LOCATION COGNA CAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Calcic Pachic Haploxerolls
TYPICAL PEDON: Cogna loam - on nearly level slope of less than 1 percent in a walnut orchard at an elevation of 80 feet. (Colors are for dry soil unless otherwise stated. When described on April 22, 1980, the soil was moist throughout).
Ap--0 to 6 inches; dark grayish brown (10YR 4/2) loam, mixed very dark grayish brown (10YR 3/2) and dark brown (10YR 3/3) moist; weak medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine, medium and common very fine roots; few very fine interstitial and tubular pores; slightly acid (pH 6.5); clear smooth boundary. (6 to 14 inches thick)
A--6 to 13 inches; dark grayish brown (10YR 4/2) loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine, fine, medium and coarse roots; common very fine tubular and interstitial pores; neutral (pH 6.7); clear smooth boundary. (6 to 10 inches thick)
AB--13 to 25 inches; brown (10YR 4/3) loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; few fine tubular pores; neutral (pH 7.0); gradual smooth boundary. (4 to 12 inches thick)
Bk--25 to 38 inches; brown (10YR 5/3) clay loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few medium, common fine and very fine roots; few very fine tubular and interstitial pores; slightly effervescent, lime segregated in seams; slightly alkaline (pH 7.5); gradual smooth boundary. (10 to 13 inches thick)
C1--38 to 49 inches; pale brown (10YR 6/3) loam, dark brown (7.5YR 4/2) moist; moderate coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few medium, common very fine and fine roots; few very fine tubular and interstitial pores; slightly effervescent; slightly alkaline (pH 7.8); gradual smooth boundary. (10 to 12 inches thick)
C2--49 to 64 inches; brown (10YR 5/3) loam, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; common very fine tubular and interstitial pores; slightly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: San Joaquin County, California; approximately 1 mile west of Linden, 750 feet west of Archerdale Road and 300 feet north of Front Road; 2,250 feet north and 1,950 feet east of the southwest corner of section 16, T.2 N., R.8 E., MDBM., Linden quadrangle.
RANGE IN CHARACTERISTICS: The mollic epipedon is 20 to 30 inches thick. Combined thickness of the A and Bk horizons is 30 to 40 inches. The mean annual soil temperature is 62 to 63 degrees F. The soil moisture control section is dry in all parts from June to October unless irrigated, and moist in all parts from December to April. The particle size control section has 18 to 35 percent clay. The predominant range is about 18 to 30 percent clay. Fine sand or coarser is less than 15 percent. In areas that are in a lower physiographic position adjacent to rivers and sloughs, there is an overwash of fine sandy loam 12 to 20 inches thick. It is slightly acid to slightly alkaline. Organic matter decreases regularly with depth and is greater than 1 percent at 20 inches. Secondary lime occurs within 30 inches.
The A horizon has color of 10YR 4/2, 4/3, 5/2, 5/3; or 7.5YR 5/2 and moist color of 10YR 3/2, 3/3; or 7.5YR 3/2. The organic matter ranges from 1 to 3 percent.
The Bk horizon has color of 10YR 6/3, 6/4, 5/3, 5/4, 4/3, 4/2; 7.5YR 6/4, 5/4 and moist color of 10YR 4/3, 4/4, 3/3, 3/4 or 7.5YR 4/4. Segregations of accumulated lime are in seams or soft masses. It is loam, silt loam, or clay loam.
The C horizon has the same colors as the B horizon. It is loam, silt loam, or clay loam.
COMPETING SERIES: This is the Boggiano series. Boggiano soils have a duripan at 40 to 60 inches.
GEOGRAPHIC SETTING: Cogna soils are on low fan terraces and alluvial fans. Slopes are 0 to 2 percent. The soils formed in alluvium derived dominantly from mixed rock sources. Elevations are 40 to 170 feet. The climate is subhumid with hot dry summers and cool moist winters. Dense ground fog often occurs in the winter months. Mean annual precipitation is 14 to 18 inches. The mean January temperature is 45 degrees F; the mean July temperature is 77 degrees F; and the mean annual temperature is 60 to 61 degrees F. Frost-free period is 260 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Boggiano soils and the Archerdale, Columbia and Honcut soils. Archerdale soils have fine textured control sections. Columbia and Honcut soils have an ochric epipedon and the Columbia soils have a stratified coarse-loamy control section.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability.
USE AND VEGETATION: These soils are used for irrigated orchard and row crops. Almonds, walnuts and cherries are the main orchard crops. Bell peppers, field beans, sugar beets and tomatoes are the main row crops. Vegetation is soft chess, wild oats, ripgut brome, turkey mullein and other annual grasses, forbs and scattered valley oaks.
DISTRIBUTION AND EXTENT: The Cogna soils occur in the northeastern San Joaquin Valley. The soils are of moderate extent in MLRA-17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Joaquin County, California, 1990.
REMARKS: The activity class was added to the classification in February of 2003.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to a depth of 25 inches (Ap, A, AB)