LOCATION BONNET CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Calcic Haploxerolls
TYPICAL PEDON: Bonnet gravelly loam - on a 2 percent slope under pasture at 2,820 feet elevation. (Colors are for dry soil unless otherwise noted. When described March 6, 1970 the soil was moist throughout).
Ap1--0 to 4 inches; grayish brown (2.5Y 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; 30 percent fine and medium (1 to 7 cm) subrounded pebbles; moderately alkaline (pH 8.20; abrupt smooth boundary. (2 to 6 inches thick)
Ap2--4 to 14 inches; grayish brown (2.5Y 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; 30 percent fine and medium (1 to 7cm) subrounded pebbles; moderately alkaline (pH 8.4), clear smooth boundary. (8 to 12 inches thick)
AC--14 to 26 inches; grayish brown(2.5Y 5/2) very gravelly loam, dark brown (10YR 3/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; 45 percent fine and fine and medium (1 to 7cm) subrounded pebbles; moderately alkaline (pH 8.4), clear smooth boundary. (10 to 14 inches thick)
C1ca--26 to 35 inches; pale brown (10YR 6/3) very gravelly loam, dark brown (10YR 3/3) moist; massive; slightly hard, friable, slightly plastic and slightly sticky; 60 percent fine and medium (1 to 7cm) subrounded pebbles; slightly effervescent with disseminated lime, strongly effervescent carbonate accumulations on the underside of about 50 percent of the pebbles, moderately alkaline (pH 8.4), abrupt smooth boundary. (6 to 12 inches thick)
C2ca--35 to 46 inches; pale brown (10YR 6/3) very gravely sandy loam, dark brown (10YR 4/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; 60 percent fine and medium (1 to 7cm) subrounded pebbles; slightly effervescent with disseminated lime, violently effervescent carbonate accumulations on the underside of 50 to 80 percent of the pebbles; moderately alkaline (pH 8.4), clear smooth boundary. (9 to 14 inches thick)
Cca3--46 to 61 inches; pale brown (10YR 6/3) extremely gravelly loamy sand, dark brown (10YR 4/3) moist; massive; slightly hard, very friable, nonsticky and nonplastic; 80 percent fine and medium pebbles; slightly effervescent with disseminated lime, violently effervescent carbonate accumulations on the underside of 80 to 90 percent of the pebbles and almost all of the larger rock fragments; moderately alkaline (pH 8.4).
TYPE LOCATION: Siskiyou County, California; west end of the county gravel pit 2 1/2 miles north of Gazelle and just south of a paved road; about 800 feet south and 1,050 feet east of the northwest corner sec. 28 T. 43 N., R. 6 W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 54 to 59 degrees F; the mean January soil temperature is 37 to 38 degrees F; the mean July soil temperature is 71 to 79 degrees F. The soil temperature exceeds 41 degrees F from March 1 to December 20 and exceeds 47 degrees F from April 1 to November 25. The soil between the depths of 10 and 30 inches is dry from July 1 to October 15 in most years (100 to 110 days) and is moist in some or all parts the rest of the year. About 5 to 15 percent of the gravel is subrounded limestone fragments. Depth to lime ranges from 20 to 30 inches. The mollic epipedon is 10 to 14 inches thick.
The A horizon is brown grayish brown or dark grayish brown 910YR 5/3, 5/2, 4/3, 4/2; 2.5Y 5/2, 4/2). Moist colors are black, very dark brown, very dark gray, very dark grayish brown or dark brown (10YR 2/1, 2/2, 3/1, 3/2, 3/3; 2.5Y 3/2). It is sandy loam, loam, gravelly sandy loam, or gravelly loam with 5 to 35 percent pebbles. It is slightly acid to moderately alkaline.
The upper C horizon is brown, yellowish brown, light yellowish brown, light olive brown, pale brown, very pale brown, or pale yellow (1YR 5/3, 5/4, 6/3, 6/4, 7/3, 7/4; 2.5Y 5/4, 6/4, 7/4). Moist colors are dark brown, dark yellowish brown, brown, or olive brown (10YR 3/3, 3/4, 4/3, 4/4; 2.5Y 4/4). It is very gravelly sandy loam or very gravelly loam and has less than 18 percent clay. It has 35 to 60 percent fine and medium gravel. The amount typically increases with increasing depth. It is slightly effervescent or strongly effervescent and has segregated secondary lime in filaments, seams or as lime coatings on the underside of pebbles. The lime coatings range from 0.5mm to 3mm thick.
The lower C horizon has the same color ranges as the upper C horizon but is loamy sand, sandy loam, or loam and is extremely gravelly with 60 to 80 percent rock fragments.
COMPETING SERIES: These are the Alpowa, Cooperton, Elquist (T), Hupp, Lakewin, and Middle series. Alpowa soils are dry for 70 to 90 consecutive days, have mostly silt loam texture, and have formed in material with a large component of loess. Copperton soils have a weakly or moderately cemented horizon at depths of 12 to 30 inches. Elquist soils have a silt loam or loam A horizon with a large component of loess and lime at a depth of 8 to 14 inches. The Cca horizon has 16 to 25 percent calcium carbonate. Hupp soils have a cambic horizon and have 18 to 24 percent clay in the particle size control section. Lakewin soils have a cambic horizon and have a very gravelly sand IIC horizon at a depth of 17 to 27 inches. Middle soils have a cambic horizon and are 20 to 40 inches deep over hard limestone.
GEOGRAPHIC SETTING: Bonnet soils are on terraces and alluvial fans. Slopes are 0 to 5 percent. The soils formed in alluvium mostly from mixed metamorphic rock sources but include some limestone. Most rock fragments are smooth and subrounded and consist of schist, shale, graywacke and siltstone. Elevations are 2,500 to 3,500 feet. The climate is continental and subhumid with warm dry summers and cold moist winters. The mean annual precipitation is 14 to 20 inches. Seasonal snowfall is 15 to 22 inches. Mean January temperature is 33 to 36 degrees F; mean July temperature is 68 to 70 degrees F; mean annual temperature is 49 to 52 degrees F. Frost-free season is 100 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Atter, Dotta, Duzel, Facey, Gazelle, Jilson, Kinkel and Stoner soils. Atter soils have an ochric epipedon, lack carbonates and have a sandy-skeletal control section. Dotta, Duzel, Facey, Gazelle, Jilson and Stoner soils have less than 35 percent coarse fragments in the control section. Also, all except Gazelle and Stoner have an argillic horizon. Gazelle soils have a duripan at depths of 20 to 40 inches and Stoner soils have an ochric epipedon.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderately rapid permeability.
USE AND VEGETATION: Used principally for irrigated or dryland hay, pasture and small grain production. A few small areas are used for potatoes. Uncultivated areas are used for rangeland. The native vegetation is bluebunch wheatgrass, Idaho fescue, Sandberg bluegrass, sagebrush, rabbitbrush, wild buckwheat, lupine and miscellaneous grasses and forbs.
DISTRIBUTION AND EXTENT: Bonnet soils are throughout the west half of Shasta Valley and the east side of Scott Valley in Siskiyou County, California. They are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Siskiyou County, California, 1978.
REMARKS: The organic carbon is assumed to be less than 0.6 percent at depths of 15 to 20 inches based on laboratory data and reference samples of other soils in the Shasta Valley Area.
Last revised by the state on 9/78.
The superactive cation exchange activity class was added in 03/2003 to the taxonomic classification by the National Soil Survey Center on request of the Reno MLRA office, without review of the soil series property data. The remainder of this document has not been updated.