LOCATION KEYES CAEstablished Series
TAXONOMIC CLASS: Clayey, mixed, active, thermic, shallow Abruptic Durixeralfs
TYPICAL PEDON: Keyes cobbly loam - in a concave intermound on nearly level slopes under annual grass pasture at an elevation of 500 feet. (Colors for dry conditions unless otherwise noted).
A--0 to 3 inches; grayish brown (10YR 5/2) cobbly loam, very dark grayish brown (10YR 3/2) moist; massive; hard, friable, slightly sticky and slightly plastic; many fine roots; many fine interstitial pores; many cobbles over the surface; moderately acid (pH 5.8); clear smooth boundary. (1 to 8 inches thick)
AB--3 to 8 inches; grayish brown (10YR 5/2) gravelly loam, dark grayish brown (10YR 4/2) moist; weak medium blocky structure; hard, friable, slightly sticky and slightly plastic; common fine roots; common fine interstitial pores; more medium gravel than in the upper 3 inches; few thin clay films bridging mineral grains; slightly acid (pH 6.2); gradual smooth boundary. (0 to 8 inches thick)
Bt1--8 to 12 inches; grayish brown (10YR 5/2) gravelly clay loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure largely obscured by the gravel content; hard, friable, sticky and plastic; few fine roots; few fine interstitial and tubular pores; thin continuous clay films on peds; slightly acid (pH 6.4); abrupt smooth boundary.(4 to 8 inches thick)
2Bt2--12 to 16 inches; grayish brown (10YR 5/2) gravelly clay, dark grayish brown (10YR 4/2) moist; massive; hard, very firm, very sticky and very plastic; thin continuous clay films on peds and lining pores; pebbles are strongly weathered; slightly acid (pH 6.4); abrupt wavy boundary. (3 to 11 inches thick)
2Bqm--16 to 30 inches; yellowish brown (10YR 5/4) dry; strongly cemented duripan enclosing considerable gravel and resembling conglomerate, dark yellowish brown (10YR 4/4) moist; slightly platy in the upper part; gradual smooth boundary. (4 to 30 inches thick)
2C--30 to 60 inches; bluish gray (5B 5/1) stratified very gravelly sandy loam and very gravelly loamy coarse sand, 45 to 65 percent andesitic gravel.
TYPE LOCATION: Stanislaus County, California; roadcut at SW corner sec. 4, T. 2 S., R. 12 E., 1/8 mile north of Hetch Hetchy aqueduct, about 5 miles SW of Knights Ferry on the Williams Ranch.
RANGE IN CHARACTERISTICS: Depth to duripan ranges from 10 to 20 inches with the greater depths on mound areas. Mean annual soil temperature is 64 to 67 degrees F and remains above 47 degrees F throughout the year. The soil is dry between 9 inches and the duripan in most years for a period of 115 to 135 days from June 1 to October 15, moist in all parts for a period of 120 to 150 days from December 1 to May 1 and moist in some part the rest of the year. Average clay content of the textural control section is 35 to 50 percent. Weighted average content of coarse fragments is 15 to 35 percent in the control section. Increase in clay content at the upper boundary of, or at a horizon boundary within, the argillic horizon is 15 to 25 percent absolute, within 1 inch.
The A horizon is 10YR 3/3, 4/2, 4/3, 5/1, 5/2, 5/3, 5/4, 6/2, 6/3, 6/4; or 7.5YR 5/2, 5/4. Moist color is 10YR 3/2, 3/3, 3/4, 4/4, 7.5YR 3/2, 3/3, 3/4 or 4/4. Mottles or slightly darker and grayer colors occur in the surface 1 to 3 inches in intermound areas. Some part of the upper 7 inches of the A horizon has a value of 6 dry, 4 moist or a chroma of 4 moist. Where cobbles are present, the soils are usually cobbly in the intermound areas and gravelly on the mound areas. Texture is sandy loam, cobbly or gravelly loam or clay loam. Content of coarse fragments is 5 to 35 percent with 0 to 15 percent cobbles. Reaction is moderately acid to neutral.
The Bt horizon is 10YR 3/4, 4/3, 5/2, 5/3, 5/4; 7.5YR 3/2, 4/4, 5/4; or 5YR 4/3. Moist color is 10YR 4/2, 3/2, 3/3, 3/4; 7.5YR 3/2, 3/4; or 5YR 3/3. Texture is gravelly sandy clay loam or gravelly clay loam. Content of coarse fragments is 15 to 35 percent with 0 to 10 percent cobbles. Reaction is slightly acid to neutral.
The 2Bt horizon is 10YR 3/4, 4/3, 5/2, 5/3, 7.5YR 3/2, 4/2, 4/4 or 5/2. Moist color is 10YR 3/3, 3/4, 4/2, 4/3, 4/4, 7.5YR 3/2, 3/4 or 4/4. Texture is gravelly clay but is heavy clay loam in the upper part of some pedons. Content of coarse fragments is 15 to 35 percent with 0 to 10 percent cobbles. Some subhorizons have 35 to 60 percent coarse fragments with 10 to 20 percent cobbles. Reaction is slightly acid to neutral.
The 2Bqm horizon is often a combination of colors. It is 10YR 5/4, 7/4; 7.5YR 5/6; 5YR 5/6 or 7/6. Moist color is 10YR 4/4, 7/6; 7.5YR 4/4, 4/6; or 5YR 4/6. The duripan is continuously silica cemented and is indurated to weakly cemented. Reaction is neutral to moderately alkaline. In some pedons, bedrock is below the duripan.
The 2C horizon is stratified very gravelly or cobbly loamy coarse sand to cobbly or gravelly sandy loam. Content of coarse fragments averages 45 to 60 percent. It is very weakly silica cemented in some areas. Reaction is neutral to moderately alkaline.
COMPETING SERIES: There are no other soils in this family.
GEOGRAPHIC SETTING: The Keyes soils are on fans, terraces and hills at elevations of 130 to 600 feet. Slopes are 0 to 15 percent. The soils formed in material weathered from valley fill sediments consisting of andesitic gravel, cobbles and tuff. Some of the gravel in the material above the 2Bt horizons is metamorphic gravel. The sediments are predominantly of the Mehrten Formation. Coarse fragments of andesite in the profile are very well rounded. The soils have mound-intermound microrelief in undisturbed areas. The microrelief is only weakly expressed in Sacramento County. Climate is subhumid, with hot dry summers and cool, moist winters. Mean annual precipitation is 13 to 20 inches. Mean annual temperature is about 60 to 62 degrees F, average January temperature is 45 degrees F and average July temperature is 79 degrees F. The freeze-free season is 250 to 275 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Centerville, Hadselville, Pardee, Pentz and Peters soils. The Centerville soils are clay throughout and have slickensides. Hadselville, Pentz and Peters soils have a mollic epipedon and lack an argillic horizon. The Pardee soils are skeletal.
DRAINAGE AND PERMEABILITY: Well drained in the mounds, moderately well drained in the intermound areas; slow to medium runoff with some minor accumulation of water in intermound areas; very slow permeability.
USE AND VEGETATION: Used for annual rangeland. Vegetation consists of soft chess, annual fescue, mouse barley, annual ryegrass and filaree. Cat's ears and toad rush are also present in intermound areas.
DISTRIBUTION AND EXTENT: Fans, terraces and hills along the western footslopes of the Sierra Nevada Mountains. The soils are moderately extensive in MLRA-17,18.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Merced Area, California, 1953.
REMARKS: This is a classification change from fine, montmorillonitic, thermic Typic Durixeralfs to clayey, mixed, thermic, shallow Abruptic Durixeralfs. CEC class added in 1996.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to 8 inches (A, AB)
Argillic horizon - the zone from 8 to 16 inches (Bt1, 2Bt2)
Duripan - the zone from 16 to 30 inches (2Bqm)
Abruptic subgroup - clay increase of 21 percent, absolute, at the abrupt boundary between the Bt1 and 2Bt2 horizons.
Mixed mineralogy - the mineralogy of the upper and lower parts of the argillic horizon are mixed. The 15 bar water to clay ratio of the upper and lower parts of the argillic are .37 and .44, respectively.
CEC- was assumed.
ADDITIONAL DATA: This pedon sampled as Cal. 50-8-1-(1 to 5), Soils Department, University of California at Davis.