LOCATION TEKOA                   WA+ID

Established Series
Rev. NCD/RWL/RJS
10/2016

TEKOA SERIES

The Tekoa series consists of moderately deep, well drained soils on mountains and hills. They formed in loess and metasedimentary residuum and colluvium with an influence of volcanic ash in surface layers. Slopes are 3 to 65 percent. The average annual precipitation is 20 to 30 inches. The mean annual air temperature is about 45 to 48 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Vitrandic Argixerolls

TYPICAL PEDON: Tekoa gravelly ashy silt loam, rangeland - (colors are for dry soils unless otherwise stated).

A1--0 to 3 inches; dark grayish brown (10YR 4/2) gravelly ashy silt loam, very dark brown (10YR 2/2) moist; weak thin and medium platy structure parting to moderate fine and medium granular; slightly hard, friable, slightly sticky and slightly plastic; many roots; many very fine and fine pores; 30 percent gravel; slightly acid (pH 6.1); clear wavy boundary. (3 to 9 inches thick)

A2--3 to 7 inches; grayish brown (10YR 5/2) gravelly ashy silt loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; many very fine and fine pores; 30 percent gravel; slightly acid (pH 6.2); clear wavy boundary. (0 to 6 inches thick)

BA--7 to 14 inches; brown (10YR 5/3) very gravelly loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; many very fine and fine pores; 35 percent gravel; slightly acid (pH 6.3); clear wavy boundary. (0 to 10 inches thick)

Bt--14 to 20 inches; pale brown (10YR 6/3) very gravelly loam, brown (10YR 4/3) moist; moderate fine and medium prismatic structure; slightly hard, friable, moderately sticky and moderately plastic; common roots; many fine and medium pores; many faint clay films on peds and in pores; 35 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (6 to 15 inches thick)

BC--20 to 38 inches; yellow (10YR 7/6) extremely gravelly loam, yellowish brown (10YR 5/6) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few roots; 80 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (0 to 18 inches thick)

R--38 inches; fractured shale.

TYPE LOCATION: Whitman County, Washington; 1,700 feet east and 200 feet south of the northwest corner of sec. 2, T. 20 N., R. 45 E. Latitude - 47 degrees, 15 minutes, 32.14 seconds North; Longitude - 117 degrees, 6 minutes, 3.2 seconds West. NAD 83. USGS Tekoa Mountain WA, ID topographic quadrangle.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 47 to 50 degrees F.
Depth to a lithic contact - 20 to 40 inches.
Moisture control section - these soils are usually moist, but are dry for 60 to 75 consecutive days in the moisture control section following summer solstice.
Rock fragments - averages 35 to 60 percent rock fragments in the particle-size control section.
Thickness of the mollic epipedon - 10 to 20 inches thick
Thickness of volcanic ash influence - 7 to 16 inches
Estimated properties of ash influence layer:
Volcanic glass content - 5 to 20 percent,
Acid-oxalate extractable Al + Fe - 0.4 to 1.0 percent
15-bar water retention - 5 to 10 percent (air dried) samples

A horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3, moist or dry
Clay content - 7 to 22 percent
Texture - ashy silt loam
Gravel content - 10 to 30 percent
Channer content - 0 to 20 percent
Cobble content - 0 to 20 percent
Total fragment content - 15 to 40 percent
Reaction - neutral to moderately acid

BA horizon (when present)
Hue - 10YR or 7.5YR
Value - 4 to 6 dry, 2 to 4 moist
Chroma - 2 to 4, moist or dry
Clay content - 10 to 25 percent
Texture - loam or silt loam
Gravel content - 20 to 55 percent
Channer content - 0 to 40 percent
Cobble content - 0 to 40 percent
Total fragment content - 30 to 55 percent
Reaction - neutral to moderately acid

Bt horizon
Hue - 10YR or 7.5YR
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 3 or 4, moist or dry
Clay content - 13 to 35 percent
Texture - loam, silt loam, clay loam, or silty clay loam
Gravel content - 20 to 55 percent
Channer content - 0 to 45 percent
Cobble content - 0 to 30 percent
Total fragment content - 25 to 70 percent (averages more than 35 percent).
Reaction - slightly acid or moderately acid

BC horizon (when present)
Hue - 10YR or 7.5YR
Value - 5 to 7 dry, 3 to 5 moist
Chroma - 3 to 6, moist or dry
Clay content - 7 to 17 percent
Texture - loam or silt loam
Gravel content - 30 to 80 percent
Channer content - 0 to 50 percent
Cobble content - 0 to 30 percent
Total fragment content - 40 to 80 percent
Reaction - slightly acid or moderately acid

COMPETING SERIES:
Ackna (WA) - are very deep
Blint (WA) - are dry for 90 to 100 days following the summer solstice
Brinkin (WA) - are very deep
Brysill (WA) - are very deep
Bunselmeier (CA) - have sandy clay loam textures and are 40 to 60 inches to unweathered cinders
Cubhill (WA) - are very deep
Hehe (OR) - are moderately deep to a paralithic contact and have 10 to 25 percent medium, coarse and very coarse sand.
Hovelton (ID) - are dominated by cobble and stone size basalt and welded tuff rock fragments in the particle-size control section
Lainand (WA) - are 40 to 60 inches to a lithic contact
Leidl (WA) - are dry for 75 to 90 days following the summer solstice
McDaniel (WA) - are very deep
Millhouse (WA) - are very deep and are dry for 100 to 120 days following the summer solstice
Nint (WA) - are dry for 75 to 90 days following the summer solstice
Norod (WA) - are 25 to 38 inches to secondary carbonates and are dry for 100 to 120 days following the summer solstice
Skooker (OR) - are 40 to 60 inches to a lithic contact

GEOGRAPHIC SETTING: Tekoa soils are on mountain slopes and hills at elevation of 2,000 to 4,000 feet. At higher elevations these soils only occur on south slopes. Slopes are 3 to 65 percent. These soils formed in loess and colluvium and residuum from sedimentary and metasedimentary rocks including shale, phyllite, argillite, sandstone, quartzite, and siltstone with an influence of volcanic ash in surface layers. The climate is characterized by warm, dry summers and cool, moist winters. Average annual precipitation is 20 to 35 inches including about 3 feet of snow. Average January temperature is 24 degrees F, average July temperature is 66 degrees F, and mean annual air temperature is 45 to 50 degrees F. The frost-free season is 90 to 140 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ardenvoir, Schumacher, Libertybutte, and McCrosket soils. Schumacher soils are on west-facing hills, are fine-loamy, and deep to bedrock. Libertybutte soils are on south and west-facing shoulders and summits of mountains and hills, and are shallow to bedrock. Ardenvoir and McCrosket soils are on north and east-facing backslopes of mountains and hills, are loamy-skeletal and are deep to bedrock.

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

USE AND VEGETATION: Grazing, wildlife, small grains, alfalfa, and grass. Native vegetation is scattered ponderosa pine, Douglas-fir, pinegrass, Idaho fescue, bluebunch wheatgrass and shrubs.

DISTRIBUTION AND EXTENT: Northeastern Washington and northern Idaho. Series is of moderate extent. MLRAs 43A and 9.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Spokane County, Washington, 1964.

REMARKS: Diagnostic horizons and features recognized in this soil include:
Mollic epipedon - the zone from the surface to 14 inches (A1, A2, and BA horizons)
Argillic horizon - the zone from 14 to 20 inches (Bt horizon)
Lithic contact - at 38 inches
Particle-size control section - the zone from 14 to 20 inches (Bt horizon)
Vitrandic feature - the zone from 0 to 7 inches (A1 and A2 horizons)

Changes made to description 1/07 using MLRA approach:
Vegetation revised to reflect a concept of a mesic soil at the transition between MLRA 9 and MLRA 43A.

Classification updated from Loamy-skeletal, mixed, superactive, mesic Ultic Argixerolls to Loamy-skeletal, mixed, superactive, mesic Vitrandic Argixerolls.
Paralithic contact changed to lithic contact.
Horizonation updated.

As of 1/2010, additional investigation is needed across the mapped extent to determine what is typical for vitrandic properties, the type of vegetation, and the shape of rock fragments (whether they are predominantly channers or gravel).

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National Cooperative Soil Survey
U.S.A.