LOCATION TRULAE CAEstablished Series
TAXONOMIC CLASS: Very-fine, smectitic, thermic Sodic Haploxererts
TYPICAL PEDON: Trulae silty clay - on a slope of less than 1 percent in an alfalfa field at an elevation of 85 feet. (Colors are for dry soil unless otherwise stated. When described on July 1, l980, the soil was dry above 6 inches, slightly moist from 6 to 15 inches and moist below.)
Ap1--0 to 6 inches; grayish brown (10YR 5/2) silty clay, dark brown (10YR 3/3) moist; strong medium subangular blocky structure; extremely hard, friable, sticky and plastic; few fine and medium roots; few very fine tubular pores; slightly effervescent with disseminated lime; moderately alkaline (pH 8.0); clear smooth boundary.
Ap2--6 to 10 inches; dark grayish brown (10YR 4/2) silty clay, very dark grayish brown (10YR 3/2) moist; strong medium and coarse subangular blocky structure; extremely hard, firm, sticky and plastic; few very fine and fine roots; common very fine tubular pores; organic matter is 1.8 percent; few thin pressure faces; slightly effervescent with disseminated lime; moderately alkaline (pH 8.0); clear wavy boundary. (Combined thickness of Ap horizon is 8 to 12 inches)
AC--10 to 15 inches; brown (10YR 5/3) silty clay, very dark graysih brown (10YR 3/2) moist; few fine distinct gray (5Y 5/1) mottles, few fine distinct olive brown(2.5Y 4/4) mottles moist;strong coarse and very coarse prismatic structure; extremely hard, extremely firm, sticky and plastic; common very fine and few fine roots; common very fine tubular pores; few thin pressure faces; slightly effervescent with disseminated lime; moderately alkaline (pH 8.0); clear wavy boundary. (4 to 10 inches thick)
Cn--15 to 45 inches; brown (10YR 5/3) clay, olive brown (2.5Y 4/4) moist; few fine distinct dark grayish brown (2.5Y 4/2) mottles moist; moderate medium and coarse angular blocky structure; very hard, very firm, sticky and plastic; few very fine roots; few very fine tubular pores; few thin pressure faces; slightly effervescent with disseminated lime; EC is 6 mmhos/cm; ESP is 42; moderately alkaline (pH 8.0); clear smooth boundary. (22 to 36 inches thick)
Ckn--45 to 63 inches; light brownish gray (2.5Y 6/2) clay loam, olive brown (2.5Y 4/4) moist; massive; hard, firm, slightly sticky and plastic; no roots; common very fine tubular pores; few thin pressure faces; strongly effervescent with disseminated lime; 10 percent durinodes; moderately alkaline (pH 8.0).
TYPE LOCATION: Merced County, California; about 5 miles northwest of the city of Los Banos, 2,700 feet east and 100 feet south of the NW corner of Section 28, T. 9 S., R. 10 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 60 degrees to 62 degrees F. The soil temperature is warmer than 47 degrees F from January 30 to December 1. It is not below 41 degrees F at any time. The soil between 6 and 18 inches is moist in all parts from January 1 to May 15 and dry in all parts from July 1 to November 1. Cracks range from 2.5 to 8 cm wide at the surface and 1 to 2 cm at depths of 20 inches from May 15 to November 15 where not irrigated. A seasonal high water table is at a depth of 48 to 60 inches in December through March.
The A and AC horizons are 10YR 4/2, 5/2, 5/3; or 2.5Y 5/2. Moist colors are 10YR 3/2, 3/3, 4/3, 4/4; 2.5Y 4/2 or 4/4. Clay content ranges from 40 to 60 percent. Intersecting slickensides and sphenoids occur throughout the A horizon. It is noneffervescent to slightly effervescent.
The Cn and Ckn horizons are 10YR 5/2, 5/3; 2.5Y 5/4, 6/2; or 5Y 4/4. Moist colors are 10YR 3/2, 4/4; 2.5Y 4/2, 4/4; or 5Y 6/4. In some horizons there are few to many faint to prominent mottles with colors 7.5YR 4/6; 10YR 4/6; 2.5Y 4/2; 5Y 5/1 or 6/1. Clay content ranges from 60 to 65 percent in the Cn horizon and 30 to 40 percent in the Ckn horizon. Calcium carbonate equivalent is less than 15. ESP ranges from 15 to 50. Intersecting slickensides occur throughout the upper C horizon.
COMPETING SERIES: These are the Capay, Eelpoint, Oswald, Triangle, Wekoda, and Willows series in other families. Capay soils have a fine texture control section and are moderately well drained. Eelpoint soils have a xeric moisture regime and are well drained. Oswald soils have siltstone at a depth of 20 to 40 inches. Triangle soils are very poorly drained and have a fine texture control section. Wekoda soils are poorly drained and have a fine texture control section. Willows soils have color of lower chroma and a fine texture control section.
GEOGRAPHIC SETTING: Trulae soils are in the valley basin and have slopes of less than 2 percent. Elevations range from 80 to 90 feet. These soils formed in mixed alluvium derived from sedimentary rock. The climate is semiarid with hot dry summers and cool moist winters. The mean annual precipitation is 9 to 12 inches. The mean January temperature is 46 degrees F; mean July temperature is 79 degrees F; and mean annual temperature is 62 degrees F. The frost-free season is 210 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Capay, Triangle and Wekoda soils and the Britto, Marcuse, Santanela, Turlock, and Volta soils. Britto, Santanela, Turlock and Volta soils have a natric horizon. Marcuse soils have a fine texture control section and are poorly drained.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained, slow runoff, very slow permeability. A seasonal high water table is at a depth of 48 to 60 inches in December through March. It is subject to brief periods of ponding after prolonged storms in December through March.
USE AND VEGETATION: These soils are used for cropland. The crops include alfalfa, sugar beets, and barley.
DISTRIBUTION AND EXTENT: These soils are located along the western edge of the Central San Joaquin Valley Basin of California. They are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Merced County, California 1984. Name is coined.
REMARKS: These soils were mapped as Willows and the now inactive Orestimba series in the Los Banos Area, Series 1939 report. They are being differentiated from the Willows series by having colors with chroma of 2 or more and by having over 60 percent clay in the texture control section. EC determined by solubridge. SAR determined by versinate method. pH determined by colorimetric method using Thymol Blue and Hellige-Truog Triplex indicators. Texture determined by modified Bouyoucos method.