting to granular; slightly hard, very friable; common very fine and fine roots; common very fine, fine and medium continuous tubular pores; common fine and medium cylindrical worm casts; slightly alkaline; clear smooth boundary. (Thickness is 10 to 38 cm [4 to 15 in].)

Bt1--10 to 28 cm (4 to 11 in); reddish brown (2.5YR 4/4) sandy clay loam, dark reddish brown (2.5YR 3/4) moist; moderate coarse prismatic structure parting to weak medium subangular blocky; very hard, friable; common very fine and fine roots between peds; common very fine and fine continuous tubular and common medium continuous tubular pores; few patchy faint dark red (2.5YR 3/6) clay films on faces of prisms and peds; common fine and medium cylindrical worm casts; neutral; gradual wavy boundary.

Bt2-- 28 to 41 cm (11 to 16 in); red (2.5YR 4/6) sandy clay loam, dark red (2.5YR 3/6) moist; moderate coarse prismatic structure parting to weak medium subangular blocky; very hard, friable; common very fine, fine and medium continuous tubular pores; few patchy faint dark red (2.5YR 3/6) clay films on faces of peds; few fine and medium cylindrical worm casts; neutral; gradual wavy boundary.

Bt3-- 41 to 56 cm (16 to 22 in); red (2.5YR 4/6) sandy clay loam, dark reddish brown (2.5YR 3/4) moist; strong coarse prismatic structure parting to weak medium subangular blocky; extremely hard, firm; common very fine and fine roots between peds; common very fine and fine continuous tubular pores; common patchy faint dark red (2.5YR 3/6) clay films on faces of peds; few fine and medium cylindrical worm casts; slightly alkaline; gradual wavy boundary.

Bt4-- 56 to 76 cm (22 to 30 in); red (2.5YR 4/6) sandy clay loam, dark red (2.5YR 3/6) moist; strong coarse prismatic structure parting to moderate medium and coarse subangular blocky; extremely hard, firm; common very fine roots between peds; common very fine and fine pores filled with coarse material; many patchy faint dark red (2.5YR 3/6) clay films on faces of peds; few fine and medium cylindrical worm casts; slightly alkaline; abrupt wavy boundary. (Combined thickness of the Bt horizons is 41 to 91 cm [16 to 36 in].)

Bkkm -- 76 to 102 cm (30 to 40 in); white (10YR 8/1) indurated caliche in plates 5cm (2 in) thick, white (10YR 8/1) moist; many very fine and fine roots in mat at top of horizon; few vertical cracks; soil material between plates and in cracks; moderately alkaline. (Thickness is 18 to 152 cm [7 to 60 in].)

BCkk -- 102 to 203 cm (40 to 80 in); white (10YR 8/1) loose to weakly cemented calcium carbonate; massive; 50 percent strongly cemented coarse fragments of calcium carbonate; moderately alkaline.

TYPE LOCATION: Andrews County, Texas. From Andrews, Texas on Texas Highway 176, 9 miles east to intersection of Farm Road 1788, 11.8 miles south on Farm Road 1788 to intersection of paved county road, 2.9 miles west on paved county road, 0.2 miles north and 0.15 miles west on unpaved oil field road, 100 ft north in rangeland. Latitude: 32 degrees, 09 minutes, 26 seconds N; Longitude: 102 degrees, 23 minutes, 38 seconds W.

RANGE IN CHARACTERISTICS:
Soil moisture: An aridic moisture regime bordering on ustic. The soil moisture control section is dry in some or all parts for more than 205 but less than 270 days, cumulative, in normal years. November through April normally is the driest months. These soils are intermittently moist in May through October.
Mean annual soil temperature: 15 to 18 degrees C (59 to 64 degrees F).
Depth to argillic horizon: 10 to 40 cm (3 to 15 in).
Depth to petrocalcic horizon: 50 to 100 cm (20 to 40 in).
Particle-size control section: 18 to 35 percent silicate clay.
Solum thickness: more than 203 cm (80 in).

A horizon:
Hue: 5YR or 7.5YR
Value: 4 to 6, 3 to 5 moist
Chroma: 3 or 4
Texture: fine sand, loamy fine sand, fine sandy loam
Effervescence: none
Reaction: neutral or slightly alkaline

Bt horizons:
Hue: 2.5YR or 5YR
Value: 4 to 6, 3 to 5 moist
Chroma: 4 to 6
Texture: sandy clay loam, clay loam
Visible calcium carbonate: less than 3 percent as masses or nodules
Effervescence: none to slight
Reaction: neutral to moderately alkaline

Bkkm horizon:
Hue: 7.5YR or 10YR
Value: 8 to 9.5, 7 or 9 moist
Chroma: 1 or 2
Effervescence: violent
The horizon has a laminar upper surface ranging in thickness from 1 to 8 cm (0.5 to 3 in). The horizon is indurated to strongly cemented, and plates vary from 5 to 20 cm (2 to 8 in) thick.

BCkk horizon:
Hue: 2.5YR or 5YR
Value: 6 to 8, 5 to 7 moist
Chroma: 1 to 3
Texture: fine sandy loam, loam, sandy clay loam, clay loam
Visible calcium carbonate: 60 to 90 percent by volume in the form of masses, nodules, and finely disseminated carbonates. Coarse fragments range from 25 to 60 percent by volume.
Calcium carbonate by weight: 50 to 80 percent
Effervescence: violent
Reaction: moderately alkaline or strongly alkaline

COMPETING SERIES: There are no competing series in the same family. Similar soils include the Kenhill, Kimbrough, Pojo, Potter, and Spraberry series and the Arvana, Friona, and Kimberson series.
Arvana soils: are moist in the moisture control section for longer periods.
Friona soils: have higher organic matter content in the A horizon and are moist in the moisture control section for longer periods.
Kenhill soils: have higher organic matter content in the A horizon and do not have Hue of 2.5YR or redder.
Kimbrough soils: have a petrocalcic horizon less than 50 cm (20 in) deep and do not have an argillic horizon.
Kimberson soils: have a petrocalcic horizon less than 50 cm (20 in) deep and do not have an argillic horizon and are moist in the moisture control section for longer periods.
Pojo soils: have less than 18 percent silicate clay in the particle-size control section, have a superactive cation exchange activity class are dry in the soil moisture control section for slightly longer periods.
Potter soils: have carbonatic mineralogy and do not have petrocalcic horizons.
Sprayberry soils: have a petrocalcic horizon less than 50 cm (20 in) deep.

GEOGRAPHIC SETTING:
Parent material: loamy eolian deposits from the Blackwater Draw Formation of Pleistocene age.
Landform: nearly level to very gently sloping plains.
Slopes: 0 to 3 percent.
Mean annual air temperature: 14 to 17 degrees C (57 to 63 degrees F).
Mean annual precipitation: 356 to 432 mm (14 to 17 in).
Frost-free period: 180 to 230 days.
Elevation: 762 to 1,402 m (2,500 to 4,600 ft).
Thornthwaite annual P-E Index Values: 20 to 26.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blakeney, Conger, Faskin, Jalmar, Ratliff, and Triomas.
Faskin, and Triomas soils: are on similar landscape positions, have argillic horizons and do not have a petrocalcic horizon.
Blakeney soils: are on lower landscape positions and have a petrocalcic less than 50 cm (20 in) and do not have an argillic horizon.
Conger soils: are on similar landscape positions and have a petrocalcic less than 50 cm (20 in) and do not have an argillic horizon.
Ratliff soils: are on similar landscape positions and do not have a petrocalcic horizon.
Jalmar soils: are on similar landscape positions and have a sandy surface more than 50 cm (20 in) thick and a loamy particle size control section.

DRAINAGE AND PERMEABILITY: Well drained. Runoff is negligible. Permeability is moderate above and below the very slowly permeable petrocalcic horizon.

USE AND VEGETATION: Used mostly for rangeland but some areas are cultivated with the major crops being cotton and grain sorghum. Vegetation consists of black grama, sideoats grama, little bluestem, hooded windmillgrass, blue grama, threeawn, plains bristlegrass, Arizona cottontop, catclaw acacia, yucca, and western honey mesquite. This soil has been correlated to the Sandy (R077DY046TX) range site in MLRA-77D.

DISTRIBUTION AND EXTENT: Southern High Plains, Southern Part (MLRA 77D in LRR H); of western Texas and eastern New Mexico. The series is moderate in extent.

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

SERIES ESTABLISHED: Andrews County, Texas; 1970.

REMARKS: Classification was changed in 1991 from Petrocalcic Ustalfic Paleargids to Petrocalcic Ustollic Paleargids based on Lincoln laboratory data (S85TX-003-004) from the type location in Andrews County, Texas. Family placement change from mixed to siliceous mineralogy is based on laboratory data from the same location.

Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon: 0 to 23 cm (0 to 9 in) (A horizon)
Argillic horizon: 23 to 76 cm (9 to 30 in) (Bt horizons)
Petrocalcic horizon: 76 to 102 cm (30 to 40 in) (Bkkm horizon)
Calcic horizon: 102 to 203 cm (40 to 80 in) (BCkk horizon)
Ustollic feature: Aridic moisture regime that borders on the ustic regime and a weighted average of sand/clay of 4.9 with 0.54 weighted average organic carbon in the upper 41 cm (16 in).

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

National Cooperative Soil Survey
U.S.A.