LOCATION DUFFAU                  TX+OK

Established Series
Rev. GLL-CLN-SCP-CMR
09/2020

DUFFAU SERIES

The Duffau series consists of very deep, well drained, moderately permeable soils that formed in sandy and loamy residuum weathered from sandstone and siltstone. These nearly level to moderately sloping soils occur on footslopes and backslopes of ridges on hills. Slope are 0 to 8 percent. Mean annual precipitation is about 864 mm (34 in) and the mean annual temperature is about 18.3 degrees C (65 degrees F).

TAXONOMIC CLASS: Fine-loamy, siliceous, active, thermic Udic Haplustalfs

TYPICAL PEDON: Duffau fine sandy loam, on an east-facing, linear, 4 percent slope in wooded pasture at an elevation of 463 m (1,519 ft). (Colors are for dry soil unless otherwise noted.)

A--0 to 10 cm (0 to 4 in); dark grayish brown (10YR 4/2) fine sandy loam, very dark grayish brown (10YR 3/2) moist; weak very fine subangular blocky and granular structure; slightly hard, friable; many fine roots; slightly alkaline; clear smooth boundary. (Thickness is 5 to 20 cm [2 to 8 in])

E--10 to 25 cm (4 to 10 in); pale brown (10YR 6/3) fine sandy loam, brown (10YR 4/3) moist; weak fine granular structure; slightly hard, friable; many fine roots; neutral; clear smooth boundary. (Thickness is 10 to 30 cm [4 to 12 in])

Bt1--25 to 102 cm (10 to 40 in); yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist; moderate fine subangular blocky structure; hard, firm, common fine roots; common distinct clay films on all faces of peds and bridging sand grains; slightly acid; gradual wavy boundary. (Thickness is 51 to 89 cm [20 to 35 in])

Bt2--102 to 137 cm (40 to 54 in); yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist; weak coarse subangular blocky structure; hard, firm; few fine roots; common distinct clay films on all faces of peds and bridging sand grains; neutral; gradual wavy boundary. (Thickness is 20 to 61 cm [8 to 24 in])

Bt3--137 to 178 cm (54 to 70 in); yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist, with a few fine faint mottles of strong brown (7.5YR 5/6); weak coarse subangular blocky structure; hard, friable; few fine roots; few faint clay films on all faces of peds. neutral; gradual wavy boundary. (Thickness is 15 to 61 cm [6 to 24 in])

BC--178 to 203 cm (70 to 80 in); reddish yellow (7.5YR 6/6) sandy clay loam, strong brown (7.5YR 5/6) moist; few fine faint yellowish red mottles; weak coarse subangular blocky, hard, friable, few fine roots; neutral.

TYPE LOCATION: Erath County, Texas; from the intersection of Farm Roads 219 and 8 in Lingleville, Texas; 4 miles northeast on Farm Road 219; then 0.8 mile north on county road 406 and 300 feet east of the road in a wooded pasture.

USGS topographic quadrangle: Huckabay, Texas
Latitude: 32 degrees, 17 minutes, 27.1 seconds N
Longitude: 98 degrees, 20 minutes, 59.4 seconds W

Decimal Degrees:
Latitude: 32.2908639 degrees
Longitude: -98.3498444 degrees
Datum: WGS84

RANGE IN CHARACTERISTICS:
Soil Moisture: An ustic soil moisture regime. The soil moisture control section is dry in some or all parts for more than 90, but less than 120 days in normal years.
Mean annual soil temperature: 19 to 21 degrees C (66 to 70 degrees F)
Depth of solum: 150 to more than 200 cm (60 to more than 80 in)
Depth to argillic horizon: 15 to 50 cm (6 to 20 in)

Particle-size control section (weighted average):
Clay content: 20 to 35 percent

A horizon:
Hue: 7.5YR to 10YR
Value: 4 to 6
Chroma: 2 to 4
Texture: fine sandy loam, very fine sandy loam, or loamy fine sand
Rock fragments: 0 to 3 percent by volume; quartz gravel
Soil reaction (pH): strongly acid to slightly alkaline (5.1 to 7.8)

E horizon:
Hue: 7.5YR to 10YR
Value: 5 to 7
Chroma: 2 to 4
Texture: fine sandy loam, very fine sandy loam, or loamy fine sand
Rock fragments: 0 to 3 percent by volume; quartz gravel
Soil reaction (pH): strongly acid to slightly alkaline (5.1 to 7.8)

Bt horizon:
Hue: 2.5YR to 7.5YR
Value: 4 to 6
Chroma: 3 to 8
Texture: sandy clay loam, loam, or clay loam
Rock fragments: 0 to 3 percent by volume; quartz gravel
Soil reaction (pH): moderately acid to neutral (5.6 to 7.3)

Btk horizon (where present):
Hue: 2.5YR to 7.5YR
Value: 4 to 6
Chroma: 3 to 8
Texture: sandy clay loam, loam, or clay loam
Rock fragments: 0 to 3 percent by volume; quartz gravel
Identifiable secondary carbonate: 1 to 3 percent; fine and very fine; carbonate masses; in matrix
Effervescence: none to slight
Soil reaction (pH): neutral to slightly alkaline (6.6 to 7.8)

BC or C horizon (where present):
Hue: 5YR to 10YR
Value: 4 to 8
Chroma: 1 or 6
Texture: fine sandy loam, very fine sandy loam, loamy fine sand, loam, sandy clay loam or clay loam
Rock fragments: 0 to 3 percent; quartz gravel
Identifiable secondary carbonate: 0 to 3 percent; fine and very fine; carbonate masses; in matrix
Effervescence: none to slight
Reaction: slightly acid to slightly alkaline (6.1 to 7.8)

COMPETING SERIES:
These are the Gholson, Lavender, May, and Personville series in the same family. Similar soils are the Bastsil, Bastrop, Flynn, and Gasil series.
Bastsil soils: have skeletans in the lower part and are underlain by sandy or gravelly alluvium
Bastrop soils: have less than 90 percent resistance minerals in the sand and silt fraction (mixed mineralogy) and are underlain by sandy or gravelly alluvium
Flynn soils: have weathered glauconite fragments in the lower part
Gasil soils: have base saturation of less than 65 percent in the argillic horizon
Fairy, Gholson, Hico, and May soils: have secondary carbonates within a depth of 150 cm (60 in)
Lavender and Personville soils: have a lithic contact within a depth of 150 cm (60 in)

GEOGRAPHIC SETTING:
Parent material: sandy and loamy residuum weathered from sandstone and siltstone of Lower Cretaceous age
Landscape: Hills
Landform: Ridges
Slope: 0 to 8 percent
Mean annual precipitation: 787 to 965 mm (31 to 38 in)
Thornthwaite P-E Index: 49 to 65
Mean annual air temperature: 16.7 to 18.9 degrees C (62 to 66 degrees F)
Frost-free period: 197 to 263 days
Elevation: 198.1 to 463 m (650 to 1519 ft)

GEOGRAPHICALLY ASSOCIATED SOILS:
These are the Keeter, May, Nimrod, Selden, Weatherford and Windthorst series.
Keeter and Weatherford soils: have a solum thickness of less than 150 cm and occur on slightly higher positions
May soils: do not have a hue redder than 7.5YR in the lower part of the argillic horizon and are in lower positions
Nimrod soils: have a sandy epipedon greater than 50 cm (20 in) in thickness and occur on higher positions
Selden soils: have redoximorphic features with chroma 2 or less within 75 cm (30 in) and occur on lower positions
Windthorst soils: have a fine textured control section and occur on similar positions

DRAINAGE AND PERMEABILITY:
Drainage class: well
Permeability class: moderate
Runoff: negligible on slopes less than 1 percent, low on 1 to 5 percent slopes, and medium on 5 to 8 percent slopes

USE AND VEGETATION:
The major uses are livestock grazing and hay production, but the soil was extensively cultivated in the past. Some areas are cultivated, with peanuts, sorghums, and small grains being the main crops. The native plant community is post oak and blackjack oak, with an understory of little bluestem, indiangrass, greenbrier, and annual grasses.

DISTRIBUTION AND EXTENT:
General location: north-central Texas and south-central Oklahoma
Land Resource Region: J-Southwestern Prairies Cotton and Forage Region
Major Land Resource Area: 84B-West Cross Timbers
Extent: large

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Temple, Texas

SERIES ESTABLISHED: Parker County, Texas, 1973. The name "Duffau" comes from the Duffau community in southeastern Erath County, Texas.

REMARKS:

Diagnostic horizons and features recognized in this pedon:
Particle-size control section: 25 to 75 cm (10 to 30 in) (Bt1 horizon)
Ochric epipedon: 0 to 25 cm (0 to 10 in) (A and E horizons)
Argillic horizon: 25 to 178 cm (10 to 70 in) (Bt horizons)

Based on numerous field observations and update projects between 2017 and 2020 it was determined that the majority of observations within the Duffau series extent have a relative clay decrease of more than 20 percent from the maximum clay content of the argillic horizon within a depth of 150 cm. This is a characteristic related to current and past climate regimes that could be utilized to compete with series in wetter climates that previously classified to the same family.

ADDITIONAL DATA:
KSSL Data: 81TX143001, 81TX143002, S2017TX497058, and S2018TX221002

TAXONOMIC VERSION: Keys to Soil Taxonomy, Twelfth Edition, 2014

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National Cooperative Soil Survey
U.S.A.