LOCATION CAPAY CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Typic Haploxererts
TYPICAL PEDON: Capay clay, cultivated. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 5 inches; dark grayish brown (2.5Y 4/2) clay, very dark grayish brown (10YR 3/2) moist; strong medium granular structure in upper 1 or 2 inches and strong coarse prismatic structure below; very hard, very firm, sticky and very plastic; many fine roots; common very fine tubular pores; slightly acid (pH 6.5); clear smooth boundary. (5 to 8 inches thick).
Bk--5 to 21 inches; dark grayish brown (2.5Y 4/2) clay, very dark grayish brown (10YR 3/2) moist; few fine prominent strong brown (7.5YR 5/6) masses of iron accumulations, moist; strong very coarse prismatic structure; very hard, very firm, sticky and very plastic; few fine roots; common very fine tubular pores; strongly effervescent, fine soft masses of lime in lower 4 inches; neutral (pH 7.0); clear wavy boundary. (12 to 16 inches thick).
Bssk1--21 to 32 inches; brown (10YR 5/3) clay, dark brown (10YR 3/3) moist; strong coarse prismatic structure; very hard, very firm, sticky and very plastic; many fine roots; common very fine tubular pores; prominent intersecting slickensides; strongly effervescent, fine soft masses of lime; moderately alkaline (pH 8.0); clear wavy boundary. (8 to 12 inches thick).
Bssk2--32 to 40 inches; brown (10YR 5/3) clay, dark yellowish brown (10YR 4/4) moist; faces of peds dark brown (10YR 3/3) moist; moderate medium prismatic structure; hard, firm, sticky and very plastic; few fine roots; many very fine tubular pores; distinct intersecting slickensides; slightly effervescent, fine soft masses of lime; moderately alkaline (pH 8.0); gradual smooth boundary. (8 to 10 inches thick).
Bssk3--40 to 50 inches; pale brown (10YR 6/3) clay, dark yellowish brown (10YR 4/4) moist; faces of peds dark brown (10YR 3/3); moist; weak coarse angular blocky structure; hard, firm, sticky and very plastic; few fine roots, many very fine tubular pores; distinct intersecting slickensides; slightly effervescent; fine soft masses of lime; moderately alkaline (pH 8.0); diffuse boundary. (8 to 10 inches thick).
B'k--50 to 62 inches; yellowish brown (10YR 5/6) clay, dark yellowish brown (10YR 4/4) moist; faces of peds dark brown (10YR 3/3); few fine distinct strong brown (7.5YR 5/6) mottles, yellowish brown (10YR 5/6) moist; weak fine and medium angular blocky structure; hard, firm, sticky and very plastic; many very fine tubular pores; slightly effervescent, fine soft masses of lime; moderately alkaline (pH 8.0).
TYPE LOCATION: Solano County, California; about 2 1/2 miles northeast of Elmira; about 200 feet east and 50 feet north of the SW corner of section 16, T.6 N., R.1 E., MDB&M.38 degrees North latitude, 21 minutes, 33 seconds, and 121 West longitude, 52 minutes, 38 seconds.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is estimated to range from 60 degrees to 66 degrees F. Some pedons are saline-sodic throughout. The soils have 1 to 2 cm wide cracks that open and close at least once each year and remain open for 150 days or less in the summer.
The A horizon is 10YR 5/2, 4/2, 3/2, 5/3, 4/3; 7.5YR 5/2, 5/4, 4/2; 2.5Y 5/2, 4/2 or 3/2, moist values are commonly one unit lower. Texture is clay, silty clay, silty clay loam or clay loam. Reaction is moderately acid to moderately alkaline becoming more alkaline with increasing depth. Some pedons have a few mottles in the A horizon. These are commonly associated with rice culture. The lower part of the A horizon may have intersecting slickensides.
The Bssk and B'k horizons are 10YR 7/2, 6/4, 6/3, 5/4, 4/2, 4/3, 4/4, 5/2, 5/3; 2.5Y 6/2, 5/2, 5/4, 5/6, 4/4; 5Y 6/4, 6/3, 5/3, 5/2 or 4/3. Moist values are the same or 1 to 2 units darker. Texture is clay, silty clay, silty clay loam or clay loam. Some pedons have loam textures in the lower part of the profile. Reaction is neutral to strongly alkaline. Lime is in concretions, soft masses and disseminated throughout the horizon.
COMPETING SERIES: These are the Ayar, Bosquejo and Maxwell series. Ayar soils are well drained and have slopes of more than 9 percent. Bosquejo soils have redoximorphic features and no secondary carbonates below the lithologic discontinuity. Maxwell soils are 24 to 56 inches deep to carbonates and have a chroma of 1.5 in the A horizon.
GEOGRAPHIC SETTING: Capay soils are on alluvial fans, alluvial flats, in interfan basins, basin rims and basins at elevations below 1,200 feet. They formed in moderately fine and fine textured alluvium derived from sandstone and shale or other mixed rock sources. Slopes are 0 to 9 percent. The soils are in a dry climate of relatively hot dry summers and cool moist winters. Mean annual precipitation ranges from 9 to 28 inches. Mean January temperature is 47 degrees F, mean July temperature is 72 degrees F, mean annual temperature ranges from 58 degrees to 63 degrees F. Frost-free season is 185 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Clear Lake, Myers, San Ysidro, Yolo and Zamora soils. Clear Lake soils are on lower positions and have chroma of less than 1.5. Myers soils have dry value of more than 5.5. San Ysidro and Zamora soils have argillic horizons. Yolo soils have less than 35 percent clay in the series control section.
DRAINAGE AND PERMEABILITY: Moderately well drained; negligible to high runoff, slow to very slow permeability. Also some pedons have a water table between depth of 4 and 6 feet. Some areas are subject to rare, occasional or frequent flooding.
USE AND VEGETATION: Used for growing irrigated crops such as tomatoes, sugar beets, beans or grain sorghum, dry farmed to small grains, and irrigated and dryland pasture. Native vegetation is a dense stand of annual grasses and forbs.
DISTRIBUTION AND EXTENT: Western edge of the Sacramento Valley and intermountain valleys of the Coast Range of northern California. The soil is extensive in MLRA-17 and has been mapped in MLRA 14 in some places
MLRA OFFICE RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Woodland Area, California, 1909.
REMARKS: Redoximorphic features in the A horizon are associated with rice culture.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of 21 inches (Ap, Bssk1).
Cracking - it is assumed from the cracking statement in the RIC that the soil does not meet Aridic subgroup criteria.
Series reclassified May 1996.
Runoff terminology adjusted 5/96 to the adjective criteria of the Soil Survey Manual, 10/93.
The previous horizonation Ap, Ak, Bssk1, Bssk2, Bssk3, Bk is updated. The suffix k indicated an accumulation of carbonates making the Ak a B horizon. The RIC stated that "The lower part of the A horizon has intersecting slickensides" but the Type Location does not have them. Thus Ak is changed to Bk and the last horizon is changed to B'k. (KP) 6/2003
ADDITIONAL DATA: NSSL pedons: S64CA-095-002 (40A-385); S64CA-113-013 (40A-3086); S91CA-099-003 (91P-344); S67CA-065-001; S64CA-113-013; S91CA-099-003 and -004 (partial pedons); S92CA-099-005 (county type location).