LOCATION PORRETT ID
Established Series
Rev. AEK/BDG/EMM
08/2013
PORRETT SERIES
The Porrett series consists of very deep, very poorly drained soils that formed in alluvium derived from a mixture of loess and volcanic ash. Porrett soils are on floodplains and floodplain steps and have slopes of 0 to 3 percent. The mean annual precipitation is about 30 inches and the mean annual temperature is about 42 degrees F.
TAXONOMIC CLASS: Fine-silty, mixed, active, frigid Aquandic Epiaqualfs
TYPICAL PEDON: Porrett silt loam, pasture. Pedon originally described August 25, 1964. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 3 inches; gray (10YR 6/1) ashy silt loam, very dark grayish brown (10YR 3/2) moist; weak thin platy structure parting to weak or moderate very fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine, fine and few medium and coarse roots; many very fine and fine pores; few fine faint brown redox concentrations; moderately acid (pH 5.8); abrupt smooth boundary. (0 to 5 inches thick)
E1--3 to 9 inches; light gray (10YR 7/2) ashy silt loam, brown (10YR 5/3) 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; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; many medium black concretions; very strongly acid (pH 4.8); abrupt smooth boundary.
E2--9 to 14 inches; light gray (10YR 7/2) ashy silt loam, light olive brown (2.5Y 5/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; many medium black concretions; moderately acid (pH 5.6); abrupt smooth boundary.
E3--14 to 17 inches; light gray (10YR 7/1) silt loam, grayish brown (2.5Y 5/2) moist; massive; slightly hard, friable, nonsticky and nonplastic; few very fine and fine roots; many very fine, fine and few coarse tubular pores; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations dark yellowish brown (10YR 4/4) moist; many medium black concretions; moderately acid (pH 6.0); abrupt smooth boundary.
E4--17 to 21 inches; light gray (10YR 7/1) silt loam, pale brown (10YR 6/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; few very fine and fine roots; many very fine and fine tubular pores; common fine and medium distinct light yellowish brown(10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; many medium black concretions; moderately acid (pH 5.9); abrupt smooth boundary. (combined thickness of E horizons is 15 to 27 inches thick)
Btg--21 to 23 inches; light gray (2.5Y 7/2) silty clay loam, grayish brown (10YR 5/2) moist; moderate or strong very coarse prismatic structure parting to weak or moderate coarse angular blocky; 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; common fine and medium distinct light yellowish brown (10YR 6/4) redox concentrations, dark yellowish brown (10YR 4/4) moist; many medium and few coarse black concretions; slightly acid (pH 6.2); abrupt smooth boundary. (0 to 5 inches thick)
Bt1--23 to 36 inches; light gray (10YR 7/2) silty clay loam, olive brown (2.5Y 4/3) moist; moderate very coarse prismatic structure parting to weak or moderate coarse angular blocky; 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 distinct dark yellowish brown (10YR 4/4) redox concentrations; many medium and few coarse black concretions; neutral (pH 6.6); clear smooth boundary. (13 to 20 inches thick)
Bt2--36 to 60 inches; light brownish gray (10YR 6/2) silty clay loam, light olive brown (2.5Y 5/3) 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 coarse distinct strong brown (7.5YR 5/6) redox concentrations, dark reddish brown (5YR 3/4) moist; many medium and few coarse black concretions; neutral (pH 6.6).
TYPE LOCATION: Benewah County, Idaho; about 100 feet southwest of Benewah schoolhouse; about 1,450 feet north and 1,185 feet east of the southwest corner of section 24, T.45N., R.4W.; Latitude 47 degrees, 13 minutes, 31 seconds North; Longitude -116 degrees, 47 minutes, 5.5 seconds West. USGS Benewah topographic quadrangle.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 43 to 46 degrees F.
Mean summer soil temperature - 48 to 53 degrees F. without an O horizon.
Thickness of the solum - 54 inches to more than 60 inches.
There is a thin O horizon in undisturbed areas.
Volcanic ash influence (aquandic feature) - 12 to 20 inches
Depth to redoximorphic features - 0 to 6 inches
Ap horizon (A horizon in some pedons)
Hue - 10YR or 2.5Y
Value - 4 to 6 dry
Chroma - 1 or 2, dry or moist
Texture - ashy silt loam
Clay content - 10 to 25 percent
Reaction - 5.5 to 6.3
E horizons
Hue - 10YR or 2.5Y
Value - 5 to 8 dry, 4 to 7 moist
Chroma - 1 to 3 dry, 2 or 3 moist
Texture - ashy silt loam in the upper part, silt loam in the lower part
Clay content - 10 to 20 percent
Reaction - 5.1 to 7.0
Btg and Bt horizons
Hue - 10YR or 2.5Y
Value - 5 to 7 dry, 4 to 6 moist
Chroma - 1 to 4 dry or moist
Texture - silty clay loam or silt loam
Clay content - 14 to 35 percent
Reaction - 5.4 to 7.3
Cg horizons (present in some pedons)
Hue - 10YR or 2.5Y
Value - 7 dry, 5 or 6 moist
Chroma - 2 to 4 dry, 3 moist
Texture - silt loam or loam
Clay content - 8 to 16 percent
Reaction - 6.8 to 6.9
COMPETING SERIES:
Teneb soils - do not have an albic horizon.
GEOGRAPHIC SETTING: Porrett soils are on floodplains, floodplain steps and drainageways. Slopes are from 0 to 3 percent. The soils formed alluvium derived from a mixture of loess and volcanic ash material. Elevations range from 2,100 to 3,200 feet. The climate is subhumid and has a mean annual precipitation of 25 to 41 inches, including 4 to 6 feet of snow. The mean annual air temperature is 41 to 46 degrees F. The frost-free season is 80 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Benewah,
Lovell and
Threebear soils. Benewah soils are on hills and are moderately well drained. Lovell soils are on floodplains and are poorly drained and have redox features at depths below 6 inches. Threebear soils are on hills and have a fragipan and are moderately well drained.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Very poorly drained; moderately high saturated hydraulic conductivity. There is a perched water table between 0 and 12 inches of the surface from December to June. Frequent flooding occurs from December to May and is long or very long.
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 false solomonseal, and lily-of-the-valley.
DISTRIBUTION AND EXTENT: Porrett soils are of small extent in northern Idaho. MLRAs 9 and 43A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) 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 17 inches (Ap, E1, E2, and E3 horizons);
Argillic horizon - from 21 to 60 inches (Btg, Bt1, and Bt2 horizons);
Aquandic feature - from 0 to 14 inches (Ap, E1 and E2 horizons);
A particle-size control section from 21 to 41 inches (Btg, Bt1, and part of the Bt2 horizon);
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.
National Cooperative Soil Survey
U.S.A.