LOCATION PORRETT IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, frigid Aquandic Epiaqualfs
TYPICAL PEDON: Porrett silt loam, forested. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 3 inches; gray (10YR 6/1) silt loam, very dark grayish brown (10YR 3/2) moist; few fine faint brown redox concentrations; weak thin plates parting to weak or moderate very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine, fine and few medium and coarse roots; many very fine and fine interstitial pores; moderately acid (pH 5.8); abrupt smooth boundary. (0 to 4 inches thick)
E1--3 to 9 inches; light gray (10YR 7/2) silt loam, brown (10YR 5/3) moist; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; moderate thin and medium platy structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine, fine and few medium and coarse roots; many very fine and fine tubular pores; many medium black concretions; very strongly acid (pH 4.8); abrupt smooth boundary. (4 to 7 inches thick)
E2--9 to 14 inches; light gray (10YR 7/2) silt loam, light olive brown (2.5Y 5/3) moist; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; many medium black concretions; moderately acid (pH 5.6); abrupt smooth boundary. (4 to 6 inches thick)
E3--14 to 17 inches; light gray (10YR 7/1) silt loam, grayish brown (2.5Y 5/2) moist; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations dark yellowish brown (10YR 4/4) moist; massive; slightly hard, friable; few very fine and fine roots; many very fine, fine and few coarse tubular pores; many medium black concretions; moderately acid (pH 6.0); abrupt smooth boundary. (3 to 6 inches thick)
E4--17 to 21 inches; light gray (10YR 7/1) silt loam, pale brown (10YR 6/3) moist; common fine and medium distinct light yellowish brown,(10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, friable; few very fine and fine roots; many very fine and fine tubular pores; many medium black concretions; moderately acid (pH 5.9); abrupt smooth boundary. (4 to 8 inches thick)
Btg--21 to 23 inches; light gray (2.5Y 7/2) silty clay loam, grayish brown (10YR 5/2) moist; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; moderate or strong very coarse prisms parting to weak or moderate coarse angular blocky structure; very hard, firm, moderately sticky and moderately plastic; few roots on prism faces; many very fine and fine tubular pores; many prominent very dark gray (10YR 3/1) clay films on vertical faces of peds and in pores; many medium and few coarse black concretions; slightly acid (pH 6.2); abrupt smooth boundary. (2 to 5 inches thick)
Bt2--23 to 36 inches; light gray (10YR 7/2) silty clay loam, olive brown (2.5Y 4/3) moist; many medium distinct dark yellowish brown (10YR 4/4) redox concentrations; moderate very coarse prisms parting to weak or moderate coarse angular blocky structure; very hard, firm, moderately sticky and moderately plastic; few roots on prism faces; many very fine and fine tubular pores; many prominent very dark gray (lOYR 3/1) clay films on vertical faces of peds and in pores; many medium and few coarse black concretions; neutral (pH 6.6); clear smooth boundary. (13 to 20 inches thick)
Bt3--36 to 60 inches; light brownish gray (10YR 6/2) silty clay loam, light olive brown (2.5Y 5/3) moist; many medium and coarse distinct strong brown (7.5Y 5/6) redox concentrations, dark reddish brown (5YR 3/4) moist; moderate very coarse prismatic structure; very hard, firm, moderately sticky and very plastic; many very fine fine and few medium pores; many prominent continuous clay films on vertical faces of peds and in pores; many medium and few coarse black concretions; neutral (pH 6.6).
TYPE LOCATION: Benewah County, Idaho; about 100 feet southwest of Benewah schoolhouse, in the NW 1/4 SW 1/4 sec. 24, T.45N., R.4W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 43 to 45 degrees F., mean summer soil temperature ranges from 48 to 53 degrees F. without an O horizon. The thickness of the sola is 54 inches to more than 60 inches. The profile ranges in pH from very strongly acid to neutral. There is a thin O horizon in undisturbed areas.
The Ap horizon has hue of 10YR or 2.5Y and chroma of 1 or 2.
The E horizon has hue of 10YR or 2.5Y, value of 5 through 7 dry, 4 or 5 moist and chroma of 1 through 3 dry and 2 or 3 moist.
The Btg and Bt horizons have hue of 10YR or 2.5Y, value of 5 through 7 dry, 4 through 6 moist and chroma of 1 through 3.
COMPETING SERIES: This the Teneb series. Teneb soils do not have an E horizon.
GEOGRAPHIC SETTING: Porrett soils are on alluvial bottomlands. Slopes are from 0 to 2 percent. The soils formed in a mixture of loess and volcanic ash material. Elevations range from 2,600 to 2,900 feet. The climate is subhumid and has a mean annual precipitation of 25 to 35 inches, including 4 to 6 feet of snow, and a frost-free season of 60 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Benewah and Helmer soils. Benewah soils are moderately well drained. Helmer soils have a fragipan and are moderately well drained.
DRAINAGE AND PERMEABILITY: Very poorly drained; slow runoff; moderately slow permeability. The water table fluctuates between 12 and 36 inches of the surface for long periods, and may be at the surface in the spring or early summer during the yearly overflow.
USE AND VEGETATION: Wildlife, pasture and woodland grazing are the main uses. Areas that are cleared are used mainly for pastures. The natural vegetation consists of an overstory of Engelmann spruce, western hemlock, western redcedar, lodgepole pine, grand fir, western larch and western white pine. The understory is myrtle pachistima, oneleaf foamflower, tiarella, big whortberry, queen beadlily, longtube twinflower, oak fern, violet, starry falsesolomonseal, and lily-of-the-valley.
DISTRIBUTION AND EXTENT: Latah, Benewah, Shoshone and Kootenai Counties in northern Idaho. It is of moderate extent.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Benewah County, Idaho, 1975.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon from the soil surface to 21 inches (Ap, E1, E2, and E3 horizons); Albic horizon from the soil surface to 8 inches (Ap, E1, E2, and E3 horizons);
Argillic horizon from 21 to 60 inches (Btg, Bt2, and Bt3 horizons);
A particle-size control section from 21 to 41 inches (Btg, Bt2, and Bt3 horizons);
Porrett soils have a frigid temperature regime and an aquic moisture regime.
The 9/2008 description reflects a change in classification from Fine-silty, mixed, superactive Typic Cryaqualfs to Fine-silty, mixed, active, frigid Aquandic Epiaqualfs based on an MLRA-wide investigation of Porrett.