LOCATION YONCALLA OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aquic Palexerolls
TYPICAL PEDON: Yoncalla silty clay loam - pasture, on a 15 percent slope at an elevation of 840 feet. (Colors are for moist soil unless otherwise stated.)
A--0 to 8 inches; very dark grayish brown (10YR 3/2) silty clay loam, dark brown (10YR 4/3) dry; moderate medium and coarse subangular blocky structure parting to moderate medium and coarse granular; very hard, firm, sticky and plastic; many very fine and fine, and common medium roots; many very fine and fine irregular pores; 5 percent gravel; strongly acid (pH 5.4); gradual smooth boundary. (6 to 11 inches thick)
Bw--8 to 15 inches; dark brown (10YR 3/3) silty clay loam, brown (10YR 5/3) dry; moderate medium and coarse subangular blocky structure; very hard, firm, sticky and very plastic; many very fine and fine, and few medium roots; many very fine and fine irregular and tubular pores; 5 percent gravel; strongly acid (pH 5.4); abrupt smooth boundary. (3 to 14 inches thick)
2Bt1--15 to 31 inches; brown (10YR 4/3) clay, brown (10YR 5/3) dry; moderate coarse angular blocky structure; extremely hard, very firm, very sticky and very plastic; few fine roots; few very fine and fine tubular pores; common distinct clay films on faces of peds and in pores; 10 percent gravel; 5 percent (1-2mm) manganese concretions; common fine distinct gray (10YR 5/1) iron depletions and common fine distinct strong brown (7.5YR 5/6) masses of iron accumulations; moderately acid (pH 6.0); gradual smooth boundary.
2Bt2--31 to 49 inches; brown (10YR 4/3) clay, brown (10YR 5/3) dry; moderate coarse angular blocky structure; extremely hard, very firm, very sticky and very plastic; few very fine and fine tubular pores; many prominent clay films on faces of peds and in pores; 10 percent gravel and 5 percent soft fragments; common fine faint gray (10YR 5/1) iron depletions and common fine faint strong brown (7.5YR 5/6) masses of iron accumulations; slightly acid (pH 6.2); abrupt smooth boundary.
2Bt3--49 to 60 inches; brown (10YR 4/3) gravelly clay, brown (10YR 5/3) dry; weak medium subangular blocky structure; extremely hard, firm, sticky and plastic; few very fine tubular pores; common distinct clay films on faces of peds and in pores; 30 percent gravel and 15 percent soft fragments; few fine distinct dark gray (10YR 4/1) iron depletions and few faint strong brown (7.5YR 5/6) masses of iron accumulations; slightly acid (pH 6.2). (Combined thickness of the 2Bt horizon is 36 to 48 inches)
TYPE LOCATION: Douglas County, Oregon, about 3 miles south of Yoncalla, about 1400 feet west and 1,815 south of the northeast corner of section 22, T.23S., R.5W. (Latitude 43 degrees, 33 minutes, 27 seconds N, Longitude 123 degrees, 16 minutes, 17 seconds W)
RANGE IN CHARACTERISTICS: The soil is usually moist but it is dry within all parts of the moisture control section for 45 to 60 consecutive days following the summer solstice. The mean annual soil temperature is 40 to 52 degrees F. Depth to bedrock is 60 inches or more. The mollic epipedon and depth to the 2Bt horizon is 12 to 20 inches. The particle-size control section has 50 to 60 percent clay. The clay increase between the Bw and 2Bt horizon is 15 to 20 percent absolute.
The A and Bw horizons have value of 2 or 3 moist, 4 or 5 dry, and chroma of 2 or 3 dry. It has 0 to 5 percent gravel. It is very strongly or strongly acid.
The 2Bt horizon has hue of 2.5Y or 10YR, value of 4 or 5 moist, 4 to 6 dry, and chroma of 1 to 4 moist and dry. It has 0 to 15 percent gravel in the upper part and up to 30 percent gravel in the lower part. It is clay or gravelly clay. It is strongly to slightly acid.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Yoncalla soils are on foot slopes, toe slopes, and alluvial fans. The soils formed in colluvium from extrusive igneous rock. Slopes are 2 to 30 percent. Elevations are 350 to 2,000 feet. The climate is characterized by warm, wet winters and hot, dry summers. The mean annual precipitation is 30 to 55 inches. The mean annual temperature is 50 to 55 degrees F. The frost-free period is 160 to 235 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Climax, Curtin, Dixonville, Edenbower, Jory, Nekia, and Philomath soils. Climax soils are on concave side slopes and drainageways and 20 to 40 inches to bedrock. Curtin soils are on footslopes and alluvial fans and have intersecting slickensides. Dixonville and Nekia soils are on convex side slopes and are 20 to 40 inches to bedrock. Edenbower soils are on convex side slopes and are 4 to 10 inches to bedrock. Jory soils are on convex side slopes are well drained and have a hue of 2.5YR or 5YR in the B horizon. Philomath soils are on convex side slopes and are 12 to 20 inches to bedrock.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; very slow permeability; there is an apparent water table at 0.5 to 2.5 feet from December to April.
USE AND VEGETATION: The soils are used for hay and pasture and small grain. Native vegetation is Oregon white oak, Pacific poison oak, rose, rushes, sedges, common snowberry, and California danthonia.
DISTRIBUTION AND EXTENT: Southwestern Oregon, MLRA 5. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Douglas County, Oregon; 1994.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 15 inches (A and Bw horizons)
Argillic horizon - from 15 to 60 inches (Bt1, Bt2, and Bt3 horizons)
Pale feature - there is an increase of at least 15 percent clay between the Bw and 2Bt horizon.
Particle-size control section - from 15 to 35 inches.
Aquic feature - redox depletions with chroma of 2 or less from 15 to 30 inches.