LOCATION BENKA                   AK

Established Series
Rev. DLM/MHC/JPM
02/2022

BENKA SERIES

Depth class: very deep
Drainage class: well drained
Parent material: volcanic ash and loess deposits overlying stratified sandy glacial outwash material
Landform: glacial outwash plains, moraines, and hills
Slope: range 0 to 60 percent
Mean annual precipitation: about 25 inches
Mean annual temperature: about 33 degrees F

TAXONOMIC CLASS: Medial over sandy or sandy-skeletal, amorphic over mixed Andic Haplocryods

TYPICAL PEDON: Benka silt loam - on a nearly level slope under quaking aspen and black spruce forest at 150 feet elevation. (All colors are for moist soil, textures are apparent field textures)

Oi--0 to 3 inches; black (10YR 2/1) slightly decomposed plant material; extremely acid (pH 4.3); clear wavy boundary. (1 to 4 inches thick)

E--3 to 5 inches; dark gray (10YR 4/1) silt loam; weak fine granular structure; very friable, nonsticky and nonplastic; common very fine and fine and few medium roots; very strongly acid (pH 4.8); abrupt wavy boundary. (1 to 3 inches thick)

Bs1--5 to 8 inches; reddish brown (5YR 4/4) silt loam; weak medium subangular blocky structure; very friable, nonsticky and nonplastic; common very fine and fine and few medium roots; strongly acid (pH 5.2); clear wavy boundary. (2 to 7 inches thick)

Bs2--8 to 10 inches; strong brown (7.5YR 4/6) silt loam; weak fine subangular blocky structure; very friable, nonsticky and nonplastic; few very fine and fine roots; strongly acid (pH 5.2); abrupt wavy boundary. (2 to 6 inches thick)

Eb--10 to 13 inches; brown (10YR 5/3) silt loam; weak medium subangular blocky structure; very friable, nonsticky and nonplastic; few very fine and fine roots; strongly acid (pH 5.4); abrupt wavy boundary. (0 to 3 inches thick)

Bsb--13 to 16 inches; brown (7.5YR 4/4) silt loam; weak coarse subangular blocky structure; very friable, nonsticky and nonplastic; few very fine roots; moderately acid (pH 5.6); gradual irregular boundary. (0 to 11 inches thick)

BC--16 to 25 inches; dark yellowish brown (10YR 4/4) silt loam; weak coarse subangular blocky structure; very friable, nonsticky and nonplastic; moderately acid (pH 5.6); clear smooth boundary. (4 to 12 inches thick)

C1--25 to 30 inches; dark yellowish brown (10YR 3/4) silt loam; weak coarse subangular blocky structure; very friable, nonsticky and nonplastic; moderately acid (pH 5.6); clear smooth boundary. (0 to 11 inches thick)

2C2--30 to 60 inches; grayish brown (2.5Y 5/2) olive brown (2.5Y 4/4) and dark brown (10YR 3/3) stratified coarse sand through fine sand with occasional pockets and strata of very fine sand and silt; massive; very friable, nonsticky and nonplastic; moderately acid (pH 5.8).

TYPE LOCATION: Susitna Valley Area, Alaska; about 3 miles north of Willow; in the NE 1/4 of the NW 1/4 of section 36, T. 20N, R. 5W., Seward Meridian.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 33 to 37 degrees F
Depth to stratified glacial outwash material: 14 to 30 inches
Loess mantle: dominated by volcanic ash; moist bulk density; less than 0.9 grams per cubic centimeter; phosphorous retention; greater than 85 percent
Weighted average particle size: contrasting substratum material is sandy.

E and Eb horizons:
Matrix moist color: hue of 7.5YR to 2.5Y; value of 4 or 5; chroma of 1 to 4
Texture: silt loam, very fine sandy loam
Reaction: very strongly acid to moderately acid

Bs and Bsb horizons:
Matrix moist color: hue of 5YR or 7.5YR; value of 3 to 5; chroma of 2 to 4
Texture: silt loam, very fine sandy loam
Reaction: very strongly acid to moderately acid

BC and C horizons:
Matrix moist color: hue of 10YR or 2.5Y; value of 3 to 5; chroma of 2 to 4 Texture: silt loam, very fine sandy loam
Reaction: strongly acid to slightly acid

2C horizon:
Matrix moist color: hue of 10YR to 5Y; value of 3 to 5; chroma of 2 to 6
Texture: stratified and includes coarse sand, sand, fine sand, loamy sand, loamy fine sand, very fine sand, silt
Coarse fragments: 0 to 5 percent gravel and cobbles
Reaction: moderately acid or slightly acid

COMPETING SERIES: These are the Chulitna (AK), Kashwitna (AK), Shoestring (WA), and Soldotna (AK) series in the same family. Chulitna soils have loess mantles thicker than 30 inches. The Kashwitna and Soldotna soils have greater than 35 percent coarse fragments in the substratum. Shoestring soils contain coarse fragments of volcanic ash.

GEOGRAPHIC SETTING:
Parent material: volcanic ash and loess deposits overlying stratified sandy glacial outwash material
Landform: glacial outwash plains, moraines, and hills
Slope: 0 to 60 percent
Climate is transitional maritime-continental
Mean annual temperature: about 33 degrees F.
Mean annual precipitation: about 25 inches.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Doroshin and Mutnala soils. Doroshin soils are very poorly drained and occur in bogs. Mutnala soils have loamy substratum and occur on similar landforms

DRAINAGE AND PERMEABILITY: Well drained low to high runoff, saturated hydraulic conductivity is moderately high in the loess mantle and moderately high to high in the underlying stratified glacial outwash.

USE AND VEGETATION: Used for cropland, pasture, and wildlife habitat. The native vegetation includes white spruce, black spruce, quaking aspen and paper birch.

DISTRIBUTION AND EXTENT: MLRA Cook Inlet Lowlands, South-central Alaska. The series is of moderate extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA

SERIES ESTABLISHED: Matanuska-Susitna Soil Survey, Alaska. 1996.

REMARKS: Diagnostic horizons and features recognized in this profile include: Albic horizons: 0 to 2 and 10 to 13 inches
Spodic horizons: 2 to 7 and 10 to 13 inches
Andic soil properties: 0 to 27 inches
Sandy particle size: 27 to 60 inches
Temperature regime: cryic
Moisture regime: udic

Lab data is available for this pedon: NSSL S87AK-170-002

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National Cooperative Soil Survey
U.S.A.