LOCATION GRADON                  OR

Established Series
Rev. MPK-TDT-JVC-JBF
03/2011

GRADON SERIES

The Gradon series consists of moderately deep to a duripan, well drained soils that formed in alluvium derived from volcanic rocks. Gradon soils are on fan remnants. Slopes are 0 to 8 percent. The mean annual precipitation is about 280 mm and the mean annual temperature is about 6 degrees C.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Argiduridic Durixerolls

TYPICAL PEDON: Gradon gravelly fine sandy loam--rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 8 cm; brown (10YR 5/3) gravelly fine sandy loam, dark brown (10YR 3/3) moist; moderate medium platy structure parting to weak fine granular; soft, very friable, slightly sticky and nonplastic; many very fine, common fine, and few medium roots; many very fine, common fine, and few medium vesicular pores; 20 percent gravel; neutral (pH 7.0); clear smooth boundary.

A2--8 to 25 cm; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure parting to weak fine granular; slightly hard, very friable, moderately sticky and moderately plastic; common very fine and fine, and few medium roots; few very fine, few medium, and common fine tubular pores; 5 percent gravel; neutral (pH 7.2); clear smooth boundary. (Combined thickness of A horizons is 18 to 30 cm thick.)

Bt--25 to 56 cm; light yellowish brown (10YR 6/4) clay loam, dark yellowish brown (10YR 3/4) moist; moderate medium angular blocky structure parting to strong fine angular blocky; hard, firm, moderately sticky and moderately plastic; few very fine, few medium, and common fine roots; few very fine, few fine, and few medium tubular pores; common distinct clay films on faces of peds; 5 percent gravel; slightly alkaline (pH 7.4); clear smooth boundary. (20 to 76 cm thick)

Btkq--56 to 81 cm; light yellowish brown (10YR 6/4) gravelly sandy loam, dark yellowish brown (10YR 3/4) moist; moderate medium subangular blocky structure; hard, firm and brittle, slightly sticky and plastic; few very fine, few fine, and few medium roots; few very fine and few fine tubular pores; common faint clay films on faces of peds; strongly effervescent with disseminated carbonates; 15 percent gravel; slightly alkaline (pH 7.6); abrupt smooth boundary. (0 to 25 cm thick)

Bkqm1--81 to 122 cm; very pale brown (10YR 7/3) cemented material, brown (10YR 5/3) moist; massive; indurated by silica and secondary carbonates; few very fine roots; violently effervescent; secondary carbonates are disseminated in the matrix and segregated in common fine irregular seams and filaments; gradual smooth boundary.

Bkqm2--122 to 140 cm; very pale brown (10YR 7/4) cemented material, yellowish brown (10YR 5/4) moist; massive; strongly cemented by silica and secondary carbonates; violently effervescent; secondary carbonates are disseminated in the matrix and segregated in common fine irregular seams and filaments; gradual smooth boundary. (Combined thickness of the Bkqm horizons is 15 to 64 cm.)

C--140 to 157 cm; pale brown (10YR 6/3) sandy loam, dark yellowish brown (10YR 4/4) moist; massive; hard, friable, slightly sticky and slightly plastic; moderately alkaline (pH 8.0).

TYPE LOCATION: Harney County, Oregon; about 0.25 mile south of Chickahominy Reservoir; about 350 feet south and 150 feet east of the northwest corner of section 33, T. 23 S., R. 26 E.; USGS Riley 7.5 minute topographic quadrangle; latitude 43 degrees 32 minutes 19 seconds N and longitude 119 degrees 36 minutes 59 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture - The soils are dry between depths of 10 and 30 cm for more than half time when the soil temperature is above 5 degrees C; aridic moisture regime that borders on xeric.
Mean annual soil temperature: 7 to 8 degrees C.
Mollic epipedon thickness: 18 to 30 cm.
Depth to base of argillic horizon: 50 to 100 cm.
Depth to duripan: 50 to 100 cm.
Depth to bedrock: More than 150 cm.

Particle-size control section - Clay content: 25 to 35 percent.
Rock fragments: Averages 5 to 25 percent mainly gravel. Lithology of fragments are volcanic rocks such as basalt.

A horizons
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 or 3, dry or moist.
Organic matter content: 1 or 2 percent.
Reaction: Neutral or slightly alkaline.

Bt horizon
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Texture: Loam, clay loam, or gravelly sandy clay loam.

Bkqm horizons
Cementation: Indurated in upper subhorizon and very strongly cemented or strongly cemented in lower subhorizon.

C horizon
Texture: Sandy loam or gravelly sandy loam.
Clay content: 5 to 15 percent.
Rock fragments: 0 to 30 percent.
Reaction: Slightly alkaline or moderately alkaline.

COMPETING SERIES: This is the Heckison series. Heckison soils have calcic horizons above the duripan and lithic contacts at depths of 56 to 100 cm from the soil surface.

GEOGRAPHIC SETTING: Gradon soils are on fan remnants. These soils formed in alluvium derived from volcanic rocks. Slopes are 0 to 8 percent. Elevations range from 1,310 to 1,615 meters. The climate is semiarid and characterized by cold, moist winters and warm, dry summers. The mean annual precipitation is 250 to 330 mm, the mean annual temperature is 6 to 7 degrees C and the frost-free period is 50 to 80 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ninemile, Vergas, and Westbutte soils. Ninemile soils are shallow to bedrock on plateaus. Vergas soils do not have a duripan and are on fan remnants. Westbutte soils are moderately deep to bedrock and are on hills.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; high surface runoff; moderately slow permeability; moderately high saturated hydraulic conductivity above the duripan.

USE AND VEGETATION: Gradon soils are used for livestock grazing. The vegetation is Idaho fescue, bluebunch wheatgrass, Thurber's needlegrass, basin big sagebrush, and Wyoming big sagebrush.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are not extensive. MLRA 23.

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

SERIES ESTABLISHED: Harney County, Oregon, 1997.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 25 cm (A1 and A2 horizons).
Argillic horizon - The zone from 25 to 81 cm (Bt and Btq horizons).
Identifiable secondary carbonates - The zone from 81 to 140 cm (Bkqm1 and Bkqm2 horizons).
Duripan - The zone from 81 to 140 cm (Bkqm1 and Bkqm2 horizons).
Particle-size control section - The zone from 25 to 75 cm (Bt and part of the Btq horizons).

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National Cooperative Soil Survey
U.S.A.