LOCATION BENBOW CA

Established Series
REV: JWH/JTB/ET
11/2010

BENBOW SERIES

The Benbow series consists of very deep, well drained soils, formed in alluvium from mixed sedimentary sources. Benbow soils are on stream terraces in mountain river valleys. Slope ranges from 2 to 9 percent. The mean annual precipitation is about 2030 mm and the mean annual temperature is about 13 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, isotic, thermic Andic Humixerepts

TYPICAL PEDON: Benbow very gravelly loam, on a southeast facing, 1 percent slope, under grass at an elevation of 134 meters. (Colors are for dry soil unless otherwise noted.) When described on May 10, 2005, the soil was moist throughout.

Ap--0 to 14 centimeters; very dark grayish brown (10YR 3/2) very gravelly loam, black (10YR 2/1) moist; moderate fine and medium granular structure; soft, very friable, nonsticky and nonplastic; many very fine, common fine, and few medium roots throughout; few fine, medium, and very fine tubular pores; 50 percent subangular gravel; extremely acid (pH 3.9); clear smooth boundary.

A1--14 to 33 centimeters; very dark grayish brown (10YR 3/2) very gravelly loam, black (10YR 2/1) moist; weak medium subangular blocky structure parting to weak fine granular; slightly hard, very friable, nonsticky and nonplastic; many very fine and few fine roots throughout; few very fine, fine and medium tubular pores; 55 percent subangular gravel; extremely acid (pH 4.3); clear smooth boundary.

A2--33 to 69 centimeters; very dark grayish brown (10YR 3/2) extremely gravelly loam, black (10YR 2/1) moist; weak fine and medium subangular blocky structure parting to weak fine granular; slightly hard, friable, nonsticky and nonplastic; common very fine and fine roots throughout; few fine and medium tubular pores; 70 percent subangular gravel; extremely acid (pH 4.4); clear wavy boundary.

A3--69 to 87 centimeters; pale brown (10YR 6/3) gravelly loam, dark brown (10YR 3/3) moist; weak very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots throughout; few fine, medium, and coarse tubular pores; 30 percent subrounded gravel; very strongly acid (pH 4.8); gradual irregular boundary.

A4--87 to 105 centimeters; pale brown (10YR 6/3) very gravelly silt loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots throughout; few fine and medium tubular pores; 40 percent subangular and subrounded gravel; strongly acid (pH 5.1); gradual irregular boundary. (combined thickness of the A horizons is 50 to 200 centimeters thick)

C1--105 to 123 centimeters; light yellowish brown (2.5Y 6/3) extremely gravelly loamy coarse sand, olive brown (2.5Y 4/3) moist; massive; slightly hard, friable, slightly sticky and nonplastic; common very fine roots throughout; few fine and medium tubular pores; 65 percent subrounded gravel; strongly acid (pH 5.3); gradual irregular boundary.

C2--123 to 151 centimeters; light yellowish brown (2.5Y 6/3) very gravelly sandy loam, dark grayish brown (10YR 4/2) moist; single grain; loose, loose, nonsticky and nonplastic; few very fine roots; 10 percent faint clay films on the tops of rock fragments in the top 5 centimeters of the horizon; 55 percent subrounded gravel and 2 percent rounded cobbles; strongly acid (pH 5.3); clear wavy boundary.

C3--151 to 200 centimeters; pale brown (10YR 6/3) extremely gravelly loamy coarse sand, dark grayish brown (10YR 4/2) moist; single grain; loose, loose, nonsticky and nonplastic; 74 percent subrounded gravel and 2 percent rounded cobbles; strongly acid (pH 5.4). (combined thickness of the C horizons is 0 to 150 centimeters thick)

TYPE LOCATION: Humboldt County, California; about 2 kilometers west of the town of Petrolia; USGS Quadrangle Garberville, CA; 40 degrees 20 minutes 20 seconds north latitude and 124 degrees 18 minutes 15 seconds west longitude; UTM Zone 10 389240mE, 4466188mN; NAD 83.

RANGE IN CHARACTERISTICS:

Soil Temperature: The mean annual soil temperature at 50 centimeters is 15 to 16 degrees C and the difference between mean summer and mean winter soil temperatures is 6 degrees C or greater. The soil has a thermic temperature regime.

Soil Moisture: The soil moisture control section, in normal years, is dry in all parts for 45 or more consecutive days in the 4 months following the summer solstice and moist in all parts for 45 or more consecutive days in the 4 months following the winter solstice. The soil has a xeric moisture regime.

Base Saturation: less than 50 percent by Ammonium Acetate throughout the soil profile

Particle-size control section (weighted average):
Clay content: 18 to 25 percent
Rock fragments: 35 to 60 percent gravel

A horizon:
Value: 3 through 6 dry, 2 or 3 moist
Chroma: 1 through 3, dry or moist
Texture: loam or silt loam
Clay content: 15 to 27 percent
Rock fragments: 15 to 75 percent subangular and subrounded strongly cemented sedimentary gravel
Reaction: extremely to strongly acid

C horizon:
Hue: 10YR or 2.5YR
Value: 5 through 7 dry, 3 or 4 moist
Chroma: 2 through 4, dry or moist
Texture of the fine earth: loam, sandy loam, coarse sandy loam, or loamy coarse sand.
Clay content: 12 to 25 percent
Rock fragments: 35 to 75 percent subrounded and rounded strongly cemented sedimentary gravel, 0 to 5 percent rounded strongly cemented sedimentary cobbles
Reaction: strongly or moderately acid

COMPETING SERIES: These are no other series in this family.

GEOGRAPHIC SETTING: Benbow soils are on uplifted stream terraces in mountain river valleys. Slopes are 2 to 9 percent. Elevations are 75 to 215 meters. These soils formed in alluvium and some colluvium derived from mixed sedimentary sources. The climate is subhumid with warm, dry summers with a marine layer influenceand cool, wet winters. Mean annual precipitation is 1250 to 2550 millimeters. Mean annual temperature is 12 to 14 degrees C. Frost free season is about 280 to 300 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Conklin (CA), Garberville (CA), Mattole (CA), and Parkland (CA) soils. Conklin, Garberville, Parkland, and Mattole soils have less than 35 percent rock fragments in the particle size control section. greater than 50 percent base saturation by ammonium acetate throughout. Garberville and Parkland soils are on alluvial fans and stream terraces. Conklin and Mattole soils are on stream terraces..

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; low runoff; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: This soil is used mainly for pasture. Natural vegetation includes annual and perennial grasses and forbs including sweet vernal grass and bracken fern.

DISTRIBUTION AND EXTENT: Coastal Redwood Belt, MLRA 4B. The series is not extensive.

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

SERIES ESTABLISHED: Humboldt County, Southern Part, California, 2010. The name is from the town of Benbow.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
1. Umbric epipedon: The zone from 0 to 69 centimeters (Ap, A1,and A2 horizons).
2. Particle size control section: The zone from 25 to 100 centimeters (A1, A2, A3, and A4 horizons)
3. Isotic feature: 15 bar water/clay is 0.6 or more and the NaF pH is greater than 8.4 in all horizons.
4. Andic feature: The zone from 0 to 69 centimeters has a 33kPa bulk density of 1.0 g/cm3 and an Al plus Fe percentage (by ammonium oxalate) of more than 1.0 (Ap, A1,and A2 horizons).

Former classification (10th Edition): Loamy-skeletal, isotic, thermic Andic Dystroxerepts

ADDITIONAL DATA: NSSL Pedon No. 05N0653
Keys to Soil Taxonomy, 10th edition.

National Cooperative Soil Survey
U.S.A.