LOCATION SNOW WA+OR

Established Series
Rev. NCD/RWL/SHB
03/2012

SNOW SERIES

The Snow series consists of very deep, well drained soils that formed in loess and alluvium from loess. These soils are on gently sloping to moderately steep terraces and terrace slopes along major drainageways adjacent to loess hills. Slope is 0 to 30 percent. Average annual precipitation is about 19 inches and average annual temperature is about 48 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Cumulic Haploxerolls

TYPICAL PEDON: Snow silt loam- cultivated. (Colors are for dry soil unless otherwise noted.)

Ap--0 to 4 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak fine and medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots; common very fine and fine pores; neutral (pH 7.0); abrupt smooth boundary.

A1--4 to 22 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak fine and medium prismatic structure; slightly hard, friable, slightly sticky and slightly plastic; many fine roots; common very fine and fine pores; neutral (pH 7.0); clear wavy boundary.

A2--22 to 33 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; common very fine and fine pores; neutral (pH 7.0); clear wavy boundary. (Combined thickness of the A horizons is 18 to 40 inches)

AC--33 to 60 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; massive; slightly hard; friable, slightly sticky and slightly plastic; few fine roots; common fine pores; slightly alkaline (pH 7.4).

TYPE LOCATION: Whitman County, Washington; about 3 miles southwest of Colfax, Wa., near the Rebel Flat Creek drainage; about 1400 feet north and 400 feet west of the southeast corner of section 20, T. 16 N. and 43 E.; USGS Wilcox, WA., topographic quadrangle; Latitude - 46 degrees, 51 minutes, 34 seconds North; Longitude - 117 degrees, 25 minutes, 0.5 seconds West; NAD 83..

RANGE IN CHARACTERISTICS: The soils are usually moist but are dry in all parts between depths of 4 and 12 inches for 60 to 80 consecutive days in the summer and fall. The mollic epipedon ranges from 30 to 48 inches thick.. Average annual soil temperature ranges from 48 to 52 degrees F.

The Ap and A horizons have value of 2 or 3 moist, 4 or 5 dry, and chroma of 1 or 2 dry or moist. Soil reaction is neutral or slightly alkaline.

AC horizon - absent in some pedons

Bw horizons present in some pedons - value of 3 or 4 moist, 5 or 6 dry, and chroma of 2 or 3 dry or moist. It is 18 to 22 percent clay. Soil reaction is neutral to moderately alkaline.

C horizons present in some pedons - hue of 10YR or 2.5Y, value of 3 or 4 moist, 5 or 6 dry and chroma of 2 to 4 moist and dry. It is silt loam or loam and 18 to 27 percent clay. It has 0 to 10 percent gravel. Soil reaction is neutral to moderately alkaline.

COMPETING SERIES: These are the Caldwell, Harana, Jett, Keigley, Loupence, Red Rock, and Rustico series. Caldwell soils have distinct redox concentrations and are somewhat poorly drained. Harana soils are moderately alkaline, calcareous, and average 27 to 35 percent clay within the particle-size control section and are well drained. Jett soils are calcareous in all or part of the A horizon and within the upper part of the particle-size control section. Keigley soils are calcareous and have 15 to 30 percent calcium carbonate equivalent throughout. Loupence soils have an aridic soil moisture regime. Red Rock soils have calcareous C horizons above depth of 40 inches. Rustico soils have redox concentrations between 50 and 60 inches, are calcareous throughout, and have an aridic soil moisture regime bordering xeric.

GEOGRAPHIC SETTING: Snow soils are on gently sloping to moderately steep terraces and terrace side slopes at elevations of 1,800 to 3,400 feet. These soils formed in loess and alluvium from loess. Slopes are 0 to 30 percent. The summers are hot and dry and winters are cool and moist. The average annual precipitation is typically 18 to 23 inches but ranges to 13 inches in northeastern Oregon. The average annual temperature is 45 to 50 degrees F.; the average January temperature is 28 degrees F.; the average July temperature is 68 degrees F. Frost-free season is 100 to 125 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Athena, Garfield, Latah, Palouse, and Thatuna soils. Athena soils are on uplands and have a regular decrease of organic matter with increasing depth. Garfield soils are on uplands and Latah soils are on bottomlands and both soils have fine textured control sections. Palouse soils are on uplands and have base saturation of less than 75 percent in all parts of the upper 30 inches. Thatuna soils are on uplands and have an argillic horizon.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: Used for production of small grains, lentils, peas, alfalfa, and of grasses for hay and pasture. Native vegetation is Idaho fescue, bluebunch wheatgrass, prairie junegrass, big bluegrass.

DISTRIBUTION AND EXTENT: Eastern Washington and Oregon, and possibly northwestern Idaho; MLRA 9. This soil is moderately extensive.

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

SERIES ESTABLISHED: South Palouse River Project, Whitman County, Washington and Latah County, Idaho, 1939.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from the surface to 33 inches (the Ap, A1, and A2 horizons).
Cumulic feature - conceptual and assumed - based on parent material (alluvium) and landform (terrace) and slopes less than 25 percent.

The Snow series and the type location are no longer recognized in Spokane County as investigated during the Spokane County update (extensive revision) mainly due to the lack soil features and properties indicative of the cumulic subgroup. The Snow investigated during the Spokane update had soil properties and qualities consistent with criteria associated with the Pachic subgroup criteria or was mapped where the dominant component was wetter than Snow. The type location was moved to Whitman County in 03/2012 because that is the largest remaining acreage extent.

MLRA 9 update notes- further investigation is needed to determine the presence and extent of the volcanic ash influence and verification of cumulic subgroup criteria on slopes greater than 3 percent up to 30 (taxonomic criteria requires slope less than 25 percent) percent. Perhaps there is a need to investigate and possibly separate (or combine in a complex) the Snow soils derived in loess (well drained, not cumulic) and Snow soils derived in loessal alluvium (soil moisture regimes wetter than well drained, cumulic). In addition, map unit complexes composed of two major components would better fit the landscape/landforms in some areas.

National Cooperative Soil Survey
U.S.A.