LOCATION SHIMA CAEstablished Series
TAXONOMIC CLASS: Sandy or sandy-skeletal, mixed, euic, thermic Terric Haplosaprists
TYPICAL PEDON: Shima muck-on a west facing slope of less than 1 percent in a cultivated asparagus field at 8 feet below sea level. (Colors are for moist soil unless otherwise stated.)
Oap--0 to 8 inches; black (10YR 2/1) muck, black (10YR 2/1) rubbed, very dark gray (10YR 3/1) dry; less than 5 percent tule and reed fibers before rubbing and a trace after rubbing; weak fine granular structure; slightly hard, loose, nonsticky and nonplastic; very strongly acid (pH 4.6); gradual smooth boundary. (8 to 10 inches thick)
Oa--8 to 21 inches; black (10YR 2/1) muck, black (10YR 2/1) rubbed, very dark gray (10YR 3/1) dry; less than 5 percent tule and reed fibers before rubbing and a trace after rubbing; weak coarse prismatic and weak fine granular structure; soft, very friable, nonsticky and nonplastic; very strongly acid (pH 4.5); clear wavy boundary. (8 to 25 inches thick)
Note: There is a lens of ashy material (burned peat) 0.5 to 1.5 inches thick between the Oa and 2C1 horizon which is brown (7.5YR 4/4) with many medium prominent yellowish red (5YR 4/8) mottles. It is slightly acid (pH 6.5).
2C1--21 to 23 inches; black (10YR 2/1) mucky clay loam, very dark gray (10YR 3/1) dry; many medium prominent yellowish red (5YR 4/8) mottles moist; massive; slightly hard, firm, sticky and plastic; common fine tubular pores; neutral (pH 7.0); abrupt smooth boundary. (0.75 to 3 inches thick)
3C2--23 to 39 inches; light olive brown (2.5Y 5/4) loamy sand; with many medium prominent reddish brown (5YR 5/4) and dark gray (N 4/0) mottles, light brownish gray (2.5Y 6/2) dry; massive; loose, nonsticky and nonplastic; few fine roots; many very fine interstitial pores; slightly effervescent with few fine soft masses; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 16 inches thick)
3C3--39 to 60 inches; olive brown (2.5Y 4/4) loamy sand, many medium distinct dark gray (N 4/0) and reddish brown (5YR 4/4) mottles, light yellowish brown (2.5Y 6/4) dry; massive; loose, nonsticky and nonplastic; many very fine interstitial pores; moderately alkaline (pH 7.9).
TYPE LOCATION: San Joaquin County; California; Rindge Tract; 1,000 feet NW of Fourteen Mile Slough; 0.8 miles NE of the junction of the Stockton Deep Water Channel and Fourteen Mile Slough; 38 degrees, 00 minutes, 25 seconds N latitude and 121 degrees, 24 minutes, 19 seconds W longitude in an unsectionized area. Terminous Quad.
RANGE IN CHARACTERISTICS: Depth to mineral layer ranges from 17 to 36 inches. The mean annual soil temperature is about 62 degrees F. Organic layers have from 40 to 65 percent organic matter but typically range from 40 to 55 percent. The fiber content ranges from a trace to 40 percent before rubbing and none to 10 percent after rubbing. An ash lens is absent in some pedons between the Oa layer and the underlying mineral layer.
The Oa horizon is 10YR 2/1; N 2/0 moist and 10YR 3/1, 4/1 dry. The upper part is 40 to 50 percent organic matter with a trace to 5 percent fibers remaining after rubbing. This upper layer has weak to strong granular structure. The lower part has 45 to 65 percent organic matter and has from a trace to 10 percent fibers remaining after rubbing. Reaction ranges from very slightly acid.
The upper C horizon is 10YR 2/1 moist and 10YR 3/1 dry. It is a mucky clay loam or mucky silty clay. Reaction ranges from very strongly acid to neutral.
The lower C horizon is 2.5Y 5/4, 4/4 moist and 2.5Y 6/2, 6/4 dry. It is sand, loamy sand, or loamy fine sand. Reaction ranges from very strongly acid to moderately alkaline depending on the moisture content.
COMPETING SERIES: This is the Currituck series. Currituck soils have a tide influenced fluctuating water table, formed in sandy marine deposits, range to extremely acid in the mineral layer and lower organic layer and have chromas of 2 or less throughout.
GEOGRAPHIC SETTING: The Shima soils are in fresh water marshes and river channels of the San Joaquin-Sacramento Delta. Slopes are less than 2 percent. They formed in hydrophytic plant remains and mixed mineral alluvium. The organic material is derived from tule and reed fibers. Elevations are 5 feet above to 15 feet below sea level and are on islands protected by levees. The climate is subhumid with hot dry summers and cool, moist winters. The mean annual precipitation is 14 to 16 inches. The mean January temperature is about 45 degrees F.; the mean July temperature is about 75 degrees F.; mean annual temperature is about 60 degrees F. Frost-free season ranges from 260 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the similar Kingile and Rindge soils and the Dello, Peltier, Retryde and Venice soils. Dello soils are sandy mineral soils. Peltier soils are mineral soils that are fine. Retryde soils are mineral soils that are fine-loamy. Venice soils have hemic organic materials to a depth of 51 inches or more. Kingile soils have clayey mineral material at depths of 17 to 36 inches. Rindge soils have continuous sapric organic materials to a depth of 51 inches or more.
DRAINAGE AND PERMEABILITY: Very poorly drained; very slow runoff; permeability is moderate in the mucky mineral horizon and very rapid in the mineral substratum. The water table is lowered by artificial drainage with open drains and pumps. The water table is usually maintained between a depth of 36 to 48 inches during the growing season and at or near the surface sometimes during the winter months.
USE AND VEGETATION: The Shima soils are used for irrigated cropland to grow field crops, vegetable crops and specialty crops. Native vegetation in uncultivated areas is sedges and tules.
DISTRIBUTION AND EXTENT: Shima soils are in the islands of the Sacramento-San Joaquin Delta of California. This series is of small extent in MLRA-16.
MLRA OFFICE RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Contra Costa County Area, California, l973.
REMARKS: The classification was updated in February 2001 using the Eighth Edition to Soil Taxonomy. This series was formerly classified as sandy or sandy-skeletal, mixed, euic, thermic Terric Medisaprists. Competing series were not checked at that time.
Diagnostic horizons and features recognized in this pedon are:
Histic epipedon - 0 to 21 inches (Oap, Oa); sapric material.