LOCATION DELVAR CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Calcic Pachic Argixerolls
TYPICAL PEDON: Delvar clay loam, in a vineyard with a 4 percent slope at an elevation of 560 feet. (When described on April 9, 1992, the soil was moist throughout. Colors are for dry soil unless otherwise stated.)
Ap1--0 to 4 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; very hard, friable, sticky and plastic; common very fine roots; few very fine tubular and common very fine interstitial pores; 3 percent gravel; electrical conductivity 2.0 decisiemens per meter; sodium adsorption ratio is 3.0; slightly acid (pH 6.2); clear smooth boundary. (1 to 8 inches thick)
Ap2--4 to 12 inches; dark grayish brown (10YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure: very hard, friable, sticky and very plastic; common fine and very fine roots; common very fine tubular and few very fine interstitial pores; 2 percent gravel; electrical conductivity 1.4 decisiemens per meter; sodium adsorption ratio is 4.0; slightly acid (pH 6.2); gradual smooth boundary. (6 to 14 inches thick)
Bt--12 to 19 inches; brown (10YR 4/3) clay, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure; very hard, friable, very sticky and very plastic; common fine and very fine, few coarse roots; common very fine and few fine tubular pores; common thin clay films in pores and on faces of peds; 2 percent gravel; electrical conductivity 1.6 decisiemens per meter; sodium adsorption ratio is 4.0; neutral (pH 6.6); clear smooth boundary. (2 to 15 inches thick)
Btk1--19 to 28 inches; brown (10YR 4/3) clay, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure; very hard, friable, very sticky and very plastic; few very fine roots; common very fine tubular pores; common moderately thick clay films in pores and on faces of peds; 2 percent gravel; strongly effervescent, carbonates are segregated in common fine and medium soft masses; electrical conductivity 2.3 decisiemens per meter; sodium adsorption ratio is 9.0; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 18 inches thick)
Btk2--28 to 34 inches; brown (10YR 4/3) clay, dark yellowish brown (10YR 3/4) moist; weak coarse subangular blocky structure; very hard, friable, very sticky and very plastic; few very fine roots; common very fine tubular pores; common moderately thick clay films in pores and on faces of peds; 2 percent gravel; strongly effervescent, carbonates are segregated in few fine filaments; electrical conductivity 3.6 decisiemens per meter; sodium adsorption ratio is 10.0; moderately alkaline (pH 8.0); clear smooth boundary. (1 to 15 inches thick)
Btk3--34 to 42 inches; brown (10YR 4/3) clay, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure; very hard, friable, very sticky and very plastic; few very fine roots; few very fine interstitial and common very fine tubular pores; common moderately thick clay films in pores and on faces of peds; 2 percent gravel; strongly effervescent, carbonates segregated in common fine filaments; electrical conductivity 6.0 decisiemens per meter; sodium adsorption ratio is 10.0; few medium faint dark yellowish brown (10YR 4/4) redox concentrations, brown (7.5YR 4/4) moist; moderately alkaline (pH 8.0); abrupt wavy boundary. (4 to 14 inches thick)
2Btkn--42 to 60 inches; yellowish brown (10YR 5/4) sandy loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; hard and very hard, friable with 15 percent brittle fragments that slake in 10 percent hydrochloric acid, sticky and slightly plastic; common very fine tubular pores; few thick and common moderately thick clay films in pores and on faces of peds; 5 percent gravel; strongly effervescent, carbonates are segregated in common fine filaments; electrical conductivity 4.4 decisiemens per meter; sodium adsorption ratio is 13.0; moderately alkaline (pH 8.0).
TYPE LOCATION: Tulare County, California; about 2 miles east of Richgrove and the intersection of the Kern County line and Highway 65; approximately 50 feet north and 200 feet east of the southwest corner of section 33, T. 24 S., R. 27 E., MDB&M; Latitude 35 degrees, 47 minutes and 28 seconds north and Longitude 199 degrees, 4 minutes and 12 seconds west; Richgrove Quadrangle.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 62 to 65 degrees F.
Mollic epipedon: 20 to 40 inches thick.
Calcium carbonate equivalent 1 to 10 percent.
Particle-size control section--Clay: Averages 40 to 55 percent clay; the clay increase relative to the A horizon is always at least 20 percent.
A Horizon--10YR 4/2, 4/3, 5/3 dry; 10YR 3/2, 3/3, 4/2 moist.
Texture: Sandy clay loam or clay loam.
Clay: 25 to 40 percent.
Coarse fragments: 0 to 15 percent gravel.
Reaction: Slightly acid to moderately alkaline; reaction is highly variable due to chemical amendments added to the soil such as sulfuric acid, which acidifies the soil.
Electrical conductivity: 0 to 4 decisiemens per meter.
Sodicity: SAR 1 to 8.
Bt, Btk Horizons--10YR 4/2, 4/3, 5/2, 5/3, 7.5YR 4/4, 5/4, 6/4 dry; 10YR 3/2, 3/3, 4/2, 7.5YR 4/4, 4/6, 5/4 moist.
Texture: Clay in the upper part and sandy loam, sandy clay loam, or clay loam in the lower part.
Clay: 40 to 55 percent in the upper part and 15 to 35 percent in the lower part.
Coarse fragments: 0 to 15 percent gravel.
Reaction: Neutral or moderately alkaline; reaction is highly variable due to chemical amendments added to the soil such as sulfuric acid, which acidifies the soil.
Salinity: Electrical conductivity 1 to 8 decisiemens per meter.
Sodicity: SAR 2 to 13 in the upper part and 13 to 20 in the lower part.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: Delvar soils are on stream terraces with slopes of 2 to 30 percent. They formed in mixed alluvium derived mainly from granitic and meta-sedimentary rocks. Elevations range from 400 to 2000 feet. The climate is semi-arid with hot, dry summers and cool, moist winters. The mean annual precipitation ranges from 8 to 12 inches. The mean annual temperature is 62 to 65 degrees F. The frost-free season is 250 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Exeter and Centerville soils. Exeter soils are fine-loamy and moderately deep to a duripan. Centerville soils are clayey throughout and have deep cracks when dry.
DRAINAGE AND PERMEABILITY: Moderately well drained; low to very high runoff; slow permeability. Flooding is rare.
USE AND VEGETATION: This soil is used for irrigated cropland and some dry land grain. It is also used for dairy and cattle production and building site development.
DISTRIBUTION AND EXTENT: In the southeastern part of the San Joaquin Valley of California. The soils are not extensive. MLRA 17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Tulare County, Western Part Soil Survey, California, 1999. The name is coined.
REMARKS: Some areas have been acidified by the use of sulfur sulfuric acid and other soil amendments. This soil was naturally slightly saline-sodic and has been modified by the addition of farm soil amendments, large amounts of irrigation water, and large amounts of organic matter.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon -- the zone from the soil surface to a depth of about 28 inches. (Ap1, Ap2, Bt and Btk1 horizons)
Argillic horizon -- the zone from 12 to 42 inches (Bt, Btk1, Btk2, Btk3 horizons)
Soft powdery carbonates -- the zone from 19 to 28 inches (Btk1)
When dry, the Bt horizon has cracks 2-7 mm wide.