LOCATION STOMAR CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Mollic Haploxeralfs
TYPICAL PEDON: Stomar clay loam - on a southwest facing slope of l percent that is cultivated at 140 feet elevation. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 11 inches; yellowish brown (10YR 5/4) clay loam, dark brown (10YR 3/3) moist; massive; hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine interstitial pores; organic carbon is 1.2 (UC Davis Lab.) neutral (pH 7.1); clear smooth boundary. (8 to 14 inches thick)
A--11 to 20 inches; yellowish brown (10YR 5/4) clay loam, dark grayish brown (10YR 4/2) moist; hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine interstitial pores; neutral (pH 6.8); clear smooth boundary. (6 to 10 inches thick)
Bt1--20 to 26 inches; yellowish brown (10YR 5/4) clay loam, brown (10YR 4/3) moist; weak coarse angular blocky structure parting to weak fine subangular blocky; hard, firm, slightly sticky and slightly plastic; common very fine roots; common very fine tubular pores; many thin clay films on faces of peds and lining pores; neutral (pH 7.1); gradual wavy boundary. (4 to 10 inches thick)
Bt2--26 to 38 inches; yellowish brown (10YR 5/4) clay, brown (10YR 4/3) moist; moderate coarse angular blocky structure parting to weak fine subangular blocky; very hard, firm, sticky and plastic; common very fine roots; common fine and very fine tubular and interstitial pores; many moderately thick clay films on ped faces and lining pores and as bridges between mineral grains; slightly alkaline (pH 7.5); abrupt smooth boundary. (10 to 16 inches thick)
Btk--38 to 60 inches; light yellowish brown (10YR 6/4) clay loam, dark yellowish brown (10YR 4/4) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine roots; many fine and very fine tubular and interstitial pores; many moderately thick clay films lining pores and as bridges between mineral grains; slightly calcareous with lime disseminated and as few fine threads; thin, discontinuous lenses of silt or silt loam; slightly alkaline (pH 7.8).
TYPE LOCATION: Stanislaus County, California; .25 mile south of Marshall Road and .25 east of Davis Road; 1,300 feet south and 1,500 feet east of the northwest corner of sec. 8, T.6 S., R.8 E., 37 degrees 25 minutes 52 seconds north latitude, 121 degrees 06 minutes 53 seconds west longtitude, Crows Landing quadrangle.
RANGE IN CHARACTERISTICS: Depth to the Btk is 26 to 50 inches. The soil between the depths of 4 and 12 inches is dry in all parts from mid May to November and is moist in all parts from mid December to May. The mean annual soil temperature ranges from 62 to 65 degrees F. and remains above 47 degrees F. Organic matter content of the upper 10 inches is 1 to 2 percent (UC Davis Lab.).
The A horizon is 10YR 5/1, 5/2, 5/3, 5/4, 4/1, 4/2, 4/3 or 7.5YR 5/4; 2.5Y 5/2. Moist colors are 10YR 3/1, 3/2, 3/3; 7.5YR 3/3. Texture is loam, clay loam or silty clay loam. The natural soil is hard or very hard and massive.
The Bt horizon is 10YR 4/1, 4/2, 5/2, 5/3, 6/3, 5/4, 6/4, 6/2 or 7.5YR 5/4, 6/4; 2.5Y 5/2, 5/4. Moist colors are 10YR 3/1, 3/2, 3/3, 4/2, 4/3, 4/4, 4/6, 5/2, 5/3; or 7.5YR 4/3, 4/4, 5/3; 2.5Y 4/4, 4/2, 3/2. Texture is clay loam, clay or gravelly clay. Structure is weak to strong angular blocky or prismatic or strong subangular blocky. Reaction is neutral to moderately alkaline.
The Btk horizon is 10YR 5/3, 5/4, 5/6, 6/3, 6/4; 7.5YR 5/4; 2.5Y 6/4, 7/4. Moist colors are 10YR 6/4, 5/6, 5/4, 5/3, 4/4, 4/3, 3/3; 7.5YR 4/4; 2.5Y 5/4. Texture is clay, clay loam, silty clay loam or gravelly clay loam. Reaction is slightly alkaline to moderately alkaline. It has segregated lime as soft masses or threads.
COMPETING SERIES: These are the Azule (CA), Rincon (CA), Shoba (T CA), Skyhigh (CA) and Sleeper (CA) soils. Azule soils have a paralithic contact between 20 to 40 inches. Rincon soils have a difference between mean summer and mean winter temperatures of less than 19 degrees F. Skyhigh soils have a lithic contact between 20 to 40 inches. Sleeper soils are on uplands and are dry in all parts for about 105 days.
GEOGRAPHIC SETTING: The Stomar soils are on old dissected alluvial fans and terraces and have slopes of 0 to 2 percent. The soils formed in material weathered from sandstone and shale. Elevations are 25 to 500 feet. The climate is subhumid, mesothermal with hot, dry summers and cool, moist winters. Mean annual precipitation is 8 to 12 inches. Mean January temperature is about 48 degrees F.; mean July temperature is 78 degrees F.; mean annual temperature varies from 57 to 62 degrees F. Frost-free period ranges from 200 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arbuckle, Capay, Pleasanton, Vernalis, Willows and Zacharias. Arbuckle and Pleasanton soils have less than 35 percent clay in the upper 20 inches of the Bt horizon. Capay and Willows soils lack argillic horizons and have cracks that open & close each year to a depth of 20 inches and have intersecting slickensides. Vernalis and Zacharias soils lack an argillic horizon and have less than 35 percent clay in the upper 20 inches of the Bt horizon.
DRAINAGE AND PERMEABILITY: Well drained; negligible to high runoff; slow permeability.
USE AND VEGETATION: Used for irrigated cropland including field crops, row crops and orchards. It is also used for dryland cropland such as grain. Some areas are used for urbanland and there are small areas used for livestock grazing. Vegetation where not cultivated is annual grasses and forbs.
DISTRIBUTION AND EXTENT: The soils are in the Upper San Joaquin Valleys. 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: This soil was established to accommodate soils that are in an interior climate area. Soils currently classified as Rincon That have a difference between mean summer and mean winter temperatures of greater than 19 degrees need to be reevaluated and may be correlated to Stomar.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the surface to 20 inches (Ap, A horizons)
Argillic horizon - the zone from 26 to 38 inches (Bt horizon)
Slow to medium runoff terminology adjusted to new notation of negligible to high, to comply with adjective criteria of the Soil Survey Manual, 10/93.
ADDITIONAL DATA: NSSL pedon S91CA-099-012 (partial analysis of type location)