LOCATION COUPEVILLE WAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Argiaquic Argialbolls
TYPICAL PEDON: Coupeville loam, cropland, on a nearly flat glacial drift plain at an elevation of 30 meters. When described on September 14, 2004 the soil was moist to 30 cm and slightly moist below. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 18 cm; black (10YR 2/1) loam, dark gray (10YR 4/1) dry; moderate coarse granular structure; slightly hard, very friable, non-sticky and slightly plastic; common very fine to medium roots; many very fine and fine interstitial pores; moderately acid (pH 5.6); clear wavy boundary.
A--18 to 30 cm; very dark brown (10YR 2/2) loam, dark grayish brown (10YR 4/2) dry; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine to medium roots; many very fine and fine interstitial pores; common distinct yellowish brown (10YR 5/6), yellow (10YR 7/6) dry iron-manganese masses throughout, common faint grayish brown (2.5Y 5/2), light gray (2.5Y 7/2) dry iron depletions throughout; slightly acid (pH 6.5); abrupt wavy boundary. (Combined thickness of Ap and A horizons is 25 to 36 cm)
2E--30 to 51 cm; grayish brown (2.5Y 5/2) clay loam, light gray (2.5Y 7/2) dry; strong medium angular blocky structure; moderately hard, friable, very sticky and very plastic; few very fine and fine roots; few fine interstitial pores; many distinct yellowish brown (10YR 5/6), yellow (10YR 7/6) dry iron-manganese masses throughout, many faint grayish brown (2.5Y 5/2), light gray (2.5Y 7/2) dry iron depletions throughout; neutral (pH 6.7); gradual wavy boundary. (13 to 21 cm thick)
2Btg1--51 to 86 cm; dark gray (2.5Y 4/1) clay loam, gray (2.5Y 6/1) dry; strong coarse angular blocky structure parting to strong fine angular blocky; hard, firm, very sticky and very plastic; few very fine and fine roots along ped faces; many fine tubular, common fine irregular pores; many distinct dark yellowish brown (10YR 4/6), yellowish brown (10YR 5/6) dry iron-manganese masses along ped faces, many faint grayish brown (2.5Y 5/2), light gray (2.5Y 7/2) dry iron depletions throughout; neutral (pH 6.8); gradual wavy boundary.
2Btg2--86 to 127 cm; dark grayish brown (2.5Y 4/2) clay loam, light brownish gray (2.5Y 6/2) dry; strong coarse angular blocky structure; very hard, very firm, very sticky and very plastic; few very fine and fine roots along ped faces; common fine tubular and irregular pores; many distinct yellowish brown (10YR 5/6), yellow (10YR 7/6) dry iron-manganese masses along ped faces, common faint grayish brown (2.5Y 5/2), light brownish gray (2.5Y 6/2) dry iron depletions throughout; neutral (pH 6.8); gradual irregular boundary. (Combined thickness of 2Btg horizons is 46 to 76 cm thick)
2Cd--127 to 152 cm; dark grayish brown (2.5Y 4/2) silty clay loam, light brownish gray (2.5Y 6/2) dry; massive; very hard, very firm, moderately sticky and very plastic; few fine irregular pores; common prominent yellowish brown (10YR 5/6), yellow (10YR 7/6) dry iron-manganese masses along cracks; neutral (pH 7.3).
TYPE LOCATION: Island County Washington, about 1 mile south of the town of Coupeville; about 335 meters north and 185 meters west of the southeast corner of Section 4, T. 31 N., R. 1 E. Willamette Baseline Meridian; USGS Coupeville NE quarter quadrangle; Latitude 48 degrees 11 minutes 55 seconds North, Longitude 122 degrees 40 minutes 59 seconds West.
RANGE IN CHARACTERISTICS: Depths to diagnostic horizons and features start from the mineral soil surface.
Average annual soil temperature - 10 to 11 degrees C.
Mollic epipedon thickness - 25 to 36 cm
Depth to redoximorphic features - 13 to 20 cm
Depth to densic contact - 100 to 152 cm
Reaction - moderately acid to slightly alkaline
Particle Size Control Section:
Rock fragments - 0 to 15 percent gravel
Clay content - 18 to 35 percent
Ap horizon
Hue - 10YR or 7.5YR
Value - 2 or 3 moist, 3 or 4 dry
Chroma - 1 or 2 moist and dry
Clay content - 10 to 20 percent
Rock fragments - 0 to 5 percent gravel
A horizon
Hue - 10YR or 7.5YR
Value - 2 or 3 moist, 3 or 4 dry
Chroma - 1 or 2 moist and dry
Texture - L or SIL
Clay content - 10 to 20 percent
Rock fragments - 0 to 5 percent gravel
E horizon
Hue - 10YR or 2.5Y
Value - 4 or 5 moist, 5 or 6 dry
Chroma - 1 or 2 moist and dry
Texture - L or CL
Clay content - 18 to 30 percent
Rock fragments - 0 to 15 percent gravel
Btg horizons
Hue - 10YR or 2.5Y
Value - 4 or 5 moist, 5 or 6 dry
Chroma - 1 or 2 moist and dry
Texture - L or CL
Clay content - 18 to 32 percent
Rock fragments - 0 to 15 percent gravel
Cd horizon
Hue - 10YR or 2.5Y
Value - 4 or 5 moist, 5 or 6 dry
Chroma - 1 or 2 moist and dry
Texture - SIL or SICL
Clay content - 15 to 30 percent
Rock fragments - 0 to 15 percent gravel
COMPETING SERIES: This is the Toko series. Toko soils are very deep and have a mollic epipedon 38 to 102 cm thick.
GEOGRAPHIC SETTING: Coupeville soils are in drainageways and valleys of glacial drift plains. Slopes range from 0 to 5 percent. These soils formed in glacial drift overlying dense glaciomarine deposits. Elevation ranges from 0 to 90 meters. The climate is characterized by warm dry summers and mild moist winters. Annual precipitation ranges from 455 to 1,015 millimeters. Average annual temperature ranges from 9 to 10 degrees C. The frost-free period is about 200 to 240 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Coveland, Sucia, and Shalcar soils. Coveland soils have an ochric epipedon and do not have redoximorphic features above 20 cm. Sucia soils have an ochric epipedon and do not have redoximorphic features above 46 cm. Shalcar soils have a histic epipedon.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Poorly drained. Saturated hydraulic conductivity is moderately high to high in the upper part (A and E horizons) and moderately low to low in the lower part (Btg and Cd horizons). Coupeville soils have a perched water table as high as 0 cm from October to April, 25 cm in May, and 60 cm in June, unless the soil is drained. Coupeville soils are subject to frequent ponding for very long durations from December to March and for brief durations during October, November, and April.
USE AND VEGETATION: Coupeville soils are used for crop production, forage crop production, livestock grazing, and wildlife habitat. Wheat, oats, barley, alfalfa and vegetables for produce and for seed are common crops. Potential natural vegetation consists of Sitka spruce, red alder, lodgepole pine, clustered rose, salmonberry, trailing blackberry, red elderberry, common snowberry, stinging nettle, swordfern, slough sedge, field horsetail, and scouring-rush horsetail.
DISTRIBUTION AND EXTENT: Puget Sound valleys in Northwest Washington;
MLRA A2, Northern Part. Series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Island County, Washington 1950. The name is taken from the town of Coupeville on Whidbey Island.
REMARKS: Diagnostic horizons and features recognized in this pedon include:
Mollic epipedon - 0 to 30 cm (A horizons)
Albic horizon - 30 to 51 cm (E horizon)
Argillic horizon - 51 to 127 cm (Btg horizons)
Densic contact - 127 cm (upper boundary of Cd horizon)
Particle-size control section - the zone from 51 to 101 cm (upper 50 cm of the argillic horizon)
Depth to redoximorphic features - 18 cm (depleted matrix with a chroma of 2 or less and iron-manganese masses)
This revision (5/2006) includes a change in classification and typical pedon based on field investigations. The previous classification was fine-loamy over clayey, mixed, superactive, mesic Typic Epiaquolls, which did not recognize the albic, argillic, nor densic horizons now described in the field. The previous pedon location was uncertain within a square mile.
ADDITIONAL DATA: NSSL pedon # 81P0672.