LOCATION YOKAYO CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Palexeralfs
TYPICAL PEDON: Yokayo sandy loam - on an east facing convex slope of 30 percent under scattered blue oak, wild oats, and dogtail at 720 feet elevation. (Colors are for dry soil unless otherwise stated. When described September 13, 1978, the soil was moist throughout).
A--0 to 8 inches; light brownish gray (10YR 6/2) sandy loam, dark grayish brown (10YR 4/2) moist; weak fine through coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; common very fine and fine tubular pores; 5 percent 2 to 75 mm pebbles and 5 percent 75 to 150 mm cobbles; medium acid (pH 6.0); abrupt wavy boundary. (8 to 20 inches thick).
Bt1--8 to 18 inches; light yellowish brown (10YR 6/4) clay, light olive brown (2.5Y 5/4) moist; moderate coarse prismatic structure parting to strong medium and coarse angular blocky; very hard, very firm, very sticky and very plastic; common very fine and few fine roots; few very fine tubular pores; common thin clay films on peds; 5 percent 2 to 75 mm pebbles; medium acid (pH 6.0); clear wavy boundary. (8 to 20 inches thick).
Bt2--18 to 32 inches; light yellowish brown (10YR 6/4) clay loam, variegated dark yellowish brown and brown (10YR 4/4, 10YR 4/3) moist; moderate fine through coarse subangular blocky structure; very hard, firm, sticky and plastic, few very fine through coarse roots; few very fine tubular pores; common thin clay films on peds; 5 percent 2 to 75 mm pebbles; medium acid (pH 6.0); clear wavy boundary. (6 to 18 inches thick)
Bt3--32 to 48 inches; pale yellow (2.5Y 7/4) clay loam, light olive brown (2.5Y 5/4) moist; weak medium subangular blocky structure; very hard, very firm, sticky and plastic; few very fine through coarse roots; few very fine tubular pores; common moderately thick clay films on peds; 10 percent 2 to 75 mm pebbles; slightly acid (pH 6.2); clear wavy boundary. (6 to 16 inches thick)
C--48 to 60 inches; pale yellow (2.5Y 7/4) loam, light olive brown (2.5Y 5/4) moist; massive; hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine tubular pores; 10 percent 2 to 75 mm pebbles; slightly acid (pH 6.5).
TYPE LOCATION: Mendocino County, California, on an east-facing slope 1,500 feet northeast of Yokayo Ranch near Ukiah, California; 300 feet north and 4,200 feet east of the southwest corner of section 31, T.16 N., R.12 W., MDDB&M.
RANGE IN CHARACTERISTICS: Thickness of the solum ranges from 30 to 50 inches and depth to semiconsolidated sediments is greater than 60 inches. The soil is dry between a depth of 8 to 22 inches from June to October, in most years, and usually moist the rest of the year. The mean annual soil temperature is 59 degrees to 61 degrees F. The clay increase from the A horizon to the Bt horizon ranges from 15 to 20 percent in a vertical distance of less than 1 inch or 20 percent or more increase within 3 inches. Base saturation is greater than 75 percent throughout the Bt horizon.
The A horizon is 10YR 6/2, 6/3, or 6/4. Moist colors are 10YR 3/2, 3/3, 4/2, 4/3, 5/4, or 5/6. It is sandy loam with 12 to 20 percent clay, 2 to 10 percent gravel and 0 to 5 percent cobbles. It is medium acid or slightly acid.
The Bt horizon is 10YR 7/3, 7/4, 6/3, 6/4, 6/6; 2.5Y 7/4 or 6/4. Some pedons have variegated colors. Moist colors are variegated 10YR 4/2, 4/3, 4/4, 5/4, 5/6, 6/3; 2.5Y 4/4, 5/4, or 5/6. It is clay loam or clay with 35 to 50 percent clay and 0 to 12 percent gravel. It is medium acid to neutral.
The C horizon is 2.5Y 7/2, 7/4; 10YR 6/3, 6/4, 6/6, 7/2, 7/4, or 7/6. Moist colors are 10YR 4/2, 4/3, 5/4, 5/6, or 6/6; 2.5Y 5/4, 5/6, or 7/4. Some pedons have variegated colors. It is loam, sandy clay loam or clay loam with 22 to 35 percent clay and 0 to 12 percent gravel. It is slightly acid or neutral.
COMPETING SERIES: These are the Cometa, Corning, Hytop, Millsap and Orognen series in the same family and the Hillgate and San Ysidro series in other families. Cometa and Orognen soil have 7.5YR and 5YR hues in the Bt horizon. Corning soils are gravelly throughout and have strongly acid Bt horizons with hues of 2.5YR, 5YR and 7.5YR. Hytop soils have a paralithic contact at 20 to 40 inches. Millsap soils have a lithic contact at 20 to 40 inches. San Ysidro and Hillgate soils have montmorillonitic mineralogy and lime in the C horizon.
GEOGRAPHIC SETTING: The Yokayo soils are on old dissected terrace tops and eroded sideslopes and have slopes of 0 to 30 percent. They formed in old alluvium weathered from sedimentary rock at elevations of 500 to 1,500 feet. The climate is subhumid with hot dry summers and cool moist winters. Mean annual precipitation is 32 to 44 inches. Mean January temperature is 46 degrees F; mean July temperature is 72 degrees F; mean annual temperature varies from 57 to 59 degrees F. Frost-free season ranges from 200 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Pinnobie (T), Pinole, and Redvine (T) soils. Pinole and Pinnobie soils have fine-loamy particle-size control sections. Redvine has a base saturation that is less than 75 percent in all parts of the argillic.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; very slow permeability.
USE AND VEGETATION: Used for vineyards, rangeland, watershed and wildlife habitat. Natural vegetation is blue oak, Oregon white oak, California black oak, wild oats, dogtail and manzanita. Most areas of this soil are cleared and cultivated.
DISTRIBUTION AND EXTENT: Northern California in the Coast Range. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendocino County, Eastern Part, California 1985.
REMARKS: Diagnostic horizons and features recognized in this pedon are: Ochric epipedon - 0 to 8 inches.
Argillic horizon - 8 yo 48 inches (Bt1, Bt2, Bt3 horizons)
Pale feature - abrupt clay increase between the A and Bt horizons.
Particle-size control section - upper 20 inches of the Bt(8 to 28 inches)
ADDITIONAL DATA: NSSL Pedon S78CA-045-124 as a taxadjunct.