Elkhorn series

The Elkhorn series consists of very deep, well drained soils on alluvial fans and marine terraces. These soils formed in old alluvium and in marine deposits. Slopes range from 0 to 50 percent. The average annual precipitation ranges from 20 to 35 inches, and the average annual air temperature is about 58 degrees F.

Elkhorn soils are similar to Danville and Pinto soils. They are mapped in a complex with Pfeiffer soils and are near Conejo, Danville, Elder, Pfeiffer, Pinto, Soquel, and Watsonville soils. Danville and Watsonville soils have a fine argillic horizon that has montmorillonitic mineralogy. Pinto soils have a mollic epipedon less than 20 inches thick. Conejo and Soquel soils do not have an argillic horizon. Elder and Pfeiffer soils have a coarse-loamy control section.

Typical pedon of Elkhorn sandy loam, 2 to 9 percent slopes, near Aptos, about 400 feet west-northwest of in tersection of New Brighton Road and McGregor Drive and 25 feet southerly from McGregor Drive, in T. 11 S., R. 1 W. (projected):

A11-0 to 3 inches; very dark grayish brown (10YR 3/2) sandy loam, very dark brown (10YR 2/2) moist; strong fine and medium granular structure; hard, friable, slightly sticky and slightly plastic; many fine roots and common medium roots; many very fine and fine interstitial and tubular pores; slightly acid; abrupt smooth boundary.

A12-3 to 15 inches; very dark grayish brown (10YR 3/2) sandy loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; many very fine interstitial pores and common very fine and fine tubular pores; about 5 percent pebbles 2 to 15 millimeters in diameter; medium acid; clear wavy boundary.

A3-15 to 21 inches; brown (10YR 4/3) sandy loam, very dark grayish brown (10YR 3/2) moist; moderate coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common medium and fine roots; many very fine interstitial pores and common very fine and fine tubular pores; few thin coatings on ped faces; slightly acid; clear wavy boundary.

B21t-21 to 29 inches; pale brown (10YR 6/3) sandy clay loam, dark yellowish brown (10YR 3/4) moist, dark brown (10YR 3/3) rubbed; many medium distinct yellowish brown (10YR 5/6) mottles and few fine prominent very dark brown (10YR 2/2) mottles, dry or moist; weak coarse and very coarse angular blocky structure; hard, friable, slightly sticky and slightly plastic; common fine roots; many very fine tubular and interstitial pores; few thin clay films as bridges between mineral grains; few fine black (10YR 2/1) flaked particles; few brown (10YR 4/3) weathered coarse sand grains; few iron and manganese krotovinas filled with material from A3 horizon; neutral; gradual wavy boundary.

B22t-29 to 41 inches; variegated light gray (10YR 7/2) and very pale brown (10YR 7/3) sandy clay loam, dark yellowish brown (10YR 4/4) and dark brown (7.5YR 4/4) moist, dark yellowish brown (10YR 4/4) rubbed; many medium and large distinct yellowish brown (10YR 5/6, 5/8) and strong brown (7.5YR 5/8) mottles; weak very coarse angular blocky structure; hard, friable, sticky and plastic; common very fine roots; common very fine interstitial pores and common very fine and fine tubular pores; few thin clay bridges between sand grains and clay films lining pores; many large thick to thin black (10YR 2/1) iron and manganese coatings in fractures; about 5 percent pebbles 2 to 15 millimeters in diameter; neutral; clear wavy boundary.

B23t-41 to 61 inches; variegated light gray (10YR 7/2) and very pale brown (10YR 7/3) sandy clay loam, grayish brown (10YR 5/2) and brown (10YR 5/3) moist, brown (7.5Y 4/4) rubbed; many medium prominent yellowish brown (10YR 5/8) and strong brown (10YR 5/8; 7.5YR 5/8) mottles; weak coarse and medium blocky structure; extremely hard, friable, sticky and plastic; few very fine roots; common very fine interstitial and tubular pores and common fine tubular pores; common thin to moderately thick clay bridges between sand grains and clay films lining pores; common black (10YR 2/1) thin to thick films of iron and magnesium in fractures and as thin bridges between sand grains; neutral.

The mollic epipedon ranges from 20 to 30 inches in thickness. The profile is 0 to 10 percent pebbles.

The A1 horizon has value of 3 to 5 when dry and chroma of 2 or 3. It ranges from medium acid to neutral.

The B2t horizon has a value of 5 to 7 and chroma of 2 to 4. In most pedons, the B2t horizon has value of 7 and chroma of 2 and 3 in a variegated pattern. Mottles occur in parts of the horizon where value is 6 or more. In some or all parts of the B2t horizon in most pedons, there are iron and manganese concretions, flakes, or coatings that have hue of 10YR, value of 2, and chroma of 1 or 2. The B2t horizon is sandy clay loam or clay loam. It is slightly acid to neutral.

A C horizon occurs in a few pedons. It has colors that are similar to those of the B2t horizon. The C horizon is typically loamy sand, sandy loam, or clay loam. It is slightly acid or neutral.