LOCATION ARROYO SECO CAEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, thermic Fluventic Haploxerolls
TYPICAL PEDON: Arroyo Seco gravelly sandy loam - irrigated crops (Colors are for dry soil unless otherwise stated.)
Ap--0 to 5 inches; grayish brown (10YR 5/2) gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; cloddy; slightly hard, very friable, nonsticky, nonplastic; common very fine roots; common very fine interstitial pores; 15 percent gravel and 2 percent cobblestones; neutral (pH 6.8); clear smooth boundary. (5 to 10 inches thick)
A12--5 to 18 inches; grayish brown (10YR 5/2) gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; weak coarse subangular blocky structure; hard, friable, nonsticky, nonplastic; few very fine roots; common very fine tubular and interstitial pores; about 20 percent gravel and 5 percent cobblestones; slightly alkaline (pH 7.5); gradual wavy boundary. (10 to 16 inches thick)
A13--18 to 29 inches; grayish brown (10YR 5/2) gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, very friable, slightly sticky, nonplastic; few very fine roots; common very fine tubular pores; about 25 percent gravel and 8 percent cobblestones; slightly alkaline (pH 7.5); gradual wavy boundary. (10 to 15 inches thick)
C1--29 to 42 inches; brown (10YR 5/3) gravelly sandy loam, dark brown (10YR 3/3) moist; massive; slightly hard, very friable, nonsticky, nonplastic; common very fine tubular pores; about 25 percent gravel and 9 percent cobblestones; slightly alkaline (pH 7.5); abrupt irregular boundary. (0 to 15 inches thick)
IIC2--42 to 58 inches; yellowish brown (10YR 5/4) very gravelly coarse sandy loam, dark yellowish brown (10YR 4/4) moist; massive; about 50 percent gravel, 20 percent cobblestones, and 5 percent stones; slightly alkaline (pH 7.5).
TYPE LOCATION: Monterey County, California; southwest of the town of Greenfield; 375 feet southwest of Twelfth Street on Greenfield-Arroyo Seco Road from El Camino Real; 500 feet southeast on field access road and 300 feet southwest into the field.
RANGE IN CHARACTERISTICS: Mean annual soil temperature is 59 to 64 degrees F. The soils are continuously dry between depths of about 8 and 24 inches from May to late October and usually are moist all the rest of the year. Pebbles and cobblestones average 10 to 34 percent of the volume to a depth of 40 inches or more. Textures are sandy loam, fine sandy loam, or loam and average less than 18 percent clay. The soil is somewhat stratified. Organic matter content is 1.5 to 3 percent in the upper 10 inches and decreases irregularly. It averages less than 1 percent below a depth of 20 inches.
The A1 horizon is grayish brown, dark grayish brown, or brown in 10YR hue. Moist values are two units lower. This horizon has subangular blocky structure with hard or slightly hard dry consistence or it is massive and is slightly hard. It is slightly acid to moderately alkaline. Generally, the soil is increasingly alkaline with depth, but the profile is not calcareous.
The C horizon is brown, grayish brown, yellowish brown, light yellowish brown or pale brown in 10YR hue and generally has higher value and higher chroma than the A horizon. It is neutral to moderately alkaline. Some pedons have 35 to 85 percent rock fragments below depth of 40 inches.
COMPETING SERIES: These are the Anacapa, Crafton, Elder, Farallone, Gorgonio, Greenfield, Hanford, Pico, and San Andreas series. Anacapa soils have mollic epipedons more than 20 inches thick and are calcareous between depths of 20 and 40 inches. Crafton and San Andreas soils have a paralithic contact within 40 inches of the soil surface. Elder soils have mollic epipedons more than 20 inches thick. Farralone soils have mesic temperature. Gorgonio soils have a sandy texture in the control section. Greenfield and Hanford soils have ochric epipedons. Pico soils are calcareous throughout.
GEOGRAPHIC SETTING: Arroyo Seco soils are on nearly level to moderately sloping flood plains and alluvial fans at elevations of 100 to 3,000 feet. The soils formed in alluvium dominantly from granitic sources, but include alluvium from schist, gneiss, sandstone, and siliceous shale. The climate is subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation is 12 to 30 inches; mean annual temperature is 58 to 60 degrees F.; average January temperature is 48 to 50 degrees F.; average July temperature is 65 to 68 degrees F. Freeze-free season is 210 to 260 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Chualar, Lockwood, Gloria, and Metz soils and the competing Elder soils. Chualar and Lockwood soils have an argillic horizon. Gloria and Placentia soils have an argillic horizon with an abrupt upper boundary. Metz and Tujunga soils are sandy in the control section.
DRAINAGE AND PERMEABILITY: Well-drained; slow and medium runoff; moderately rapid permeability.
USE AND VEGETATION: Used mostly for growing vegetables, field, and forage crops; also deciduous orchards, vineyards, and annual pasture. Vegetation on the uncultivated areas is annual grasses and forbs with scattered oaks.
DISTRIBUTION AND EXTENT: Central coast valleys of California. The soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Monterey County (Lower Salinas Valley), California, 1901.
REMARKS: The Arroyo Seco soils were formerly classified as Brunizems. The series was inactive from 1913 to 1971 and was redefined in 1971. The series as presently defined is in the same geographic area and with about the same concept as initially provided for in 1901.
The activity class was added to the classification in January of 2003. Competing series were not checked at that time. - ET
OSED scanned by SSQA. Last revised by state on 8/72.