LOCATION TREGONING          CA 
Established Series
Rev. NHS-CAR-CEJ
9/98

TREGONING SERIES


The Tregoning series consists of moderately deep to hardpan, poorly drained soils formed in eolian sands. Tregoning soils are on marine terraces and have slopes of 0 to 15 percent. The mean annual precipitation is about 50 inches and the mean annual temperature is about 53 degrees F.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, nonacid, isomesic Humic Epiaquepts

TYPICAL PEDON: Tregoning sandy loam on a west facing slope of 3 percent under Mendocino cypress and Bishop pine at 100 feet elevation. (Colors are for dry soil unless otherwise stated. When described on October 3l, 1986, the soil was slightly moist throughout).

Oi--2 to 0 inches; partially decomposed Bishop pine and tanoak litter.

A1--0 to 5 inches; gray (10YR 5/1) sandy loam, very dark grayish brown (10YR 3/2) moist; weak, fine and medium subangular blocky structure; soft, friable, slightly sticky and non-plastic; common very fine and fine and few medium and coarse roots; many very fine interstitial and few fine tubular pores; extremely acid (pH 4.2); clear wavy boundary. (1 to 6 inches thick)

A2--5 to 9 inches; gray (10YR 6/1) sandy loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; soft, friable, slightly sticky and nonplastic; common medium and fine and few coarse roots; common very fine interstitial and few very fine tubular pores; extremely acid (pH 4.2); clear wavy boundary. (0 to 5 inches thick)

E--9 to 15 inches; light gray (10YR 7/1) sandy loam, light brownish gray (2.5Y 6/2) moist; massive; slightly hard, firm, slightly sticky and nonplastic, slightly smeary; medium fine and few coarse roots; few very fine interstitial and tubular pores; extremely acid (pH 4.2); abrupt wavy boundary. (5 to 12 inches thick)

Bg--15 to 23 inches; light gray (5Y 7/1) weakly cemented loamy sand, grayish brown (2.5Y 5/2) moist; common fine and medium very pale brown (10YR 7/3) mottles, yellowish brown (10YR 5/6) moist; ped faces are stained dark brown (7.5YR 4/2) with humic material; strong fine and medium subangular blocky structure; hard, very firm, nonsticky and nonplastic; few very fine and fine roots; few very fine interstitial and tubular pores; strongly acid (pH 5.5); abrupt wavy boundary. (5 to 10 inches thick)

Bhsm--23 to 45 inches; light gray (2.5Y 7/2) strongly cemented loamy sand, grayish brown (2.5Y 5/2) moist; common large light yellowish brown (10YR 6/4) and common medium and large brown (7.5YR 5/4) mottles, yellowish brown (10YR 5/6) and dark brown (7.5YR 4/4) moist; massive; extremely hard, extremely firm, nonsticky and nonplastic; slightly acid (pH 6.5); gradual wavy boundary. (10 to 25 inches thick)

Bsm--45 to 62 inches; pale brown (10YR 6/3) weakly cemented sand, light olive brown (2.5Y 5/4) moist; massive; extremely hard, very firm, nonsticky and nonplastic; slightly acid (pH 6.4).

TYPE LOCATION: Mendocino County, California; about 400 feet south and about 200 feet east of the northwest corner of section 19, T.18 N., R.17 W., MDBM, Fort Bragg quadrangle.

RANGE IN CHARACTERISTICS: Depth to bedrock is greater than 80 inches. Depth to hardpan ranges from 20 to 40 inches. The mean annual soil temperature ranges from 50 to 56 degrees F. The difference between mean summer and mean winter temperature is 6 to 9 degrees F. The soil is saturated above the pan for extended periods during the months of December through April. Base saturation ranges from 5 to 30 percent throughout.

The A horizon is 2 to 10 inches thick. It is 10YR 5/1 or 6/1. Moist color is 10YR 3/1, 3/2 or 3/3. Clay content ranges from 5 to 12 percent. Reaction is extremely or very strongly acid (pH 4.3 to 5.0).

The E horizon is 10YR 7/1 or 8/1. Moist color is 2.5Y 6/2; 10YR 5/2, 6/1, or 6/2. It is loamy sand or sandy loam. Clay content ranges from 3 to 12 percent. Reaction is extremely or very strongly acid (pH 4.3 to 5.0).

The Bg horizon is 5Y 7/1; 2.5Y 6/2 or 7/2. Moist color is 2.5Y 5/2, 6/1, or 6/2. Mottle colors are 10YR 7/3, 7/4, or 7/6. Moist mottle colors are 10YR 5/6 or 6/6. Clay content ranges from 3 to 10 percent. Nodule content ranges from 0 to 15 percent. Reaction is strongly or moderately acid.

The Bhsm horizon is 2.5Y 6/2, 7/2; 10YR 5/2, or 5/3. Moist color is 2.5Y 4/2, 5/2; 10YR 4/1, 4/2 or 4/3. Mottle colors are 10YR 6/4, 6/6 or 7.5YR 5/4. Moist mottle colors are 10YR 5/6, 5/8 or 7.5YR 4/4. Clay content ranges from 3 to 10 percent. Reaction is moderately or slightly acid.

The Bsm horizon is 10YR 6/3, 7/3, 7/4. Moist color is 2.5Y 5/4 or 10YR 5/4. Clay content ranges from 0 to 5 percent. Reaction is moderately or slightly acid.

COMPETING SERIES: There are no other series in the same family.

GEOGRAPHIC SETTING: Tregoning soils are on marine terraces. Slopes are 0 to 15 percent. Elevations range from 40 to 250 feet. The soil formed in eolian sands. The climate is humid with cool foggy summers and cool moist winters. A strong marine influence limits the diurnal and annual range of temperature. Mean annual precipitation ranges from 40 to 55 inches. Mean January temperature is about 48 degrees F. Mean July temperature is about 57 degrees F., and the mean annual temperature is 53 degrees F. The frost-free period is 290 to 330 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cabrillo, Cleone, Harecreek and Heeser soils. Cabrillo soils are fine-loamy and somewhat poorly drained and lack a strongly cemented hardpan. Harecreek soils are somewhat poorly drained and lack a strongly cemented hardpan. Heeser soils are somewhat excessively drained and lack a strongly cemented hardpan.

DRAINAGE AND PERMEABILITY: Poorly drained. The soil is saturated with water for extended periods from December through April. The saturated zone starts between the depths of 10 and 30 inches and extends to the top of the hardpan. The soil is also saturated beneath the hardpan for extended periods. Surface runoff under bare soil conditions is very slow through medium. Permeability is moderately rapid above the hardpan, very slow in the hardpan and rapid below the hardpan.

USE AND VEGETATION: This soil is used for homesite development. Vegetation consists of Bishop pine, cypress, wax myrtle, evergreen huckleberry, rhododendron, salal and small amounts of tanoak and Douglas-fir.

DISTRIBUTION AND EXTENT: Northern coastal California. The series is not extensive.

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

SERIES PROPOSED: Mendocino County, California, Western part, 1988.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon (with albic horizon) -- the zone from 0 to 15 inches (A1, A2, E)

Spodic horizon (ortstein -- the zone from 23 to 45 inches (Bhsm).

Aquic moisture regime -- is saturated between a depth of 10 to 30 inches and the hardpan for extended periods during the rainy season. Low chromas and mottles occur within this zone, indicating reduced conditions.


National Cooperative Soil Survey
U.S.A.