LOCATION PERVINA OREstablished Series
TAXONOMIC CLASS: Fine, mixed, active, mesic Typic Hapludults
TYPICAL PEDON: Pervina silt loam, woodland. (Colors are for moist soil unless otherwise noted.)
01--1 inch to 0; twigs, needles, and leaves.
A1--0 to 4 inches; dark brown (7.5YR 3/2) silty clay loam, brown (10YR 5/3) dry; moderate fine, subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common medium, fine and very fine roots; many very fine irregular and tubular pores; few 2 to 5 millimeter concretions; medium acid (pH 6.0); abrupt smooth boundary. (4 to 5 inches thick)
A3--4 to 8 inches; dark brown (7.5YR 4/4) silty clay loam, light brown (7.5YR 6/2) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and plastic; common medium to very fine roots; many very fine tubular pores; few 2 to 5 millimeter concretions; medium acid (pH 5.8); clear smooth boundary. (4 to 7 inches thick)
B1--8 to 16 inches; reddish brown (5YR 4/5) silty clay loam, light brown (7.5YR 6/4) dry; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; few medium to very fine roots; many very fine tubular pores; medium acid (pH 5.8); clear smooth boundary. (8 to 15 inches thick)
B21t--16 to 29 inches; yellowish red (5YR 4/6) silty clay loam, light brown (7.5YR 6/4) dry; moderate coarse parting to medium subangular blocky structure; hard, friable, sticky and plastic; few fine roots; many very fine tubular pores; few thin clay films on peds; few firm weathered siltstone fragments; medium acid (pH 5.6); clear smooth boundary. (10 to 20 inches thick)
B22t--29 to 41 inches; yellowish red (5YR 5/6) silty clay, strong brown (7.5YR 5/6) dry; moderate medium subangular blocky structure; hard, firm, sticky and very plastic; few fine roots; many very fine tubular pores; common moderately thick clay films on peds and in pores; 10 percent weathered siltstone fragments; medium acid (pH 5.6); clear smooth boundary. (8 to 12 inches thick)
B3t--41 to 55 inches; brown (7.5YR 5/6) silty clay, brown (7.5YR 5/4) dry; moderate fine subangular blocky structure; hard, friable, sticky and very plastic; few fine roots; many very fine tubular pores; common thin clay films on peds; 15 percent weathered siltstone fragments; strongly acid (pH 5.4); clear smooth boundary. (6 to 15 inches thick)
Cl--55 to 60 inches; yellowish red (5YR 5/8) with streaks of yellowish brown (10YR 5/6) silty clay loam, strong brown (7.5YR 5/8) dry; massive; hard, friable, sticky and plastic; few fine roots; many very fine irregular pores; common moderately thick clay films on rock fragments and in pores; 50 percent weathered siltstone fragments; strongly acid (pH 5.4).
TYPE LOCATION: Washington County, Oregon; 40 feet east of Bacona Road; southwest 1/4 northeast 1/4, sec. 33, T.3N., R.4W., W.M.
RANGE IN CHARACTERISTICS: These soils are usually moist and are dry between depths of 4 to 12 inches for less than 45 consecutive days during the summer. The mean annual soil temperature ranges from 50 to 55 degrees F. The solum ranges from 40 to more than 60 inches thick over firm, fractured, partially consolidated siltstone and shale. Weathered, fine siltstone or shale fragments are scattered throughout the solum and increase to 15 to 20 percent in the B3t horizon.
The A horizon has hue of 10YR to 5YR, value of 3 or 4 moist, 5 or 6 dry, and chroma of 2 to 4 moist and dry. It has moderate or strong subangular blocky or granular structure.
The B horizon commonly has hue of 5YR but ranges to 7.5YR in some part, value of 4 or 5 moist, 5 or 6 dry, and chroma of 4 to 6 moist and dry. It has moderate fine to coarse subangular blocky structure. This horizon is medium to strongly acid. The Bt horizon is silty clay loam to silty clay and averages 35 to 50 percent clay. Clay films range from few, thin to common, moderately thick on peds and in pores.
The C horizon consists of partially weathered, fractured siltstone or shale with moderately fine-textured material filling the fractures.
COMPETING SERIES: These are the Agnos, Boden, Braddock, Gassville, Groseclose, Howell, Monmouth, Muse, Sequoia, Trappist and Unison series in the same family, and the Apt, Edson, Honeygrove, Olyic, Orford, and Peavine soils. All competing soils in this family formed in southern and eastern states. Agnos and Gassville soils have more than 60 percent clay in the B2t horizons, and Gassville soils have a paralithic contact at depths of 30 to 40 inches. Boden soils have less than 20 percent silt in the B2t horizon. Braddock soils have more than 20 percent sand in the B2t horizon. Groseclose and Unison soils have sola less than 40 inches thick. Howell and Monmouth soils have hue of 2.5Y or 5Y in the lower part of the argillic horizons, and Monmouth soils also have more than 40 percent sand in the argillic horizon. Muse soils are mottled in the lower part of the argillic horizon. Sequoia soils have a paralithic contact at depth of 20 to 40 inches. Trappist soils have a lithic contact at depths of 20 to 40 inches. All of the other soils have high organic matter and have 0.9 percent or more organic carbon in the upper 6 inches of the argillic horizon. Apt, Honeygrove, Olyic, Orford, and Peavine soils have moist value of 3 or less to 10 inches or more. Also, Peavine soils are 20 to 40 inches deep to a paralithic contact.
GEOGRAPHIC SETTING: Pervina soils are on gently rolling to very steep uplands at elevations of 400 to 1,500 feet. The soils formed in fine-textured colluvium and residuum weathered from siltstone and shale. The winters are cool and moist and the summers are dry and warm. Mean annual precipitation is 6 to 80 inches. The mean January temperature is 37 degrees F; mean July temperature is 65 degrees F; average annual temperature is 48 to 52 degrees F. The frost-free period is about 145 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Melby and Tolke soils and the competing Olyic soils. Melby and Tolke soils lack argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Used mostly for timber production. Less than one-half of these soils have been cleared for cultivation. Orchards, small grains, hay and pasture are the principal crops. Native vegetation is Douglas-fir, red alder, big-leaf maple, some western red cedar and western hemlock, vine maple, bracken and swordfern, salal, red huckleberry, and hazelbrush.
DISTRIBUTION AND EXTENT: On low hills along the western side of the Tualatin Valley and the Coast Range footslopes in northwestern Oregon. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Washington County, Oregon, 1975.