LOCATION GUARD CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, calcareous, thermic Duric Endoaquolls
TYPICAL PEDON: Guard clay loam - on a nearly level slope of less than 1 percent under corn stubble at sea level. (Colors are for dry soil unless otherwise stated). When described on November 14, 1980, the soil was dry from 0 to 15 inches and moist below.
Ap--0 to 5 inches; dark gray (10YR 4/1) clay loam, very dark gray (10YR 3/1) moist; moderate medium subangular blocky structure; slightly hard, friable, sticky and plastic; many very fine and fine roots; many very fine interstitial pores; strongly effervescent with disseminated lime; moderately alkaline (pH 8.0); gradual wavy boundary. (4 to 9 inches thick)
A--5 to 15 inches; gray (10YR 5/1) clay loam, very dark gray (10YR 3/1) moist; common fine distinct pale olive (5Y 6/3) mottles, olive (5Y 5/3) moist; moderate coarse angular blocky structure; hard, friable, sticky and plastic; many very fine and common fine roots; common very fine tubular and interstitial pores; slightly effervescent with disseminated lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (8 to 16 inches thick)
Bkq1--15 to 27 inches; variegated light gray (5Y 7/2) and light olive gray (5Y 6/2) clay loam, gray (5Y 5/1) moist; common fine distinct and prominent yellow (10YR 7/8) and strong brown (7.5YR 5/6) mottles, dark yellowish brown (10YR 4/6) moist; massive; hard, brittle, sticky and plastic; few very fine and fine roots; few very fine and fine interstitial and tubular pores; many durinodes; strongly effervescent with disseminated lime and concretions of lime; moderately alkaline (pH 8.0); abrupt smooth boundary. (8 to 20 inches thick)
Bkq2--27 to 72 inches; light gray (5Y 7/2) clay loam, dark gray (5Y 4/1) moist; common fine distinct and prominent strong brown (7.5YR 5/6) and brownish yellow (10YR 6/6) mottles, olive (5Y 4/3) and dark brown (10YR 3/3) moist; massive; hard, weakly cemented, sticky and plastic; few fine and very fine roots; few very fine and fine interstitial pores; many durinodes; strongly effervescent, disseminated and concretions of lime (1 percent calcium carbonate); moderately alkaline (pH 8.0); abrupt wavy boundary. (42 to 48 inches thick)
TYPE LOCATION: San Joaquin County, California; about 5 1/2 miles east of Terminous, 1,200 feet north of Hwy. 12, 165 feet east of Guard Road, 38 degrees 7 minutes, 9 seconds north Lat., 121 degrees 25 minutes 14 seconds Long. (in an unsectionized area) Terminous quadrangle.
RANGE IN CHARACTERISTICS: Depth to weakly cemented brittle layer with 30 to 40 percent durinodes is 14 to 23 inches. The mollic epipedon is 14 to 23 inches thick. The soil between 5 and 20 inches are not dry at any time unless artificially drained. The texture control section from a depth of 10 to 40 inches is 20 to 35 percent clay. The mean annual soil temperature is 62 to 63 degrees F.
The A horizon has dry color of 10YR 5/1, 5/2, 4/1, 4/2; N 5/0, or N 4/0 and moist color of 10YR 2/1, 3/1, 3/2; N 2/0, or N 3/0. Mottles are distinct or prominent in the lower part. It is clay loam or sandy clay loam with 2 to 5 percent organic matter.
The Bkq horizon has dry color of 10YR 7/1, 6/1, 6/2, 6/3, 6/4, 5/1, 5/2, 5/3, 5/4; 5Y 7/2, 6/2, 4/1; N 7/0, or N 6/0 and moist color of 10YR 6/1, 5/1, 5/2, 4/2; 5Y 5/1, 4/1; N 5/0, or N 4/0. Mottles are distinct or prominent. The amount of durinodes increases with depth but never becomes a duripan within 80 inches. It is clay loam or sandy clay loam.
COMPETING SERIES: There are no other soils in this family. Rioblancho and Devries series are similar soils in other families. Rioblancho and Devries soils have duripans at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Guard soils are on basin rims of the San Joaquin Delta. Slopes are 0 to 2 percent. The soils formed in alluvium from mixed rock sources. Elevations are 5 feet below sea level to 25 feet above sea level. 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 12 to 16 inches. Mean January temperature is 45 degrees F; mean July temperature is 77 degrees F; and mean annual temperature is 60 degrees F. Frost-free period is 260 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Egbert, Kingile and Retryde soils. Egbert soils have more than 35 percent clay. Kingile soils have more than 35 percent organic matter. Retryde soils have thick mollic epipedons and have an irregular decrease in organic matter. In addition, all of these soils lack cementation and durinodes.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; slow permeability. A perched water table occurs at a depth of 18 to 36 inches from January to December. The water table has been lowered to a depth below 5 feet in some areas. The soil may be saturated above the cemented layers for short periods after heavy rains in the winter months. The soils are rarely to occasionally flooded for brief periods between December and March. Some areas do not flood.
USE AND VEGETATION:
DISTRIBUTION AND EXTENT: Guard soils occur on the eastern rim of the San Joaquin Delta in Central California. The soils are moderately extensive 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. Competing series were not checked at that time. - ET
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to a depth of 15 inches (Ap,A)
Duric subgroup - the zone from 15 to 72 inches contain many durinodes (Bkq1,Bkq2).