LOCATION DELENA OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Humic Fragiaquepts
TYPICAL PEDON: Delena silt loam, cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 7 inches; very dark grayish brown (10YR 3/2) silt loam, gray (10YR 5/1) dry; moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many fine irregular pores; common fine concretions; moderately acid (pH 6.0); abrupt smooth boundary. (5 to 10 inches thick)
A--7 to 13 inches; very dark grayish brown (10YR 3/2) heavy silt loam, grayish brown (10YR 5/2) dry; few fine distinct yellowish brown (10YR 5/6) redox concentrations; moderate fine subangular blocky and granular structure; slightly hard, friable, slightly sticky and moderately plastic; common very fine roots; many very fine pores; common fine concretions; moderately acid (pH 5.8); clear smooth boundary. (5 to 8 inches thick)
BA--13 to 18 inches; dark grayish brown (10YR 4/2) silty clay loam, light brownish gray (10YR 6/2) dry; many fine prominent dark reddish brown (5YR 3/3) redox concentrations; moderate fine subangular blocky structure; firm, moderately sticky and moderately plastic; few very fine roots; common very fine pores; common fine soft concretions; moderately acid (pH 5.8); clear smooth boundary. (4 to 7 inches thick)
Bw--18 to 23 inches; grayish brown (10YR 5/2) silty clay loam, light gray (10YR 7/1) dry; many fine prominent reddish brown (5YR 4/4) redox concentrations; moderate fine subangular blocky structure; firm, slightly brittle, slightly sticky and moderately plastic; few very fine roots; common very fine pores; slightly acid (pH 6.4); clear smooth boundary. (5 to 8 inches thick)
2Btx1--23 to 33 inches; grayish brown (10YR 5/2) silty clay loam, light gray (10YR 7/1) dry; many fine prominent reddish brown (5YR 4/4) and yellowish red (5YR 4/6) redox concentrations; weak coarse prismatic and weak coarse blocky structure; firm, brittle, moderately sticky and moderately plastic; common very fine pores; common distinct clay films in pores; channels and on some ped faces; slightly acid (pH 6.4); clear smooth boundary. (8 to 11 inches thick)
2Btx2--33 to 40 inches; variegated dark grayish brown (10YR 4/2), dark grayish brown (2.5Y 5/2) and yellowish red (5YR 4/6) silty clay loam; weak coarse prismatic and weak coarse blocky structure; firm, slightly brittle, slightly sticky and moderately plastic; common very fine pores; distinct clay films in pores and on some ped surfaces; neutral (pH 6.6).
TYPE LOCATION: Multnomah County, Oregon; about 300 feet west of Skyline blvd. in the SW1/4 SW1/4 NW1/4 section 24, T.2N., R.2W., W.M.
RANGE IN CHARACTERISTICS: The soils are saturated with water during the winter and spring unless artificially drained. Soil depth is more than 5 feet but rooting depth is restricted by seasonal water table of less than 30 inches. Depth to fragipan is 20 to 30 inches. Mean annual soil temperature is 51 degrees to 55 degrees F. Umbric epipedon is 10 to 18 inches thick.
The A horizon has hue of 2 or 3 moist, 4 or 5 dry and chroma of 1 or 2 moist and dry. It has granular or subangular blocky structure.
The Bw horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist, 6 or 7 dry, and chroma of 2 moist and 1 or 2 dry. Redox concentrations are distinct or prominent. The texture is commonly silty clay loam but includes silt loam in the upper part in some pedons.
The 2Btx horizon (fragipan) has hue of 10YR or 2.5Y, value of 4 or 5 moist, 6 or 7 dry and chroma of 1 or 2 moist and dry. The coatings on peds and tongues have the lower chroma and yellower hue. This horizon is firm or very firm and commonly brittle clay films are common to many and faint to distinct in pores and on cleavage planes or polygonal cracks.
COMPETING SERIES: There are no other series in this family. Similar soils include the Huberly series. Huberly soils lack or umbric epipedon.
GEOGRAPHIC SETTING: The Delena soils are in concave swales and draws on smooth or rolling hills at 100 to 1,400 foot elevations. The soils formed in loess-like material over mixed, silty and clayey alluviums or residuum weathered from basalt. The climate is humid temperate with cool moist winters and warm dry summers. The average July temperature is 67 degrees F., average January temperature is 39 degrees F., and the mean annual temperature is 50 degrees to 54 degrees F. Average annual precipitation is 50 to 70 inches. Frost-free season is 165 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cascade, Cornelius, Goble, Kinton and Helvetia soils. Cascade soils are somewhat poorly drained and have chroma of 3 or more in the B horizon. Cornelius, Goble and Kinton soils are moderately well drained. Helvetia soils lack fragipans and are moderately well drained.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; very slow permeability.
USE AND VEGETATION: These soils are used mainly for woodland but small grain and seed, hay and pasture are grown in some areas. Native vegetation is mainly Douglas-fir, western red cedar, ash, snowberry, wild currant, grasses and weeds.
DISTRIBUTION AND EXTENT: Northwestern Oregon. The soil is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Washington County, Oregon, 1975.
REMARKS: Diagnostic horizons and other features:
Umbric epipedon - 0 to 13 inches
Fragipan - 23 to 40 inches