LOCATION LOS BANOS CAEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Calcic Haploxeralfs
TYPICAL PEDON: Los Banos clay loam - on a slope of 3 percent under soft chess, wild oats, foxtail fescue, foxtail barley, wild mustard and other annual grasses and forbs at an elevation of 620 feet. (Colors are for dry soil unless otherwise stated. When described on August 2, 1978, the soil was dry from 0 to 15 inches and slightly moist from 15 to 63 inches).
A--0 to 9 inches; brown (7.5YR 5/4) clay loam, brown (7.5YR 4/4) moist; moderate coarse subangular blocky structure; hard, friable, very sticky and moderately plastic; common very fine roots; few very fine and fine tubular pores; slightly alkaline (pH 7.5); gradual smooth boundary. (2 to 11 inches thick)
BA--9 to 15 inches; brown (7.5YR 5/4) clay, brown (7.5YR 4/4) moist; moderate coarse subangular blocky and weak medium prismatic structure; hard, friable, very sticky and very plastic; common very fine roots; common very fine and few fine tubular pores; few thin clay films on faces of peds; slightly effervescent, carbonates disseminated, calcium carbonate equivalent is 9 percent; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 11 inches thick)
Btk1--15 to 25 inches; strong brown (7.5YR 5/6) clay, strong brown (7.5YR 4/6) moist; strong medium subangular blocky structure; very hard, friable, very sticky and very plastic; common very fine roots; common very fine tubular pores; few thin clay films on faces of peds and in pores; strongly effervescent, carbonates disseminated and segregated as few irregular soft masses, calcium carbonate equivalent is 17 percent; moderately alkaline (pH 8.0); clear smooth boundary. (7 to 11 inches thick)
Btk2--25 to 38 inches; strong brown (7.5YR 5/6) clay, yellowish red (5YR 5/6) moist; moderate medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; few very fine roots; common very fine tubular pores; common moderately thick clay films on faces of peds and in pores; strongly effervescent, carbonates disseminated and segregated as many fine and medium soft masses, calcium carbonate equivalent is 24 percent; moderately alkaline (pH 8.0); clear wavy boundary. (10 to 14 inches thick)
Btk3--38 to 55 inches; yellowish red (5YR 5/8) clay, yellowish red (5YR 4/6) moist; moderate medium subangular blocky structure; very hard, firm, moderately sticky and very plastic; few very fine roots; few very fine tubular pores; common thin clay films on faces of peds and in pores, with many thick pressure faces on peds; strongly effervescent, carbonates disseminated and segregated as common fine and medium soft masses, calcium carbonate equivalent is 23 percent; moderately alkaline (pH 8.0); abrupt wavy boundary. (0 to 18 inches thick)
C--55 to 63 inches; reddish yellow (5YR 6/8) cobbly clay loam; yellowish red (5YR 4/6) moist; massive; weakly cemented; hard, friable, moderately sticky and moderately plastic; common very fine tubular pores; strongly effervescent, carbonates disseminated, calcium carbonate equivalent is 23 percent; 15 percent cobbles, 3 to 8 inches long and 5 percent gravel from mixed sources; moderately alkaline (pH 8.0).
TYPE LOCATION: Merced County, California; approximately 8 miles southwest of Los Banos, 1.2 miles west southwest of the Los Banos Creek Detention Dam and 1,300 feet south of Los Banos Reservoir; 1700 feet south and 750 feet west of the northeast corner of section 14, T. 11 S., R. 9 E., MDB&M; Latitude 36 degrees, 58 minutes, 47 seconds north and Longitude 120 degrees, 56 minutes, 51 seconds west; USGS Ortigalita Peak Topographic Quadrangle, NAD 27.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 61 to 66 degrees F and the soil temperature is below 47 degrees F. in part of January and February and is not below 41 degrees F. at any time. The soil between the depths of 4 and 12 inches is moist throughout from about January 1 to May 1 and dry from July 1 to October 31.
The A horizon has color of 10YR 5/3, 5/4; 7.5YR 5/4 or 4/4. Moist color is 10YR 3/3, 3/4, 4/3, 4/4; 7.5YR 4/4 or 3/4. Organic matter content is 0.5 to 4 percent. Clay content is 27 to 40 percent. Calcium carbonate equivalent is 0 to 15 percent. Gravel content is 0 to 14 percent. Cobble content is 0 to 5 percent. Reaction is slightly alkaline or moderately alkaline. The lower boundary is clear or gradual.
The BA and Bt horizon, when present, have color of 10YR 5/3, 5/4; 7.5YR 5/4 or 4/4. Moist color is 10YR 4/3, 4/4; 7.5YR 4/3, 4/4 or 3/4. Texture is clay loam or clay. Clay content is 27 to 50 percent. The upper part of the B horizon has an increase in clay content of 5 to 15 percent (absolute). Calcium carbonate equivalent is 1 to 15 percent. Gravel content is 0 to 14 percent. Cobble content is 0 to 5 percent. Reaction is slightly alkaline or moderately alkaline.
The Btk horizon has color of 10YR 5/6, 5/4; 7.5YR 5/8, 5/6, 5/5, 5/4; 5YR 5/8, 5/6, 5/4, 4/8, 4/4. Moist color is 10YR 8/2, 5/4, 4/4; 7.5YR 5/6, 5/4, 4/6, 4/5, 4/4, 4/3; 5YR 3/6, 4/4, 4/6 or 5/6. Texture is clay loam or clay. Clay content is 35 to 55 percent. Calcium carbonate equivalent is 15 to 30 percent and there are more than 5 percent identifiable secondary carbonates in this calcic horizon. Gravel content is 0 to 14 percent. Cobble content is 0 to 5 percent. Reaction is slightly alkaline or moderately alkaline.
Some pedons have a 2Bk horizon. The 2Bk horizon has color of 5YR 4/6, 5/6; 7.5YR 5/6, 6/6; 10YR 6/5 or 8/2. Moist color is 5YR 4/4, 4/6; 7.5YR 5/4; 10YR 6/4 or 7/3. Texture is stratified very gravelly clay loam or very gravelly clay. Clay content is 35 to 50 percent. Calcium carbonate equivalent is 15 to 25 percent and there are more than 5 percent identifiable secondary carbonates in this calcic horizon. Gravel content is 35 to 60 percent. Cobble content is 0 to 10 percent.
The C horizon, when present, has color of 7.5YR 6/8 or 5YR 6/8. Moist color is 7.5YR 4/6 or 5YR 4/6. Texture is very cobbly sandy clay loam, cobbly sandy clay loam, very cobbly clay loam, cobbly clay loam, very gravelly sandy clay loam, very gravelly clay loam, gravelly sandy clay loam or gravelly clay loam. Clay content is 25 to 40 percent. Calcium carbonate equivalent is 1 to 25 percent. Cobble and/or gravel content is 25 to 60 percent. In some pedons the C horizon is not present.
COMPETING SERIES: There are no competing series at this time.
GEOGRAPHIC SETTING: Los Banos soils are on dissected terraces and fan remnants. These soils formed in calcareous gravelly alluvium derived from mixed rocks. Slope is 0 to 15 percent. Elevation is 130 to 2,000 feet. The climate is semiarid with hot dry summers and cool moist winters. The average annual precipitation is 8 to 12 inches. Mean January temperature is 45 degrees F; mean July temperature is 80 degrees F; mean annual temperature is 60 to 64 degrees F. The frost-free season is 200 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Ayar, Bapos, Contra Costa, and Pleito soils. Ayar soils, on foothills, have wide cracks and intersecting slickensides within 40 inches of the surface. Bapos soils, on terraces and fan remnants, have an abrupt A horizon to B horizon boundary with more than 15 percent clay increase in the upper part of the B horizon. Contra Costa soils, on mountains, have a lithic contact at a depth of 20 to 40 inches. Pleito soils, on alluvial fans, terraces and fan remnants, have a mollic epipedon and a fine-loamy particle-size control section.
DRAINAGE AND PERMEABILITY: Well drained; low to high runoff; slow permeability.
USE AND VEGETATION: These soils are used for cotton and sugar beet production. Where irrigation water is not available they are used for livestock grazing and dryland barley production. The vegetation is soft chess, red brome, filaree, clover, wild oats, foxtail fescue, and other annual grasses and forbs.
DISTRIBUTION AND EXTENT: These soils occur on the western edge of the San Joaquin Valley and in intermountain valleys of the Diablo Range of the California Coast Ranges. They are moderately extensive. MLRA 17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Los Banos Area, 1940. Revised in Merced County, Western Part, 1980.
REMARKS: These soils were formerly classified as Haplargids with mixed clay mineralogy and as Haploxeralfs. Presence of carbonates was determined by 10 percent HCl. Calcium carbonate equivalent was determined by HCl and syringe field kit. Organic matter determined by Walkley-Black digestion method.
Soils mapped in San Benito County with slopes greater than 15 percent are excluded from the series concept. Geomorphically, the taxonomic unit is unlikely to occur at both 0 percent slopes and 50 percent slopes. Soils with slope greater than 15 percent will be correlated to either taxadjuncts or a new series. The mean annual precipitation range in characteristics was not expanded to accommodate the 5 to 8 inches of mean annual precipitation that the San Benito County Soil Survey uses. This climatic data is questionable and it is estimated that all areas where Los Banos series is mapped in San Benito County have more than 8 inches mean annual precipitation.
In the conversion from SCS-5 and MUIR data to NASIS on the Merced County, Western Part, California Soil Survey, several of the calcium carbonate percents were not entered correctly. The correct percentages should be entered in NASIS as follows: A horizon - 5 to 15 percent calcium carbonate; BA, Btk horizons - 15 to 30 percent calcium carbonate; C horizon - 1 to 25 percent calcium carbonate.
ADDITIONAL DATA: NSSL pedons S87CA-019-007 (1406-1414), S87CA-019-011 (1450-1458) and S87CA-047-002 (taxadjuncts)