LOCATION ALO                CA
Established Series


The Alo series consists of moderately deep, well drained soils. They formed in material weathered from shale or sandstone on mountains. Alo soils have slopes of 2 to 75 percent. The mean annual precipitation is about 17 inches and the mean annual temperature is about 61 degrees F.

TAXONOMIC CLASS: Fine, smectitic, thermic Aridic Haploxererts

TYPICAL PEDON: Alo silty clay - annual range (Colors are for dry soil unless otherwise stated.)

A--0 to 14 inches; dark grayish (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; strong coarse and medium subangular blocky structure; very hard, firm, sticky and very plastic; many very fine interstitial and tubular pores; mildly alkaline (pH 7.6); gradual way boundary. (8 to 16 inches thick)

Bss--14 to 30 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate coarse prismatic structure; very hard, very firm, very sticky and very plastic; common very fine roots mostly along faces of peds; many very fine tubular pores; many slickensides; very slightly effervescent with disseminated lime; mildly alkaline (pH 7.8); gradual wavy boundary. (8 to 18 inches thick)

Bk--30 to 36 inches; light olive brown (2.5Y 5/4) silty clay, olive brown (2.5Y 4/4) moist; massive; very hard, firm, sticky and very plastic; few very fine roots; common very fine interstitial and tubular pores; strongly effervescent with lime disseminated and few irregular soft bodies; moderately alkaline (pH. 8.0); gradual wavy boundary. (6 to 16 inches thick)

Cr--36 to 50 inches; light yellowish brown (2.5Y 6/4) soft shale.

TYPE LOCATION: Monterey County, California; Mee Ranch, 2 1/4 miles north of Highway 25, 1 1/2 miles SSE of Cleveland Rock; NW 1/4 NW 1/4 sec. 36, T. 19 S., R. 10 E., projected.

RANGE IN CHARACTERISTICS: Depth to a paralithic contact of shale is 24 to 40 inches. The mean annual soil temperature is about 60 to 66 F. at 20 inch depth. From about late April or May until November the soils are continuously dry and cracks 1/2 to 2 inches wide extend from the surface to a depth of 20 inches or more. The rest of the year the soils are moist in some or all parts below 5 inches and the cracks are closed. Few to many slickensides are present in some part from near the surface to near the contact with soft shale.

The A horizon is 10YR 4/2, 4/3, 5/2 or 5/3; 2.5Y 4/2 or 5/2 with moist values of 3 or more. It is clay loam, silty clay, or clay and has 35 to 55 percent clay. Coarse fragments of shale and other rock fragments are less than 5 percent. This horizon is slightly acid to moderately alkaline, but is not calcareous in the upper 12 to 20 inches or none of the A horizon is calcareous. In the less alkaline soils, alkalinity increases with depth.

The Bk horizon is 10YR 4/4, 5/2, 5/3, 5/4, 6/2, 6/3, 6/4; 2.5Y 5/2, 5/4, 6/4 and value is one or two units higher than in the A horizon. It is clay loam, silty clay or clay. Coarse fragments of shale and other rock fragments are 0 to 10 percent.

COMPETING SERIES: These are the Aido (CA), Altamont (CA), Auld (CA), Ayar (CA), Bosanka (CA), Centerville (CA), Cibo (CA), Climara (CA), Cropley (CA), Myers (CA), Porterville (CA), and Vaquero (CA) series. Altamont, Auld, Ayar, Centerville, Cropley, Myers, and Porterville soils have a paralithic contact at depths of more than 40 inches. Aido soils have cracks that are closed for 90 days or less. Cibo and Climara soils have a lithic contact. Vaquero soils are calcareous throughout with a moist color value of more than 3 throughout.

GEOGRAPHIC SETTING: The Alo soils are on mountains at elevations of 200 to 3,250 feet. They formed in material weathered from shale and sandstone. The climate is dry subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation is 9 to 25 inches. Mean annual temperature is 59 to 63 degrees F.; average January temperature is 48 to 58 degrees F.; average July temperature is 67 to 70 degrees F. Frost-free period is 200 to 310 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Altamont, Ayar, Diablo, and Vaquero soils and, Gazos, Los Osos, Nacimiento, San Benito. Gazos, Nacimiento and San Benito soils have less than 35 percent clay. Los Osos soils have an argillic horizon.

DRAINAGE AND PERMEABILITY: Well-drained; low to very high runoff; slow permeability after soil cracks are swollen shut.

USE AND VEGETATION: Used mainly for livestock grazing with small areas used for the production of small grains, hay and specialty crops. Vegetation in uncultivated areas is annual grasses and forbs.


DISTRIBUTION AND EXTENT: Coast Range in central and southern California. The soils are of moderate extent in MLRA-15.

SERIES ESTABLISHED: Monterey County, California, 1972.

REMARKS: The Altamont series has been split into two series. Soils deeper than 40 inches to a paralithic contact are retained in the Altamont series. Soils less than 40 inches deep to a paralithic contact are placed in the Alo series. On July 17, 1984, a decision was made about the lowest possible limit of the mean annual precipitation. This lowest limit appears to be 9 inches because it seems to keep the climate and the moisture necessary for a Xeric moisture regime.

Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - the zone from the surface to a depth of 30 inches (A1,A2)

Paralithic contact - the boundary at 36 inches (Cr)

Series reclassified on June 1996

Runoff terminology adjusted 6/96 to the adjective criteria of the Soil Survey Manual, 10/93.

ADDITIONAL DATA: Twp pedons sampled in Orange Co. as Solano. They occur in MLRA outside what is typical for the series: NSSL pedons S71CA-059-008 and -009.

National Cooperative Soil Survey