LOCATION CONOSTA CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Mollic Haploxeralfs
TYPICAL PEDON: Conosta clay loam - on a north facing slope of 30 percent under red brome and fescue at an elevation of 900 feet. (Colors are for dry soil unless otherwise stated. When described on April 27, 1978, the soil was moist throughout).
A1--0 to 8 inches; brown (7.5YR 4/4) clay loam, dark brown (7.5YR 3/4) moist; moderate very fine to coarse granular structure; very hard, friable, slightly sticky and moderately plastic; common very fine roots; common very fine and few fine tubular pores and common very fine interstitial pores; 10 percent gravel 2 to 20mm in size; neutral (pH 7.2); clear smooth boundary. (5 to 11 inches thick)
A2--8 to 14 inches; dark brown (7.5YR 3/4) clay loam, dark brown (7.5YR 3/4) moist; moderate coarse subangular blocky structure; very hard, friable, slightly sticky and moderately plastic; common very fine roots; common very fine and few fine tubular pores; few thin clay films on faces of peds; 0.8 percent organic matter; 5 percent gravel 2 to 20mm in size; slightly alkaline (pH 7.8); clear wavy boundary. (3 to 7 inches thick)
BAt--14 to 19 inches; brown (7.5YR 4/4) cobbly clay loam, reddish brown (5YR 4/4) moist; moderate coarse subangular blocky structure; very hard, friable, slightly sticky and moderately plastic; few very fine roots; common very fine tubular pores; common thin clay films on faces of peds and in pores; 30 percent cobbles and gravel 75 to 120mm and 2 to 20mm in size; moderately alkaline (pH 8.0); abrupt smooth boundary. (0 to 8 inches thick)
Bt--19 to 27 inches; strong brown (7.5YR 5/6) gravelly clay, strong brown (7.5YR 5/6) moist moderate medium angular blocky structure; very hard, friable, moderately sticky and moderately plastic; few very fine roots; few very fine tubular pores; many moderately thick clay films on faces of peds and in pores; 20 percent gravel 2 to 20mm in size; moderately alkaline (pH 8.0); clear wavy boundary. (6 to 10 inches thick)
BCt--27 to 32 inches; strong brown (7.5YR 5/6) very gravelly clay loam, strong brown (7.5YR 5/8) moist; moderate medium angular blocky structure; hard, friable, moderately sticky and moderately plastic; few very fine roots; few very fine tubular pores; many moderately thick clay films on faces of peds; 40 percent gravel and cobbles 2 to 15mm and 75 to 130mm in size; moderately alkaline (pH 8.0); clear wavy boundary. (3 to 8 inches thick)
Cr--32 to 36 inches; strongly weathered conglomerate rock.
TYPE LOCATION: Merced County, California, approximately 10 miles southwest of the city of Los Banos, 1.6 miles south of Los Banos Creek; 2,000 feet west and 500 feet north of the southeast corner of section 21, T. 11 S., R. 9 E., MDB&M; Latitude 36 degrees, 57 minutes, 23 seconds north and Longitude 120 degrees, 59 minutes, 16 seconds west; USGS Ortigalita Peak NW Topographic Quadrangle, NAD 27.
RANGE IN CHARACTERISTICS: Depth to strongly weathered conglomerate rock is 20 to 40 inches. The moisture control section of 6 to 16 inches is moist throughout from about January 1 to May 1 and dry throughout from about July 1 to November 1. 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 never below 41 degrees F. Organic matter content is 1 to 2 percent in the upper 4 inches. The particle-size control section averages less than 35 percent rock fragment content.
The A horizon has color of 10YR 4/4; 7.5YR 3/4, 4/4 or 5/4. Moist color is 10YR 3/4 or 7.5YR 3/4. Clay content is 27 to 35 percent. Gravel and cobble content is 3 to 15 percent. Reaction is neutral or slightly alkaline. BAt horizons occur in some profiles.
The Bt horizon has color of 7.5YR 3/4, 4/4, 4/6, 5/4, 5/6; 5YR 5/4, 5/6 or 6/6. Moist color is 7.5YR 3/4, 4/4, 4/6, 5/6; 5YR 4/4, 4/6, or 5/6. Texture is very gravelly clay loam, cobbly clay loam, gravelly clay loam, gravelly clay or clay. Clay content is 35 to 45 percent. Gravel content is 5 to 40 percent. Cobble content is 0 to 20 percent. Reaction is slightly alkaline or moderately alkaline.
The BCt horizon, when present, has color of 7.5YR 5/4, 5/6, 6/6; 5YR 5/4 or 5/6. Moist color is 7.5YR 4/4, 5/6, 5/8; 5YR 4/4 or 4/6. Texture is very cobbly clay loam, very gravelly clay loam or very gravelly clay. Clay content is 35 to 45 percent. Gravel content is 15 to 40 percent. Cobble content is 7 to 27 percent. Reaction is slightly alkaline or moderately alkaline. Some pedons have a Btk horizon instead of a BCt horizon.
COMPETING SERIES: These are the Contra Costa and Trabuco series. Contra Costa soils (MLRA 15), on foothills and mountains, have a lithic contact at a depth of 20 to 40 inches. Trabuco soils (MLRA 18), on foothills, have a paralithic contact of weathered basic rock at a depth of 40 to 80 inches.
GEOGRAPHIC SETTING: Conosta soils are on foothills and strath terraces on hills. Slope is 2 to 50 percent. These soils formed in material weathered from conglomerate rock. Elevation is 200 to 1,800 feet. The climate is semiarid with hot dry summers and cool moist winters. The mean annual precipitation is 9 to 12 inches. Mean January temperature is 44 degrees F; mean July temperature is 76 degrees F. and the mean annual temperature is 60 to 64 degrees F. The frost-free season is 200 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arburua, Bapos, Los Banos, and Wisflat soils. Arburua soils, on foothills, hills and mountains, have a fine-loamy particle-size control section. Bapos soils, on terraces and fan remnants, are more than 60 inches deep. Los Banos soils, on terraces and fan remnants, are more than 60 inches deep. Wisflat soils, on foothills, hills and mountains, have a lithic contact at a depth of 10 to 20 inches and have a coarse-loamy particle-size control section.
DRAINAGE AND PERMEABILITY: Well drained; medium to very high runoff; slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing and as wildlife habitat. The vegetation is wild oats, soft chess, filaree, red brome, foxtail, and other annual grasses and forbs.
DISTRIBUTION AND EXTENT: These soils are on the eastern edge of the Diablo Range, north of Little Panoche Creek in the California Coast Ranges bordering the western edge of the Central San Joaquin Valley of California. 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 mapped as Los Banos, Kettleman, and Contra Costa series. They are being differentiated from Los Banos series by being moderately deep, from Kettleman series by having a xeric moisture regime and from Contra Costa series by having a paralithic contact. Former competing series Argonaut, Fancher, Kilaga and Phipps are not in a superactive cation-exchange activity class.