LOCATION SPOKANE WA+IDEstablished Series
TAXONOMIC CLASS: Coarse-loamy, isotic, mesic Vitrandic Haploxerolls
TYPICAL PEDON: Spokane ashy loam, woodland. (Colors are for dry soil unless otherwise noted)
Oi--0 to 1 inch; partially decomposed organic litter, composed of pine needles, leaves, twigs, and cones; strongly acid (pH 5.5); abrupt smooth boundary. (0 to 1 inch thick)
A1--1 to 4 inches; grayish brown (10YR 5/2) ashy loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, friable, slightly sticky and slightly plastic; many roots; many very fine interstitial pores; 5 percent gravel; slightly acid (pH 6.4); clear smooth boundary.
A2--4 to 10 inches; brown (10YR 5/3) ashy sandy loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; many roots; many very fine tubular and irregular pores; 10 percent gravel; slightly acid (pH 6.2);a clear smooth boundary. (combined thickness of the A horizon is 7 to 16 inches)
Bt--10 to 18 inches; pale brown (10YR 6/3) gravelly coarse sandy loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common roots; many very fine tubular and irregular pores; few patchy faint clay films in pores and on mineral grains; 20 percent gravel; slightly acid (pH 6.3); clear wavy boundary. (6 to 20 inches thick)
BCt--18 to 26 inches; pale brown (10YR 6/3) gravelly coarse sandy loam, brown (10YR 4/3) moist; weak fine subangular blocky structure; soft, friable, nonsticky and nonplastic; common roots; many very fine tubular and irregular pores; few irregular horizontal bands of dark yellowish brown (10YR 4/4) moist loam, 2 to 5 mm. thick, containing faint patchy clay films in pores; 20 percent gravel; slightly acid (pH 6.5); gradual irregular boundary. (0 to 15 inches thick)
Cr--26 inches; pale brown (10YR 6/3), light gray (10YR 7/2), and gray (10YR 5/1) weathered granite; crumbles to gravelly loamy coarse sand; few roots; neutral (pH 6.9).
TYPE LOCATION: Spokane County, Washington; about 1.5 miles northeast of Foothills, WA. and 200 feet west and 1,870 feet north of the southeast corner of section 1, T. 26 N., R. 44 E.; USGS Foothills, Wash. Topographic quadrangle; (Latitude 47 degrees, 46 minutes, 45 seconds N. and Longitude 117 degrees, 10 minutes, 38 seconds W.) NAD83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature (at a depth of 20 inches) - 47 to 53 degrees F.
Soil moisture regime dry 75 to 90 consecutive days during summer and autumn
Base saturation (sum of cations) - less than 75 percent in the upper 30 inches
Rock fragment content 15 to 35 percent
Depth to weathered bedrock -20 to 40 inches
Depth to hard bedrock - 40 to more than 60 inches
Mollic epipedon 7 to 16 inches
Soil reaction slightly acid to neutral
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
Texture ashy loam, ashy sandy loam
Rock fragments - 0 to 15 percent gravel, 0 to 5 percent cobbles, 0 to 15 percent stones
Bt or Bw horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma 3 or 4
Texture - loam, sandy loam, coarse sandy loam
Rock fragments - 10 to 30 percent gravel, 0 to 10 percent cobbles (total less than 35 percent)
BCt or BC horizon
Hue - 10YR or 2.5Y
Value - 5 to 7 dry, 4 or 5 moist
Chroma - 2 to 4
Texture - sandy loam, coarse sandy loam, loamy coarse sand
Rock fragments - 5 to 30 percent gravel, 0 to 5 percent cobbles.
A C horizon may be present in some pedons.
COMPETING SERIES: These are the Donavan, Fourmound (T), Goldlake and Usk series. A similar soil that has mixed mineralogy is the Stevens series. Donavan soils have a densic contact at a depth of 20 to 40 inches. Fourmound soils have a lithic contact at a depth of 40 to 60 inches. Goldlake soils have a densic contact at a depth of 40 to 60 inches. Stevens soils have a densic contact at a depth of 25 to 40 inches. Usk soils are dry for 60 to 75 consecutive days following the summer solstice.
GEOGRAPHIC SETTING: Spokane soils are on foothills, mountains, and ridgetops at elevations of 1,800 to 4,000 feet. They formed in colluvium and residuum weathered from granite, gneiss, and schist mixed with loess and volcanic ash in the upper part. The climate is characterized by warm, relatively dry summers and cool, moist winters. Slopes are 5 to 65 percent. The mean annual precipitation is 15 to 24 inches. The mean annual temperature is 46 to 51 degrees F. The frost-free period is 100 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Centralpeak, Donavan, Dragoon, Green Bluff, Mobate, Micapeak, Raisio, Skanid, and Tekoa soils. Centralpeak soils have an ochric epipedon, are frigid and are on side slopes of mountains. Donavan soils are more than 40 inches deep and are on side slopes of hills and mountains. Mobate and Skanid soils are 10 to 20 inches deep and are on mountains. Dragoon and Tekoa soils have an argillic horizon with more than 18 percent clay and are on mountains. Green Bluff soils have an ochric epipedon, are more than 40 inches deep and are on basalt plateaus. Micapeak soils are frigid, have an ochric epipedon and are on side slopes of mountains and foothills. Raisio soils are loamy-skeletal and are on south-facing side slopes of mountains.
DRAINAGE AND PERMEABILITY: Well-drained; moderately rapid permeability.
USE AND VEGETATION: These soils are used for rural home sites, grazeable woodland, livestock grazing, timber production, wildlife habitat, and some dryland cropland. Native vegetation is ponderosa pine and scattered Douglas-fir, with an understory of common snowberry, snowbrush ceanothus, bluebunch wheatgrass, Idaho fescue, baldhip rose, and pinegrass. Native vegetation on dry sites is ponderosa pine with an understory of Idaho fescue and antelope bitterbrush.
DISTRIBUTION AND EXTENT: Northeastern Washington and northern Idaho; MLRA 43. Series is extensive.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Spokane County, Washington, 1964.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 1 to 10 inches (A1 and A2 horizons)
Cambic horizon - the zone from 10 to 26 inches (Bt and BCt horizons) with presence of oriented clay but less than a 20 percent increase in clay from the overlying horizon.
Vitrandic feature - the zone from 1 to 10 inches
Ultic feature - the zone from 1 to 26 inches having a base saturation (sum) of less than 75 percent.
Paralithic contact - the zone beginning at 26 inches.
Particle-size control section - the zone from 11 to 26 inches.
Depth to diagnostic horizons and features are measured from the top of the first mineral layer.
ADDITIONAL DATA: NSSL laboratory data are available on this soil. Pedon number 84P164806-813, sample number S83WA019-001, NSSL, Lincoln, NE. 10/88.