LOCATION LLANOSECO CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Chromic Haploxererts
TYPICAL PEDON: Llanoseco silty clay loam, on less than 1 percent slope under a cover of annual grasses at an elevation of 107 feet, (33 m). When described on 5/10/95, the soil was slightly moist below 18 inches, (46 cm). (Colors are for dry soil unless otherwise noted).
Ap--0 to 8 inches, (0 to 20 cm); pale brown (10YR 6/3) silty clay loam, dark grayish brown (10YR 4/2) moist; 33 percent clay; moderate fine subangular blocky structure; soft, friable, slightly sticky and moderately plastic; many very fine and few fine roots; common very fine tubular pores; moderately acid, pH 6.0 by pH meter 1:1 water; abrupt smooth boundary. (6 to 12 inches, (15 to 31 cm) thick)
2A--8 to 18 inches, (20 to 46 cm); grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; 38 percent clay; moderate medium prismatic parting to moderate fine angular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few fine roots; common very fine tubular pores; neutral, pH 6.6 by pH meter 1:1 water; clear smooth boundary. (6 to 10 inches, (15 to 25 cm) thick)
3Bss1--18 to 28 inches, (46 to 71 cm); brown (10YR 5/3) silty clay, dark grayish brown (10YR 4/2) moist; 42 percent clay; moderate medium prismatic structure parting to moderate fine angular blocky; slightly hard, friable, moderately sticky and very plastic; very few very fine roots; common very fine tubular pores; common slickensides; slightly alkaline; pH 7.4 by pH meter 1:1 water; gradual smooth boundary.
3Bss2--28 to 41 inches, (71 to 104 cm); brown (10YR 5/3) silty clay, dark grayish brown (10YR 4/2) moist; 42 percent clay; moderate medium prismatic structure parting to moderate fine angular blocky; slightly hard, friable, moderately sticky and very plastic; very few very fine roots; common very fine tubular pores; common slickensides; slightly alkaline, pH 7.7 by pH meter 1:1 water; gradual smooth boundary.
3Bss3--41 to 57 inches, (104 to 145 cm); brown (10YR 5/3) silty clay, dark grayish brown (10YR 4/2) moist; 43 percent clay; moderate medium prismatic structure parting to moderate fine angular blocky; very hard, firm, moderately sticky and very plastic; very few very fine roots; few very fine tubular pores; common very fine and fine gray (10YR 5/1) moist, irregular iron depletions lining pores; common slickensides; slightly alkaline, pH 7.8 by pH meter 1:1 water; clear smooth boundary.
3Bss4--57 to 71 inches, (145 to 180 cm); brown (10YR 5/3) silty clay, dark grayish brown (10YR 4/2) moist; 43 percent clay; moderate medium angular blocky structure; very hard, firm, moderately sticky and very plastic; very few very fine roots; common very fine tubular pores; common slickensides; moderately alkaline, pH 8.2 by pH meter 1:1 water; clear smooth boundary. (Combined thickness of the 3Bssb horizons are 40 to 60 inches, (102 to 152 cm) or more thick)
3Bk1--71 to 85 inches, (180 to 216 cm); pale brown (10YR 6/3) silty clay, brown (10YR 4/3) moist; 43 percent clay; moderate fine angular blocky structure; hard, friable, moderately sticky and very plastic; common very fine tubular pores; 2 percent calcium carbonate; strongly alkaline, pH 8.5 by pH meter 1:1 water; clear smooth boundary.
3Bk2--85 to 91 inches, (216 to 231 cm); yellowish brown (10YR 5/4) silty clay, dark yellowish brown (10YR 4/4) moist; moderate fine angular blocky structure; hard, very friable, moderately sticky and very plastic; common very fine tubular pores; strongly effervescent; 2 percent calcium carbonate; strongly alkaline, pH 8.5 by pH meter 1:1 water; abrupt wavy boundary. (Combined thickness of the 3Bkb horizons are 15 to 25 inches, (38 to 64 cm) thick)
4Bkqm--91 to 93 inches, (231 to 236 cm); indurated duripan; pink (7.5YR 8/4), reddish yellow (7.5YR 6/6) moist; massive parting to platy; 1/8 inch thick silica and lime cemented capping; strongly effervescent; 49 percent calcium carbonate.
TYPE LOCATION: Butte County, California; about 5.5 miles southwest of Dayton, approximately 20,370 feet north and 700 feet east of the northwest corner of Section 2, Township 19 N., Range 1 W.; in an unsectionized area in the Llano Seco Land Grant; 39 degrees, 35 minutes, 32 seconds North latitude and 121 degrees, 56 minutes, 43 seconds West longitude, NAD27. U.S.G.S. Quad: Llano Seco, California.
RANGE IN CHARACTERISTICS: Depth to duripan ranges from 60 to 120 inches, (152 to 305 cm). The mean annual soil temperature is 62 to 64 degrees F, (17 to 18 degrees C). The soil moisture control section is dry from May to October 15 (about 165 days). The particle-size control section ranges from 40 to 50 percent clay. Mineralogy is smectitic. Organic matter ranges from 1 to 3 percent to a depth of 28 inches, (71 cm) and ranges from 0.1 to 0.5 percent from 28 to 91 inches, (71 to 231 cm). Base saturation by ammonium acetate ranges from 93 to 100 percent throughout. Reversible surface-initiated cracks 1/2 to 1 inches, (12.7 to 25.4 mm) wide extend to a depth of 40 to 60 inches, (102 to 152 cm) from May to October (165 days) when the soil is not irrigated. Slickensides range from few to common in the 2Bss horizons from 18 to 72 inches, (46 to 183 cm). A fluctuating water table can occur between the top of the duripan and 54 inches, (137 cm) below the surface of the soil from December through March. Some pedons have redoximorphic features such as manganese or oxidized iron masses below a depth of 40 inches, (102 cm).
The Ap horizon dry color is 10YR 6/3, 6/2 or 5/2. Moist color is 10YR 4/2 or 4/3. Clay content ranges from 27 to 35 percent. Reaction ranges from moderately acid to slightly acid.
The 2A horizon dry color is 10YR 6/2, 5/2 or 5/3. Moist color is 10YR 4/2, 3/2 or 4/3. Clay content ranges from 35 to 40 percent. Reaction ranges from slightly acid to neutral.
The 3Bss horizon dry color is 10YR 6/3 or 5/3. Moist color is 4/3, 4/2 or 3/3. Texture is silty clay or clay. Clay content ranges from 40 to 60 percent. Reaction ranges from neutral to strongly alkaline.
The 3Bk horizon dry color is 10YR 5/4 or 6/3. Moist color is 10YR 4/3 or 4/4. Clay content ranges from 40 to 50 percent. Reaction ranges from moderately alkaline to strongly alkaline. Effervescence ranges from non-effervescent to strongly effervescent.
COMPETING SERIES: These are the Asolt and Hollenbeck series. Asolt soils are deep to lithic contact of basalt, have slopes of 15 to 50 percent, have 20 to 35 percent cobbles and stones, and are on mountains. Hollenbeck soils have a duripan at 40 to 60 inches, (102 to 152 cm).
GEOGRAPHIC SETTING: Llanoseco soils are in flood basins adjacent to overflow channels and flood plains of the Sacramento River. Slopes range from 0 to 2 percent. These soils formed in alluvium weathered from mixed rocks. Elevation is 90 to 105 feet, (27 to 33 m). Mean annual precipitation is 18 to 19 inches, (457 to 483 mm). The mean annual temperature is 60 degrees F, (16 degrees C). Frost free season is 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Dodgeland, Whitecabin, Parrott and Farwell soils. Dodgeland soils are very deep to a duripan, are poorly drained and are in overflow channels and in flood basins. Whitecabin soils are deep to a duripan, have redoximorphic features and are in flood basins. Parrott soils are very deep, are fine-silty and are on flood plains. Farwell soils are very deep, are fine-loamy, have an irregular decrease in organic matter and are in overflow channels and flood plains.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; high runoff, moderately slow saturated hydraulic in the A and B horizons and very slow to impermeable in the duripan. The soils are occasionally to frequently flooded for brief periods in December through March. A fluctuating water table can occur between the top of the duripan and 54 inches, (137 cm) below the surface of the soil from December through March. Water rarely ponds up to 2 inches, (5 cm) above the surface for brief duration from December through March.
USE AND VEGETATION: This soil is used for dryland grain, pasture, and wildlife habitat.
DISTRIBUTION AND EXTENT: Butte County, California. MLRA 17 - Sacramento Valley. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Butte County, California 2005. Source of name from Rancho Llano Seco.
REMARKS: These soils were previously mapped as Landlow in the Soil Survey of Chico Area, California 1925.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 18 inches, (0 to 46 cm) (Ap, 2A).
Cambic horizon - 18 to 91 inches, (46 to 231 cm) (3Bss1, 3Bss2, 3Bss3, 3Bss4, 3Bk1, 3Bk2).
Duripan - 91 to 93 inches, (231 to 236 cm) (4Bkqmb).
Soil moisture control section - 6 to 17 inches, (15 to 43 cm).
Particle-size control section - 10 to 40 inches, (25 to 102 cm).
This soil occurs on a landform characterized by consisting of an uplifted (anticline) basin and associated overflow channels which divide the Sacramento River meander belt and floodplain from the Butte Basin. This area is occasionally flooded and often thin layers of sediment are deposited on the surface.
ADDITIONAL DATA: Characterization data from lab pedon number: 95P0517, NSSL, Lincoln, NE.