LOCATION HELMICK OREstablished Series
TAXONOMIC CLASS: Very-fine, mixed, superactive, mesic Vertic Haploxerepts
TYPICAL PEDON: Helmick silt loam, cultivated. (Colors are for moist soil unless otherwise noted.)
A--0 to 5 inches; dark brown (10YR 3/3) silt loam, pale brown (10YR 6/3) dry; strong fine and medium granular and strong fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine pores; many very fine and fine roots; moderately acid (pH 5.8); clear wavy boundary. (3 to 8 inches thick)
Bw1--5 to 10 inches; brown (10YR 4/3) silty clay loam, pale brown (10YR 6/3) dry; moderate fine and medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many very fine and fine pores; many very fine roots; moderately acid (pH 5.6); clear wavy boundary. (3 to 12 inches thick)
Bw2--10 to 16 inches; brown (10YR 4/3) silty clay loam, pale brown (10YR 6/3) dry; moderate medium and coarse subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many very fine pores; many very fine roots; strongly acid (pH 5.4); abrupt wavy boundary. (5 to 9 inches thick)
2BC--16 to 22 inches; grayish brown (10YR 5/2) clay, light brownish gray (10YR 6/2) dry; weak medium prismatic structure; extremely hard, very firm, very sticky and very plastic; common very fine pores; many very fine and fine roots; few small pressure faces; many medium distinct yellowish brown (10YR 5/6) masses of iron accumulation; strongly acid (pH 5.2); clear wavy boundary. (4 to 9 inches thick)
2C1--22 to 28 inches; gray (10YR 5/1) clay; gray (10YR 6/1) dry; massive; extremely hard, very firm, very sticky and very plastic; common very fine pores; common very fine roots; few small pressure faces; common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation and common medium faint very dark gray (10YR 3/1) iron depletions and concentrations; strongly acid (pH 5.2); clear wavy boundary. (5 to 10 inches thick)
2C2--28 to 36 inches; grayish brown (10YR 5/2) clay, light gray (10YR 7/2) dry; massive; extremely hard, very firm, very sticky and very plastic; common very fine pores; few very fine roots; few small pressure faces; common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation and common medium faint gray (10YR 5/1) iron depletions; strongly acid (pH 5.2); clear wavy boundary. (6 to 10 inches thick)
2C3--36 to 50 inches; light brownish gray (10YR 6/2) clay, light gray (10YR 7/2) dry; massive; extremely hard, very firm, very sticky and very plastic; few very fine pores; few very fine roots; few small pressure faces; common fine distinct yellowish brown (10YR 5/6) masses of iron accumulation and few medium faint gray (10YR 5/1) iron depletions; strongly acid (pH 5.2); clear wavy boundary. (10 to 16 inches thick)
2C4--50 to 62 inches; variegated light brownish gray (2.5Y 6/2) and strong brown (7.5YR 5/6) clay; massive; extremely hard, very firm, very sticky and very plastic; few very fine pores; very strongly acid (pH 5.0).
TYPE LOCATION: Polk County, Oregon; 2.5 miles south of the community of Independence; about 2,800 feet east and 2,200 feet north of the SW corner of section 5, T.9S., R.4W.; Willamette Meridian; Monmouth, Oregon USGS 7.5 minute topographic quadrangle. Latitude 44 degrees, 48 minutes, 58 seconds N. and Longitude 123 degrees, 12 minutes, 13 seconds W.; NAD 27.
RANGE IN CHARACTERISTICS: The soils are usually moist, but are dry for 45 to 60 consecutive days between depths of 4 and 12 inches during the summer. The mean annual soil temperature ranges from 53 degrees 55 degrees F. Depth to sedimentary bedrock is greater than 60 inches. Thickness of the solum above the nonconforming 2BC or 2C horizon ranges from 12 to 28 inches. The particle-size control section averages 60 to 65 percent clay, 0 to 5 percent rock fragments and 0 to 10 percent pararock fragments. Redoximorphic features with chroma of 2 or less are within 30 inches of the surface.
The A horizon has hue of 10YR or 7.5YR, value of 3 or 4 moist, 5 or 6 dry and chroma of 2 or 3 moist and dry. Texture is silt loam with 18 to 27 percent clay. It has 0 to 5 percent gravel and 0 to 10 percent paragravel. Reaction is moderately acid.
The Bw horizon has hue of 10YR, value of 4 or 5 moist, 5 or 6 dry and chroma of 3 or 4 moist and dry. The upper part is silty clay loam with 27 to 35 percent clay. The lower part is silty clay loam or silty clay with 30 to 45 percent clay. It has 0 to 5 percent gravel and 0 to 10 percent paragravel. Reaction is strongly acid or moderately acid.
The 2BC or 2C horizons have hue of 10YR or 2.5Y, value of 5 or 6 moist, 6 or 7 dry and chroma of 1 to 4 moist and dry. Texture of the fine-earth fraction is clay. It has 60 to 70 percent clay, 0 to 5 percent gravel, and 0 to 15 percent paragravel. The lower part of the 2C horizon has 0 to 35 percent paragravel. Reaction is very strongly acid or strongly acid.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Helmick soils are on low rolling hills that merge into the main valley terraces. Elevation is 250 to 400 feet. Slopes are 3 to 50 percent. The soils formed in silty glaciolacustrine deposits and colluvium over clayey residuum derived from sandstone and siltstone bedrock. The climate is characterized by warm, wet winters and hot, dry summers. The average January temperature is 39 degrees F. and average July temperature is 67 degrees F. The mean annual temperature is 50 to 54 degrees F. The mean annual precipitation ranges from 40 to 60 inches. The frost-free season averages 165 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bellpine, Dupee, Hazelair, Santiam, Steiwer, Suver and Willakenzie soils. Bellpine, Hazelair, Steiwer and Willakenzie soils are 20 to 40 inches to a paralithic contact and occur on more linear or convex parts of the hillslope. Dupee, Santiam and Suver soils have an argillic horizon with less than 60 percent clay and occur on fans or foot slopes.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; very slow permeability. A perched water table is at its uppermost limit from November to April.
USE AND VEGETATION: Most of these soils have been cleared for cultivation. Cereal grains, grass seed crops, hay and pasture are the principal crops. Natural vegetation is annual and perennial grasses and forbs, rose, snowberry, poison oak and Oregon white oak.
DISTRIBUTION AND EXTENT: These soils are on low foothills adjacent to the Willamette Valley, Oregon; MLRA 2. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Polk County, Oregon, 1977.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Ochric epipedon - the zone from the soil surface to a depth of 5 inches (A horizon)
Cambic horizon - the zone from 5 to 16 inches (Bw1 and Bw2 horizons)
Vertic feature - the zone from 0 to 40 inches having an estimated linear extensibility of 6.0 cm or more.