LOCATION RIOBLANCHO CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, calcareous, thermic Typic Duraquolls
TYPICAL PEDON: Rioblancho clay loam - on a nearly level slope of less than 1 percent under valley oaks and annual grasses at an elevation of 7 feet. (Colors are for dry soil unless otherwise stated. When described on November 14, 1980, the soil was dry from 0 to 7 inches and moist below).
Ap--0 to 7 inches; gray (10YR 5/1) clay loam, very dark gray (10YR 3/1) moist; moderate coarse subangular blocky structure; very hard, firm, sticky and plastic; many very fine roots; few very fine tubular and common very fine interstitial pores; slightly alkaline (pH 7.5); gradual smooth boundary. (7 to 10 inches thick)
Bk1--7 to 16 inches; gray (10YR 5/1) clay loam, very dark gray (10YR 3/1) moist; common fine distinct brown (10YR 5/3) moist mottles; moderate very coarse angular blocky structure; hard, firm, sticky and plastic; many very fine roots; many very fine tubular and common very fine interstitial pores; strongly effervescent with disseminated lime and common fine soft masses of lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (8 to 12 inches thick)
Bk2--16 to 28 inches; variegated light gray (10YR 7/1) and very pale brown (10YR 7/3) clay loam, pale brown (10YR 6/3) and dark grayish brown (10YR 4/2) moist; common fine distinct light olive brown (2.5Y 5/6) moist mottles; massive; hard, firm, slightly sticky and slightly plastic; common very fine tubular pores; violently effervescent (20 percent calcium carbonate) with disseminated lime and common fine soft masses of lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (6 to 12 inches thick)
Bk3--28 to 39 inches; variegated very pale brown (10YR 7/4) and light yellowish brown (10YR 6/4) sandy loam, yellowish brown (10YR 5/4) and dark yellowish brown (10YR 4/4) moist; common fine faint yellowish brown (10YR 5/6) moist mottles; massive; hard, friable, slightly sticky and slightly plastic; common very fine tubular pores; weakly cemented in lower part; slightly effervescent with disseminated lime and few fine seams of lime; moderately alkaline (pH 8.0); abrupt smooth boundary. (2 to 11 inches thick)
2Bqkm--39 to 44 inches; variegated light gray (10YR 7/2) and light yellowish brown (10YR 6/4) strongly silica cemented duripan; yellowish brown (10YR 5/4) and dark yellowish brown (10YR 4/4) moist; common fine distinct light olive brown (2.5Y 5/6) moist mottles; massive, hard and brittle, strongly cemented continuous laminar capping 2 to 5 mm thick; strongly effervescent with disseminated lime and common fine seams of lime; moderately alkaline (pH 8.0); gradual smooth boundary. (3 to 7 inches thick)
2Bqk--44 to 80 inches; variegated light gray (10YR 7/2) and light yellowish brown (10YR 6/4) weakly to strongly silica cemented sandy loam; yellowish brown (10YR 5/4) and dark yellowish brown (10YR 4/4) moist; common fine distinct light olive brown (2.5Y 5/6) moist mottles; massive, hard and brittle; strongly cemented in 25 percent of the matrix and weakly cemented in the remainder; strongly effervescent with disseminated lime and segregated lime in seams; moderately alkaline (pH 8.0).
TYPE LOCATION: San Joaquin County, California; approximately 3 miles northwest of Lincoln Village in Oak Grove Regional Park, 2,650 feet south and 2,325 feet east of the northwest corner of sec. 6, T.2N., R.6E., MDBM., Lodi South quadrangle.
RANGE IN CHARACTERISTICS: Depth to duripan is 20 to 40 inches. The mean annual soil temperature is 62 to 63 degrees F. The soil between the depth of 5 to 20 inches is not dry at any time unless artificially drained.
The A horizon has color of 10YR 5/1, 5/2, 4/1, 4/2; 2.5Y 5/2, 4/2; N 5/0 or N 4/0 and moist color of 10YR 3/1, 3/2, or N 3/0. Distinct or prominent mottles are present in the lower part. Organic matter content ranges from 2 to 5 percent.
The Bk horizons have color of 10YR 6/4, 7/1, 7/3, 7/4; 2.5Y 8/2, 7/2, 6/2; 5Y 7/2, 6/3, 6/2, or N 8/0 and moist color of 10YR 4/2, 4/4, 5/4, 6/3, 6/2, 6/1; 2.5Y 6/2, 5/2; 5Y 5/2, 5/3; or N 7/0. Faint or distinct mottles are present. Calcium carbonate content ranges from 15 to 22 percent in the lower part. It is clay loam or loam in the upper part and sandy loam in the lower part.
The 2Bqkm is strongly cemented or indurated. The 2Bqkm and 2Bqk horizon has color of 10YR 7/2, 6/2, 6/3, 6/4; 2.5Y 7/2, 7/4; 5Y 6/2 or 5/2 and moist color of 10YR 5/4, 4/4; 2.5Y 4/2, 4/4; 5Y 4/2 or 5/2.
COMPETING SERIES: There are no other soils in the same family.
GEOGRAPHIC SETTING: Rioblancho soils are on basin rims. Slopes are 0 to 2 percent. The soils formed in alluvium from mixed rock sources. Elevations are 0 to 30 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 inches. The mean January temperature is 45 degrees F; the mean July temperature is 77 degrees F; and the mean annual temperature is 60 degrees F. The frost-free period is 260 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Egbert, Kingile and Ryde soils. Egbert, Kingile and Ryde soils lack duripans.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; moderately slow permeability. Depth to the apparent water table is presently greater than 6 feet, but the soil may be saturated above the hardpan for short periods after heavy rains in the winter months.
USE AND VEGETATION: Predominantly irrigated cropland used to produce field and row crops. Vegetation is soft chess, annual and perennial rye grass, salt grass, plantain and other annual grasses, forbs and scattered valley oaks.
DISTRIBUTION AND EXTENT: Rioblancho soils occur on basin rims in the San Joaquin Delta in Central California. The soils are not extensive in MLRA-17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Joaquin County, California, 1990.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to a depth of 16 inches (Ap, Bk1)
Duripan - the zone from 39 to 44 inches (2Bkqm)
The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET