LOCATION SWALESILVER OR

Established Series
Rev. TM/JBF
06/2011

SWALESILVER SERIES

The Swalesilver series consists of very deep, somewhat poorly drained soils that formed in alluvium and lacustrine deposits derived from volcanic rocks and volcanic ash. Swalesilver soils are on depressions on plateaus and lake terraces. Slopes are 0 to 2 percent. The mean annual precipitation is about 280 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Fine, smectitic, frigid Aquic Palexeralfs

TYPICAL PEDON: Swalesilver silt loam--rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 8 cm; very pale brown (10YR 7/3) silt loam, brown (10YR 4/3) moist; moderate medium platy structure; slightly hard, very friable, slightly sticky and slightly plastic; few coarse, and many fine and medium roots; many fine and medium irregular pores; neutral (pH 6.8); clear smooth boundary. (5 to 28 cm thick)

A2--8 to 15 cm; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; moderate medium platy structure; slightly hard, very friable, slightly sticky and slightly plastic; few coarse, and many fine and medium roots; many fine and medium irregularly shaped pores; few fine prominent yellowish red (5YR 4/6) masses of iron accumulation; neutral (pH 7.0); abrupt smooth boundary. (0 to 15 cm thick)

2Bt1--15 to 46 cm; light brownish gray (10YR 6/2) clay, grayish brown (10YR 5/2) moist; strong medium prismatic structure parting to strong coarse angular blocky; hard, firm, moderately sticky and very plastic; common medium roots; few fine tubular pores; many prominent clay films on faces of peds; slightly alkaline (pH 7.4); clear smooth boundary. (10 to 30 cm thick)

2Bt2--46 to 58 cm; light brownish gray (2.5Y 6/2) clay loam, grayish brown (2.5Y 5/2) moist; strong medium angular blocky structure parting to strong fine angular blocky; hard, firm, moderately sticky and moderately plastic; few medium roots; few fine tubular pores; many prominent clay films on faces of peds; slightly alkaline (pH 7.6); clear smooth boundary. (13 to 25 cm thick)

3Bk--58 to 86 cm; light gray (2.5Y 7/2) silt loam, grayish brown (2.5Y 5/2) moist; moderate fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few medium roots; many fine and medium irregularly shaped pores; slightly effervescent, secondary carbonates segregated as common filaments or threads; moderately alkaline (pH 8.2); clear smooth boundary. (0 to 80 cm thick)

3C1--86 to 124 cm; light gray (2.5Y 7/2) silt loam, grayish brown (2.5Y 5/2) moist; massive; hard, friable, slightly sticky and slightly plastic; few medium roots; many fine and medium irregularly shaped pores; slightly alkaline (pH 7.8); abrupt smooth boundary. (30 to 50 cm thick)

3C2--124 to 155 cm; pale yellow (5Y 7/3) silt loam, olive (5Y 5/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few medium roots; many very fine and fine irregularly shaped pores; slightly alkaline (pH 7.8).

TYPE LOCATION: Harney County, Oregon; at Foster Flat; about 1,000 feet north and 1,000 feet west of the southeast corner of section 11, T. 30 S., R. 29 E.; USGS Keg Springs Valley West 7.5 minute topographic quadrangle; latitude 43 degrees 58 minutes 32 seconds N and longitude 120 degrees 14 minutes 28 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in some part of the moisture control section from about mid-September through late July; xeric moisture regime that borders on aridic.
Mean annual soil temperature: 6 to 8 degrees C.
Temperature at 50 cm: Above 5 degrees C from about early June through late November.
Aquic conditions: Occurs seasonally from the soil surface to a maximum depth of about 25 cm.
Depth to base of argillic horizon: 50 to 66 cm.
Abrupt textural change: An abrupt horizon boundary is normally present between the A or A2 horizon and the 2Bt1 horizon accompanied by an absolute increase in clay content of 20 to 40 percent.

Particle-size control section - Clay content: Averages 40 to 60 percent.

A1 horizon
Value: 6 or 7 dry, 3 through 5 moist.
Chroma: 1 through 3, dry or moist.
Reaction: Slightly acid through slightly alkaline.
Clay content: 15 to 25 percent.
Redoximorphic features: Redox concentrations may occur as distinct and/or prominent masses of iron accumulation. Redox depletion of iron and/or clay is evident in many pedons as the low chroma matrix.

A2 horizon (when present)
Value: 7 or 8 dry, 4 through 6 moist.
Chroma: 1 or 2 dry, 1 through 3 moist.
Clay content: 5 to 10 percent.
Reaction: Neutral or slightly alkaline.
Redoximorphic features: Redox concentrations occur as distinct and/or prominent masses of iron accumulation. Redox depletion of iron and/or clay is evident as the low chroma matrix.

2Bt horizons
Hue: 10YR or 2.5Y.
Value: 4 through 6 dry, 3 through 5 moist.
Chroma: 2 or 3 dry or moist.
Texture: Clay, silty clay, or clay loam.
Clay content: 35 to 65 percent.
Reaction: Slightly alkaline or moderately alkaline.

3Bk or 3BC horizon
Hue: 10YR or 2.5Y.
Value: 5 through 7 dry, 4 or 5 moist.
Chroma: 2 through 4, dry or moist.
Texture: Silt loam, silty clay loam, loam, or clay loam.
Reaction: Slightly alkaline through strongly alkaline.
Salinity (EC): 2 to 4 mmhos/cm.
Identifiable secondary carbonates: Occurs in some pedons as few or common filaments or threads.
Calcium carbonate equivalent: 0 to 2 percent.

3C horizon
Hue: 10YR to 5Y.
Value: 6 through 8 dry, 3 through 5 moist.
Chroma: 2 through 4, dry or moist.
Texture: Stratified silt loam to clay loam.
Structure: Massive or has rock structure. Rock structure consists of fractured lacustrine sediments which are strong angular blocky.
Effervescence: Noneffervescent to strongly effervescent.
Reaction: Slightly alkaline through strongly alkaline.
Salinity (EC): 2 to 4 mmhos/cm.

COMPETING SERIES: At present, there are no other series in this family.

GEOGRAPHIC SETTING: Swalesilver soils are on depressions on plateaus and lake terraces. These soils formed in alluvium and lacustrine deposits derived from volcanic rocks and volcanic ash. Slopes are 0 to 2 percent. Elevation ranges from 1,280 to 1,910 meters. The climate is characterized by cold, moist winters and warm, dry summers. The mean annual temperature is 4 to 7 degrees C, mean annual precipitation is 200 to 300 mm, and the frost-free period is 50 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Floke, Ninemile, Ratto, Spangenburg, and Swaler soils.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Somewhat poorly drained; very high surface runoff; low saturated hydraulic conductivity. Episaturation is present with perched free water between the soil surface and 30 cm (very shallow free water occurrence class) from November through May. Cumulative annual duration classes are Common or Persistent. These soils are susceptible to frequent ponding for long duration at some time from November through May with water depths of 3 to 30 cm.

USE AND VEGETATION: Swalesilver soils are used for livestock grazing and wildlife habitat. The vegetation is mainly silver sagebrush, Nevada bluegrass, creeping wildrye, and mat muhly.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are moderately extensive. MLRA 23.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Lake County (Southern Part), Oregon, 1991.

REMARKS: A revision in 2001 moved the type location from Lake County to Harney County, Oregon to better represent the series concept. The prior type location had high glass content in the A horizons and classified as a vitrandic intergrade. Future study is needed on this soil to document whether enough active ferrous iron occurs in the A horizons, when aquic conditions are present, to give positive reactions to alpha,alpha-dipyridyl.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 15 cm (A1 and A2 horizons).
Aquic conditions - The conditions of episaturation, reduction, and redoximorphic features between the soil surface and 15 cm at certain times during normal years (A1 and A2 horizons).
Argillic horizon - The zone from 15 to 58 cm (2Btl and 2Bt2 horizons).
Abrupt textural change - The abrupt clay increase of more than 20 percent at 15 cm (between the A2 and 2Bt1 horizons).
Identifiable secondary carbonates - The zone from 58 to 86 cm (3Bk horizon).
Particle-size control section - The zone from 15 to 58 cm (2Btl and 2Bt2 horizons).

ADDITIONAL DATA: Previous authors and editors include: TDT-MPK-JVC.

National Cooperative Soil Survey
U.S.A.