LOCATION POWELL OR+WA

Established Series
Rev. RWL/AON
06/2011

POWELL SERIES

The Powell series consists of deep, somewhat poorly drained soils that formed in silty materials over old silty alluvium. Powell soils are on broad high terraces and have slopes of 0 to 30 percent. The mean annual precipitation is 55 inches and the mean annual air temperature is about 52 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Humic Fragixerepts

TYPICAL PEDON: Powell silt loam, cultivated. (Colors are for moist soil unless otherwise noted.)

Ap--0 to 8 inches; dark brown (10YR 3/3) silt loam, brown (10YR 5/3) dry; moderate very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine irregular pores; few fine firm peds or concretions; strongly acid (pH 5.3); abrupt smooth boundary. (7 to 9 inches thick)

Bw1--8 to 13 inches; brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; moderate very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; few fine firm peds or concretions; moderately acid (pH 5.6); clear smooth boundary. (5 to 8 inches thick)

Bw2--13 to 16 inches; brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; common fine distinct yellowish red (5YR 4/6) and few fine faint grayish brown (10YR 5/2) mottles; moderate fine and very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine tubular pores; few fine firm peds or concretions; strongly acid (pH 5.5); abrupt wavy boundary. (3 to 10 inches thick)

2Bx1--16 to 25 inches; brown (10YR 4/3) and dark yellowish brown (10YR 4/4) silt loam, pale brown (10YR 6/3) and light yellowish brown (10YR 6/4) dry; many medium distinct light brownish gray (10YR 6/2), grayish brown (10YR 5/2) and reddish brown (5YR 4/3, 4/4) redox concentrations,; weak thin platy structure; firm, brittle, hard, slightly sticky and slightly plastic; few very fine roots; many very fine tubular pores; few fine and medium black stains; strongly acid (pH 5.4); clear wavy boundary. (8 to 10 inches thick)

2Bx2--25 to 39 inches; brown (10YR 4/3) silt loam, very pale brown (10YR 7/3) dry; many fine distinct yellowish red (5YR 5/6, 5/8) redox concentrations; light brownish gray (10YR 6/2) and grayish brown (10YR 5/2) wedge-shaped silt coatings up to 1 inch thick on vertical faces of prisms; weak medium and coarse prismatic structure; firm, brittle, hard, slightly sticky and slightly plastic; few fine and common very fine tubular pores; few fine black stains; moderately acid (pH 5.7); clear wavy boundary. (12 to 14 inches thick)

2Bx3--39 to 60 inches; variegated brown (10YR 5/3), yellowish brown (10YR 5/6), yellowish red (5YR 4/6) and pinkish gray (5YR 6/2) silt loam with light brownish gray (10YR 6/2), light yellowish brown (10YR 6/4) and very pale brown (10YR 7/3) streaks in fractures; massive; firm, brittle, hard, slightly sticky and slightly plastic; many very fine and few medium tubular pores; few very fine black stains; slightly acid (pH 6.1).

TYPE LOCATION: Multnomah County, Oregon; Salquist Road; SW1/4 SE1/4 NW1/4 section 13, T. 1 S., R. 3 E.

RANGE IN CHARACTERISTICS: The mean annual soil temperature is 54 to 56 degrees F. The soils are usually moist but are dry throughout between depths of 4 and 12 inches for 45 to 60 consecutive days during the period of 120 days following the summer solstice. Depth to the fragipan is 15 to 24 inches. Depth to bedrock is more than 60 inches. The umbric epipedon is 7 to 9 inches thick.

The A horizon has chroma of 2 or 3 moist and dry.

The Bw horizon has hue of 10YR or 7.5YR, value of 5 or 6 dry and chroma of 3 or 4 moist and dry. It has few faint and distinct redox concentrations at depths between 12 inches and the fragipan. This horizon is silt loam and has more than 18 percent clay on the basis of 15 bar water of 9 or 10 percent.

The 2Bx horizon (fragipan) has variegated colors, distinct high or low chroma redox features and tongues or coatings with chroma of 2. It has massive, prismatic or platy structure and is firm or very firm.

COMPETING SERIES: These are the Glohm and Kinton series. Glohm soils are moderately well drained with a udic moisture regime and are 20 to 40 inches deep to a fragipan. Kinton soils lack redox features with chroma of 2 above 30 inches.

GEOGRAPHIC SETTING: Powell soils are on smooth terraces at elevations at 300 to 600 feet. Slopes are 0 to 30 percent. The soils formed in loess over old alluvium. The climate is humid. The mean January temperature is about 39 degrees F., the mean July temperature is about 67 degrees F., and the mean annual temperature is about 52 degrees F. The frost-free season is 165 to 210 days. The mean annual precipitation is 50 to 60 inches.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cornelius and Wollent soils. Cornelius soils have an argillic horizon, are moderately well drained and are 30 or 40 inches deep to the fragipan. Wollent soils are poorly drained and lack a fragipan.

DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow to medium runoff; slow permeability.

USE AND VEGETATION: Berries, truck crops, nursery stock, small grain, hay and pasture are the major crops. Native vegetation is Douglas-fir, western redcedar, red alder, grand fir, bigleaf maple, willow, rose, salal, vine maple, common snowberry, grasses and forbs.

DISTRIBUTION AND EXTENT: Northwestern Oregon and southwestern Washington; MLRA 2. The series is inextensive.

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

SERIES ESTABLISHED: Multnomah County, Oregon, 1919.

REMARKS: Diagnostic horizons and other features;
Umbric epipedon - from 0 to 8 inches; only 7 inches are needed since the top of the fragipan is at 16 inches
Fragipan - from 16 to 60 inches
Cambic horizon - from 8 to 16 inches

ADDITIONAL DATA: Characterization data for two pedons (S70-Oreg-26-1 and 2) reported in Riverside Soil Survey Laboratory computer printout for soils sampled in Multnomah, Clackamas and Washington Counties, Oregon, 1971.

National Cooperative Soil Survey
U.S.A.