LOCATION BIGPRAIRIE AZEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Haplusterts
TYPICAL PEDON: Bigprairie clay - rangeland (Colors are for dry soil unless otherwise noted.) The surface is covered by about 3 percent gravel.
A--0 to 2 inches; brown (7.5YR 4/3) clay, dark brown (7.5YR 3/3) moist; moderate medium platy structure parting to moderate fine and medium granular; moderately hard, friable, very sticky and very plastic; many very fine and fine roots; many very fine and fine pores; 1 percent basalt gravel; noneffervescent; neutral (pH 7.2); abrupt smooth boundary. (1 to 6 inches thick)
Btss1--2 to 23 inches; dark reddish gray (5YR 4/2) clay, dark reddish brown (5YR 3/2) moist; strong medium and coarse angular blocky and strong fine and medium wedge structure; extremely hard, very firm, very sticky and very plastic; common very fine and fine and few medium roots; common very fine and fine pores; many prominent slickensides; common distinct clay films on faces of peds; 1 percent gravel; noneffervescent; neutral (pH 7.2); gradual wavy boundary.
Btss2--23 to 40 inches; dark reddish gray (5YR 4/2) clay, dark reddish brown (5YR 3/2) moist; strong fine and medium angular blocky and strong fine and medium wedge structure; extremely hard, very firm, very sticky and very plastic; common very fine and fine and few medium roots; few very fine and fine pores; common prominent slickensides; common distinct clay films on faces of peds; 1 percent gravel; noneffervescent; slightly alkaline (pH 7.8); clear wavy boundary. (Combined thickness of the Btss horizons is 15 to 50 inches.)
2Bt1--40 to 57 inches; brown (7.5YR 5/4) clay loam, brown (7.5YR 4/4) moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; hard, friable, very sticky and very plastic; few very fine and fine roots; few very fine and fine pores; common distinct clay films on faces of peds and few distinct clay films on rock fragments; few fine concretions and common medium and coarse masses of iron-manganese; 10 percent gravel; noneffervescent; slightly alkaline (pH 7.8); clear wavy boundary.
2Bt2--57 to 65 inches; brown (7.5YR 5/4) loam, dark brown (7.5YR 3/4) moist; weak coarse prismatic structure parting to weak fine and medium subangular blocky; hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; few very fine pores; few distinct clay films on faces of peds and on rock fragments; common medium masses of iron-manganese; 3 percent gravel and 1 percent cobbles; slightly effervescent; slightly alkaline (pH 7.8). (Combined thickness of the 2Bt horizons is 13 to 40 inches.)
TYPE LOCATION: Graham County, AZ; located about 1,713 feet south and 1,374 feet west of the northeast corner of Sec. 3, T.1 N., R.25 E.; Topographic quadrangle: Sawbuck Mountain, AZ; Latitude: 33 degrees, 27 minutes, 40.6 seconds N; Longitude: 109 degrees, 43 minutes, 24.5 seconds W; NAD 83.
RANGE IN CHARACTERISTICS:
Soil Moisture: Typic-ustic soil moisture regime. Intermittently moist in some part of the soil moisture control section during July-September and December-February. Driest during May and June.
Particle-size control section (weighted average)
Clay content: 35 to 60 percent
Rock fragments: 0 to 10 percent
Surface Fragments: 0 to 30 percent
Surface texture averages 30 percent or more clay when mixed to 7 inches
Vertic features: slickensides and/or wedge shaped peds within 20 inches of the soil surface and cracks that are 5mm or more wide that open and close periodically
Cracks:
Width: 0.2 to 1.5 inches
Depth: surface to 30 inches or more
A horizon
Hue: 7.5YR, 10YR
Value: 3 to 5 dry, 2 to 3 moist
Chroma: 1 to 3, dry or moist
Texture: clay loam, clay
Rock fragments: 0 to 25 percent
Effervescence: noneffervescent
Reaction: neutral or slightly alkaline (6.6 to 7.8)
Bt and Btss horizons
Hue: 5YR, 7.5YR
Value: 3 to 5 dry, 2 to 4 moist
Chroma: 2 to 4, dry or moist
Texture: clay, silty clay, clay loam
Clay content: 30 to 60 percent
Rock fragments: 0 to 15 percent
Effervescence: noneffervescent to slightly effervescent
Reaction: neutral or slightly alkaline (6.6 to 7.8)
2Bt or Btk horizons
Hue: 5YR, 7.5YR
Value: 3 to 6 dry, 2 to 5 moist
Chroma: 3 to 6, dry or moist
Texture: clay, clay loam, sandy clay loam, loam
Clay content: 20 to 60 percent
Rock fragments: 1 to 60 percent
Calcium carbonate equivalent: 0 to 15 percent
Effervescence: noneffervescent to strongly effervescent
Reaction: neutral to moderately alkaline (6.6 to 8.4)
Some pedons have a Bk horizon that is similar to the Btk horizon, but does not include clay texture.
COMPETING SERIES: These are the
Goessel(KS) and
Millboro(SD) series.
The Goessel soils have redoximorphic features within 40 inches of the surface and are moderately well drained. The Millboro soils have hues of 2.5Y or 5Y in the Bkss and C horizons.
GEOGRAPHIC SETTING: Bigprairie soils occur on linear to slightly concave positions of stream and fan terraces and formed in alluvium derived from volcanic and sedimentary rocks. Elevation ranges from 5,800 to 7,200 feet. Slope ranges from 0 to 5 percent. Mean annual air temperature ranges from 45 to 57 degrees F. and mean annual precipitation ranges from 18 to 24 inches. Precipitation falls mainly during July-September and December-February and driest during May and June. Frost-free period is 100 to 180 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brolliar, Dedal, and Sponiker series. The Brolliar soils occur on higher hillslopes and are moderately deep to basalt. The Dedal soils occur on higher hillslopes and are shallow or very shallow to basalt. The Sponiker soils occur on similar or slightly higher positions and do not have vertic properties within 40 inches (100 cm).
DRAINAGE AND PERMEABILITY: Well drained; runoff is medium; very slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing and wildlife habitat. The present vegetation is blue grama, sideoats grama, western wheatgrass, prairie junegrass, bottlebrush squirreltail and snakeweed.
DISTRIBUTION AND EXTENT: Central Arizona; LRR D; MLRA is 38; These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: San Carlos Indian Reservation, AZ; Parts of Gila and Graham Counties, (AZ675); 2009. The name is from the area in the San Carlos Reservation where this soil is described.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 0 to 40 inches (A, Btss1, and Btss2 horizons)
Slickensides- the zone from 2 to 40 inches (Btss1 and Btss2 horizons)
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006