LOCATION ROCHE WA

Established Series
Rev. EED/SBC
09/2011

ROCHE SERIES

The Roche series consists of moderately deep, moderately well drained soils formed in glacial drift over dense glaciomarine deposits on hills and outwash plains. Slopes are 0 to 30 percent. The average annual precipitation is about 545 millimeters. The average annual air temperature is about 9 degrees C.

TAXONOMIC CLASS: Coarse-loamy, isotic, mesic Aquic Dystroxerepts

TYPICAL PEDON: Roche loam, forested on an east-facing slope of 7 percent at 79 meters elevation. (All colors are for moist soil unless otherwise noted.)

Oi--0 to 3 cm; slightly decomposed plant material; abrupt smooth boundary (3 to 5 cm thick)

A--3 to 13 cm; very dark brown (10YR 2/2) loam, very dark grayish brown (10YR 3/2) dry; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots, common coarse roots, and few medium roots: many very fine and fine irregular pores; 5 percent gravel; moderately acid (pH 5.7); clear wavy boundary. (10 to 23 cm thick)

Bw1--13 to 38 cm; dark yellowish brown (10YR 3/4) gravelly sandy loam, dark yellowish brown (10YR 4/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; many medium and common very fine, fine, and coarse roots; many very fine and fine irregular pores; 15 percent gravel; moderately acid, (pH 5.8); clear wavy boundary. (10 to 36 cm thick)

2Bw2--38 to 58 cm; brown (7.5YR 5/2) loam, brown (7.5YR 5/3) dry; massive; slightly hard, firm, nonsticky and nonplastic; few fine, medium, and coarse roots; common fine irregular pores; 5 percent gravel; moderately acid (pH 6.0); gradual wavy boundary. (10 to 36 cm thick)

2Bg--58 to 99 cm; dark reddish gray (5YR 4/2) loam, reddish gray (5YR 5/2) dry; massive; hard, firm, nonsticky and nonplastic; few very fine roots; few very fine irregular pores; many distinct medium gray (7.5YR 6/1) iron depletions throughout; many prominent medium red (2.5YR 4/6) iron masses throughout; 5 percent gravel; neutral (pH 6.7); gradual wavy boundary. (13 to 46 cm thick)

2Cd--99 to 152 cm; brown (7.5YR 4/2) silt loam, brown (7.5YR 4/3) dry; massive; hard, firm, slightly sticky and slightly plastic; no roots and no pores; neutral (pH 6.9).

TYPE LOCATION: San Juan County, Washington; 146 meters south and 650 meters east of the northwest corner of sec. 34, T. 36 N., R. 2 W. Willamette Baseline Meridian; USGS Eastsound SE quarter quadrangle; latitude 48 degrees 39 minutes 30 second N. and longitude 122 degrees 56 minutes 8 seconds W.

RANGE IN CHARACTERISTICS: Depths to diagnostic horizons and features start from the mineral soil surface.

Average annual soil temperature - 10 to 11 degrees C.
Moisture control section - dry 75 to 90 days following the summer solstice
Depth to densic contact - 50 to 100 cm
Depth to redoximorphic features - 46 to 91 cm
Reaction - moderately acid to neutral
Particle size control section:
clay content - 2 to 18 percent
rock fragments - 0 to 35 percent gravel

A horizon
Hue - 10YR or 7.5YR
Value - 2 to 4 moist, 3 to 5 dry
Chroma - 2 or 3 moist and dry
Rock fragments - 0 to 15 percent gravel

Bw1 horizon
Hue - 10YR or 7.5YR
Value - 3 to 5 moist and dry
Chroma - 3 or 4 moist and dry
Texture - L, SL, LS
Rock fragments - 0 to 35 percent gravel

2Bw2 horizon
Hue - 10YR or 7.5YR
Value - 4 or 5 moist, 5 to 7 dry
Chroma - 2 to 4 moist and dry
Texture - L or SL
Rock fragments - 0 to 35 percent gravel

2Bg horizon
Hue - 5YR to 2.5Y
Value - 4 or 5 moist, 5 or 6 dry
Chroma - 2 or 3 moist and dry
Texture - L or SL
Rock fragments - 0 to 35 percent gravel

2Cd horizon
Hue - 7.5YR to 2.5Y
Value - 3 or 4 moist, 3 to 7 dry
Chroma - 2 or 3 moist and dry
Texture - SL, L, SIL
Rock fragments - 0 to 35 percent gravel

COMPETING SERIES: These are the Morancreek and Zylstra series. Morancreek soils are very deep. Zylstra soils are 20 to 41 cm to redoximorphic features.

GEOGRAPHIC SETTING: Roche soils occur on hills and outwash plains. Slopes range from 0 to 30 percent. These soils formed in glacial drift over dense glaciomarine deposits. Elevation is sea level to about 91 meters. The climate is characterized by warm dry summers and mild moist winters. The annual precipitation ranges from 455 to 765 millimeters. The average annual air temperature ranges from 9 to 10 degrees C. The frost-free period is 200 to 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cady, Haro, Hoypus, Killebrew, Mitchellbay, and Sholander series. Cady and Haro soils occur on adjacent bedrock controlled hills and have a lithic contact. Hoypus soils are on adjacent hills and outwash plains, are greater than 150 cm to a densic contact, and have a sandy-skeletal particle-size control section. Killebrew and Mitchellbay soils are on hills of outwash plains, have 18 to 35 percent clay in the particle-size control section, and redoximorphic features from 20 to 50 cm. Sholander soils occur in valleys and drainageways, have a densic contact at 100 to 150 cm, and a sandy particle-size control section.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Moderately well drained. Saturated hydraulic conductivity is high to moderately high in the A, Bw, and 2Bg horizons, and low in the Cd horizon. Roche soils have a perched water table as high as 38 cm from November to March, and 58 cm in April and October. Roche soils are not subject to ponding.

USE AND VEGETATION: These soils are used for livestock grazing, forage crop production, forestry and homesites. Potential natural vegetation consists of Douglas-fir, Pacific madrone, lodgepole pine, oceanspray, baldhip rose, salal, Cascade Oregongrape, rattlesnake plantain, and bracken fern.

DISTRIBUTION AND EXTENT: Northwestern Washington; MLRA 2. Series is of small extent.

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

SERIES ESTABLISHED: San Juan County, Washington; 1956. Name is taken from Roche Harbor on northwestern San Juan Island.

REMARKS: Diagnostic horizon and features recognized in this pedon are:
Ochric epipedon
Cambic horizon - 13 to 58 cm (Bw horizons)
Densic contact - 99 cm (upper boundary of 2Cd horizon)
Particle-size control section - the zone from 28 to 99 cm
Depth to redoximorphic features - 58 cm (depleted matrix with chroma of 2 or less and iron masses)

ADDITIONAL DATA: Reference sample pedons 40A0965 and 40A0980) Riverside, California Lab.

National Cooperative Soil Survey
U.S.A.