LOCATION VERBOORT OREstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Xerertic Argialbolls
TYPICAL PEDON: Verboort silty clay loam, cultivated. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; very dark brown (10YR 2/2) silty clay loam, grayish brown (10YR 5/2) dry; strong fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; many very fine roots; many very fine pores; moderately acid (pH 5.8); abrupt smooth boundary. (6 to 10 inches thick)
A--8 to 12 inches; very dark brown (10YR 2/2) silty clay loam, grayish brown (10YR 5/2) dry; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine roots; common very fine pores; moderately acid (pH 5.8); clear smooth boundary. (0 to 7 inches thick)
E--12 to 19 inches; very dark gray (10YR 3/1) silty clay loam, gray (10YR 6/1) dry; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine roots; common very fine pores; many fine prominent dark reddish brown (5YR 3/2) masses of iron accumulation; moderately acid (pH 6.0); abrupt smooth boundary. (6 to 9 inches thick)
2Bt--19 to 28 inches; very dark gray (N 3/ ) clay, grayish brown (2.5Y 5/2) dry; weak medium prismatic and weak medium subangular blocky structure; very hard, very firm, very sticky and very plastic; common very fine roots between prisms, and very few fine roots within the prisms; few very fine pores; many faint clay films on prism faces and in pores and channels; some pressure faces on larger prisms; slightly acid (pH 6.4); abrupt smooth boundary. (6 to 30 inches thick)
2BCt--28 to 33 inches; dark grayish brown (2.5Y 4/2) silty clay, light brownish gray (2.5Y 6/2) dry; weak fine prismatic and weak fine subangular blocky structure; very hard, very firm, moderately sticky and very plastic; few very fine roots between prisms and ped surfaces; common very fine pores; many faint very dark gray (N 3/ moist) clay films on many surfaces; neutral (pH 6.6) gradual smooth boundary. (0 to 15 inches thick)
2C--33 to 60 inches; dark grayish brown (2.5Y 4/2) silty clay loam, light gray (2.5Y 7/2) dry; massive; firm, moderately sticky and moderately plastic; few very fine roots; few fine and medium pores with very dark gray (N 3/ ) films; many medium prominent brown (7.5YR 4/2) masses of iron accumulation; neutral (pH 6.6).
TYPE LOCATION: Washington County, Oregon; 20 feet west of Helvetia Road; about 2,700 feet wet and 2,000 feet south of the NE corner of section 10, T. 1 N., R. 2 W., W.M. Hillsboro, Oregon USGS 7.5 minute quad; Latitude 45 degrees, 35 minutes, 07 seconds N.; Longitude 122 degrees, 55 minutes, 10 seconds W. NAD 27.
RANGE IN CHARACTERISTICS: The profiles are usually saturated with water during many months of the year unless drained. The mean annual soil temperature ranges from 52 to 55 degrees F. The soil is deeper than 60 inches to bedrock. Depth to aquic conditions with chroma of 2 or less is 0 to 10 inches. Depth to the 2Bt horizon is 16 to 26 inches. The mollic epipedon is 10 to 17 inches thick.
The A horizon has value of 2 or 3 moist and chroma of 1 or 2 moist and dry. It has 27 to 35 percent clay. A few dark reddish brown masses of iron accumulation are in some pedons. Reaction is moderately acid or strongly acid.
The E horizon has hue of 10YR or neutral, value of 3 or 4 moist and chroma of 1 or less. Texture is silt loam or silty clay loam with 25 to 35 percent clay. Redoximorphic features are faint to prominent. Reaction is moderately acid or strongly acid.
The 2Bt horizon has hue of 2.5Y, 5Y, or neutral, value of 3 or 4 moist and chroma of 2 or less. It has faint to prominent iron depletions and concentrations. Texture is clay or silty clay with 40 to 50 percent clay. Reaction is moderately acid to neutral.
The 2BCt horizon has hue of 2.5Y or 5Y, value of 4 or 5 moist, 6 or 7 dry and chroma of 2 or 3 moist and dry. Texture is clay, silty clay or silty clay loam with 35 to 50 percent clay. Reaction is moderately acid to neutral.
The 2C horizon has hue of 2.5Y or 5Y and value of 4 or 5 moist, 6 or 7 dry. Texture is silt loam or silty clay loam with 25 to 35 percent clay. Reaction is slightly acid or neutral.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Verboort soils are on narrow low stream terraces and have slopes of 0 to 3 percent. Elevations are 150 to 300 feet. The soils formed in stratified moderately fine and fine textured alluvium of mixed origin. The soils formed under a cool, moist winter and a warm dry summer climate. The average July temperature is 65 to 67 degrees F. and the average January temperature is 39 to 40 degrees F. The average annual temperature is 51 to 54 degrees F. The average annual precipitation is 40 to 50 inches. The frost-free period is 165 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aloha, Amity, Cove, Dayton, Waldo, Wapato, Willamette and Woodburn soils. Aloha and Amity soils have aquic soil conditions with chroma of 2 or less at a depth of 10 to 20 inches and are fine-silty. They occur on higher terraces. Cove and Waldo soils do not have an abrupt textural change and occur on flood plains. Wapato soils are fine-silty and occur on flood plains. Dayton soils have an ochric epipedon and occur in depressions on terraces. Willamette and Woodburn soils are fine-silty and occur on higher terraces.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; very slow permeability. Verboort soils are subject to frequent flooding for brief periods from December to April. A perched water table is at its uppermost limit from November to April. This soil also has an apparent water table.
USE AND VEGETATION: Most of these soils are cultivated. Spring grain, hay and pasture are the principal crops and vegetable crops are grown in some areas. Native vegetation is mainly ash, willow, sedges and grass.
DISTRIBUTION AND EXTENT: Verboort soils are distributed throughout the Willamette Valley, Oregon; MLRA 2. The soil is inextensive.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Washington County, Oregon, 1975.
REMARKS: Diagnostic horizons and features include:
Mollic epipedon - the zone from 0 to 12 inches (Ap and A horizons).
Albic horizon - the zone from 12 to 19 inches (E horizon).
Argillic horizon - the zone from 19 to 33 inches (2Bt and 2BCt horizon).
Albolls feature - an albic horizon that has concretions or masses of iron accumulation.
Vertic feature - an estimated COLE of 7.2 cm from 0 to 40 inches.
Classification revised 2/2000 from Typic Argialbolls to Xerertic Argialbolls based on estimate of COLE and addition of Vertic Subgroup to Soil Taxonomy.
Further investigation is needed as to the potential smectitic mineralogy origin.