LOCATION STU ID

Established Series
Rev. ALH/RWL
07/2012

STU SERIES

The Stu series consists of shallow, well drained soils with moderate permeability that formed in colluvium and residuum from lacustrine deposits. Slopes range from 50 to 90 percent in foothills. The average annual precipitation is about 13 inches and the average annual temperature is about 53 degrees F.

TAXONOMIC CLASS: Loamy, mixed, superactive, calcareous, mesic, shallow Xeric Torriorthents

TYPICAL PEDON: Stu very fine sandy loam -- on a convex southwest-facing slope of 85 percent, in rangeland at 3,050 feet elevation. When described on June 27, 1995, the soil was dry throughout. (Colors are for air-dry soil unless otherwise stated.)

A1--0 to 3 inches; light yellowish brown (2.5Y 6/3) very fine sandy loam, olive brown (2.5Y 4/3) moist; moderate medium platy structure parting to weak fine and medium subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine, few medium roots; few very fine and fine irregular pores; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary.

A2--3 to 7 inches; light yellowish brown (2.5Y 6/3) very fine sandy loam, olive brown (2.5Y 4/3) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; few very fine and fine tubular and irregular pores; 5 percent pararock fragments; strongly effervescent; strongly alkaline (pH 8.5); clear smooth boundary. (combined A - 3 to 8 inches thick)

C--7 to 12 inches; light yellowish brown (2.5Y 6/4) extremely paragravelly very fine sandy loam, olive brown (2.5Y 4/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots (matted); 80 percent pararock fragments; slightly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (5 to 12 inches thick)

Cr--12 to 22 inches; slightly fractured consolidated fine sand lacustrine deposit with seams of iron concentration.

TYPE LOCATION: Ada County, Idaho; in Boise; 1,650 feet south and 2,200 feet west of the northeast corner of section 27, T.4 N., R.2 E.; USGS Boise North Quadrangle; (Latitude - 43 degrees, 39 minutes, 29 seconds N. and Longitude - 116 degrees, 12 minutes, 03 seconds W.)

RANGE IN CHARACTERISTICS:
Depth to paralithic contact - 10 to 20 inches
Particle-size control section - 10 to 18 percent clay
Calcium carbonate equivalent - 1 to 15 percent
Salinity - slightly or moderately saline
Reaction - slightly alkaline through strongly alkaline
Moisture control section - moist less than 90 consecutive days when the soil temperature is greater than 47 degrees F.
Average annual soil temperature - 54 to 55 degrees F.

A horizon
Hue - 2.5Y or 10YR
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 or 4 dry or moist
Rock fragment content (hard) - 0 to 5 percent gravel

C horizon
Hue - 2.5Y or 10YR
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - VFSL or L
Clay content - 10 to 18 percent
Pararock fragment content - 15 to 90 percent

COMPETING SERIES: These are the Coppereid, Foxcan, Grina, Holborn, Hundraw, Jacratz (T), Puett, Tert and Whilphang series. Coppereid soils are 5 to 10 inches deep and have 15 to 35 percent hard gravel. Foxcan soils are 4 to 10 inches deep. Grina soils have 20 to 35 percent clay in the particle-size control section. Holborn soils are 6 to 10 inches deep and have 18 to 30 percent clay in the particle-size control section. Hundraw soils are 4 to 10 inches deep and have a Bk horizon. Jacratz soils are 4 to 10 inches deep and have 25 to 35 percent clay in the particle-size control section. Puett soils have 5 to 10 percent clay in the particle-size control section and soil temperatures of 47 to 52 degrees F. Tert soils are 4 to 7 inches deep and have 18 to 27 percent clay in the particle-size control section. Whilphang soils have 15 to 35 percent rock fragments in the particle-size control section and are moist in some part of the soil moisture control section for 10 to 20 days between July and October.

GEOGRAPHIC SETTING: Stu soils are very steep on south-facing hill backslopes at elevations of 2,700 to 3,400 feet. Slopes range from 50 to 90 percent. These soils formed in residuum and colluvium from lacustrine deposits. The climate is cool and moist in the winter and warm and dry in the summer. Average annual precipitation is 12 to 14 inches. Average annual temperatureis 52 to 53 degrees F. Frost-free period is 150 to 155 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Polecat and Quailridge soils. Polecat and Quailridge soils have more than 18 percent clay in the particle-size control section and mollic epipedons. Polecat soils are on less steep landscape positions. Quailridge soils are on similar landscape positions.

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

USE AND VEGETATION: Stu soils are used mainly for rangeland and wildlife habitat. The dominant natural vegetation is basin big sagebrush, bluebunch wheatgrass and Thurber needlegrass.

DISTRIBUTION AND EXTENT: Southwestern Idaho. MLRA 10. Stu soils are not extensive.

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

SERIES ESTABLISHED: Ada County, Idaho, 2012.

REMARKS: Diagnostic horizons and features recognized in this pedon:
Ochric epipedon - zone 0 to 7 inches (A1 and A2 horizons)
Paralithic contact - at 12 inches (Cr horizon)
Particle-size control section - zone 0 to 12 inches
Soil moisture regime - aridic bordering on xeric

National Cooperative Soil Survey
U.S.A.