LOCATION PHILOMATH OREstablished Series
TAXONOMIC CLASS: Clayey, smectitic, mesic, shallow Vertic Haploxerolls
TYPICAL PEDON: Philomath silty clay, pasture. (Colors are for moist soil unless otherwise noted.)
A1--0 to 4 inches; very dark brown (10YR 2/2) silty clay, very dark grayish brown (10YR 3/2) dry; moderate medium subangular blocky structure; hard, firm, very sticky and very plastic; many very fine roots; many fine tubular pores; slightly acid (pH 6.4); clear wavy boundary. (2 to 6 inches thick)
A2--4 to 13 inches; very dark brown (10YR 2/2) clay, very dark grayish brown (10YR 3/2) dry; moderate medium subangular blocky structure; very hard, very firm, very sticky and very plastic; common fine roots; common very fine tubular pores; 5 percent paragravel; neutral (pH 6.6); clear wavy boundary. (3 to 9 inches thick)
A3--13 to 19 inches; very dark grayish brown (10YR 3/2) clay, dark grayish brown (10YR 4/2) dry; moderate medium subangular blocky structure; very hard, very firm, very sticky and very plastic; few fine roots; common very fine tubular pores; 5 percent paragravel; neutral (pH 6.6); abrupt wavy boundary. (0 to 9 inches thick)
2Cr--19 inches; dark yellowish brown (10YR 4/6) weathered basalt
TYPE LOCATION: Linn County, Oregon; NE1/4 SW1/4 NW1/4 of section 16, T.12S, R.1W. Willamette Meridian; Onehorse Slough, Oregon USGS 7.5 minute topographic quadrangle. Latitude 44 degrees, 31 minutes, 45 seconds N. and Longitude 122 degrees, 49 minutes, 13 seconds W.; NAD 27.
RANGE IN CHARACTERISTICS: These soils are usually moist but are dry between depths of 4 and 12 inches for 60 to 80 consecutive following the summer solstice. The mean annual soil temperature ranges from 50 to 56 degrees F. The depth to a paralithic contact of weakly to moderately cemented igneous rock is 12 to 20 inches. The mollic epipedon is 12 to 20 inches thick. The pscs averages 40 to 60 percent clay, 0 to 35 percent rock fragments and 0 to 5 percent pararock fragments. The profile cracks throughout its depth during the summer.
The A1 horizon has value of 2 or 3 moist, 2 to 4 dry and chroma of 1 or 2 moist or dry. Texture is silty clay loam, silty clay or cobbly silty clay with 30 to 55 percent clay. It has 0 to 15 percent gravel and 0 to 20 percent cobbles. Reaction is moderately acid or slightly acid.
The A2 horizon has hue of 10YR or 7.5YR, value of 2 or 3 moist, 2 to 4 dry and chroma of 1 or 2 moist or dry. Texture is silty clay loam, clay, silty clay, cobbly silty clay or cobbly clay with 35 to 55 percent clay. It has 0 to 15 percent gravel, 0 to 20 percent cobbles and 0 to 5 percent paragravel. Reaction is moderately acid to neutral.
The A3 horizon, when present, has hue of 10YR or 7.5YR, value of 2 or 3 moist, 2 to 4 dry and chroma of 1 or 2 moist or dry. Texture is silty clay, clay, cobbly silty clay or cobbly clay with 40 to 60 percent clay. It has 0 to 20 percent gravel, 0 to 20 percent cobbles and 0 to 10 percent paragravel. Reaction is moderately acid to neutral.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: The Philomath soils are on convex hills at elevations of 300 to 2,000 feet. These soils formed in fine textured residuum or colluvium weathered from basic igneous rock. Slopes are 3 to 70 percent. The climate is characterized by warm, wet winters and hot, dry summers. The mean annual precipitation is 30 to 60 inches. The mean annual temperature is 49 to 55 degrees F. The mean January temperature is 38 to 40 degrees F. and the mean July temperature is 64 to 68 degrees F. The frost-free season is 160 to 235 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dixonville, Gellatly, Hazelair, Ritner, Witham, and Witzel soils. Dixonville, Gellatly, Hazelair, Ritner and Witham soils are greater than 20 inches to bedrock. Dixonville soils occur on linear or convex parts of the hillslope. Gellatly soils occur on linear or concave parts of the hillslope. Hazelair soils occur on the concave parts of the hillslope. Ritner soils occur on convex parts of the hillslope at higher elevations. Witham soils occur on fans, footslopes, or toeslopes. Withzel soils are skeletal and occur on convex parts of the hillslope.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: About 80 percent of this soil is in natural and unimproved pasture. It is also used for water supply and for wildlife habitat. The native vegetation is grass, baldhip rose, and Pacific poison-oak with a few patches of Oregon white oak.
DISTRIBUTION AND EXTENT: Foothills of the Coast Range and the Cascade Mountains in Western Oregon; MLRA 2, 5. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Benton County (Benton Area), Oregon, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Mollic epipedon - the zone from the soil surface to 19 inches (A1, A2, and A3 horizons)
Vertic feature - the zone from 0 to 19 inches having an assumed COLE of greater than 6.0.
Particle-size control section - the zone from 10 to 19 inches.
ADDITIONAL DATA: Characterization data for 4 pedons with Soil Survey Laboratory soil survey sample numbers S00OR-003-004, S00OR-039-001, S00OR-039-002, and S00OR-043-003.