LOCATION RATTO                   OR+NV

Established Series
Rev. WMA-ELS-JVC-JBF
05/2011

RATTO SERIES

The Ratto series consists of shallow to a duripan, well drained soils that formed in alluvium and colluvium derived dominantly from volcanic rocks. Ratto soils are on lava plateaus and fan remnants. Slopes are 2 to 15 percent. The mean annual precipitation is about 280 mm and the mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Clayey, smectitic, frigid, shallow Xeric Argidurids

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

A--0 to 8 cm; light brownish gray (10YR 6/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; weak thin platy structure; soft, very friable, slightly sticky and nonplastic; many very fine and medium roots; many very fine and fine vesicular pores; 30 percent gravel, 15 percent cobbles, and 5 percent stones; neutral (pH 6.6); abrupt smooth boundary. (5 to 15 cm thick)

AB--8 to 15 cm; grayish brown (10YR 5/2) gravelly clay loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; soft, friable, moderately sticky and slightly plastic; many very fine and fine roots; few very fine interstitial pores; 20 percent gravel and 5 percent cobbles; neutral (pH 6.6); abrupt smooth boundary. (8 to 12 cm thick)

Bt1--15 to 23 cm; brown (10YR 5/3) gravelly clay loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, firm, moderately sticky and moderately plastic; many very fine and fine roots; few fine interstitial pores; 20 percent gravel and 5 percent cobbles; common faint clay films on faces of peds and lining pores; neutral (pH 6.6); abrupt smooth boundary. (20 to 25 cm thick)

Bt2--23 to 33 cm; pale brown (10YR 6/3) clay loam, brown (10YR 4/3) moist; moderate very fine and medium angular blocky structure parting to moderate fine prismatic; slightly hard, firm, moderately sticky and moderately plastic; many very fine and fine roots; few very fine interstitial pores; 10 percent gravel; many distinct clay films on faces of peds and lining pores; moderately alkaline (pH 7.9); abrupt smooth boundary. (15 to 36 cm thick)

Bk--33 to 38 cm; light brownish gray (10YR 6/2) gravelly clay loam, brown (10YR 4/3) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine roots; few very fine interstitial pores; 30 percent gravel most of which is less than 0.6 cm in diameter; strongly effervescent; secondary carbonates segregated in many fine irregularly shaped seams and filaments; strongly alkaline (pH 8.5); abrupt irregular boundary. (0 to 8 cm thick)

2Bkqm--38 to 48 cm; cemented material; massive; very gravelly alluvium indurated by opaline silica; abrupt wavy boundary. (10 to 30 cm thick)

2Bk--48 to 152 cm; light gray (10YR 7/2) gravelly loamy sand, light brownish gray (10YR 6/2) moist; single grain; loose, nonsticky and nonplastic; 30 percent gravel most of which is less than 0.6 cm in diameter; strongly effervescent; secondary carbonates segregated in many fine irregularly shaped seams and filaments; violently effervescent, strongly alkaline (pH 8.5).

TYPE LOCATION: Lake County, Oregon; on the Hart Mountain National Antelope Refuge about 1 mile southeast of Flook Knoll and 150 feet east of the Frenchglen Road; in the NW 1/4 of the NW 1/4 of the NW 1/4 of section 23, T. 34 S., R. 27 E.; USGS Flook Lake 7.5 minute topographic quadrangle; approximately latitude 42 degrees 37 minutes 05 seconds N and longitude 119 degrees 31 minutes 16 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in winter and early spring, dry in late spring, summer, and fall; aridic moisture regime that borders on xeric.
Mean annual soil temperature: 7 to 8 degrees C.
Mean summer soil temperature: 16 to 17 degrees C.
Argillic horizon thickness: 18 to 50 cm.
Depth to base of argillic horizon: 30 to 50 cm.
Depth to duripan: 30 to 50 cm.
Depth to bedrock - More than 150 cm.

Particle-size control section - Clay content: Averages 35 to 45 percent.
Rock fragments: 0 to 30 percent, mainly gravel. Lithology of fragments are mainly volcanic rocks such as basalt and tuff.

A horizon
Value: 5 through 7 dry, 3 or 4 moist; The upper 18 cm has an average value of more than 5.5 dry, or the organic matter content averages less than 1 percent.
Chroma: 2 through 4, dry or moist.
Structure: Platy or granular.
Consistence: Soft or slightly hard.

Bt1 horizon
Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Structure: Prismatic, angular blocky, or subangular blocky structure.
Texture: Clay loam or gravelly clay loam.
Clay content: 27 to 35 percent.
Rock fragments: 0 to 30 percent.
Reaction: Neutral or slightly alkaline.

Bt2 horizon
Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Structure: Prismatic or angular blocky.
Texture: Clay loam, gravelly clay loam, or clay.
Clay content: 35 to 45 percent.
Rock fragments: 0 to 30 percent.
Reaction: Slightly alkaline through strongly alkaline.

2Bkqm horizon
Value: 7 or 8 dry, 4 through 6 moist.
Chroma: 2 or 3, dry or moist.
Structure: Massive or has platy structure.

2Bk horizon
Texture: Very gravelly loamy sand, very gravelly sand, or gravelly loamy sand.
Clay content: 0 to 10 percent.
Rock fragments: 15 to 45 percent.
Calcium carbonate equivalent: 3 to 10 percent.

COMPETING SERIES: This is the Actem series. Actem soils have lithic contacts at depths of 50 to 76 cm from the soil surface.

GEOGRAPHIC SETTING: Ratto soils are on lava plateaus and fan remnants. These soils formed in alluvium and colluvium derived from volcanic rocks in Oregon and in alluvium derived from mixed rocks strongly influenced by the Newark Canyon Formation in Nevada. Slopes are 2 to 15 percent. Elevations range from 1,780 to 1,890 meters. The climate is semiarid with cool, moist winters and warm, dry summers. The mean annual precipitation is 200 to 300 mm that comes primarily as snow. The mean annual temperature is 6 to 8 degrees C. The frost-free period is 50 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Coglin and McConnel soils. Coglin soils are very deep and do not have duripans. McConnel soils are sandy-skeletal, very deep, and have cambic horizons.

DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; slow permeability; moderately low saturated hydraulic conductivity.

USE AND VEGETATION: Ratto soils are used for livestock grazing and wildlife habitat. The vegetation is mainly Wyoming big sagebrush, Sandberg's bluegrass, bluebunch wheatgrass, and bottlebrush squirreltail. Scattered Utah juniper grows on these soils in central Nevada.

DISTRIBUTION AND EXTENT: South-central Oregon and central Nevada. These soils are moderately extensive. The original series concept is in MLRA 28B in Nevada, while the main acreage and new type location occurs in MLRA 23 in Oregon.

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

SERIES ESTABLISHED: Eureka County (Diamond Valley Area), Nevada, 1971.

REMARKS: This revision of March 2004 updates the taxonomic class from Clayey, smectitic, frigid, shallow Haploxeralfic Argidurids based on use of the series in Oregon. The type location is moved to a more representative area in Lake County, Oregon. Future study is needed of the Ratto soils as mapped in Eureka County, Nevada to determine both the degree of cementation in the duripan and whether the typical depth class is actually moderately deep instead of shallow.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 15 cm (A and AB horizons).
Argillic horizon - The zone from 15 to 33 cm (Bt1 and Bt2 horizons).
Identifiable secondary carbonates - The zone from 33 to 152 cm (Bk, 2Bkqm, and 2Bk horizons).
Duripan - The zone from 38 to 48 cm (2Bkqm horizon).
Particle-size control section - The zone from 15 to 33 cm (Bt1 and Bt2 horizons).

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National Cooperative Soil Survey
U.S.A.