LOCATION MT. VERNON WAEstablished Series
TAXONOMIC CLASS: Ashy over loamy, amorphic over isotic, mesic Aquic Vitrixerands
TYPICAL PEDON: Mt. Vernon very fine sandy loam - cultivated. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 10 inches; dark brown (10YR 3/3) very fine sandy loam, brown (10YR 5/3) dry; weak coarse subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common very fine and fine irregular pores; NaF pH 10.3; neutral (pH 6.6); abrupt smooth boundary. (10 to l4 inches thick)
C1--10 to 14 inches; dark yellowish brown (10YR 4/4) stratified fine sandy loam and very fine sandy loam, pale yellow (2.5Y 7/4) dry; common medium dark grayish brown (2.5Y 4/2), olive brown (2.5Y 4/4) strong brown (7.5YR 4/6) mottles; massive; soft, very friable, nonsticky and nonplastic; common very fine roots; common very fine irregular pores; NaF pH 11.0; neutral (pH 6.6); clear wavy boundary. (4 to 10 inches thick)
C2--14 to 29 inches; grayish brown (2.5Y 5/2) stratified very fine sandy loam, loamy fine sand and fine sand, light brownish gray (2.5Y 6/2) dry; common medium gray (10YR 6/1) strong brown (7.5YR 5/6) mottles; massive; soft, very friable, nonsticky and nonplastic; common very fine roots, few very fine irregular pores; contains a thin strata of very dark brown (10YR 2/2) silt loam, 2 cm thick; NaF pH 11.3; neutral (pH 6.6); clear wavy boundary. (0 to 15 inches thick)
2C3--29 to 42 inches; grayish brown (2.5Y 5/2) stratified fine sandy loam, loamy fine sand and silt loam, light brownish gray (2.5Y 6/2) dry; common medium olive brown (2.5Y 4/4) mottles; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; NaF pH less than 9.0; neutral (pH 6.8); clear wavy boundary. (5 to 15 inches thick).
2C4--42 to 60 inches; olive gray (5Y 4/2) stratified fine sand, loamy fine sand, and very fine sandy loam, light olive gray (5Y 6/2) dry; common medium olive brown (2.5Y 4/4) mottles; massive; soft, very friable, nonsticky and nonplastic; NaF pH less than 9.0; neutral (pH 6.8).
TYPE LOCATION: Skagit County, Washington; about 1 mile south of Allen; 380 feet east and 1,900 feet south of the northwest corner sec. 24, T.35 N., T. 3 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 48 to 53 degrees F. Thickness is influenced by volcanic ash and depth to the 2C horizon is 15 to 30 inches. These soils are usually moist, but are dry in the moisture control section for 45 to 60 consecutive days following summer solstice. Reaction ranges from moderately acid to neutral. Depth to the apparent water table is 2 to 4 feet during the winter and early spring.
The Ap horizon has hue of 2.5Y or 10YR, value of 2 or 3 moist, 4 to 6 dry, and chroma of 1, 2 or 3 moist or dry. Dry values of 6 are below 10 inches.
The C horizon has hue of 10YR, 2.5Y or 5Y, value of 4 or 5 moist, 5 through 7 dry, and chroma of 2 through 4 moist or dry. It is stratified very fine sandy loam, fine sandy loam, loamy fine sand, and very fine sandy loam.
The 2C horizon has hue of 10YR through 5Y, value of 4 or 5 moist, 6 or 7 dry, and chroma of 2 or 3 moist or dry. It is stratified silt loam, very fine sandy loam, fine sandy loam, loamy fine sand, and fine sand.
COMPETING SERIES: These are the Rose Crrek and Tygh series and the similar Malo, Newberg, Okanogan, Puyallup, and Siler series in other families. Puyallup, Newberg, Okanogan, and Siler soils lack grayish mottles within 30 inches of the surface. Rose Creek soils are mildly to strongly alkaline and commonly calcareous. Tygh soils have a crhoma of 2 or less throughout the C horizon.
GEOGRAPHIC SETTING: Mt. Vernon soils are on river flood plain splays and natural levees at elevations of 10 to 100 feet. These soils formed in mixed recent alluvium with an admixture of volcanic ash in the upper part. Slopes are 0 to 3 percent. Average annual precipitation is 25 to 50 inches. Mean January temperature is about 38 degrees F., mean July temperature is about 63 degrees F. Mean annual temperature is about 51 degrees F. The frost-free season is 160 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Briscot, Puyallup, Skagit and Sumas soils. Briscot, Skagit and Sumas soils lack a mollic epipedon. Puyallup soils lack grayish mottles and are coarse loamy over sandy or sandy-skeletal.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; moderate permeability. These soils are subject to occasional, brief flooding unless protected. An apparent high water table is as high as 2 to 4 feet from December through April.
USE AND VEGETATION: Mt. Vernon soils are used for cropland. Row crops, hay, and pasture are principal crops. Native vegetation is Douglas-fir, western hemlock, red alder, bigleaf maple, and western redcedar with an understory of western swordfern, vine maple, ladyfern, geranium, western brackenfern, trailing blackberry, Oregon-grape, salal, and salmonberry.
DISTRIBUTION AND EXTENT: Northwestern Washington. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skagit County Area, Washington, 1981.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy. This draft reflects a change in classification from coarse-loamy, mixed, mesic Fluvaquentic Haploxerolls to ashy over loamy, mixed, mesic Aquic Vitrixerands. Diagnostic horizons and features recognized in this soil are:
a.mollic epipedon from the surface to 10 inches, grayish mottles from 10 to 30 inches and an assumed irregular decrease of organic carbon with depth.