LOCATION DANVILLE CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Pachic Argixerolls
TYPICAL PEDON: Danville sandy clay loam, irrigated cropland. (Colors are for dry soil unless otherwise noted.)
Ap1--0 to 5 inches; very dark grayish brown (10YR 3/2) sandy clay loam, very dark brown (10YR 2/2) moist; moderate medium and coarse subangular blocky structure; hard, friable, sticky and plastic; many very fine roots; common very fine tubular pores; slightly alkaline (pH 7.5); clear wavy boundary (mixed with lower horizon from tillage operation). (4 to 9 inches thick)
Ap2--5 to 18 inches; very dark grayish brown (10YR 3/2) sandy clay loam, very dark brown (10YR 2/2) moist; strong very coarse and weak medium and coarse subangular blocky structure; very hard, friable, sticky and plastic; many very fine roots; common very fine and few fine tubular pores; moderately alkaline (pH 8.0); clear wavy boundary. (7 to 15 inches thick)
Bt1--18 to 38 inches; very dark grayish brown (10YR 3/2), dry and moist) clay, dark brown (10YR 3/3) rubbed moist; moderate medium and coarse prismatic and moderate medium and coarse angular blocky structure; prisms have weakly expressed rounded caps at the top 3 inches of horizon; very hard, firm, sticky and very plastic; common very fine roots; many very fine tubular pores; continuous moderately thick clay films on faces of peds and lining pores; few thick clay films line pores; moderately alkaline (pH 8.3); gradual wavy boundary. (16 to 36 inches thick)
Bt2--38 to 53 inches; dark brown (10YR 3/3) gravelly sandy clay loam, dark brown (7.5YR 3/2) moist; massive; hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine and few fine tubular pores; many thin clay films line pores and common thin films as bridges between mineral grains; about 17 percent by volume angular fine pebbles (2 to 10 mm); moderately alkaline (pH 8.2); gradual wavy boundary. (4 to 15 inches thick)
Bt3--53 to 67 inches; brown (7.5YR 4/4) gravelly light sandy clay loam, dark brown (7.5YR 4/2) moist; massive; hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine interstitial, common very fine and coarse tubular pores; few moderately thick clay films in pores and as bridges between mineral grains; about 5 percent by volume angular fine pebbles (2 to 10 mm); moderately alkaline (pH 8.0); gradual wavy boundary.
Btk--67 to 78 inches; mixed strong brown (7.5YR 5/6) and brown (7.5YR 5/4) heavy clay loam, dark brown (7.5YR 4/4) broken; 7.5YR 4/2 rubbed) moist; massive; hard, friable, sticky and plastic; few very fine roots; many very fine and medium and few fine tubular pores; few moderately thick clay films line pores and as bridges between grains; common thin clay films line pores; slightly effervescent with carbonates segregated in seams; moderately alkaline (pH 8.0).
TYPE LOCATION: Monterey County, California; about 3 miles north of Gonzales, 2.2 miles northwest on Iverson Road from intersection with Johnson Canyon Road 0.21 miles southwest on dirt road from Iverson Road, 30 yards due north of crossroad.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 59 to 64 degrees F. and the soil temperature usually is not below 47 degrees F. at any time. The soil between depths of 4 and 12 inches is usually dry all of the time from late April or May until November or early December and is moist in some or all parts all the rest of the year. Rock fragments range up to 15 percent.
The A horizon is dark gray, black, dark grayish brown, very dark grayish brown, or very dark brown. It is clay loam, sandy clay loam, gravelly clay loam, or silty clay loam. This horizon has weak to strong granular or subangular blocky structure. It is moderately acid to moderately alkaline and has 75 to 100 percent base saturation. Soil amendments and fertilizers have altered reaction in some pedons. Organic matter content ranges from 2 to 3 percent in upper parts and decreases regularly with about 1 percent at about 30 inches.
The Bt horizon is very dark grayish brown, dark grayish brown to dark brown (10YR 3/2, 3/3, 4/2, 4/3; 7.5YR 4/2, 4/4, 5/4). It is clay, sandy clay, or gravelly sandy clay loam. The upper boundary is gradual or clear. This horizon is neutral to moderately alkaline. It has weak or strong prismatic or angular blocky structure.
The C horizon, when present, is brown, dark brown, strong brown, dark grayish brown and dark yellowish brown and the hue is 7.5YR or 10YR. It is sandy loam, gravelly sandy clay loam, loamy sand or clay loam and is somewhat stratified. This horizon is generally slightly or moderately alkaline. In some pedons the lower part of the profile is calcareous.
COMPETING SERIES: There are no other soils in this family.
GEOGRAPHIC SETTING: The Danville soils are on fans and terraces, at elevations of 100 to 1,500 feet. Slopes range from 0 to 9 percent. The soils formed in alluvium with some coarse sand derived from sedimentary and crystalline rocks. The climate is subhumid mesothermal with warm, dry summers and cool, moist winters. The mean annual precipitation is 12 to 25 inches. The average July temperature is 67 degrees F.; the average January temperature is 48 degrees F.; and the mean annual temperature is 58 to 63 degrees F. The frost free season is 250 to 330 days. Phases exist along the coast of California that have average January temperatures of about 56 degrees F. and frost free seasons of 320 to 350 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Chualar soils and the Diablo, McCoy, Placentia, Rinco, and Yolo soils. Diablo soils have intersecting slickensides. McCoy soils have a paralithic contact at depths of less than 40 inches. Placentia soils have natric horizons. Rincon soils have hard and massive epipedons. Yolo soils lack a mollic epipedon and an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; slow permeability.
USE AND VEGETATION: Used for growing irrigated row, truck and field crops. Minor areas used for growing small grain. Uncultivated areas have annual grasses, forbs and scattered trees.
DISTRIBUTION AND EXTENT: Valleys in the central part of the Coast Range in California. The soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Contra Costa County (Livermore Valley Area), California, 1910.
The series concept has been widened to include soils that are silty and soils that are gritty and somewhat gravelly.
Horizonation updated in June 2001