LOCATION SEARLES            OR+CA ID NV UT

SEARLES SERIES

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Aridic Argixerolls

TYPICAL PEDON: Searles very stony loam--rangeland. (Colors are for dry soil unless otherwise noted.)

A--0 to 3 inches; grayish brown (10YR 5/2) very stony loam, very dark grayish brown (10YR 3/2) moist; weak thin platy structure parting to weak fine granular; soft, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine irregular pores; 25 percent gravel; about 10 percent of the surface covered with stones and cobbles; neutral (pH 6.8); clear smooth boundary. (2 to 13 inches thick)

AB--3 to 8 inches; grayish brown (10YR 5/2) gravelly loam, very dark brown (10YR 2/2) moist; weak medium platy structure parting to weak fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine and few fine and medium roots; many very fine pores; 25 percent gravel and 5 percent cobbles and stones; neutral (pH 6.8); clear irregular boundary. (0 to 8 inches thick)

Bt1--8 to 18 inches; brown (10YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; weak fine and medium prismatic structure parting to moderate fine and medium subangular blocky; hard, firm, moderately sticky and moderately plastic; common very fine and few fine and medium roots; many very fine pores; few faint clay films on surfaces of peds and in pores; 50 percent gravel and 10 percent cobbles and stones; neutral (pH 7.0); gradual smooth boundary. (2 to 12 inches thick)

Bt2--18 to 25 inches; brown (10YR 5/3) extremely gravelly clay loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine and few fine and medium roots; many very fine pores; few faint clay films on surfaces of peds and in pores; 60 percent gravel and 10 percent cobbles and stones; neutral (pH 7.3); gradual smooth boundary. (4 to 18 inches thick)

C--25 to 40 inches; brown (10YR 5/3) extremely cobbly loam, brown (10YR 4/3) moist; massive; slightly hard, friable, slightly sticky and moderately plastic; few very fine roots; many very fine pores; 50 percent stones and cobbles and 30 percent gravel; carbonates on bottom surfaces of some rock fragments; neutral (pH 7.2); abrupt irregular boundary. (0 to 15 inches thick)

R--40 inches; fractured rhyolite; common distinct clay films lining fractures.

TYPE LOCATION: Crook County, Oregon; on a south-facing slope north of a trail; in the SE1/4 of the SW1/4 of the NE1/4 of section 9, T. 16 S., R. 15 E.

RANGE IN CHARACTERISTICS:

Soil moisture - The soils are continuously dry between depths of 4 and 12 inches during the 3-month period following the summer solstice and are dry throughout between depths of 4 and 12 inches for more than half the time (cumulative) when the soil temperature is above 41 degrees F.; Aridic moisture regime that borders on xeric.

Mean annual soil temperature - 47 to 54 degrees F.

Mollic epipedon thickness - 10 to 18 inches.

Depth to base of argillic horizon - 20 to 40 inches.

Depth to bedrock - 20 to 40 inches to a lithic contact.

Particle-size control section - Clay content: Averages 25 to 35 percent; Rock fragments: Averages 50 to 70 percent, mainly gravel and cobbles. Lithology of fragments are volcanic rocks such as rhyolite and basalt.

Other features - The percentage of the soil surface covered with stones and cobbles ranges from 0.1 to 15 percent.

A horizon - Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Texture: Loam or sandy loam.
Rock fragments: 0 to 50 percent.
Structure: Weak to moderate; platy, granular, angular blocky or subangular blocky.
Reaction: Slightly acid through slightly alkaline.

Bt horizons - Hue: 10YR or 7.5YR.
Value: 4 through 6 dry, 3 through 5 moist.
Chroma: 3 or 4, dry or moist.
Texture: Loam, sandy clay loam, clay loam, or silty clay loam.
Clay content: 25 to 40 percent.
Rock fragments: 50 to 80 percent.
Fine sand or coarser content: More than 15 percent.
Structure: Weak or moderate; prismatic, subangular blocky, or angular blocky.
Reaction: Neutral or slightly alkaline.

C or BC horizon (when present) - Hue: 10YR or 7.5YR.
Value: 5 or 6 dry, 4 or 5 moist.
Chroma: 3 or 4, dry or moist.
Rock fragments: 50 to 80 percent.
Other features: Some of the rock fragments in this horizon may have carbonates coats on the bottom surfaces.

COMPETING SERIES: These are the Ashue, Badena, Badenaugh, Eaglerock, Gitabyte (T), Grinrod, Ister, Lemm, Leviathan, Nosrac, Oest, Searvar, Shawmount, Shree, Shroe, Trid, and Tristan series.
Ashue, Badena, Badenaugh, Lemm, Leviathan, Nosrac, Oest, Shawmount, Shree, Shroe, and Tristan soils do not have bedrock within 40 inches of the soil surface. Eaglerock, Searvar and Trid soils have a paralithic contact at depths of 20 to 40 inches from the soil surface. Gitabyte soils have mollic epipedons that are 7 to 10 inches thick. Grinrod soils cannot be adequately separated (see remarks). Ister soils have an O horizon and average 35 to 50 percent rock fragments in the particle-size control section.

GEOGRAPHIC SETTING: Searles soils are on south-facing slopes of uplands, mountains, and lava plains. These soils formed in very gravelly or very cobbly medium and moderately fine textured residuum and colluvium overlying fractured rhyolite or basalt. Slopes are 0 to 80 percent. Elevations range from 2,000 to 6,590 feet. The climate is semiarid with cool winters and warm dry summers. The mean annual precipitation is 9 to 15 inches. The mean annual temperature is 45 to 52 degrees F., mean winter temperature is 30 to 34 degrees F., and mean summer temperature is 61 to 64 degrees F. The frost-free period is 50 to 155 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ayres, Deschutes, Holmzie, Simas, and Statz soils. Ayres soils have ochric epipedons and duripans. Deschutes soils do not have an argillic horizon and are coarse-loamy. Simas soils have a clayey argillic horizon and have less than 35 percent rock fragments. Statz soils have a duripan at depths of 10 to 20 inches and are non-skeletal.

DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability (moderately high saturated hydraulic conductivity).

USE AND VEGETATION: Searles soils are used for livestock grazing and wildlife habitat. The potential native plants are bluebunch wheatgrass, Idaho fescue, Sandberg's bluegrass, Wyoming big sagebrush, basin big sagebrush, antelope bitterbrush, and western juniper.

DISTRIBUTION AND EXTENT: Central Oregon, west-central Idaho, northwestern California, Nevada, and Utah. The series is extensive. MLRAs 10, 23, 25, and 26.

MLRA OFFICE RESPONSIBLE: Reno, Nevada.

SERIES ESTABLISHED: Crook County (Prineville Area), Oregon, 1964.

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

Mollic epipedon - The zone from the soil surface to 18 inches (A, AB, and Bt1 horizons).

Argillic horizon - The zone from 8 to 25 inches (Bt1 and Bt2 horizons).

Lithic contact - The boundary at 40 inches to underlying hard, unweathered bedrock (R layer).

The Grinrod series (WA) is an established soil and will need further investigation during an MLRA update to determine its series differentia when compared with the Searles soil. Grinrod is of moderate extent and mapped throughout central Washington within MLRA 8. It appears that soil climatic differences may be present in the Grinrod soil in addition to the influence of loess and volcanic ash (St. Helens). Within the Searles series, the use of a C horizon which may or may not be present in addition to carbonate accumulation on undersides of some rock fragments within this horizon, does not provide adequate competing differentia.

ADDITIONAL DATA: Characterization data on 1 profile (S55 Oreg. 7-7 and 1-7) reported in Riverside Soil Survey Laboratory report for soil sampled in Prineville Area, Crook and Jefferson Counties, Oregon, 1955. Organic carbon data believed not to be reliable. (Too high in the lower B and C horizon.)