LOCATION CASTLEROCK ID

Established Series
Rev. ALH/RWL
07/2011

CASTLEROCK SERIES

The Castlerock series consists of deep, well drained soils with moderately slow saturated hydraulic conductivity that formed in alluvium from tuff and volcaniclastic sediments. Slopes range from 4 to 35 percent in foothills. The average annual precipitation is about 14 inches and the average annual temperature is about 50 degrees F.

TAXONOMIC CLASS: Fine, smectitic, mesic Torrertic Argixerolls

TYPICAL PEDON: Castlerock loam -- on a slightly convex south-facing slope of 6 percent, in rangeland at 3,020 feet elevation. When described on October 12, 1995, the soil was dry to 12 inches and slightly moist below. (Colors are for air-dry soil unless otherwise stated.)

A--0 to 3 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; strong thin platy structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine and fine, few medium and coarse roots; many very fine and fine, few medium irregular pores; neutral (pH 7.2); abrupt smooth boundary. (1 to 4 inches thick)

Bt1--3 to 12 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium prismatic structure parting to moderate fine and medium angular blocky; hard, firm, moderately sticky and moderately plastic; common very fine and fine, few medium and coarse roots; few very fine and fine tubular pores; many faint clay films on faces of peds and in pores; few vertical cracks less than 2 mm wide; neutral (pH 6.9); abrupt smooth boundary.

Bt2--12 to 23 inches; brown (10YR 5/3) clay, brown (10YR 4/3) moist; moderate medium prismatic structure; very hard, firm, very sticky and very plastic; common very fine and fine, few medium roots; few very fine and fine tubular pores; many prominent clay films on faces of peds and in pores; few distinct stress surfaces; few vertical cracks less than 2 mm wide; 5 percent gravel at lower boundary; neutral (pH 7.2); clear smooth boundary. (combined Bt - 8 to 20 inches thick)

Btk1--23 to 28 inches; pale brown (10YR 6/3) clay, brown (10YR 5/3) moist; moderate fine and medium prismatic structure; very hard, firm, very sticky and very plastic; few very fine and fine roots; few very fine, fine and medium tubular pores; many prominent clay films on faces of peds and in pores; common fine violently effervescent masses of segregated calcium carbonate; slightly alkaline (pH 7.4); clear smooth boundary.

Btk2--28 to 40 inches; very pale brown (10YR 7/3) clay loam, pale brown (10YR 6/3) moist; moderate fine and medium subangular blocky structure; hard, friable, very sticky and very plastic; few very fine and fine roots; few very fine and fine tubular pores; common faint clay films on faces of peds and in pores; violently effervescent, many fine seams and masses of calcium carbonate; slightly alkaline (pH 7.8); clear smooth boundary. (combined Btk - 10 to 18 inches thick)

Bk1--40 to 45 inches; very pale brown (10YR 8/3) paragravelly clay loam, pale brown (10YR 6/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; few very fine and fine roots; common very fine and fine tubular pores; 15 percent pararock fragments; violently effervescent, common fine seams of calcium carbonate; slightly alkaline (pH 7.8); clear wavy boundary.

Bk2--45 to 54 inches; light yellowish brown (2.5Y 6/4) extremely paragravelly loam, olive brown (2.5Y 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine tubular pores; 85 percent pararock fragments; strongly effervescent; slightly alkaline (pH 7.7); clear wavy boundary. (combined Bk - 5 to 20 inches thick)

Cr--54 to 60 inches; slightly fractured tuff.

TYPE LOCATION: Ada County, Idaho; about 1/2 mile northeast of the Old Idaho State Penitentiary in Boise; 950 feet west and 750 feet north of the southeast corner of section 12, T.3 N., R.2 E.; USGS Boise South Quadrangle; Latitude - 43 degrees, 36 minutes, 22 seconds N. and Longitude - 116 degrees, 09 minutes, 22 seconds W., NAD 83.

RANGE IN CHARACTERISTICS:
Mollic epipedon thickness - 10 to 20 inches
Depth to calcium carbonates - 10 to 24 inches
Depth to base of argillic horizon - 24 to 40 inches
Depth to paralithic contact - 40 to 60 inches
Moisture control section - moist less than 90 consecutive days when the soil temperature is greater than 47 degrees F.
Average annual soil temperature - 51 to 53 degrees F.

A horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Rock fragment content - 0 to 5 stones, 0 to 10 cobbles, 0 to 15 gravel and 0 to 25 percent total

Bt horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 2 or 3 dry or moist
Texture - C, CL or SICL
Clay content - 35 to 50 percent
Rock fragment content - 0 to 5 stones, 0 to 10 cobbles, 0 to 15 gravel and 0 to 25 percent total
Stress surfaces - none through common
Reaction (pH) - neutral or slightly alkaline

Btk horizon
Hue - 7.5YR or 10YR
Value - 5 through 7 dry, 4 through 6 moist
Chroma - 3 or 4 dry or moist
Texture - C or CL
Clay content - 30 to 45 percent
Rock fragment content - 0 to 5 stones, 0 to 15 cobbles, 0 to 20 gravel and 0 to 35 percent total
Calcium carbonate equivalent - 1 to 15 percent
Effervescence - slight to violent
Reaction (pH) - slightly alkaline or moderately alkaline

Bk horizon
Hue - 7.5YR through 2.5Y
Value - 6 though 8 dry, 4 through 6 moist
Chroma - 3 or 4 dry or moist
Texture - L or CL
Clay content - 20 to 35 percent total
Rock fragment content - 0 to 5 stones, 0 to 15 cobbles, 0 to 20 gravel and 0 to 35 percent total
Pararock fragment content - 5 to 90 percent
Calcium carbonate equivalent - 1 to 15 percent
Effervescence - slight to violent
Reaction (pH) - slightly alkaline or moderately alkaline

COMPETING SERIES: This is the Meloza series. Meloza soils have argillic horizons to depths greater than 60 inches and are 30 to 60 inches deep to secondary carbonates.

GEOGRAPHIC SETTING: Castlerock soils are on southerly facing structural benches and landslides at elevations of 2,750 to 3,650 feet. Slopes range from 4 to 35 percent. These soils formed in alluvium from tuff and volcaniclastic sediments. Average annual precipitation ranges from 13 to 16 inches. Average annual temperature ranges from 49 to 51 degrees F. Frost-free period is 130 to 150 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adelmann, and Lockdown soils. Adelmann soils are very deep, noncalcareous and on similar geomorphic positions. Lockdown soils are cracked to the surface, do not have a mollic epipedon and are on similar, but eroded geomorphic positions.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; moderately low saturated hydraulic conductivity.

USE AND VEGETATION: Castlerock soils are used mainly for rangeland and wildlife habitat. The dominant natural vegetation is basin big sagebrush, bluebunch wheatgrass and Thurber needlegrass.

DISTRIBUTION AND EXTENT: Southwestern Idaho. MLRA 11. Castlerock soils are not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: Ada County, Idaho, 2011

REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - zone 0 to 12 inches (A and Bt1 horizons)
Argillic horizon - zone 3 to 40 inches (Bt1, Bt2, Btk1 and Btk2 horizons)
Linear extensibility - 6.0 cm or more from the soil surface to 40 inches
Paralithic contact - at 54 inches (Cr horizon)

Particle-size control section - zone 3 to 23 inches
Soil moisture regime - aridic bordering on xeric
These soils are drier than other Xerolls in the region under similar precipitation due to early runoff and extended period of high evapotranspiration.

National Cooperative Soil Survey
U.S.A.