LOCATION JENKS CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Aridic Haploxerolls
TYPICAL PEDON: Jenks clay loam on a north facing slope of 15 percent under cultivation of dryland barley (area had a harvested crop in 1982, in 1983 the area was under summer fallow) at 2,350 feet elevation. (Colors are for dry soil unless otherwise stated. When described on July 27, 1983, soil was dry to 6 inches and moist below).
Ap--0 to 6 inches; grayish brown (10YR 5/2) clay loam, dark brown (10YR 3/3) moist; cloddy; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine tubular pores; moderately alkaline (pH 8.0); clear smooth boundary. (2 to 8 inches thick)
A--6 to 16 inches; brown (10YR 5/3) clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; slightly hard, friable, sticky and slightly plastic; few very fine roots; common very fine and fine tubular pores; moderately alkaline (pH 8.0); gradual wavy boundary. (8 to 11 inches thick)
Bt--16 to 27 inches; variegated brown (10YR 5/3) and light yellowish brown (10YR 6/4) clay loam, variegated dark brown (10YR 4/3) and dark yellowish brown (10YR 4/4) moist; weak fine subangular blocky structure; slightly hard, friable, sticky and plastic; few very fine roots; common very fine and fine tubular pores; few thin clay films on peds; moderately alkaline (pH 8.0); clear wavy boundary. (10 to 21 inches thick)
Cr--27 to 35 inches; variegated white (10YR 8/2) very pale brown (10YR 8/3 and 10YR 7/3) weathered calcareous fine grained sandstone.
TYPE LOCATION: San Luis Obispo County, California, approximately 3.6 miles north from Highway 58 to telephone line on the road to the Las Yeguas Ranch, and 400 feet north and 350 feet west of the southeast corner of sec. 13, T. 29 S., R. 18 E., 300 feet uphill from dirt road by telephone line magnetic bearing 280 degrees; USGS Las Yeguas Ranch Quadrangle; lat. 35 degrees, 23 min., 48 sec. N. and long. 119 degrees, 59 min., 15 sec. W.
RANGE IN CHARACTERISTICS: Depth to soft, calcareous sandstone or shale is 20 to 40 inches. Mean annual soil temperature ranges from 60 to 67 degrees F. The moisture control section between depths of 6 and 18 inches is moist in some parts for at least 90 days from December until May and is moist in all parts from 45 consecutive days between mid-January and mid-March. The soil is dry for about 210 days and has a Xeric bordering on an Aridic moisture regime. The soil is, clay loam or silty clay loam.
The A horizon has dry color of 10YR 5/2, 5/3; 2.5YR 4/2 or 5/2 and moist color of 10YR 3/2, 3/3; 2.5YR 3/2. Gravel content is 0 to 15 percent.
The B horizon has dry color of 10YR 5/2, 5/3, 6/2, 6/3 or 6/4 and moist color of 10YR 3/2, 3/3, 4/2, 4/3, 4/4 or 5/4. In some pedons it is slightly to violently effervescent with disseminated lime. Gravel content is 0 to 15 percent.
COMPETING SERIES: These are the Live oak, Saurin and Tisdale series in other families. Live oak and Tisdale soils are on low alluvial terraces. Saurin soils are dry for 120 days.
GEOGRAPHIC SETTING: Jenks soils are on hills and have slopes of 2 to 50 percent. The soils formed in material weathered from soft, calcareous sandstone or shale. Elevations are 1,800 feet to 2,600 feet. The climate is semiarid with hot dry summers and cool moist winters. Mean annual precipitation is 8 to 10 inches. Mean January temperature is 46 degrees F, mean July temperature is 77 degrees F, mean annual temperature varies from 58 to 62 degrees F. Frost-free season is 175 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beam (T), Panoza (T), Thompson (T) and Yeguas (T) series. Beam soils are less than 20 inches deep. Panoza soils have orchic epipedons. Thompson and Yeguas soils are on alluvial plains and are deep.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is slow and medium on the gentler slopes and high on the steeper slopes. Permeability is moderately slow.
USE AND VEGETATION: The soil is used for non-irrigated cropland - mostly wheat and barley - and rangeland. Natural vegetation is mainly soft chess, red brome and filaree.
DISTRIBUTION AND EXTENT: Hills of the Temblor Range and northern area of the Carrizo Plain in California, MLRA 15. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: San Luis Obispo County, California; Carrizo Plain Area, 1985. Soil name was derived from Jenks Spring.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Jenks soils have a Xeric bordering on Aridic moisture regime.
Mollic epipedon - the zone from the surface of the soil to a depth of 16 inches (Ap and A horizons).
Cambic horizon - 16 to 27 inches - few thin clay films, slight clay increase but not enough for an argillic horizon.