LOCATION TIERRA CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Mollic Palexeralfs
TYPICAL PEDON: Tierra loam, annual grasses, formerly cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 7 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; massive; hard, friable, slightly sticky and slightly plastic; many very fine roots; common very fine interstitial and common very fine and medium tubular pores; strongly acid (pH 5.5); gradual smooth boundary. (5 to 10 inches thick)
A12--7 to 11 inches; gray (10YR 5/1) loam, very dark gray (10YR 3/1) moist; massive; hard, friable, slightly sticky and slightly plastic; common very fine roots; common very fine interstitial, many very fine interstitial and many very fine tubular pores; medium acid (pH 6.0); abrupt smooth boundary. (5 to 14 inches thick)
B21t--12 to 16 inches; very dark grayish brown (10YR 3/2) clay, very dark brown (10YR 2/2) moist; moderate coarse prismatic structure; very hard, very firm, very sticky and very plastic; few very fine roots concentrated along faces of peds; few very fine interstitial and few very fine tubular pores; many moderately thick clay films on faces of peds, continuous thin clay films lining pores; slightly acid (pH 6.5); gradual smooth boundary. (4 to 20 inches thick)
B22t--16 to 25 inches; dark brown (10YR 4/3) clay (not as fine as horizon above), dark brown (10YR 3/3) moist; weak coarse prismatic structure and moderate medium angular blocky; very hard, very firm, very sticky and very plastic; few very fine roots on faces of peds; few very fine interstitial and few very fine tubular pores; continuous thin clay films on faces of peds and lining pores; slightly acid (pH 6.5); gradual smooth boundary. (8 to 12 inches thick)
B3t--25 to 43 inches; light brownish gray (10YR 6/2) heavy clay loam, grayish brown (10YR 5/2) moist; many larger prominent mottles of reddish brown (5YR 5/4, 4/4); moderate medium angular blocky structure; very hard, firm, sticky and plastic; few very fine roots; few fine interstitial and common very fine and fine tubular pores; many thin and few moderately thick clay films on faces of peds, few moderately thick clay films lining tubular pores; moderately alkaline (pH 8.0); clear smooth boundary. (15 to 20 inches thick)
C--43 to 62 inches; pale brown (10YR 6/3) clay loam, dark brown (10YR 4/3) moist; many large prominent mottles of reddish brown (2.5YR 5/4) and yellowish brown (10YR 5/4); strong medium angular blocky structure; very hard, firm, sticky and plastic; few very fine interstitial and tubular pores; common thin very dark brown clay films on faces of peds and joints; mildly alkaline (pH 7.5).
TYPE LOCATION: Santa Barbara County, California; 2 1/4 miles south of Guadalupe; 0.9 mile west on Brown Road from intersection with California Highway No. 1 and 1,980 feet south of Brown Road.
RANGE IN CHARACTERISTICS: Usually the soil between the depths of about 5 and 15 inches is continuously moist from November until late April or May and is dry all the rest of the year. The mean annual soil temperature is 59 degrees to 64 degrees F. The mean summer soil temperature is about 68 degrees F., and the mean winter soil temperature is about 57 degrees F. Except for some C horizons deep in the profile, the amount of rock fragments is low, less than 15 percent.
The A1 horizon is gray to very dark gray or grayish brown to dark grayish brown, or brown (10YR 5/1, 4/1, 3/1, 5/2, 4/2; N 5/, 2.5Y 5/1, 5/2, 5/3). It is loamy sand to clay loam, but in most pedons it is fine sandy loam or loam. This horizon is massive and is hard or very hard in some or all parts. It has 1.5 to 5 percent organic matter. It is slightly to strongly acid and has base saturation of 50 to 75 percent.
The A2 horizon is gray, light gray, light brownish gray, white, pale brown, or very pale brown and has one or two units of value higher than the A1 horizon and in most pedons, one to three units higher than the B2t horizon.
The upper part of the B2t horizon is grayish brown, dark grayish brown or very dark grayish brown. The lower part of the B2t horizon is light brownish gray, grayish brown, yellowish brown, dark yellowish brown, pale brown or brown. Hue is dominantly 10YR in all of the B2t horizon, but 2.5Y hue is included. The exterior of the peds has lower value and lower chroma, with generally less staining and lighter and brighter color in the lower part. This horizon has 35 to 50 percent clay, an abrupt upper boundary and has 15 to 30 percent more clay (absolute) than the A horizon. The B2t horizon has moderate to strong prismatic structure in the upper part and weak to moderate prismatic or moderate to strong prismatic structure in the upper part and weak to moderate prismatic or moderate to strong angular blocky structure in the lower part. Some pedons have coarse mottles or blotches of brighter colors, particularly in the lower part of this horizon. The B2t horizon is neutral to medium acid and in most pedons becomes less acid as depth increases. Base saturation is more than 75 percent in most or all parts. The lower less acid as depth increases. Base saturation is more than 75 percent in most or all parts. The lower boundary of the Bw5 horizon is gradual or there is a B3 horizon 15 to 30 inches thick.
The C horizon has hue of 2.5Y or 10YR and dry value of 6 or 7. It is sandy loam, loam, clay loam or sandy clay loam and is slightly hard to very hard when dry. In some pedons, some or all of this horizon is weakly cemented and dense. It is medium acid to moderately alkaline and in a few pedons has free lime in disseminated or segregated form.
COMPETING SERIES: These are the Kimball, Milpitas, Newville, Nicolaus and Positas series. Kimball soils lack an A2 horizon and have hue of 5YR or 2.5YR in the B2t horizon. Milpitas soils have chroma of 4 or more in all parts of the B2t horizon. Newville soils lack an A2 horizon and have chroma of 4 or more in all parts of the B2t horizon. Nicolaus soils are underlain by a weakly cemented layer. Positas soils have a hue of 7.5YR or 5YR and a chroma of 3 or more in the upper part of the B2t horizon.
GEOGRAPHIC SETTING: Tierra soils are gently sloping to steep and are on dissected terraces and low hills at elevations of 100 to 1,200 feet. Slopes are 2 to 50 percent. The series formed in weakly consolidated somewhat stratified old alluvium interspersed with beds of sandstone. The climate is subhumid mesothermal with cool moist winters and cool dry summers. The mean annual precipitation is 12 to 25 inches. Mean annual temperature is about 57 degrees to 59 degrees F., average January temperature is about 52 degrees F., and average July temperature is about 63 degrees F. The average frost-free season is 200 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arnold, Chamise, Los Osos, San Andreas, and Santa Lucia soils and the competing Positas soils. Arnold soils are sand throughout the profile. Chamise and Los Osos soils have a mollic epipedon. San Andreas and Santa Lucia soils have a mollic epipedon and lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to rapid runoff; very slow permeability.
USE AND VEGETATION: Used for grazing and growing small grains and small areas of large number of crops. Many cultivated areas have reverted to grass. Vegetation dominantly is annual grasses and forbs.
DISTRIBUTION AND EXTENT: Areas within 30 miles of the coast in central and south-central California. The soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Monterey County (Salinas Area), California, 1925.