LOCATION SEDGWAY ID

Established Series
Rev. TAM/TB/CLM
08/2021

SEDGWAY SERIES

The Sedgway series consists of very deep, well drained soils with moderately slow permeability. They are on mountain slopes and foothills. They formed in mixed alluvium and colluvium from a variety of sedimentary and metasedimentary rocks with some loess influence in the upper part. Slopes range from 8 to 60 percent. Average annual precipitation is about 660 millimeters and the average annual temperature is about 4 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Alfic Argicryolls

TYPICAL PEDON: Sedgway gravelly silt loam - on a 44 percent north-facing mountain slope under Douglas-fir at 2150 meters elevation. (Colors are for air-dry soil unless otherwise noted. When described the soil was moist below 53 cm.)

Oi--0 to 3 cm; undecomposed needles, leaves, twigs, and grass. (0 to 10 cm)

Oe--3 to 6 cm; decomposed and partly decomposed needles, leaves, twigs, and grass. (0 to 5 cm)

A1--6 to 19 cm; very dark grayish brown (10YR 3/2) gravelly silt loam, black (10YR 2/1) moist; weak coarse subangular blocky structure parting to weak fine subangular blocky; soft, very friable, slightly sticky and slightly plastic; many fine and very fine and common coarse and medium roots; many very fine tubular and common very fine irregular pores; about 15 percent pebbles and 5 percent cobbles; moderately acid (pH 5.7); abrupt smooth boundary. (5 to 28 cm thick)

A2--19 to 36 cm; dark grayish brown (10YR 4/2) very cobbly silt loam, very dark brown (10YR 2/2) moist; weak coarse and medium subangular blocky structure parting to weak fine subangular blocky; soft, very friable, slightly sticky and slightly plastic; common coarse, fine and very fine and few medium roots; many very fine tubular and few very fine irregular pores; about 15 percent pebbles, 20 percent cobbles and 10 percent stones; moderately acid (pH 5.7); clear smooth boundary. (13 to 23 cm thick)

E--36 to 53 cm; pale brown (10YR 6/3) very cobbly loam, brown (10YR 4/3) moist; weak coarse and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common coarse and few medium, fine and very fine roots; common very fine tubular pores; about 15 percent pebbles, 30 percent cobbles, and 10 percent stones; moderately acid (pH 6.0); clear wavy boundary. (13 to 28 cm thick)

Bt/E--53 to 75 cm; 80 percent yellowish brown (10YR 5/4) very cobbly clay loam, dark yellowish brown (10YR 3/4) moist; 20 percent pale brown (10YR 6/3) very cobbly loam, dark yellowish brown (10YR 4/4) moist E material which occurs in pockets and as coatings on the faces of peds; moderate coarse and medium angular blocky structure; hard, firm, very sticky and very plastic; common coarse and few medium, fine and very fine roots; common very fine and few fine tubular pores; common distinct clay films on the faces of peds and in pores; about 20 percent pebbles, 25 percent cobbles, and 10 percent stones; moderately acid (pH 6.0); gradual wavy boundary. (0 to 20 cm thick)

Bt1--75 to 87 cm; yellowish brown (10YR 5/4) very cobbly clay loam, dark yellowish brown (10YR 3/4) moist; moderate coarse and medium angular blocky structure; hard, firm, very sticky and very plastic; few medium, fine and very fine roots; common very fine tubular pores; many distinct clay films on the faces of peds and in pores; about 20 percent pebbles, 25 percent cobbles, and 10 percent stones; slightly acid (pH 6.3) gradual wavy boundary. (13 to 51 cm thick)

Bt2--87 to 156 cm; yellowish brown (10YR 5/4) very cobbly clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium angular blocky structure; hard, firm, sticky and plastic; few medium, fine and very fine roots; common very fine tubular pores; continuous distinct clay films on the faces of peds and in pores; about 15 percent pebbles, 25 percent cobbles, and 10 percent stones; slightly acid (pH 6.3).

TYPE LOCATION: Bannock County, Idaho; about 1.6 km southeast of the Smith Canyon Road; about 30 meters north and 288 meters west of the southeast corner of sec. 19, T. 10 S., R. 38 E.

RANGE IN CHARACTERISTICS:

Average annual soil temperature - 3 to 6 degrees C
Depth to the top of the argillic horizon - 41 to 61 cm
Depth to the base of the argillic horizon - 100 cm or more
Mollic epipedon thickness - 25 to 41 cm

Particle-size control section (upper 50 cm of the Argillic horizon)
Clay - 18 to 34 percent
Rock fragments - 35 to 60 percent

A horizon
Value - 3 to 5 dry, 2 or 3 moist
Chroma - 1 through 3 dry or moist
Reaction - moderately acid to neutral

E horizon
Value - 6 or 7 dry, 3 to 5 moist
Chroma - 3 or 4 dry or moist
Clay - 15 to 25 percent
Rock fragments - 5 to 55 percent
Texture - CBV-SIL, CBV-L, SL
Reaction - moderately acid to neutral

Bt horizon
Hue - 2.5YR through 10YR
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 3 through 6 dry or moist
Clay - 18 to 34 percent
Rock fragments - 35 to 60 percent
Texture - CBV-CL, CBV-SICL, GRV-SCL, GRV-CL
Reaction - moderately acid to neutral

BC and C horizons are present in some pedons.

COMPETING SERIES: This is the Pando series. Pando soils have the base of the argillic horizon and depth to sandy-skeletal material at 50 to 100 cm and have 8 to 18 percent clay in the Bt horizon.

GEOGRAPHIC SETTING: Sedgway soils are on slightly convex to concave mountain slopes and foothills at elevations of 1830 to 2590 meters. Slopes range from 8 to 60 percent. The soils formed in alluvium and colluvium from a variety of sedimentary and metasedimentary rocks with some loess influence in the upper part. The average annual temperature ranges from 2 to 5 degrees C and the average annual precipitation ranges from 560 to 760 millimeters. The frost-free season is less than 60 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beaverdam, Cedarhill, Greys, Harkness, Ireland, Mikesell, and Toponce series. Beaverdam soils have fine particle-size control sections. Cedarhill and Ireland soils have calcic horizons and frigid temperature regimes. Greys soils are fine-silty. Harkness and Mikesell soils lack mollic epipedons. Toponce soils are pachic and have fine particle-size control sections. The Beaverdam soil is on mountain slopes but usually occupies a more concave position lower on the slope. The Cedarhill and Ireland soils are on south or west aspects on mountain slopes. The Greys and Toponce soils are at lower elevations on mountain footslopes of less than 30 percent. The Harkness and Mikesell soils are on mountain slopes at higher elevations.

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

USE AND VEGETATION: This Sedgway soil is used mainly for timber production and grazing. The principal native plants at climax are an overstory of Douglas-fir with an understory dominated by pine reedgrass.

DISTRIBUTION AND EXTENT: Southeastern Idaho. This series is not extensive.

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

SERIES ESTABLISHED: Bannock County, Idaho, 1983.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Mollic epipedon - The zone from the mineral soil surface to 36 cm (A and AB horizons)

Argillic horizon - The zone from 53 to 156 cm (Bt/E, Bt1, and Bt2 horizons)

Boralfic feature - Above the argillic horizon a horizon that has color values too high for a mollic epipedon and a chroma too high for an albic horizon (E horizon)

Particle-size control section - The zone from 53 to 104 cm (Bt/E, Bt1, and part of the Bt2 horizons)

Soil moisture regime - Udic

National Cooperative Soil Survey
U.S.A.