LOCATION EXETER CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Typic Durixeralfs
TYPICAL PEDON: Exeter loam, annual grasses and forbs. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 7 inches; brown (10YR 5/3) loam, dark brown (7.5YR 3/2) moist; massive; hard, friable, slightly sticky and slightly plastic; many very fine pores; neutral (pH 6.8); gradual smooth boundary. (4 to 8 inches thick)
A--7 to 14 inches; dark yellowish brown (10YR 4/4) loam, dark yellowish brown (10YR 3/4) moist; massive; hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine pores; neutral (pH 7.0); gradual smooth boundary. (0 to 10 inches thick)
BAt--14 to 20 inches; brown (7.5YR 4/4) loam, dark reddish brown (5YR 3/4) moist; massive; hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine pores; few thin clay films lining pores and bridging sand grains; slightly alkaline (pH 7.5); clear smooth boundary. (0 to 6 inches thick)
Bt1--20 to 25 inches; reddish brown (5YR 5/4) sandy clay loam, reddish brown (5YR 4/4) moist; massive; hard, firm, sticky and plastic; many very fine roots; many very fine and few fine pores; few thin clay films lining pores and bridging sand grains; slightly alkaline (pH 7.8); gradual smooth boundary. (5 to 12 inches thick)
Bt2--25 to 30 inches; yellowish red (5YR 5/6) clay loam, yellowish red (5YR 4/6) moist; massive; hard, firm, sticky and plastic; many very fine roots; many very fine and few fine pores; common moderately thick clay films lining pores and bridging sand grains; slightly alkaline (pH 7.8); abrupt wavy boundary. (3 to 20 inches thick)
Bqm--30 to 43 inches; reddish brown (5YR 5/4) indurated duripan, reddish brown (5YR 4/4) moist; massive; does not soften or slake after prolonged soaking in water and can be chipped with hand tools with extreme difficulty; many very fine tubular pores; light brown (7.5YR 6/4) silica layer 1 to 3 mm thick caps the surface of the duripan; abrupt wavy boundary. (6 to 30 inches thick)
2C1--43 to 47 inches; light yellowish brown (10YR 6/4) sand, yellowish brown (10YR 5/4) moist; single grained; loose, dry and moist; nonsticky and nonplastic; about 14 percent pebbles; strongly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (4 to 12 inches thick)
2C2--47 to 60 inches; light yellowish brown (10YR 6/4) gravelly coarse sand, yellowish brown (10YR 5/4) moist; single grain; loose; 15 percent gravel; moderately alkaline (pH 8.0).
TYPE LOCATION: Tulare County, California; about 1/2 mile north of Ducor; 400 feet east of Road 236 and 430 feet north of Avenue 60; SW1/4 SE1/4 of section 27, T.23 S., R.27 E., Ducor Quadrangle.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 60 to 66 degrees F. and the soil temperature usually is not below 47 degrees F. at any time.
Depth to duripan: 20 to 40 inches.
Rock fragments: 0 to 10 percent throughout the solum.
A Horizon--10YR 4/4, 5/2, 5/3, 5/4, 5/6, 6/2, 6/3, 6/4; 7.5YR 5/2, 5/4, 6/4, or 7/4 dry. 10YR 3/2, 3/3, 3/4, 4/2, 4/3, 4/4; 7.5YR 3/4, 4/4, 5/4 moist.
Texture: Sandy loam, very fine sandy loam, sandy clay loam or loam.
Reaction: Slightly acid to moderately alkaline.
Bt Horizon--10YR 5/4, 6/2, 6/3, 6/4; 7.5YR 5/2, 5/4, 5/6, 6/6; 5YR 4/3, 4/4, 5/3, 5/4, and 5/6 dry. Moist colors are generally 1 or 2 units of value less and are the same or are 1 unit of chroma less than dry colors.
Texture: Loam, sandy clay loam or clay loam.
Clay content: 18 to 35 percent clay.
Reaction: Neutral to moderately alkaline.
Bqm Horizon--10YR 5/3, 5/4, 5/6, 6/3; 7.5YR 5/2, 5/4, 5/6, 6/6; 5YR 5/3, 5/4 or 5/6 dry. Moist colors are generally 1 or 2 units of value less and are the same or are 1 unit of chroma less than dry colors.
Other features: In some pedons, the duripan is capped with a thin layer of carbonates or the carbonates may be segregated as few, fine seams or filaments in fine fractures, but the duripan matrix is always noncalcareous.
The 2C1 and 2C2 horizons are variable. They usually consist of sand or gravelly sand underlain by stratified layers of sandy loam to silt loam. Some pedons have buried 2Bt and 2Btk horizons underlying the duripan that are stratified very gravelly loamy coarse sand to loam with 15 to 50 percent pebbles and 2 to 15 percent clay. Carbonates may be present in these horizons as few soft masses or disseminated.
COMPETING SERIES: These are the Fiddyment, Monserate and Rocklin series. Fiddyment soils have very thin duripans underlain directly by a paralithic contact and have an abrupt clay increase of 15 to 25 percent within one inch above the duripan. Monserate soils are slightly acid to neutral in the argillic horizon, do not have less than 27 percent clay in the Bt, and have an abrupt clay increase with at least a 10 percent increase from the A to the Bt. Rocklin series have cementation below the indurated duripan and textures below the duripan are not sandy.
GEOGRAPHIC SETTING: Exeter soils are on hummocky, undulating to gently rolling alluvial fans and stream terraces at elevations of 20 to 700 feet. Slopes range from 0 to 9 percent. The soils formed in alluvium mainly form granitic sources. In most areas the hummocky relief has been smoothed by leveling. The climate is dry subhumid with hot, dry summers and cool, moist winters. The mean annual precipitation is 7 to 20 inches. The average January temperature is 46 degrees F.; the average July temperature is 82 degrees F.; and the mean annual temperature is 62 to 65 degrees F. The frost-free period is 250 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Centerville, Porterville and Yokohl soils. Centerville and Porterville soils are clayey and lack duripans. Yokohl soils average more than 35 percent clay in the argillic horizon.
DRAINAGE AND PERMEABILITY: Moderately well drained; very slow to medium runoff; moderately slow permeability above the duripan. Permeability of the duripan is very slow.
USE AND VEGETATION: This soil is used for irrigated cropland growing oranges, olives and deciduous orchards, vineyards and row crops. It is also used for dairy and cattle production and building site development. Vegetation in uncultivated areas is mainly annual grasses and forbs.
DISTRIBUTION AND EXTENT: Eastern side of San Joaquin Valley. The soils are extensive in MLRA-17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Tulare County, California, 1908.
REMARKS: Exeter soils in Fresno and Riverside counties may have coarse-loamy particle size families.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 14 inches (Ap, A)
Argillic horizon - the zone from 14 to 30 inches (BAt, Bt1, Bt2)
Duripan - the zone from 30 to 42 inches (Bqm)