LOCATION YEGUAS CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Haploxeralfs
TYPICAL PEDON: Yeguas loam, fallow, on a slope of 2 percent. (When described on September 12, 1984, the soil was moist below 11 inches. Colors are for dry soil unless otherwise noted.)
Ap1--0 to 3 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; cloddy; hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine and fine tubular pores; slightly alkaline (pH 7.5); clear smooth boundary. (3 to 8 inches thick)
Ap2-- 3 to 11 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; massive; very hard, friable, slightly sticky and slightly plastic; few very fine roots; few very fine tubular pores; neutral (pH 7.0); gradual smooth boundary. (0 to 8 inches thick)
A-- 11 to 19 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; massive; hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine and few fine and medium tubular pores; slightly alkaline (pH 7.5); gradual wavy boundary. (7 to 13 inches thick)
Bt1-- 19 to 24 inches; mixed light brownish gray (10YR 6/2) and light yellowish brown (10YR 6/4) clay loam, mixed dark grayish brown (10YR 4/2) and yellowish brown (10YR 5/4) moist; massive; very hard, friable, sticky and plastic; few very fine roots; common very fine tubular pores; few thin clay films on ped faces and in pores; slightly alkaline (pH 7.5); gradual wavy boundary. (4 to 14 inches thick)
Bt2-- 24 to 35 inches; light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; strong medium and coarse angular blocky structure; very hard, friable, very sticky and plastic; few very fine roots, few very fine tubular pores; many moderately thick clay films on ped faces; slightly alkaline (pH 7.5); clear wavy boundary. (6 to 14 inches thick)
Bt3-- 35 to 45 inches; light yellowish brown (10YR 6/4) clay loam, yellowish brown (10YR 5/4) moist; moderate fine and medium angular blocky structure; hard, firm, slightly sticky and slightly plastic; common very fine and fine tubular pores; few thin clay films on ped faces; moderately alkaline (pH 8.0); clear wavy boundary. (8 to 15 inches thick)
Bk-- 45 to 51 inches; very pale brown (10YR 7/4) loam, yellowish brown (10YR 5/4) moist; moderate medium angular blocky structure; hard, friable, slightly sticky and slightly plastic; violently effervescent with disseminated lime and lime segregated into common fine seams; moderately alkaline (pH 8.0); clear wavy boundary. (6 to 13 inches thick)
2C-- 51 to 62 inches; very pale brown (10YR 7/4) gravelly coarse sandy loam, yellowish brown (10YR 5/4) moist; massive; loose, nonsticky and nonplastic; 15 percent pebbles; strongly effervescent with disseminated lime; moderately alkaline (pH8.0).
TYPE LOCATION: San Luis Obispo County, California; near the second metal high line tower, on the north side of the dirt road, east of the P.G.& E. substation in the Carrizo Plain, then from the towers northeast leg go 135 feet magnetic bearing north 350 degrees then 105 feet magnetic bearing east 80 degrees. It is 2,600 feet east and 60 feet north of the southwest corner of section 22, T.29 S., R.18 E., USGS La Panza Topographic Quadrangle; lat. 35 degrees, 22 minutes, 52 seconds N. and long. 120 degrees, 1 minutes, 51 seconds W.
RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 40 to 60 inches. The mean annual soil temperature ranges from 60 to 67 degrees F. The soil between the depths of 6 and 17 inches is moist in some part from December 15 until May 1 and is moist in all parts for at least 45 consecutive days. The soil is dry in all parts for about 210 days and has a xeric bordering on aridic moisture regime.
The A horizon has dry color of 10YR 5/2, 5/3, 6/2 or 6/3; 2.5Y 5/2 or 6/2 and moist color of 10YR 3/2 or 3/3; 2.5Y 3/2. Clay content is 20 to 27 percent. Gravel content is 0 to 5 percent. It is neutral to moderately alkaline.
The Bt horizon has dry color of 10YR 5/2, 5/3, 5/4, 6/2, 6/3 or 6/4; 2.5Y 5/2, 5/3 or 6/3 and moist color of 10YR 3/2, 3/3, 4/2, 4/3, 4/4 or 5/4; 2.5Y 3/2, 3/3, 4/2, 4/3 or 4/4. Textures are clay loam or clay. Clay content is 35 to 45 percent. Gravel content is 0 to 10 percent. It is slightly or moderately alkaline.
The Bk horizon has dry color of 10YR 6/3, 6/4, 7/2, 7/3 or 7/4; 2.5Y 6/3, 6/4 or 7/2 and moist color of 10YR 4/2, 4/3, 4/4, 4/6, 5/3, 5/4, 6/4 or 7/4; 2.5Y 4/4 or 5/4. Textures are loam or clay loam. Clay content is 18 to 32 percent. Gravel content is 0 to 10 percent. It is slightly or moderately alkaline. The 2C horizon is not always present.
COMPETING SERIES: These are the Artois, Francisquito, and Goldeagle series. Artois soils are somewhat poorly drained and have MAP of 15 to 20 inches. Francisquito soils have slopes of 5 to 15 percent, are moist for 210 days, are slightly to mildly acid throughout and the MAP is 25 to 35 inches. Godeagle soils have slopes of 30 to 75 percent, are slightly acid in the Bt horizon, have a paralithic contact from 40 to 80 inches and the MAP is 16 to 18 inches.
GEOGRAPHIC SETTING: Yeguas soils are on alluvial plains, alluvial fans, and alluvial flats. Slopes are 0 to 5 percent. They formed in alluvium from weathered mixed sources. Elevations are 1900 to 2500 feet. The climate is semi- arid with hot summers and cool moist winters. Mean annual precipitation is 8 to 10 inches. Mean January temperature is about 46 degrees F, the mean July temperature is about 77 degrees F and the mean annual temperature ranges from 58 to 62 degrees F. Frost-free season is 175 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Beam (T),
Jenks (T),
Panoza (T),
Pinspring (T),
Polonio and
Thomhill (T) soils.
Beam (T) soils on hills above the Yeguas soils and are less than 20 inches to a paralithic contact. Jenks (T) and Panoza (T) soils are on hills above the Yeguas soils and are 20 to 40 inches to a paralithic contact. Polonio soils lack an argillic horizon. Thomhill(T) soils are on similar topographic positions as the Yeguas soils but have a mollic epipedon and lack an argillic horizon. Pinspring(T) soils are on similar topographic positions as the Yeguas soils but are moderately well drained and the textural control section is fine-loamy.
DRAINAGE AND PERMEABILITY: Well drained; negligible to medium runoff; slow permeability.
USE AND VEGETATION: The soil is used for dryfarmed small grain crops and some livestock grazing. The main crops grown on the soil are barley and wheat.
DISTRIBUTION AND EXTENT: Eastern San Luis Obispo County in the Carrizo Plain Area, MLRA 17. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: San Luis Obispo County, California; Carrizo Plain Area, 1984. Soil name was coined from the Las Yeguas Ranch Quadrangle.
REMARKS:
Major Diagnostic Horizons recognized in this pedon are:
1. Ochric Epipedon:
1.1 Epipedon is massive and hard when dry.
1.2 Organic carbon is less than 0.67 throughout the A horizon.
1.3 Clay content when mixed is 20 to 25 percent.
2. Argillic Horizon:
2.1 Clay content when mixed is 35 to 43 percent.
3. Xeric moisture regime - Soil is moist in all parts for at
least 45 consecutive days and dry in all parts for about 210
days.
4. Fine textural control section - clay content of the B horizon
is 35 to 45 percent.
ADDITIONAL DATA: NSSL Pedon No. 84CA-079-033 (Lab sample No. 84P 0928)