LOCATION DUCKWORTH CA

Established Series
Rev. KDA-BRY-KP
10/2011

DUCKWORTH SERIES

The Duckworth series consists of very deep, well drained soils on mountain slopes. These soils formed in colluvium over residuum derived from serpentinite. Slope is 20 to 65 percent. The mean annual temperature is about 11 degrees C (51.8 degrees F), and the mean annual precipitation is about 58 centimeters (22.8 inches).

TAXONOMIC CLASS: Fine-loamy, magnesic, mesic Typic Argixerolls

TYPICAL PEDON: Duckworth loam; on a west-southwest slope of 25 percent under manzanita, California foothill pine, and leather oak. The elevation is 1,244 meters (4,080 feet). (Color is for dry soil unless otherwise stated. When described on March 3, 1990 the soil was moist throughout). The surface is covered by 25 percent 2 to 75 millimeter serpentine pebbles.

A1 -- 0 to 30 centimeters (0 to 12 inches); grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, friable, non-sticky and slightly plastic; common medium and coarse roots; common fine and medium tubular pores; 10 percent 2 to 75 millimeter pebbles; neutral (pH 7.0); gradual smooth boundary.

Bt1 -- 30 to 71 centimeters (12 to 28 inches); yellowish brown (10YR 5/4) loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; few thin clay bridging between sand grains; 10 percent 2 to 75 millimeter pebbles; neutral (pH 7.0); gradual smooth boundary.

Bt2 -- 71 to 142 centimeters (28 to 56 inches); brown (7.5YR 5/4) gravelly sandy clay loam, dark yellowish brown (10YR 4/6) moist; moderate coarse subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common medium and coarse roots; many medium and coarse tubular pores; many thick clay films on faces of peds and in pores; 25 percent 2 to 75 millimeter pebbles; neutral (pH 7.0); gradual smooth boundary.

C -- 142 to 183 centimeters 56 to 72 inches; light yellowish brown (2.5Y 6/3) very gravelly sandy loam, olive brown (2.5Y 4/4) moist; massive; slightly hard, friable, non-sticky and non-plastic; common coarse roots; common medium and coarse tubular pores; 45 percent 2 to 75 millimeter pebbles; neutral (pH 7.2); gradual smooth boundary.

TYPE LOCATION: San Benito County, California, in Clear Creek Management Area; about 420.6 meters (1,380 feet) north-northeast of Asbestos Ridge Mine; about 666.0 meters (2,185 feet) south and 527.3 meters (1,730 feet) west of the northeast corner of section 26, T. 18 S., R. 12 E., Mount Diablo Base and Meridian; latitude 36 degrees 20 minutes 4.4 seconds north and longitude 120 degrees 37 minutes 53.70 seconds west; USGS San Benito Mountain, California Quadrangle, NAD83.

RANGE IN CHARACTERISTICS: Surface fragments are composed of serpentinite; 15 to 40 percent, 2 to 75 millimeter pebbles and 0 to 5 percent, 75 to 250 millimeter cobbles.

A horizon:
Hue: 10YR, 7.5YR, and 5YR dry and moist
Value: 3 to 5 dry and 2 to 4 moist
Chroma: 1 to 4 dry and moist
Texture of the fine earth fraction: loam
Content of clay: 20 to 27 percent
Content of organic matter: 2.0 to 4.0 percent
Reaction: slightly acid or neutral
Content of rock fragments: 5 to 25 percent, 2 to 75 millimeter pebbles and 0 to 5 percent 75 to 250 millimeter cobbles

Bt horizon:
Hue: 10YR, 7.5YR, 5YR, or 2.5Y dry and moist
Value: 4 to 6 dry and 4 moist
Chroma: 3 to 6 dry and moist
Texture of the fine earth fraction: loam, clay loam or sandy clay loam
Content of clay: 24 to 35 percent with a gradual increase in content of clay that exceeds 1.2 times that of the A horizon in some part
Content of organic matter: 1.0 to 3.0 percent
Reaction: slightly acid or neutral
Content of rock fragments: 5 to 30 percent, 2 to 75 millimeter pebbles and 0 to 5 percent 75 to 250 millimeter cobbles

C horizon:
Hue: 10YR, 7.5YR, 5Y, or 2.5Y dry and moist
Value: 5 or 6 dry and 3 or 4 moist
Chroma: 1 to 6 dry and moist
Texture of the fine earth fraction: sandy loam or sandy clay loam
Content of clay: 15 to 30 percent
Content of organic matter: 0.2 to 0.8 percent
Reaction: slightly acid or neutral
Content of rock fragments: 35 to 55 percent, 2 to 75 millimeter pebbles and 0 to 5 percent 75 to 250 millimeter cobbles

COMPETING SERIES: This is the Delmexico series. Delmexico series have a paralithic contact at a depth of 102 to 152 centimeters (40 to 60 inches).

GEOGRAPHIC SETTING: Duckworth soils are on mountain slopes at elevations of 796 to 1,598 meters (2,612 to 5,243 feet). Slope is 20 to 65 percent. Duckworth soils formed in colluvium and/or residuum derived from serpentinite. The climate consists of hot dry summers and cool moist winters. Mean annual precipitation is 533 to 610 millimeters (21 to 24 inches). Mean annual temperature is 9 to 14 degrees C (48.2 to 57.2 degrees F). Frost-free period is 150 to 200 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Borreguero, Delmexico, and Idriapeak, and soils. Borreguero soils are shallow and loamy. Delmexico is coarse-loamy, moderately deep, has an argillic horizon, and magnesic mineralogy. Idriapeak is loamy-skeletal, moderately deep, and has magnesic mineralogy.

DRAINAGE AND PERMEABILITY: Well drained; medium to high runoff; high saturated hydraulic conductivity.

USE AND VEGETATION: These soils are used for recreation and wildlife. The vegetation is California buckwheat, yucca, Indian paintbrush, California foothill pine, blue oak, chamise, buckbrush, scrub oak, and fescue.

DISTRIBUTION AND EXTENT: These soils are in the Clear Creek Management Area in the California Coast Ranges. They are not extensive. MLRA 15.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

SERIES PROPOSED: San Benito County, California, 2009. Named after Duckworth Canyon that is in the area.

REMARKS: The typical pedon identification for Duckworth Series is 09CA069071.

ADDITIONAL DATA: Other supporting pedons are 90CA069009, 90CA069060, 90CA069010, 90CA069022, 90CA069053, and 90CA069057.

National Cooperative Soil Survey
U.S.A.