LOCATION HORST CAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Pachic Haploxerolls
TYPICAL PEDON: Horst silt loam - on a nearly level slope of less than 1 percent under walnut trees at an elevation of 85 feet. (Colors are for dry soil unless otherwise stated. When described on May 9, l985, the soil was slightly moist throughout.)
Ap--0 to 10 inches; brown (10YR 4/3) silt loam, dark brown (7.5YR 3/2) moist; moderate coarse prismatic structure parting to moderate coarse subangular blocky; hard, friable, sticky and plastic; common very fine and few medium roots; few very fine tubular pores; neutral (pH 7.0); clear smooth boundary. (3 to 12 inches thick)
A--10 to 26 inches; brown (10YR 4/3) silt loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; few very fine and medium roots; few very fine tubular pores; slightly alkaline (pH 7.5); gradual wavy boundary. (12 to 30 inches thick)
Bt1--26 to 39 inches; brown (10YR 4/3) silt loam, dark brown (7.5YR 3/4) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; few very fine and medium roots; many very fine tubular pores; few, thin clay films on faces of peds and lining pores; slightly alkaline (pH 7.8); gradual wavy boundary. (8 to 15 inches thick)
Bt2--39 to 49 inches; brown (7.5YR 5/4) silt loam, dark brown (7.5YR 3/4) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; few very fine roots; many very fine and few fine tubular pores; few thin clay films on faces on peds and lining pores; slightly alkaline (pH 7.8); gradual wavy boundary. (8 to 12 inches thick)
Bt3--49 to 60 inches; brown (7.5YR 5/4) silt loam, dark brown (7.5YR 3/4) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; common very fine and few fine tubular pores; few thin clay films on faces of peds and lining pores; slightly alkaline (pH 7.8); gradual wavy boundary. (7 to 13 inches thick)
BCt--60 to 70 inches; brown (7.5YR 5/4) loam, dark brown (7.5YR 3/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and few fine tubular pores; few thin clay films lining pores; slightly alkaline (pH 7.8).
TYPE LOCATION: Yuba County, California; about 0.75 miles east of Wheatland on Spenceville Road, about 1350 feet south and 200 feet east of the intersection of Spenceville Road and Jasper Lane in a nonsectionized area of the Johnson Rancho land grant, T.14 N., R.5 E., MDBM Wheatland Quadrangle.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 64 to 66 degrees F. The soil temperature is above 47 degrees F. the entire year. The 6 to 18 inch section is dry in all parts from May 15 to October 31 and moist in all parts from November 15 to May 1. Clay content for the 10 to 40 inch particle-size control section ranges from 18 to 27 percent; fine sand and coarser sand ranges from 6 to 12 percent. Organic carbon content is 1 to 3 percent in the upper 35 inches. The mollic epipedon is 20 or more inches thick.
The A horizon has dry color of 10YR 5/3, 5/2, or 4/3 and moist color of 10YR 3/3, 3/2; or 7.5YR 3/2. Reaction is moderately acid to slightly alkaline.
The B horizon has dry color of 10YR 5/4, 4/3; 7.5YR 6/4 or 5/4 and moist color of 10YR 3/3; 7.5YR 4/4 or 3/4. Reaction is neutral or slightly alkaline. Texture is silt loam or loam.
Some pedons lack a BC horizon. Some pedons have a sandy loam and loamy sand overwash. Some pedons do not have a Bt horizon, or have clay percentages that remain constant or decrease with depth.
COMPETING SERIES: These are the Crow Hill and the Suey series. The Crow Hill soils have a paralithic contact at a depth of 20 to 40 inches. Suey soils have a difference of 12 degrees F. between mean winter and mean summer.
GEOGRAPHIC SETTING: Horst soils are on stream terraces. Slopes range 0 to 2 percent. The soils formed in alluvium from mixed rock sources. Elevation is 40 to 95 feet. The climate has hot, dry summers and cool, moist winters. The average annual precipitation is about 18 to 22 inches. The average January temperature is 46 degrees F.; the average July temperature is 79 degrees F.; the mean annual temperature is 61 to 63 degrees F. The frost-free season is 270 to 290 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Columbia, Conejo and Holillipah soils. Columbia soils lack mollic epipedons and have coarse loamy textural control sections. Conejo soils are in similar landscape positions and are fine-loamy. Hollillipah soils lack mollic epipedons and have sandy textural control sections. Columbia and Holillipah soils are on slightly lower flood plains.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability. Subject to rare flooding.
USE AND VEGETATION: Used for irrigated orchards.
DISTRIBUTION AND EXTENT: Southeastern part of the Sacramento Valley, California. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Yuba County, California, l988.
REMARKS:
Last revised by the state on 11/96.
No longer used in Butte Co. Removed edits made in 11/96 to cover use in Butte.