LOCATION JAHANT CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Mollic Palexeralfs
TYPICAL PEDON: Jahant loam - on a nearly level slope of less than 1 percent in a vineyard at an elevation of 40 feet. (Colors are for dry soil unless otherwise noted. When described on November 20, 1984, the soil was moist throughout).
Ap1--0 to 5 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 tubular and interstitial pores; slightly acid (pH 6.5); gradual wavy boundary. (4 to 6 inches thick)
Ap2--5 to 14 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; massive; very hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine tubular and interstitial pores; slightly acid (pH 6.1); clear wavy boundary. (4 to 9 inches thick)
Bt1--14 to 22 inches; pale brown (10YR 6/3) loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; very hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine tubular and interstitial pores; few thin clay films as bridges between mineral grains and on faces of peds; slightly acid (pH 6.1); gradual wavy boundary. (6 to 10 inches thick)
Bt2--22 to 31 inches; dark brown (7.5YR 4/4) loam, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; very hard, friable, slightly sticky and slightly plastic; few very fine roots; many very fine tubular and interstitial pores; common thin clay films as bridges between mineral grains, lining pores and on faces of peds; slightly acid (pH 6.3); abrupt wavy boundary. (6 to 10 inches thick)
Bt3--31 to 36 inches; brown (7.5YR 5/4) and dark brown (7.5YR 4/4) clay loam, dark brown (7.5YR 4/4) moist; moderate coarse angular blocky structure; extremely hard, firm, sticky and plastic; few very fine roots; common very fine tubular and interstitial pores; many moderately thick clay films lining pores and on faces of peds; neutral (pH 7.2); abrupt wavy boundary. (4 to 6 inches thick)
Bt4--36 to 49 inches; brown (7.5YR 5/4) and dark brown (7.5YR 4/4) clay, dark brown (7.5YR 4/4) moist; moderate coarse angular blocky structure; extremely hard, firm, sticky and plastic; many very fine and few fine tubular pores; many moderately thick clay films lining pores and on faces of peds; neutral (ph 7.0); abrupt wavy boundary. (12 to 14 inches thick)
Bqm1--49 to 53 inches; brown (7.5YR 5/4) and dark brown (7.5YR 4/4) strongly cemented duripan, dark brown (7.5YR 4/4) moist; extremely hard, brittle; few roots matted on top of duripan and in fractures; opal coating on fracture faces; strong silica cementation estimated to be 40 to 60 percent of matrix; neutral (pH 7.2); abrupt wavy boundary. (4 to 6 inches thick)
Bqm2--53 to 60 inches; light brown (7.5YR 6/4) and brown (7.5YR 5/4) indurated duripan, dark brown (7.5YR 3/4 or 4/4) moist; extremely hard.
TYPE LOCATION: San Joaquin County, California; 50 feet south and 2,550 feet east of the northwest corner of sec. 22, T.4 N., R.6 E., Lodi North quadrangle.
RANGE IN CHARACTERISTICS: Combined thickness of the A and Bt horizons and depth to the duripan is 40 to 60 inches. Unless irrigated, the soil between depths of 5 and 15 inches is moist in all parts from December to late April and is dry in all parts from June 1 thru October 15. The mean annual soil temperature is 62 degrees to 63 degrees F. Layers with more than 35 percent clay occur below the particle size control section.
The A horizon has color of 10YR 6/3, 5/3, 5/2; 7.5YR 5/2 or 4/2 and moist color of 10YR 3/2, 3/3; or 7.5YR 3/2. It is sandy loam or loam with 10 to 25 percent clay. Organic matter is 1 to 3 percent in the upper part and decreases to less than 1 percent in the lower part. Reaction is slightly acid or neutral.
The upper part of the Bt horizon is 7.5YR 4/4, 5/4, 6/4; 10YR 6/3 or 6/4. Moist color is 7.5YR 4/4; 10YR 3/3, 4/3 or 4/4. It is loam or clay loam with 20 to 30 percent clay. The lower part of Bt is 7.5YR 4/4, 4/6, 5/4, 5/6, 6/4; 10YR 5/2, 5/4, 5/6 or 6/4. Moist color is 7.5YR 3/4, 4/4, 4/6; 10YR 4/4 or 4/6. It has an abrupt upper boundary with an absolute clay increase of 15 to 30 percent more than the overlying horizon. It is clay loam or clay with 35 to 60 percent clay.
The Bq or Bqm horizon is strongly cemented to indurated. It has similar colors as the B horizon. Primary cementing agents are silica and iron.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: The Jahant soils are on old alluvial terraces. Slopes are 0 to 8 percent. The soils formed in alluvium from mixed but mainly granitic rock sources. Elevations range from 20 to 160 feet. The climate is subhumid with hot, dry summers and cool, moist winters. Dense ground fog often occurs in the winter months. The mean annual precipitation is 14 to 16 inches. Mean January temperature is 45 degrees degrees F.; mean July temperature is 77 degrees F.; mean annual temperature is 60 degrees F. Frost-free period ranges from 260 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Bruella, Corning and San Joaquin soils. Bruella soils average less than 35 percent clay and are on stream terraces often dissecting areas of Jahant soils. Corning soils have moist values in the A horizon of more than 4 and are on relatively older, higher terraces. San Joaquin soils have a duripan at 20 to 40 inches and are in similar landscape positions.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; very slow permeability.
USE AND VEGETATION: Used for irrigated crops, pasture, dryland small grain and livestock grazing. Vegetation is annual grasses and forbs and scattered California White Oak.
DISTRIBUTION AND EXTENT: Sacramento and San Joaquin valleys of California. The soils are moderately extensive in MLRA-17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Joaquin County, California, l990.
REMARKS: The activity class was added to the classification in January of 2003. Competing series were not checked at that time. - ET
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of 14 inches (Ap1, Ap2)
Argillic horizon - the zone from 14 to 49 inches (Bt1, Bt2, Bt3, Bt4)