LOCATION BAPOS CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Mollic Palexeralfs
TYPICAL PEDON: Bapos clay loam - on a slope of 2 percent under soft chess, red brome, filaree, tarweed and other annual grasses and forbs at 1,020 feet elevation. (Colors are for dry soil unless otherwise stated. When described on May 3, 1978, the soil was moist throughout).
A1--0 to 4 inches; reddish brown (5YR 4/4) clay loam, dark reddish brown (5YR 3/3) moist; strong medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; common very fine tubular pores; 3 percent gravel, 5 to 40 mm in size; neutral (pH 7.2); clear irregular boundary. (4 to 6 inches thick)
A2--4 to 12 inches; yellowish red (5YR 4/6) clay loam, dark reddish brown (5YR 3/4) moist; weak fine and medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; few very fine tubular pores; 3 percent gravel, 5 to 50 mm in size; slightly effervescent, carbonates segregated as few fine soft masses; moderately alkaline (pH 8.0); abrupt wavy boundary. (5 to 11 inches thick)
Btk1--12 to 26 inches; reddish brown (5YR 4/4) clay, reddish brown (5YR 4/4) and yellowish red (5YR 5/6) moist; strong coarse angular blocky structure; slightly hard, firm, very sticky and very plastic; few very fine roots; common very fine tubular pores; 2 percent gravel, 2 to 20 mm in size; common moderately thick clay films on faces of peds and lining pores; slightly effervescent, carbonates segregated as few fine soft masses; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 15 inches thick)
Btk2--26 to 38 inches; reddish brown (5YR 4/4) clay, yellowish red (5YR 4/6) moist; moderate coarse angular blocky structure; hard, firm, moderately sticky and moderately plastic; few very fine roots; common very fine tubular pores; 3 percent gravel, 5 to 50 mm in size; common moderately thick clay films on faces of peds and lining pores; strongly effervescent, carbonates segregated as few fine and medium soft masses; moderately alkaline (pH 8.0); clear smooth boundary. (10 to 17 inches thick)
BCtk--38 to 45 inches; strong brown (7.5YR 5/6) clay, yellowish red (5YR 4/6) moist; weak coarse angular blocky structure; hard, firm, moderately sticky and moderately plastic; no roots; few fine tubular pores; 7 percent gravel, 2 to 50 mm in size; common moderately thick clay films on faces of peds and lining pores; strongly effervescent, carbonates segregated as few fine soft masses; moderately alkaline (pH 8.0); abrupt wavy boundary. (7 to 10 inches thick)
2C--45 to 60 inches; yellowish red (5YR 4/6) very gravelly clay loam, yellowish red (5YR 4/6) with few fine prominent black (5YR 2/1) mottles moist; massive; slightly hard, firm, moderately sticky and moderately plastic; no roots; few very fine tubular pores; 50 percent gravel, 2 to 50 mm in size; common thin pressure faces; slightly effervescent, carbonates disseminated; moderately alkaline (pH 8.0).
TYPE LOCATION: Merced County, California; approximately 6.8 miles south of the pumping plant at the end of Marvel Road, 5.75 miles north northeast of Ortigalita Peakand 10 miles south southwest of the city of Los Banos; 900 feet north and 100 feet east of the southwest corner of section 21, T. 12 S., R. 10 E., MDB&M; Latitude 36 degrees, 52 minutes, 07 seconds north and Longitude 120 degrees, 53 minutes, 27 seconds west; USGS Ortigalita Peak Topographic Quadrangle, NAD 27.
RANGE IN CHARACTERISTICS: The soil is more than 60 inches deep. The mean annual soil temperature is 59 to 65 degrees F. and is below 47 degrees F. in parts of January and February and is not below 41 degrees F at any time. The soil between the depths of 6 and 14 inches is moist in all parts from January 1 to May 1 and dry in all parts from July 1 to October 31.
The A horizon has color of 10YR 5/3, 6/2; 7.5YR 3/3, 3/4, 4/4, 5/4, 6/4; 5YR 3/4, 4/4 or 4/6. Moist color is 10YR 3/3, 4/2, 4/3; 7.5YR 3/3, 3/4; 5YR 3/3 or 3/4. The upper part of the A horizon has moist color values of 3. Organic matter content is 0.5 to 2 percent and the upper part has organic matter content of 1 to 2 percent. Texture is sandy clay loam or clay loam. Clay content is 20 to 35 percent. Calcium carbonate equivalent is 0 to 5 percent. Gravel content is 0 to 15 percent. Reaction is neutral to moderately alkaline. Some pedons have thin E horizons.
The Btk horizons have color of 10YR 6/4, 6/6; 7.5YR 3/4, 4/4, 4/6, 5/4; 5YR 4/4, 4/6 or 5/3. Moist color is 10YR 4/4, 5/6; 7.5YR 3/4, 4/4, 4/6, 5/4; 5YR 4/3, 4/4, 4/6 or 5/6. Texture is clay loam or clay. Clay content is 38 to 55 percent. Clay content abruptly increases by at least 15 percent more than the A horizon. Calcium carbonate equivalent is 5 to 15 percent. Gravel content is 0 to 15 percent. Reaction is slightly alkaline or moderately alkaline.
The BCtk horizon, when present, has color of 7.5YR 4/4, 4/6, 5/4 or 5/6. Moist color is 7.5YR 4/4, 4/6, 5/4 or 5YR 4/6. Texture is clay or clay loam. Clay content is 35 to 50 percent. Structure is weak coarse angular blocky or is massive. Gravel content is 0 to 15 percent. The boundary is abrupt or clear.
The 2C and 3C horizons have color of 5Y 5/8; 7.5YR 4/6, 5/4, 5/6; 5YR 4/6, 5/6, 5/8 or 2.5YR 5/4. Moist color is 2.5Y 4/2; 7.5YR 4/6, 5/1, 5/6; 5YR 5/6, 5/8 or 6/8. Texture is gravelly sandy clay loam, very gravelly clay loam or gravelly clay loam. Gravel conent is 15 to 55 percent. Reaction is slightly alkaline or moderately alkaline. Some pedons have a gypsic horizon.
COMPETING SERIES: This is the Honker series. Honker soils (MLRA 15), on mountains, have a lithic contact at a depth of 20 to 40 inches.
GEOGRAPHIC SETTING: Bapos soils are on terraces and fan remnants just above the valley floor. Slope is 0 to 15 percent. The soils formed in gravelly alluvium from mixed rock sources. Elevation is 140 to 1,240 feet. The climate is semiarid with hot dry summers and cool moist winters. The mean annual precipitation is 9 to 12 inches. The mean annual temperature is 60 to 64 degrees F. Mean annual January temperature is 45 degrees F; mean annual July temperature is 80 degrees F. Frost-free season is 200 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ayar, Conosta, Los Banos and Pleito soils. Ayar soils, on foothills, have wide cracks and intersecting slickensides within 40 inches of the surface. Conosta soils, on foothills, have clear A/B boundaries with less than 15 percent clay content increase in the upper B horizon and have a strongly weathered conglomerate at a depth of 20 to 40 inches. Los Banos soils, on terraces and fan remnants, have less than 15 percent clay content increase in the upper B horizon. Pleito soils, on terraces and fan remnants, have a mollic epipedon and a fine-loamy particle-size control section.
DRAINAGE AND PERMEABILITY: Well drained; medium to very high runoff; very slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing. The vegetation is soft chess, red brome, filaree, clover, wild oats, tarweed and other annual grasses and forbs.
DISTRIBUTION AND EXTENT: These soils occur on the western edge of the San Joaquin Valley. They are not extensive. MLRA-15.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Merced County, California, 1984.
REMARKS: These soils were formerly included with and mapped as the Positas series in the Los Banos Area, California 1939 series report. These soils are being differentiated by higher pH and carbonates content. Former competing series included the Benridge, Hellman and Kimball soils. All three of these series may have an "active" cation exchange activity class that differentiates them from the Bapos and Honker series.
Diagnostic horizons and features recognized in this pedon are:
Ochric Epipedon - The zone from the surface to a depth of 12 inches (A1, A2 horizons)
Argillic Horizon - The zone from 12 to 38 inches (Btk1, Btk2 horizons)