LOCATION POTLATCH           ID

POTLATCH SERIES

The Potlatch series consists of very deep, poorly drained soils formed in mixed alluvium. Permeability is very slow in the solum. These soils are on depressions of alluvial fans and terraces and have slopes of 0 to 2 percent. Average annual precipitation is about 28 inches and average annual air temperature is about 42 degrees F.

TAXONOMIC CLASS: Fine, smectitic Aquic Haplocryalfs

TYPICAL PEDON: Potlatch silt loam - on a concave 1 percent slope in a pasture at 2,520 feet elevation. (Colors are for moist soil unless otherwise stated. When described the soil was slightly moist to 36 inches and moist below.)

A1--0 to 4 inches; gray (10YR 5/1) silt loam, very dark gray (10YR 3/1) moist; weak fine subangular blocky structure that parts to moderate fine and medium granular structure; slightly hard, firm, slightly sticky, slightly plastic; many fine and medium roots; common fine and very fine tubular pores; few faint iron stains, moderately acid (pH 6.0); clear wavy boundary. (4 to 6 inches thick)

A2--4 to 7 inches; gray (10YR 5/1) silt loam, very dark gray (10YR 3/1) moist; moderate fine and medium subangular blocky structure; hard, firm, slightly sticky, slightly plastic; many fine and medium roots; common very fine and fine tubular pores; few faint iron stains; moderately acid (pH 6.0); abrupt wavy boundary. (3 to 5 inches thick)

B2--7 to 12 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky structure; hard, firm, slightly sticky, slightly plastic; common fine and medium roots; many very fine and common fine tubular pores; few faint iron stains; moderately acid (pH 6.0); clear wavy boundary. (4 to 10 inches thick)

A'21g--12 to 16 inches; light gray (10YR 7/1) silt loam, dark gray (10YR 4/1) moist; few distinct yellowish brown (10YR 5/6) mottles; moderate medium subangular blocky structure; hard, firm, slightly sticky, slightly plastic; common fine and medium roots; many fine and medium tubular pores; few mica flakes; few black concretions; moderately acid (pH 6.0); abrupt wavy boundary. (3 to 5 inches thick)

A'22g--16 to 22 inches; light gray (10YR 7/1) silt loam, dark gray (10YR 4/1) moist; few distinct yellowish brown (10YR 5/6) mottles; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic; few fine and medium roots; common fine and few medium tubular pores; few mica flakes; few black concretions; few thin clay films in pores and on ped faces; moderately acid (pH 6.0); abrupt smooth boundary. (4 to 7 inches thick)

B'21tg--22 to 31 inches; light brownish gray (10YR 6/2) silty clay, grayish brown (10YR 5/2) moist; few distinct yellowish brown (10YR 5/6) mottles; strong medium and coarse prismatic structure that parts to strong medium angular blocky structure; very hard, very firm, very sticky, very plastic; few very fine and fine roots that follow ped surfaces; many very fine and fine tubular pores; many very dark gray (10YR 3/1) stains covering faces of peds; common moderately thick clay films in pores and on ped faces; few distinct iron stains; neutral (pH 7.0); clear smooth boundary. (6 to 12 inches thick)

B'22tg--31 to 38 inches; light brownish gray (2.5Y 6/2) silty clay, dark grayish brown (2.5Y 4/2) moist; many fine and medium distinct yellowish brown (10YR 5/6) mottles; weak medium prismatic structure that parts to moderate medium angular blocky structure; very hard, very firm, very sticky, very plastic; few very fine and fine roots following ped surfaces; common very fine, fine, and medium tubular pores; common very dark gray (10YR 3/1) stains on ped faces; few mica flakes; few black concretions; common moderately thick clay films in pores and on ped faces; neutral (pH 7.3); clear wavy boundary. (5 to 10 inches thick)

B'3tg--38 to 44 inches; light brownish gray (2.5Y 6/2) silty clay, dark grayish brown (2.5Y 4/2) moist; few fine faint yellowish brown (10YR 5/4) mottles; moderate medium angular blocky structure; very hard, very firm, sticky, plastic; few very fine and fine tubular pores; few black stains on ped faces; common moderately thick clay films in pores; neutral (pH 7.3); clear wavy boundary. (5 to 8 inches thick)

Cg--44 to 60 inches; light brownish gray (2.5Y 6/2) silty clay loam, grayish brown (2.5Y 5/2) moist; common fine distinct yellowish brown (10YR 5/6) mottles; massive; very hard, very firm, sticky, plastic; few very fine tubular pores; few thin clay films in pores; many distinct iron stains; few black concretions; many mica flakes; neutral (pH 7.2).

TYPE LOCATION: Kootenai County, Idaho; about 9 miles northwest of Worley, 1,750 feet south and 1,450 feet west of the northeast corner, sec. 17, T. 48 N., R. 5 W.

RANGE IN CHARACTERISTICS:

Solum thickness - 36 to 60 inches
Average annual soil temperature - 41 to 46 degrees F
Average summer soil temperature - 52 to 54 degrees F

A1 horizon
Color value, moist - 2 or 3
Value, dry - 3 to 5
Chroma, moist or dry - 1 or 2
Reaction - strongly acid or medium acid
Base saturation - 30 to 60 percent

B2 horizon
Color value, moist - 3 or 4
Value, dry - 5 or 6
Chroma, moist or dry - 1 to 3
Texture - silt loam or silty clay loam
Reaction - strongly acid or medium acid

A'2g horizon
Color hue - 2.5Y, 5Y, or 10YR
Value, moist - 4 to 6
Value, dry - 6 to 8
Chroma, moist or dry - 1 or 2
Mottles, hue - 10YR or 7.5YR
Value, moist - 4 or 5
Chroma - 4 to 6
Contrast - distinct or prominent
Texture - silt or silt loam
Reaction - strongly acid or medium acid

B'2tg horizon
Color hue - 2.5Y, 5Y, or 10YR
Value, moist - 4 to 6
Value, dry - 6 or 7
Chroma, moist or dry - 1 or 2
Mottles, hue - 5YR through 10YR
Value, moist - 4 or 5
Value, dry - 5 or 6
Chroma, moist or dry - 4 to 8
Contrast - distinct or prominent
Texture - silty clay loam or silty clay
Clay content - 35 to 50 percent
Reaction - slightly acid or neutral

Cg horizon
Color hue - 2.5Y, 5Y, 5BG
Value, moist - 4 or 5
Value, dry - 6 or 7
Chroma, moist or dry - 1 or 2
Texture - silty clay loam, silt loam, silt, or very fine sandy loam

COMPETING SERIES: This is the Latacho series. Clay content of the textural control section is less than 35 percent and average summer temperature is above 55 degrees F.

GEOGRAPHIC SETTING: Potlatch soils are on depressions of alluvial fans and terraces and have slopes of 0 to 2 percent. Elevations range from 2,200 to 2,900 feet. The soils formed in mixed alluvium. Average annual air temperature ranges from 41 to 44 degrees F. Average annual precipitation range from 25 to 35 inches. The frost-free season is 60 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Helmer, Pokey, Nakarna, Santa, and Taney soils. Helmer, Santa, and Taney soils are moderately well drained. Pokey soils have fine sandy loam A1 horizons and lack argillic horizons. Nakarna soils are well drained soils on adjacent mountain slopes.

DRAINAGE AND PERMEABILITY: Poorly drained; very slow runoff; very slow permeability in the solum. The soils have a high water table at depths of 18 to 42 inches during the spring and early summer months. They are frequently flooded for very long periods during the spring months.

USE AND VEGETATION: These soils are used mainly for hay, pasture, and wildlife habitat. Natural vegetation consists of sedges, grasses, and water-tolerant forbs. Some trees and brush have encroached along the edges of the wet meadows.

DISTRIBUTION AND EXTENT: Northern Idaho. These soils are inextensive.

MLRA OFFICE RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Latah County, Idaho, 1915.

REMARKS: Type location moved to Kootenai County, Idaho, January, 1981.