The Westfan series consists of very deep, well drained soils on relict alluvial fans. 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 60 to 62 degrees F.

Taxonomic class: Fine-loamy, mixed, superactive, thermic Pachic Haploxerolls

Westfan loam, 0 to 2 percent slopes, cropland. When described on October 25, 1988, the soil was moist below 18 inches.

Ap1—0 to 4 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine and fine interstitial pores; neutral (pH 6.9); abrupt smooth boundary.

Ap2—4 to 14 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak moderate subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine and fine tubular pores; neutral (pH 7.3); clear smooth boundary.

ABt—14 to 24 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak coarse prismatic structure parting to moderate fine angular block; hard, friable, slightly sticky and slightly plastic; common very fine roots; common very fine tubular pores; continuous moderately thick clay films lining pores and on ped faces; slightly alkaline (pH 7.5); clear smooth boundary.

Btk—24 to 33 inches; brown (10YR 4/3) fine sandy loam, dark brown (10YR 3/3) moist; strong medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine tubular and few very fine interstitial pores; common moderately thick clay films on ped faces and lining pores; strongly effervescent; disseminated lime in seams; slightly alkaline (pH 7.7); clear smooth boundary.

Ck1—33 to 42 inches; yellowish brown (10YR 5/4) fine sandy loam, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine tubular and interstitial pores; moderately alkaline (pH 7.9); strongly effervescent with disseminated lime in seams and concretions; clear smooth boundary.

Ck2—42 to 55 inches; brown (10YR 5/3) fine sandy loam, brown (10YR 4/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine interstitial pores; strongly effervescent with disseminated line in seams and nodules; moderately alkaline (pH 7.9); gradual smooth boundary.

C1—55 to 69 inches; light yellowish brown (10YR 6/4) fine sandy loam, mixed dark brown (10YR 3/3) and brown (10YR 4/3) moist; massive; hard, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine interstitial pores; moderately alkaline (pH 8.0); gradual wavy boundary.

C2—70 to 92 inches; light yellowish brown (10YR 6/4) loam, dark yellowish brown (10YR 4/4) moist; massive; very hard, very friable, sticky and plastic; few very fine interstitial pores; moderately alkaline (pH 8.2); gradual smooth boundary.

2C—92 to 100 inches; light yellowish brown (10YR 6/4) silty clay loam, yellowish brown (10YR 5/4) moist; massive; very hard, firm, very sticky and very plastic; few very fine interstitial pores; moderately alkaline (pH 8.3).

Type location: Colusa County, California; located about 1 mile east of Williams; 3200 feet west and 720 feet south of the northeast corner of section 19, T. 15 N., R. 2 W., MDB&M; 39 degrees, 08 minutes, 45 seconds north latitude and 122 degrees, 07 minutes, 35 seconds west longitude; USGS Williams, California topographic quadrangle.

Solum thickness ranges from 25 to greater than 60 inches. The mean annual soil temperature is 63 to 65 degrees F. and the temperature is above 47 degrees F. the entire year. The 6 to 17 inch soil moisture control section is dry in all parts from May 15 to October 31 and is moist in some or all parts from November 1 to May 31. This soil is calcareous below a depth of 20 to 40 inches. The 10 to 40 inch textural control section averages 18 to 27 percent clay. Some pedons are strongly alkaline throughout.

The Ap horizon is 10YR 5/3, 5/2, 4/3, 4/2. Moist color is 10YR 3/3, 3/2. Texture is clay loam, loam, or gravelly loam. Reaction is neutral to slightly alkaline.

The ABt horizon is 10YR 5/3, 4/3. Moist color is 10YR 4/3, 3/3. Texture is sandy clay loam, loam, or gravelly loam. Reaction is neutral to moderately alkaline.

The Btk horizon is 10YR 5/4, 5/3, 4/3. Moist color is 10YR 4/4, 4/3, 3/3. Texture is sandy clay loam, loam, fine sandy loam, or gravelly loam. Reaction is neutral to moderately alkaline.

The C and 2C horizon is 10YR 6/4, 5/4, 5/3. Moist color is 10YR 3/3, 3/4, 4/4, 4/3, 5/4. Texture is silty clay loam, loam, sandy clay loam or fine sandy loam. Reaction is slightly to moderately alkaline.