LOCATION PAWTOOT                 ID

Established Series
Rev. MEJ/ALH/RWL
07/2012

PAWTOOT SERIES

The Pawtoot series consists of very deep, well drained soils with very slow permeability that formed in slope alluvium and residuum from lacustrine deposits. Pawtoot soils are on foothills and have slopes of 4 to 25 percent. The average annual precipitation is about 14 inches and the average annual temperature is about 51 degrees F.

TAXONOMIC CLASS: Fine, smectitic, mesic Vertic Natrixerolls

TYPICAL PEDON: Pawtoot silt loam -- on a 8 percent convex west-facing slope at 2,920 feet elevation in rangeland. When described on September 5, 1995, the soil was dry throughout. (Colors are for dry soil unless otherwise noted.)

A--0 to 2 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium platy structure; soft, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; many very fine and fine tubular pores; neutral (pH 7.2); clear smooth boundary. (1 to 3 inches thick)

BA--2 to 6 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium platy structure parting to weak fine subangular blocky; soft, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; common very fine and fine tubular pores; neutral (pH 7.0); clear smooth boundary. (2 to 5 inches thick)

E--6 to 7 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; common very fine and fine tubular pores; neutral (pH 6.8); abrupt smooth boundary. (1 to 2 inches thick)

Btn1--7 to 13 inches; dark grayish brown (10YR 4/2) clay, very dark brown (10YR 2/2) moist; strong medium and coarse prismatic structure; extremely hard, firm, very sticky and very plastic; few very fine and fine roots; few very fine and fine tubular pores; many distinct clay films on faces of peds and in pores; tops of prisms are coated with uncoated silt grains; cracks 1mm to 4cm wide; ESP 5, SAR 5; slightly alkaline (pH 7.8); clear wavy boundary. (3 to 12 inches thick)

Btn2--13 to 32 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong medium subangular blocky; very hard, friable, very sticky and very plastic; few very fine and fine roots; few very fine and fine tubular pores; common distinct clay films on faces of peds and in pores; ESP 9, SAR 8; slightly saline; moderately alkaline (pH 8.0); clear wavy boundary. (11 to 22 inches thick)

Btkn--32 to 41 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; very hard, friable, sticky and plastic; few very fine and fine roots; common very fine and fine tubular pores; few distinct clay films on faces of peds and in pores; slightly effervescent; about 5 percent calcium carbonate segregated as coats and splotches on faces of peds; ESP 15, SAR 11; slightly saline, moderately alkaline (pH 8.2); gradual wavy boundary. (5 to 13 inches thick)

Bkny1--41 to 56 inches; very pale brown (10YR 7/3) silt loam, brown (10YR 5/3) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine tubular pores; strongly effervescent; about 10 percent disseminated calcium carbonate; ESP 22, SAR 14; gypsum segregated as common coast on peds; moderately saline; moderately alkaline (pH 8.0); gradual wavy boundary.

Bkny2--56 to 67 inches; very pale brown (10YR 8/3) silt loam, brown (10YR 5/3) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine tubular pores; strongly effervescent; about 10 percent disseminated calcium carbonate; ESP 30, SAR 15; gypsum segregated as few coats on peds; slightly saline; moderately alkaline (pH 8.0); gradual wavy boundary. (combined thickness 12 to 30 inches thick)

Crky--67 inches; very pale brown (10YR 8/3), brown (10YR 5/3) moist, stratified silty lacustrine deposits with very thin calcium carbonate and gypsum coats on horizonal and vertical sediment planes.

TYPE LOCATION: Ada County, Idaho; about 4.5 miles east and 2 miles north of Eagle; about 1,700 feet south and 1,800 feet east of the northwest corner of section 6, T. 4 N., R. 1 E.; USGS Eagle Quadrangle; (Latitude - 43 degrees, 44 minutes, 09 seconds N. and Longitude - 116 degrees, 15 minutes, 55 seconds W.)

RANGE IN CHARACTERISTICS:
Average annual soil temperature - 52 to 53 degrees F.
Thickness of mollic epipedon - 8 to 20 inches
Depth to secondary calcium carbonates - 30 to 40 inches
Depth to paralithic contact - 60 inches or more
Moisture control section - moist less than 90 consecutive days when the soil temperature is greater than 47 degrees F.

A and BA horizons
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Clay content - 15 to 20 percent
Rock fragments - 0 to 5 percent gravel
Reaction - neutral or slightly alkaline

E horizon
Value - 6 or 7 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Texture - SIL or L
Clay content - 15 to 20 percent
Rock fragments - 0 to 5 percent gravel

Btn horizon
Value - 4 through 6 dry, 2 through 4 moist
Chroma - 2 or 3 dry or moist
Texture - SIC, SICL or C
Clay content - 35 to 55 percent
Rock fragments - 0 to 5 percent gravel
Reaction - slightly alkaline or moderately alkaline
ESP - 5 to 10 percent
SAR - 5 to 10 percent

Btkn horizon
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 2 or 3 dry or moist
Texture - SICL or CL
Clay content - 27 to 35 percent
Rock fragments - 0 to 5 percent gravel
Calcium carbonate equivalent - 1 to 10 percent
Calcium sulfate equivalent - 5 to 10 percent
ESP - 15 to 17 percent
SAR - 10 to 15 percent

Bkny horizon
Value - 6 through 8 dry, 4 through 6 moist
Chroma - 2 or 3 dry or moist
Clay content - 20 to 27 percent
Rock fragments - 0 to 5 percent gravel
Calcium carbonate equivalent - 3 to 15 percent
Calcium sulfate equivalent - 1 to 5 percent
Salinity - slightly or moderately saline
ESP - 15 to 30 percent
SAR - 12 to 15 percent

COMPETING SERIES: These are the Shadoval (T) and Susanville series. Shadoval soils are moderately deep to a paralithic contact. Susanville soils are dry for more than 160 consecutive days following the summer solstice and lack a gypsic horizon.

GEOGRAPHIC SETTING: Pawtoot soils are on hill backslopes and footslopes and have slopes of 4 to 25 percent. The soils formed in slope alluvium and residuum from lacustrine deposits. The elevation ranges from 2,750 to 3,650 feet. The average annual precipitation is 12 to 16 inches and the average annual temperature is 50 to 51 degrees F. The frost-free period is 140 to 150 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aldape, Polecat and competing Shadoval soils. Aldape soils do not have E horizons and are 40 to 60 inches to a duripan. Polecat soils are 40 to 60 inches deep to a paralithic contact and do not have an abrupt textural change from the soil surface to the argillic horizon. These soils all occur on the same landform as the Pawtoot series.

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

USE AND VEGETATION: Pawtoot soils are used mainly for rangeland. Natural vegetation is basin big sagebrush and bluebunch wheatgrass.

DISTRIBUTION AND EXTENT: Ada County, Idaho. MLRA 10. The soils are of limited extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Ada County, Idaho, 2012.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to 13 inches (A, BA, E and Btn1 horizons).
Note - when the surface horizons (A and BA) meet all requirements for a mollic epipedon except thickness, the mollisol criteria is met based on an underlying thin albic (E) horizon separating the upper part of the argillic horizon (Btn1) which meets color, organic carbon, base saturation, and structure requiremnts of a mollic epipedon.
Albic horizon - zone from 6 to 7 inches (E horizon)
Argillic horizon - zone from 7 to 41 inches (Btn1, Btn2 and Btkn horizons)
Abrupt texture change - at 7 inches; estimated 20 percent absolute clay increase within 1 inch (upper boundary of Btn1 horizon).
Gypsic horizon - zone from 41 to 67 inches (Bkny1 and Bkny2 horizons)
Particle-size control section - the zone from 7 to 27 inches (Btn1 and Btn2 horizons)
Paralithic contact - at 67 inches (Crky horizon)
Linear extensibility - 6cm or more in the upper 40 inches (assumed)
ESP and SAR values in this pedon have been estimated from lab data for the associated Shadoval series.
Classification revised 4/99 from Aridic Palexerolls to Vertic Natrixerolls based on lab data from associated Shadoval series.
Soil moisture regime - aridic bordering on xeric
These soils are drier than other Xerolls in the region under similar precipitation due to early runoff and extended period of high evapotranspiration.

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National Cooperative Soil Survey
U.S.A.