LOCATION ROSSI CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Aquic Natrixeralfs
TYPICAL PEDON: Rossi clay loam - on a west facing slope of less than 1 percent under cultivation at 7 feet elevation. (Colors are for moist soil unless otherwise noted. When described the soil was moist throughout).
Ap--0 to 10 inches; grayish brown (2.5Y 5/2) clay loam, very dark grayish brown (2.5Y 3/2) moist; massive; hard, friable, sticky and plastic; common very fine roots; few fine tubular pores; violently effervescent with dissiminated lime; moderately alkaline (pH 8.2); clear wavy boundary. (8 to 10 inches thick).
Btn--10 to 21 inches; gray (5Y 5/1) silty clay, very dark gray (5Y 3/1) moist; common fine distinct olive (5Y 5/4) mottles, olive (5Y 4/4) moist; strong very coarse prismatic structure; very hard, friable, sticky and plastic; few very fine roots; common very fine tubular pores; common thin clay films and pressure faces on peds; strongly effervescent with disseminated lime; gradual wavy boundary; moderately alkaline (pH 8.2); (10 to 12 inches thick).
Btkn--21 to 42 inches; gray (5Y 5/1) silty clay, dark gray (5Y 4/1) moist; common fine distinct olive (5Y 5/4,5/6) mottles, olive (5Y 5/4) moist; strong very coarse prismatic structure; very hard, friable, sticky and plastic; few very fine roots; few very fine tubular pores; common thin clay films and pressure faces on peds; strongly effervescent with common fine soft masses of lime; moderately alkaline (pH8.2); clear wavy boundary. (10 to 25 inches thick).
C1--42 to 54 inches; gray (5Y 6/1) silty clay loam, dark grayish brown (2.5Y 4/2) moist; common fine distinct strong brown (7.5YR 5/6, 5/8) mottles, reddish brown (5YR 4/4) and yellowish red (5YR 4/6) moist; massive; hard, friable, sticky and plastic; few very fine tubular pores; slightly effervescent with disseminated lime; moderately alkaline (pH 8.2); gradual wavy boundary. (10 to 12 inches thick).
C2--52 to 60 inches; gray (5Y 6/1) silty clay loam, dark grayish brown (2.5Y 4/2) moist; common medium distinct strong brown (7.5YR 5/6, 5/8) mottles, reddish brown (5YR 5/4) and yellowish red (5YR 4/6) moist; massive; slightly hard, friable, sticky and slightly plastic; common very fine tubular pores; slightly effervescent with disseminated lime; moderately alkaline. (pH 8.2);
TYPE LOCATION: San Joaquin County, California; about 800 feet north of Sugar Road and about 2175 feet east fo Tracy Blvd.; 37 degrees 46' 35" north Lat., 121 degrees 25' 35" west Long. (in an unsectioned area) Union Island quadrangle.
RANGE IN CHARACTERISTICS: Rossi soils have mottles less than 20 inches below the surface. Mean annual soil temperature ranges from about 59 degrees to 63 degrees F.
The A horizon is 10YR 4/1, 4/2, 5/1,5/2, 6/2, 7/2; 2.5Y and 5Y 4/1, 5/1, 5/2, 6/1, 6/2, 7/2; N5/0 or N4/0. Moist color is 10YR 4/2, 5/2, 2.5Y 3/2 or 4/2. Electrical conductivity is 4 to 8 mmho/cm and exchangeable sodium percentage is 10 to 18 percent. It is loam, clay loam or silty clay loam. It is slightly to violently effervescent. Organic matter is .5 to 1 percent. Reaction is mildly alkaline or moderately alkaline.
The upper part of the B horizon is 10YR 4/2, 5/2; 5Y 4/3, 4/4; 2.5Y 4/2, 5/2, 5/3, 5/4, 6/2 or 6/3. Moist color is 10YR 3/2, 4/2; 2.5Y 3/2, 4/2; 5Y 3/1, 3/2, 4/2 or N3/0. The lower part is 5Y 5/1, 5/2 or 6/1. Moist color is 5Y 3/2, 4/1 or 4/2. Distinct or prominent mottles are present. It is silty clay or clay with 40 to 60 percent clay, and a 5 to 15 percent (absolute) clay increase over the A horizon. Electrical conductivity is 4 to 16 mmho/cm and exchangeable sodium percentage is 15 to 25 percent. It is strongly or violently effervescent with segregated lime in soft masses or seams in the lower part. Reaction is moderately alkaline or strongly alkaline.
The C horizon is 2.5Y 5/2, 5Y 6/1 or 6/2. Moist color is 2.5Y 4/2 or 5Y 4/2. Distinct or prominent mottles are present. It is silty clay loam or clay loam. Electrical conductivity is 4 to 16 mmho/cm and exchangeable sodium percentage is 10 to 25 percent. It is slightly to strongly effervescent with disseminated lime. Reaction is moderately alkaline or strongly alkaline.
COMPETING SERIES: These are the Pescadero soils in the same family. The Pescadero soils have a ca/mg ratio less than one.
GEOGRAPHIC SETTING: Rossi soils are in level basins at elevations of 5 to 200 feet. They formed in alluvium from sedimentary rocks. They are in areas that have a dry subhumid mesothermal climate. Summers are hot and dry and winters are cool and moist. Mean annual precipitation is 8 to 12 inches. Mean annual temperature is about 60 degrees F., average January temperature about 45 degrees F., and average July temperature about 77 degrees F. Frost-free season averages from 250 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Capay, Egbert, Merritt and Willows soils. Capay, Egbert and Willows soils lack natric horizons. Merritt soils have fine-silty control sections.
DRAINAGE AND PERMEABILITY: Poorly drained; very slow or slow runoff; very slow permeability. Flooding is none to rare due to protection by levees.
USE AND VEGETATION: Most areas are strongly saline-sodic affected. These soils were used mainly for grazing. Some reclaimed areas are used for irrigated field or row crops and irrigated pasture. Commonly cultivated crops are sugar beets, alfalfa, corn and tomatoes. The natural vegetation is mainly saltgrass, pickleweed, annual grasses and forbs.
DISTRIBUTION AND EXTENT: The Rossi soils occur in the western side of the San Joaquin Valley. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Kings County, California 1939.
REMARKS: Rossi soils as mapped in Eastern Fresno County and Madera County with fine loamy family are now excluded from the Rossi series.
Diagnostic horizons and features recognized in the pedon are:
Ochric epipedon - 0 to 10 inches (Ap).
Natric horizon - 10 to 42 inches (Btn, Btkn).