LOCATION SHIMMON CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Typic Argixerolls
TYPICAL PEDON: Shimmon sandy loam, rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 10 inches; dark gray (10YR 4/1) loam, very dark gray (10YR 3/1) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine and few fine roots; many very fine and fine tubular and interstitial pores; slightly acid (pH 6.5); gradual wavy boundary. (8 to 17 inches thick)
Bt1--10 to 21 inches; yellowish brown (10YR 5/4) clay loam, dark yellowish brown (10YR 4/4) moist; moderate coarse prismatic structure; very hard, very firm, sticky and very plastic; few fine and medium roots; common very fine and fine tubular pores; common thin clay films lining pores and on faces of peds; slightly acid (pH 6.5); gradual wavy boundary. (6 to 12 inches thick)
Bt2--21 to 29 inches; very pale brown (10YR 7/4) clay loam, light yellowish brown (10YR 6/4) moist; weak coarse prismatic structure; very hard, firm, sticky and very plastic; few fine and medium roots; common very fine and fine tubular pores; many thin clay films lining pores and on faces of peds; slightly acid (pH 6.5); gradual irregular boundary. (6 to 11 inches thick)
Cr--29 to 39 inches; very pale brown (10YR 7/4) weathered fine grained sandstone; slightly acid (pH 6.5).
TYPE LOCATION: San Luis Obispo County, California; about 2,800 feet west and 4,1OO feet south from the NE corner of section 2, T.25S., R.9E.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact is 20 to 40 inches. The mean annual soil temperature is 59 F to 65 F. The moisture control section is moist in some part from December until May and is dry in all parts from July until October.
The A horizon is 10YR 5/1, 4/1, 5/2, 4/2, 4/3 or 5/3 dry, and 10YR 3/1, 3/2, 3/3) moist. It is sandy loam, fine sandy loam or loam. This horizon is hard and very hard. It is slightly acid to slightly alkaline.
The Bt horizon is 10YR 4/2, 5/2, 5/3, 5/4, 6/3, 6/4, 7/4; 7.5YR 4/3, 6/4, 5/4. It is clay loam or sandy clay loam and averages 18 to 34 percent clay. This horizon is moderately acid to moderately alkaline.
Some pedons have calcareous Cr horizons.
COMPETING SERIES: These are the Foothill and Franciscan soils in the superactive family and the Ballard, Bohna, Chualar, Chuloak, Gilroy, Havala, Los Gatos, Los Osos, Pinto, Soper and Tehachapi series.which do not have CEC activity class determined. Ballard, Bohna, Chualar, Chuloak, Havala, Pinto and Tehachapi soils are deep and lack a paralithic contact. Foothill soils are dry from about June 1 to November 1 (140 to 160 days) and have granitic parent material. .Franciscan soils are moderately deep to a lithic contact Gilroy soils have a lithic contact. Los Gatos soils have a lithic contact and a mesic temperature regime. Los Osos soils have a fine textural control section. Soper soils have an argillic horizon that contains 15 to 35percent by volume gravel or cobbles.
GEOGRAPHIC SETTING: Shimmon soils are on hills and mountains with slopes of 15 to 75 percent. They formed in material weathered from fine-grained sandstone. Elevations are 700 to 2,500 feet. The climate is subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation is 12 to 24 inches. Average January temperature is about 46 F., the average July temperature is about 71 F., and the mean annual temperature is about 57 F to 61 F. The average frost-free season is about 175 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
San Andreas soils. Dibble soils have ochric epipedons with fine textural control. Gaviota soils have a coarse-loamy textural control with a lithic contact less than 20 inches deep. Hanford and Pico soils are deep soils with a coarse-loamy textural control and lack paralithic contacts. San Andreas soils are coarse-loamy
DRAINAGE AND PERMEABILITY: Well drained; medium to high runoff; moderately slow permeability.
USE AND VEGETATION: This soil is used for dryfarmed grain and rangeland. Natural vegetation is mainly blue and scrub oak with an understory of annual grasses.
DISTRIBUTION AND EXTENT: Hills and mountains of the south half of the Coast Range in California, MLRA 15. The soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Luis Obispo County, California, Paso Robles Area, 1977.
OSED scanned by SSQA. Last revised by state on 2/77.