LOCATION AIKEN CAEstablished Series
TAXONOMIC CLASS: Fine, parasesquic, mesic Xeric Haplohumults
TYPICAL PEDON: Aiken loam, forested. (Colors are for dry soil unless otherwise stated.)
0--1/2 inch to 0; partially decomposed forest litter.
A--0 to 9 inches; dark brown (7.5YR 4/4) loam, dark brown (7.5YR 3/4) moist; strong very fine and fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine, few medium and coarse roots; many very fine and fine, few medium and coarse roots; many very fine, fine, and medium, and few coarse pores; many very fine and few fine concretions; medium acid (pH 6.0); gradual smooth boundary. (8 to 18 inches thick)
AB--9 to 20 inches; reddish brown (5YR 4/4) loam, dark reddish brown (5YR 3/3) moist; moderate very fine and fine granular structure; soft, very friable, nonsticky and slightly plastic; many very fine and fine, few medium and coarse roots; many very fine, fine and medium, and few coarse pores; many very fine and few fine concretions; medium acid (pH 6.0); gradual smooth boundary. (6 to 15 inches thick)
BAt1--20 to 29 inches; yellowish red (5YR 5/6) clay loam, yellowish red (5YR 3/6) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; many very fine, fine and medium, few coarse roots; many very fine, fine and medium pores; continuous thin clay films, mainly in pores; common very fine and few fine concretions; medium acid (pH 6.0); gradual smooth boundary. (7 to 10 inches thick)
BAt2--29 to 40 inches; yellowish red (5YR 5/6) heavy clay loam, dark red (2.5YR 3/6) moist; massive; slightly hard, firm, slightly sticky and plastic; common very fine and fine, few medium and coarse roots; many very fine, fine, and medium pores; continuous thin clay films in pores and bridges; common very fine and few fine concretions; medium acid (pH 6.0); gradual smooth boundary. (3 to 10 inches thick)
Bt1--40 to 54 inches; yellowish red (5YR 5/6) clay, dark red (2.5YR 3/6) moist; massive; hard, firm, sticky and plastic; few very fine to coarse roots; many very fine and few fine pores; continuous moderately thick clay films in pores and bridges; common very fine concretions; medium acid (pH 6.0); diffuse smooth boundary. (10 to 18 inches thick)
Bt2--54 to 69 inches; yellowish red (5YR 5/6) clay, dark red (2.5YR 3/6) moist; massive; hard, firm, sticky and plastic; few very fine to coarse roots; many very fine and few fine pores; continuous moderately thick clay films in pores and bridges; common very fine concretions; strongly acid (pH 5.5); clear irregular boundary. (10 to 15 inches thick)
Bt3--69 to 92 inches; light brown (7.5YR 6/4) clay, reddish brown (5YR 4/4) moist; massive; hard, firm, slightly sticky and plastic; few roots; common very fine and few fine pores; continuous thin clay films in pores and bridges; very strongly acid (pH 5.0); gradual smooth boundary. (13 to 25 inches thick)
BCt--92 to 100 inches; light brown (7.5YR 6/4) clay loam, reddish brown (5YR 4/4) moist; massive, hard, very firm, slightly sticky and slightly plastic; few roots; common very fine and fine pores; few thin clay films in pores and along cleavage planes; very strongly acid (pH 4.8).
TYPE LOCATION: Amador County, California; 13 miles east of Fiddletown, 2 miles west of Fiddletown Road, 0.12 miles northeast of center of sec. 34, T. 8 N., R. 12 E. 38 degrees North latitude, 30 minutes, 17 seconds, 120 degrees West longitude, 32 minutes, 44 seconds.
RANGE IN CHARACTERISTICS: Thickness of solum and depth to weathered rock is 60 to 140 inches. The mean annual soil temperature is about 47 degrees to 55 degrees F. The soils between depths of about 4 and 12 inches, are usually moist but are dry from June until October. Common 1-2 mm concretions are present throughout the upper 60 inches. Some pedons have up to 25 percent rock fragments, with the larger amounts in the uppermost and lowermost horizons. Iron oxide plus gibbsite to clay ratio is greater than 0.2 Also kaolinite averages less than 40 percent in the control section. Depth to a clay layer ranges from about 35 to 45 inches.
The A horizon has dry color of 7.5YR 3/2, 4/2, 3/4, 4/4, 5/2, 5/4; 5YR , 3/2, 3/3, 3/4, 4/3, 4/4, 4/6, 5/3, 5/4, 5/6 and 5/8. Moist colors are 2.5YR 3/4, 3/6; 5YR 2.5/2, 3/2,3/3, 3/4; 7.5YR 3/2, 3/4, 4/2, or 4/4. Organic matter of the upper 10 inches averages 4 to 6 percent and remains above 3 percent to a depth of 20 inches. It has moderate or strong granular structure. It is neutral to medium acid.
The BAt and Bt horizons have dry colors of 5YR 4/6, 5/4, 5/6, 6/4, 4/8, 5/8; 2.5YR 3/6, 4/6, 4/8, 5/6 or 5/8. Moist colors are 2.5YR 3/6, 4/4, 4/6, 4/8, 5/4, 5/6, 5/8; 5YR 3/6, 4/3, 4/4, 4/6, 5/3, 5/4, 5/6 or 5/8 in the upper part. Also included in the lower part are colors of 7.5YR 4/6, 5/4, 5/6, 6/4; 5YR 3/4, 4/4, 4/6, 5/4 or 5/6 and 7.5YR 4/2, 4/4, 5/2 or 5/4 moist. The upper 20 inches of the argillic horizon is clay loam and has an average clay content of 35 to 40 percent. The lower part of the argillic averages from 35 to 50 percent clay. It is medium acid to very strongly acid. Base saturation ranges from 10 to 35 percent throughout the argillic horizon.
COMPETING SERIES: This is the Sites series in the same family and the Hesson, Horseshoe, Prather and Salkum series in other families. Sites soils have a clay layer within 35 inches of the soil surface. In addition they have argillic horizons in which the clay content decreases by more than 20 percent above a depth of 60 inches or the argillic horizon is not 60 inches thick. Hesson, Prather, Salkum soils have kaolinitic mineralogy. Horseshoe soils are fine-loamy.
GEOGRAPHIC SETTING: These soils are on broad gently sloping tabular ridges with moderately steep to steep sideslopes of 2 to 70 percent at elevations of about 1,200 to 5,000 feet. They formed in material weathered from basic volcanic rocks, principally tuff breccia. The climate has warm dry summers and cool moist winters. Mean annual precipitation is 30 to 85 inches, some of which is snow. Mean annual temperature is about 50 degrees to 60 degrees F; average January temperature about 40 degrees F; and average July temperature about 72 degrees F. Freeze-free season is about 130 to 225 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Horseshoe soils and the Holland, Josephine and McCarthy soils. Holland soils have a base saturation of 50 to 75 percent in all or some parts of the argillic horizon. Josephine soils have a base saturation of 35 to 50 percent in the argillic horizon. McCarthy soils lack argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Used mainly for timber, with some areas cleared and used for deciduous fruit orchards. Native vegetation is typically coniferous forest with associated hardwoods. Principal trees are ponderosa pine, Douglas-fir, incense-cedar, white fir, black oak, and madrone.
DISTRIBUTION AND EXTENT: The Sierra Nevada and Cascade mountains of California and Oregon. The series is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Marshfield Area, Oregon 1909.
REMARKS: The Aiken soils formerly were classified as clayey, kaolinitic, mesic Xeric Haplohumults. A review of existing data from both the National Soil Survey Laboratory and the University of California as well as soil survey reports where this soil has been mapped, indicate some variability in the concept. Some areas have low bulk density in the upper part of the soil, have kaolinitic mineralogy, fine-loamy particle-size control section and base saturation of more than 35 percent at depths of 30 to 70 inches. Until further investigations can be made on areas mapped in the past, this soil will remain as a clayey, oxidic, mesic Xeric Haplohumult.
ADDITIONAL DATA: NSSL Pedons S59CA-005-012 (the series type location which meets Palehumult criteria). The OC is greater than .90 in 17 cm of upper argillic. Pedon S59CA-005-011 sampled as Aiken which is a Haploxeralf. Both pedons are in fine, parasesquic, mesic families.
Series needs to be reclassified. Poor dispersion in surface horizons suggests possible andic subgroup. Analyses of Aiken pedons in El Dorado County by Dr. Janis Boettinger, USU, were andic subgroup. Slope range needs to be narrowed.