LOCATION RED BLUFF               CA

Established Series
Rev: SBJ/LCL/WCL/DJE
01/2023

RED BLUFF SERIES

The Red Bluff series consists of very deep, well drained soils formed in old mixed alluvium. Red Bluff soils are on terraces and have 0 to 9 percent slopes. The mean annual precipitation is about 25 inches and the mean annual air temperature is about 62 degrees F.

TAXONOMIC CLASS: Fine, kaolinitic, thermic Ultic Palexeralfs

TYPICAL PEDON: Red Bluff gravelly loam - on a 2 percent south-facing slope in a pasture field under annual grasses at 350 feet elevation. (Colors are for dry soil unless otherwise stated).

Ap--0 to 6 inches; reddish brown (5YR 4/4) gravelly loam, dark reddish brown (2.5YR 3/4) moist; weak medium and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many very fine tubular pores; few small (2-3mm) hard concretions which are yellowish red when crushed; 20 percent pebbles; very strongly acid (pH 5.0); abrupt smooth boundary. (4 to 8 inches thick)

A1--6 to 10 inches; reddish brown (5YR 4/4) gravelly loam, dark reddish brown (2.5YR 3/4) moist; weak medium and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many fine tubular pores; few small (2-3mm) hard concretions; 20 percent pebbles; very strongly acid (pH 4.9); clear wavy boundary.

A2--10 to 20 inches; reddish brown (5YR 4/4) loam, dark reddish brown (2.5YR 3/4) moist; weak medium and fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; many very fine and fine tubular pores; common dark coatings on peds react strongly with peroxide; 10 percent pebbles; very strongly acid (pH 5.0); abrupt irregular boundary. (Combined thickness of the A horizons is 15 to 21 inches).

Bt1--20 to 27 inches; red (2.5YR 4/6) clay loam, weak red (10R 4/4) moist; strong medium and fine angular blocky structure; hard, firm, slightly sticky and slightly plastic; few very fine roots; many very fine tubular pores; common clay films bridge mineral grains, thin continuous clay films in pores; many dark stains on ped faces; 10 percent pebbles; very strongly acid (pH 5.0); gradual wavy boundary.

Bt2--27 to 37 inches; red (2.5YR 4/6) clay loam, weak red (10R 4/4) moist; strong medium and fine angular blocky structure; hard, firm, slightly sticky and plastic; few very fine roots; many very fine tubular pores; common clay films bridge mineral grains, thin continuous clay films in pores; many dark stains on pet faces; brittle dry, weakly cemented with iron oxide; 10 percent pebbles; very strongly acid (pH 5.0); diffused wavy boundary. (Combined thickness of the Bt horizons is 15 to 20 inches).

2Bt3--37 to 55 inches; red (2.5YR 4/6) gravelly clay loam, weak red (10R 4/4) moist; strong medium and fine angular blocky structure; hart, firm, slightly sticky and plastic; few very fine roots; many very fine tubular pores; common clay films bridge mineral grains, thin continuous clay films in pores; common dark stains on ped faces; brittle dry; very weakly cemented with iron oxide; 30 percent pebbles; strongly acid (pH 5.2); clear wavy boundary. (15 to 30 inches thick)

2BCt--55 to 72 inches; red (2.5YR 4/6) gravelly clay loam, weak red (10R 4/4) moist; weak medium and fine angular blocky structure; hard, firm, slightly sticky and plastic; few very fine roots; many very fine tubular pores; common thin clay films bridge mineral grains, few thin clay films in pores; common dark stains on ped faces; 20 percent pebbles; strongly acid (pH 5.4).

TYPE LOCATION: Tehama County, California; west of Red Bluff Municipal Airport. About 0.4 miles west on Live Oak Road from the intersection with Paskenta Road and 200 feet south of road in a pasture; 2,300 feet west and 2,800 feet south from the northeast corner of sec. 36, T. 27 N., R. 4 W., Red Bluff West Quadrangle 7.5 minute series.

RANGE IN CHARACTERISTICS: Thickness of the solum is over 60 inches and the percentage of clay decrease from the maximum amount at 60 inches by 3 to 10 percent absolute. The mean annual soil temperature is 62 to 66 degrees F and exceeds 41 degrees F all year. The soil between a depth of 7 and 21 inches is dry in all parts from June to October and moist in some or all parts the rest of the year. The upper 20 inches of the argillic averages more than 35 percent clay and ranges from 27 to 60 percent clay. Base saturation (sum) ranges from 45 to 75 percent throughout the argillic horizon.

The A horizon is 5YR 4/4, 5/6; 6/6; 7.5YR 5/4, 4/4, 5/6, 6/6, and moist color of 2.5YR 3/4, 3/6; 5YR 3/3, 3/4, 4/4; 7.5YR 3/4 or 4/4. Texture is loam or gravelly loam with a clay content of 15 to 27 percent. Gravel content is 0 to 30 percent. Reaction is very strongly acid to medium acid.

The Bt ant 2Bt horizon color is 2.5YR 4/4, 4/6, 3/6, 3/4, 5/4, 5/6, or 4/8; 5YR 4/4, 4/6, 5/4, 5/6, 5/8, 6/4 ant moist colors of 2.5YR 3/4, 3/6, 4/4, 4/6; 5YR 3/4, 4/4, 4/6; 10R 4/4 or 4/6. Texture is clay loam, gravelly clay loam, clay or gravelly clay with 27 to 60 percent clay content and 5 to 35 percent gravel. Clay content increases with depth. Reaction is very strongly acid to slightly acid. BS ranges from 45 to 75 percent (sum) throughout the argillic horizon.

Where present, the 2BCt horizon color is 2.5YR 4/6, 3/6, 3/4, 5/4, 5/6, 4/8; 5YR 4/4, 4/6, 5/4, 5/6, 5/8, 6/4 and moist colors of 2.5YR 3/4, 3/6, 4/6; 5YR 3/4, 4/4, 4/6; 10R 4/4 or 4/6. Texture is gravelly clay loam, very gravelly clay loam, gravelly clay or very gravelly clay with 30 to 50 percent clay content and 15 to 60 percent gravel. Reaction is very strongly acid to slightly acid.

COMPETING SERIES: These are the Corning and Tehama series in other families. Corning and Tehama soils have mixed mineralogy.

GEOGRAPHIC SETTING: The Red Bluff soils are on terraces and have slopes of 0 to 9 percent. The soils formed in mixed alluvium at elevations of 75 to 1,500 feet. The climate is Mediterranean with hot dry summers and cool moist winters. Mean annual precipitation varies from 15 to 40 inches. Mean January temperature is about 45 degrees F; mean July temperature is about 80 degrees F; mean annual air temperature is about 62 degrees F. Frost-free season ranges from 250 to 280 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Corning, Redding, Tehama, and Yolo soils. Corning soils have thin gravelly clay subsoils. Redding soils have a duripan within 20 to 40 inches. Tehama soils have silty textured and slightly acid subsoils. Yolo soils are on low recent alluvial fans and have neutral loamy subsoils.

DRAINAGE AND PERMEABILITY: Well trained; slow to medium runoff; and moderately slow permeability.

USE AND VEGETATION: Small grains and pasture are grown where dry farmed. Row crops, pasture and a few orchards are grown under irrigation. Native vegetation consists of blue oak, live oak, manzanita, soft chess, wild oats and annual forbs. In lower rainfall areas, oaks and brush are absent.

DISTRIBUTION AND EXTENT: Sacramento Valley, California. Red Bluff soils are moderately extensive.

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

SERIES ESTABLISHED: Tehama County, California, 1961.

REMARKS: Laboratory data by National Soil Survey Laboratory Tehama County, California (54557-6) and Shasta County, California (S4557-8). Also, Lincoln, Nebraska (84T7185) and Sacramento County, California (S79CA067-5).

ADDITIONAL REMARKS: Diagnostic horizons and features recognized in this pedon are: Ochric epipedon--extents from O to 20 inches. Argillic horizon 20 to 72 inches has an average of 36 percent clay and the clay distribution does not decrease from its maximum amount by as much as 20 percent of that maximum throughout to a depth of 1.5 m from the soil surface or skeletons are present if decrease is greater than 20 percent. The upper 20 inches average over 35 percent clay.

OSED scanned by SSQA. Last revised by state on 6/86.

---

National Cooperative Soil Survey
U.S.A.