LOCATION MULTNOMAH               OR

Established Series
Rev. RWL/RTS/AON
06/2011

MULTNOMAH SERIES


The Multnomah series consists of deep, well drained soils that formed in gravelly alluvium. Multnomah soils are on broad convex terraces and have slopes of 0 to 60 percent. The mean annual precipitation is about 50 inches and the mean annual temperature is about 53 degrees F.

TAXONOMIC CLASS: Coarse-loamy over sandy or sandy-skeletal, mixed, superactive, mesic Humic Dystroxerepts

TYPICAL PEDON: Multnomah 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 4/3) dry; moderate fine and very fine granular structure; friable, slightly sticky and slightly plastic; common very fine roots; many very fine pores; many fine and very fine concretions; 10 percent gravel; moderately acid (pH 5.6); abrupt smooth boundary. (5 to 9 inches thick)

Bw1--8 to 16 inches; brown (7.5YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; weak fine and very fine subangular blocky structure; friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine pores; 15 percent gravel; slightly acid (pH 6.1); gradual wavy boundary. (7 to 10 inches thick)

Bw2--16 to 25 inches; brown (7.5YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; weak fine and very fine subangular blocky structure; friable, slightly sticky and slightly plastic; few fine and coarse roots; many very fine pores; 10 percent gravel; slightly acid (pH 6.1); clear wavy boundary. (8 to 12 inches thick)

C1--25 to 39 inches; dark yellowish brown (10YR 4/4) gravelly silt loam, light yellowish brown (10YR 6/4) dry; massive; friable, nonsticky and nonplastic; few fine and coarse roots; many very fine pores; few thin clay films on lower side of rock fragments; 25 percent gravel, 5 percent cobbles; moderately acid (pH 6.0); clear wavy boundary. (4 to 16 inches thick)

2C2--39 to 60 inches; very dark grayish brown (10YR 3/2), dark brown (10YR 3/3) and brown (10YR 4/3) very gravelly sand, grayish brown (10YR 5/2) and brown (10YR 5/3) dry; single grained; loose; many very fine pores; 45 percent gravel, 10 percent cobbles; slightly acid (pH 6.1).

TYPE LOCATION: Multnomah County, Oregon; about 100 feet west of shed; SW corner; SE1/4SE1/4SE1/4 section 7, T. 1 S., R. 3 E.

RANGE IN CHARACTERISTICS: The mean annual soil temperature is 54 to 56 degrees F. The soils are ususally moist but are dry between depths of 4 and 12 inches for 45 to 80 consecutive days during the 120-day period following the summer solstice. Thickness of the solum is 20 to 30 inches. Depth to contrasting texture is 24 to 40 inches. Rock fragments are a mixture of basalt and andesite.

The A horizon has hue of 10YR or 7.5YR, value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 or 3 moist and dry. It is loam, gravelly loam, silt loam, cobbly silt loam, or gravelly silt loam and has 0 to 25 percent gravel and 0 to 20 percent cobbles.

The Bw horizon has hue of 7.5YR or 10YR, value of 5 or 6 dry, and chroma of 3 or 4 moist and dry. It is loam or gravelly loam, silt loam, bouldery silt loam or gravelly silt loam and has 5 to 35 percent gravel, 0 to 5 percent cobbles and 10 to 25 percent boulders. It is slightly acid to medium acid.

The C1 horizon is gravelly silt loam and has 20 to 35 percent gravel.

The 2C2 horizon is very gravelly, very bouldery, extremely bouldery, or very cobbly sand or loamy sand. It has 20 to 75 percent coarse fragments, of which 0 to 30 percent may be cobbles or boulders.

COMPETING SERIES: There are no competing series. Series in other families include the Hugo, Hurlbut, Madonna, Schnorbush, Tebo, Yeary and Salem series in other families. All of these soils except Salem lack contrasting textures in the particle-size control section. Salem soils have a mollic epipedon and an argillic horizon.

GEOGRAPHIC SETTING: The Multnomah soils are on broad terraces at elevations of 100 to 400 feet. Slopes are mainly 0 to 8 percent but range to 60 percent on terrace fronts and sideslopes of drainages. The soils formed in stratified medium and very gravelly or cobbly coarse textured mixed alluvium. The climate is humid temperate. The winters are cool and moist and summers are warm and dry. The mean January temperature is about 39 degrees F., mean July temperature is about 67 degrees F., and the mean annual temperature is about 53 degrees F. The mean annual precipitation is 40 to 60 inches. The frost-free season is 165 to 210 days. The soils are on the Champoeg geomorphic surface.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Latourell, Powell and Quatama soils. Latourell soils have an argillic horizon and lack contrasting textures within depth of 40 inches. Powell soils are somewhat poorly drained and have a fragipan. Quatama soils are moderately well drained, have an argillic horizon and lack contrasting textures.

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

USE AND VEGETATION: These soils are used mainly for truck crops, nursery stock, grain, fruit production, pasture, homesites, and wildlife habitat. Native vegetation is Douglas-fir, Oregon white oak, bigleaf maple, western redcedar, vine maple, western hazel, common snowberry, rose, grasses and forbs.

DISTRIBUTION AND EXTENT: Along the Columbia and northern Willamette Rivers and tributaries on terraces in Multnomah, Clackamas and Columbia Counties, Oregon; MLRA 2. The series is moderately extensive.

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

SERIES ESTABLISHED: Multnomah County, Oregon, 1977.

REMARKS:Diagnostic horizons and other features;
Ochric epipedon
Humic subgroup - color requirement is meet from 0 to 8 inches
Cambic horizon - from 8 to 25 inches
Particle-size control section - from 10 to 40 inches; 10 to 39 inches is coarse-loamy and 39 to 40 is sandy-skeletal

ADDITIONAL DATA: Characterization data on two profiles (S70-OR-26-8 and 9) reported in Riverside Soil Survey Laboratory computer printout for soils sampled in Multnomah County, Oregon, 1970.


National Cooperative Soil Survey
U.S.A.