LOCATION RUBSON                  ID+MT

Established Series
Rev. CJW-BDG-RJS
05/2017

RUBSON SERIES

The Rubson series consists of very deep, well drained soils that formed in glaciolacustrine sediments with minor amounts of volcanic ash in the surface layers. Rubson soils are on terraces. Slope ranges from 0 to 20 percent. The mean annual precipitation is about 775 mm, and the mean annual air temperature is about 6.1 degrees C.

TAXONOMIC CLASS: Coarse-silty, mixed, superactive, frigid Vitrandic Hapludalfs

TYPICAL PEDON: Rubson silt loam, forested; on a 1 percent slope at 695 meters elevation. When described on October 18, 1972, the soil was moist throughout. Pedon was re-described on August 30, 1995. (Colors are for dry soil unless otherwise noted.)

Oi--0 to 5 cm; needles, leaves, and twigs.

Oe--5 to 8 cm; partially decomposed needles, leaves, and twigs mixed with Mt. St. Helens volcanic ash.

A--8 to 13 cm; pale brown (10YR 6/3) ashy silt loam, brown (7.5YR 4/2) moist; moderate fine granular structure; soft, friable, slightly sticky and slightly plastic; many fine, medium, and coarse roots; many very fine pores; slightly acid (pH 6.1); clear wavy boundary. (3 to 10 cm thick)

Bw1--13 to 28 cm; pale brown (10YR 6/3) ashy silt loam, brown (7.5YR 5/4) moist; weak fine granular structure; soft, friable, slightly sticky and slightly plastic; many fine, medium, and coarse roots; many very fine and few fine and medium pores; slightly acid (pH 6.2); clear wavy boundary. (13 to 20 cm thick)

Bw2--28 to 43 cm; pale brown (10YR 6/3) ashy silt loam, brown (7.5YR 5/4) moist; weak fine and medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many fine, medium, and coarse roots; many very fine pores; moderately acid (pH 5.9); clear wavy boundary. (15 to 20 cm thick)

Bt1--43 to 66 cm; very pale brown (10YR 7/3) silt loam, pale brown (10YR 6/3) moist; weak coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine, medium, and coarse roots; many very fine and fine pores; few faint clay films on faces of peds and lining pores; few thin lamellae 2 to 4 mm thick; slightly acid (pH 6.1); clear wavy boundary. (20 to 60 cm thick)

Bt2--66 to 81 cm; very pale brown (10YR 7/3) silt loam, pale brown (10YR 6/3) moist; weak coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine, medium, and coarse roots; many very fine pores; few faint clay films on faces of peds and lining pores; common thin yellowish brown (10YR 5/4) lamellae .25 to .5 inch thick; slightly acid (pH 6.3); abrupt wavy boundary. (8 to 15 cm thick)

Bt3--81 to 89 cm; reddish yellow (7.5YR 6/6) silt loam, yellowish brown (10YR 5/4) and dark yellowish brown (10YR 3/4) moist; weak coarse subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine roots; many very fine and fine pores; many faint clay films on faces of peds and lining pores; moderately acid (pH 5.7); abrupt wavy boundary. (8 to 15 cm thick)

Bt4--89 to 135 cm; very pale brown (10YR 7/3) very fine sandy loam, pale brown (10YR 6/3) moist; weak coarse subangular blocky structure; hard, friable, nonsticky and nonplastic; few fine, medium, and coarse roots; many very fine pores; few faint clay films on faces of peds and lining pores; common wavy and discontinuous yellowish brown (10YR 5/4) lamellae about 0.5 to 2 inches thick; slightly acid (pH 6.3); abrupt wavy boundary. (35 to 64 cm thick)

Bt5--135 to 147 cm; yellowish brown (10YR 5/4) very fine sandy loam, dark yellowish brown (10YR 4/4) moist; weak coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine pores; few faint clay films and lamellae; slightly acid (pH 6.4); abrupt wavy boundary. (8 to 15 cm thick)

C--147 to 172 cm; light gray (10YR 7/2) loamy very fine sand, grayish brown (2.5Y 5/2) moist; massive; soft, very friable, nonsticky and nonplastic; many fine pores; slightly alkaline (pH 7.7).

TYPE LOCATION: Boundary County, Idaho; about 1.6 kilometers northeast of the junction of U. S. 2/95 and Paradise Valley Road; about 3.5 miles south of Bonners Ferry Ranger Station; about 60 meters west and 90 meters north of the southeast corner sec. 16, T.61N., R.1E. Latitude - 48 degrees, 37 minutes, 53 seconds North; Longitude - 116 degrees, 19 minutes, 37 seconds West; USGS Bonners Ferry Quadrangle.

RANGE IN CHARACTERISTICS:
Average annual soil temperature -- 5.6 to 7.8 degrees C.
Average summer soil temperature -- 11.1 to 13.3 degrees C. (with an O horizon)
Moisture control section -- dry 15 to 30 days (August to mid September); moist mid September through July; Udic moisture regime.

Volcanic ash influence
Thickness -- 30 to 50 cm
Glass content -- 5 to 20 percent
Acid-oxalate extractable Al + 1/2 Fe -- 0.4 to 1.0 percent
Moist bulk density -- 1.0 to 1.2 g/cc
Phosphate retention -- 25 to 55 percent

A, Ap (where present) horizons
Value: 4 to 6 dry; 2 to 4 moist
Chroma: 2 or 3 dry or moist
Texture (less than 2mm fraction): ashy silt loam, ashy very fine sandy loam
Clay content: 5 to 10 percent
Reaction: pH 5.6 to 7.3

Bw1, Bw2 horizons
Value: 5 to 7 dry; 3 to 5 moist
Chroma: 3 or 4 dry or moist
Texture (less than 2mm fraction): ashy silt loam, ashy very fine sandy loam
Clay content: 5 to 10 percent
Reaction: pH 5.6 to 7.3

Bt1, Bt2, Bt3, Bt4, Bt5 horizons
Hue: 10YR, 7.5YR, 2.5Y dry or moist
Value: 5 to 7 dry; 3 to 6 moist
Chroma: 3 to 6 dry or moist
Texture (less than 2mm fraction): silt loam, very fine sandy loam
Clay content: 5 to 17 percent
Lamellae: 1/16 to 2 inches thick, 10YR or 7.5YR 4/4, 4/6, 5/4 moist, clay content 16 to 25 percent
Reaction: pH 5.6 to 7.3

C horizon
Chroma: 2 or 3 dry or moist
Texture (less than 2mm fraction): very fine sandy loam, loamy very fine sand
Clay content: 0 to 5 percent
Reaction: pH 6.6 to 7.8

COMPETING SERIES:
Frycanyon soils: have secondary calcium carbonate

GEOGRAPHIC SETTING: Rubson soils are on terraces. Slopes range from 0 to 20 percent. These soils formed in glaciolacustrine sediments with minor amounts of volcanic ash in the surface layers. The climate is subhumid with cold wet winters and warm relatively dry summers. Elevation is 530 to 860 meters. The average annual precipitation is 625 to 825 mm, and average annual air temperature is 5.6 to 7.8 degrees C. The average frost-free period is 100 to 135 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Artnoc, Caboose, Crash, Elmira, Frycanyon, Porthill, Selle, and Wishbone soils. Artnoc, Caboose, Crash, and Wishbone soils are on terrace escarpments, have hues of 5Y in the solum and are not vitrandic. Elmira and Selle soils are on dunes and terraces and are sandy. Frycanyon soils are on terraces and have Bk horizons. Porthill soils are on terraces and are fine textured in the argillic horizon.

DRAINAGE AND PERMEABILITY: Well-drained; slow to medium runoff; moderate permeability.

USE AND VEGETATION: Woodland, wildlife habitat, recreation and dry cropland. The principal crops are small grains, alfalfa hay, clover seed and pasture. Some areas are used for Christmas tree plantations and homesites. Natural vegetation is mainly western hemlock, western redcedar, western white pine, Douglas-fir, grand fir, and western larch with an understory of myrtle pachystima, baldhip rose, longtube twinflower, queencup beadlily; starry false Solomon's seal, common prince's pine, darkwoods violet, and western rattlesnake plantain.

DISTRIBUTION AND EXTENT: Northern Idaho, Montana, and possibly northeastern Washington. The series is moderately extensive. MLRA 44A

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Boundary County, Idaho, 1974.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon -- 0 to 13 cm (Oi, Oe, A horizons)
Argillic horizon -- 43 to 147 cm (Bt1, Bt2, Bt3, Bt4, Bt5 horizons)
Volcanic ash influence -- 8 to 43 cm (A, Bw1, Bw2 horizons)
Particle-size control section -- 43 to 93 cm (Bt1, Bt2, Bt3, part of Bt4 horizons)

Additional Data: Laboratory data are available for this series: KSSL Pedon No.94P0242 (partial pedon) from Boundary County, Idaho; Pedon No. 98P0033 from Boundary County, Idaho; Pedon No. 98P0041 from Boundary County, Idaho.

Taxonomic version: Keys to Soil Taxonomy, Twelfth Edition, 2014.

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National Cooperative Soil Survey
U.S.A.