The Corbiere series consists of very deep, somewhat poorly drained soils on basin rims. These soils formed in alluvium derived from mixed sources. Slope ranges from 0 to 2 percent. The mean annual precipitation is 14 to 16 inches, and the mean annual temperature is 61 to 63 degrees F.

Taxonomic class: Fine, mixed, superactive, thermic Cumulic Vertic Endoaquolls

Corbiere silt loam, 0 to 1 percent slopes, cropland. When described on October 25 1988 the soil was dry to 20 inches and moist below.

Ap—0 to 7 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; hard, friable, very sticky and very plastic; many very fine and few fine roots; common fine interstitial pores; strongly effervescent with disseminated lime; neutral (pH 7.3); clear smooth boundary.

Bw1—7 to 14 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; hard, friable, sticky and plastic; common very fine roots; common very fine tubular pores; strongly effervescent with disseminated lime; few, fine, prominent very dark grayish brown (2.5Y 3/2) moist masses of iron accumulation; slightly alkaline (pH 7.4); clear smooth boundary.

Bw2—14 to 22 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; hard, firm, sticky and slightly plastic; few very fine roots; common very fine tubular pores; strongly effervescent with disseminated lime; common, fine, prominent very dark grayish brown (2.5Y 3/2) moist masses of iron accumulation; neutral (pH 7.3); gradual smooth boundary.

2Bw—22 to 35 inches; brown (10YR 5/3) silty clay, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; very hard, firm, sticky and plastic; few very fine roots; few very fine tubular pores; strongly effervescent with disseminated lime; common, fine, prominent dark yellowish brown (10YR 4/4) moist masses of iron accumulation; slightly alkaline (pH 7.6); abrupt smooth boundary.

3Ab—35 to 46 inches; grayish brown (2.5Y 5/2) silty clay, very dark grayish brown (2.5Y 3/2) moist; moderate medium subangular blocky structure; very hard, firm, sticky and plastic; few very fine roots; few very fine tubular pores; strongly effervescent with disseminated lime; common, fine, faint dark yellowish brown (10YR 4/6) masses of iron accumulation; slightly alkaline (pH 7.4); clear smooth boundary.

3Bssb1—46 to 60 inches; grayish brown (2.5Y 5/2) silty clay, very dark grayish brown (2.5Y 3/2) moist; moderate medium subangular blocky structure; very hard, very firm, very sticky and very plastic; few very fine roots; few very fine interstitial and tubular pores; slightly effervescent; lime segregated in fine soft masses; many slickensides and common distinct pressure faces; common fine white sulfate crystals; slightly alkaline (pH 7.4); gradual smooth boundary.

3Bssb2—60 to 74 inches; grayish brown (2.5Y 5/2) silty clay, very dark grayish brown (2.5Y 3/2) moist; moderate medium subangular blocky structure; very hard, very firm, sticky and plastic; few very fine roots; few very fine interstitial and tubular pores; strongly effervescent; lime segregated in fine soft masses; many slickensides and many fine distinct pressure faces; common fine white sulfate crystals; slightly alkaline (pH 7.5).

3C1—74 to 96 inches; grayish brown (2.5Y 5/2) clay, olive brown (2.5Y 4/4) moist; moderate medium subangular blocky structure; very hard, very firm, sticky and plastic; few very fine roots; few very fine interstitial and tubualar pores; srtongly effervescent; dark gray (10YR 4/1) redoximorphic depletions; moderately alkaline (pH 8.0).

3C2—96 to 114 inches; light olive brown (2.5Y 5/4) clay; gray (10YR redoximorphic depletions; moderately alkaline (pH 8.0).

Type location: Colusa County, California; located about 4 1/2 miles northwest of Grimes, California 1.25 miles west on Sachreiter Basin Road from Dry Slough Road, 200 feet north into field; 1260 feet west and 2585 feet north of the southeast corner of section 4, T. 14 N., R. 1 W., MDB&M; 39 degrees, 05 minutes, 00 seconds north latitude and 121 degrees, 58 minutes, 15 seconds west longitude; USGS Grimes, California topographic quadrangle.

Mean annual soil temperature ranges from 63 to 65 degrees F. and the temperature remains above 47 degrees F. all year. The 10 to 40 inch textural control section weighted average clay content ranges from 35 to 50 percent. The sodium adsorption ratio ranges from 5 to 13 throughout. The 5 to 16 inch soil moisture control section is dry in all parts from May 15 to October 31 and is moist in all parts from November 15 to May 1.

The Ap horizon is 10YR 5/2, 5/3; 2.5Y 5/2. Moist color is 10YR 3/2, 3/3; 2.5Y 3/2. Texture is silt loam. Clay content ranges from 20 to 27 percent. Reaction is neutral or slightly alkaline.

The Bw horizon is 10YR 5/3, 5/2; 2.5Y 5/3, 5/2. Moist color is 10YR 4/2, 3/3, 3/2. Texture is silt loam or silty clay loam and averages 20 to 35 percent clay. Reaction is neutral to slightly alkaline.

The 2Bw horizons are 10YR 5/3, 5/2, 4/3; 2.5Y 5/3, 5/2. Moist color is 10YR 4/2 , 3/3, 3/2; 2.5Y 4/2. Texture is silty clay and ranges from 40 to 55 percent clay. Reaction is slightly or moderately alkaline.

The 3Ab horizon is 2.5Y 5/2; 10YR 5/3, 5/2. Moist color is 2.5Y 3/2; 10YR 3/3, 3/2. Texture is silty clay with 40 to 50 percent clay. Reaction is slightly to moderately alkaline.

The 3Bssb horizon is 10YR 5/3, 5/2; 2.5Y 6/3, 5/3, 5/2. Moist color is 10YR 4/2, 3/2; 2.5Y 4/3, 4/2, 3/2. Texture is silty clay with 40 to 55 percent clay. Reaction is slightly alkaline to moderately alkaline.