Established Series


The Spofford series consists of very deep and deep, moderately well drained soils formed in loess on plateaus and hills. Slopes are 0 to 45 percent. Average annual precipitation is about 14 inches and average annual temperature is about 50 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Natrixerolls

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

Ap--0 to 7 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium granular structure; slightly hard, friable, nonsticky and nonplastic; common roots; numerous fine and medium pores; neutral (pH 6.6); abrupt smooth boundary. (6 to 10 inches thick)

Bt/E--7 to 12 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium prismatic structure with granular filling of E material between peds; hard, firm, nonsticky and nonplastic; common roots; faint patchy clay films on vertical surfaces of peds and in pores; slightly alkaline (pH 7.5); abrupt smooth boundary. (0 to 8 inches thick)

Btn1--12 to 20 inches; dark grayish brown (10YR 4/2) silt loam, dark brown (10YR 3/3) moist; strong coarse prismatic or columnar structure; very hard, very firm, slightly sticky and slightly plastic; few roots; many fine pores; organic matter and prominant patchy clay films in pores and prominent continuous clay films on both vertical and horizontal ped surfaces; moderately alkaline (pH 8.4); clear wavy boundary. (2 to 12 inches thick)

Btn2--20 to 25 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak medium prismatic parting to moderate fine subangular blocky structure; hard, firm, slightly sticky and slightly plastic; few roots; faint continuous clay films; some lime between peds; strongly alkaline (pH 8.8); clear wavy boundary. (4 to 10 inches thick)

Bk1--25 to 36 inches; pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; carbonates as filaments; strongly alkaline (pH 8.8); diffuse wavy boundary. (8 to 12 inches thick)

Bk2--36 to 60 inches; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; massive; soft, friable, nonsticky and nonplastic; strongly effervescent; strongly alkaline (pH 8.8).

TYPE LOCATION: Walla Walla County, Washington; 1 1/2 miles south of Braden School; 100 yards northwest of intersection of railroad tracks and Oregon-Washington State line road; 2,000 feet south and 1,300 feet east of northwest corner of sec. 17, T. 6 N., R. 36 E.

RANGE IN CHARACTERISTICS: The mean annual soil temperature is 50 to 54 degrees F. These soils are usually moist but are dry in all parts between depths of 4 and 12 inches for 90 to 105 consecutive days during summer and fall. The mollic epipedon is 7 to 14 inches thick and may include part of the natric horizon. Depth to the calcic horizon is 15 to 40 inches. Depth to lithic contact with basalt is 40 to more than 60 inches. Some phases have duripan at 40 to 60 inches.

The A horizon has value of 4 or 5 dry, 2 or 3 moist, and chroma of 1 or 2 moist, 1 to 3 dry. It is massive, subangular blocky or weak granular structure. Reaction is neutral or slightly alkaline. It has 10 to 15 percent clay.

The Btn horizon has value of 4 to 6 dry, 3 or 4 moist, and chroma of 2 to 4 dry or moist. It is silt loam or silty clay loam. It has weak to strong prismatic, columnar structure or subangular blocky structure. It is moderately alkaline to very strongly alkaline. SAR is 13 to 40. It has 20 to 30 percent clay.

The Bk horizon has value of 4 to 7 dry, 4 or 5 moist, and chroma of 2 to 4 dry or moist. It is moderately alkaline to very strongly alkaline.

COMPETING SERIES: These are the Fridlo and Hatwai series. The Fridlo soils are dry for 60 to 90 consecutive days and have a mollic epipedon 14 to 20 inches thick. Hatwai soils are dry for 75 to 90 consecutive days.

GEOGRAPHIC SETTING: Spofford soils typically occur at the base of slopes, in depressions or basins, or concave areas on sloping uplands at an elevation of 500 to 3,400 feet. Individual bodies range in size mainly from 1/4 acre to about 5 acres. The soils formed in loess. Summers are warm and dry, and winters are cool and moist. Average annual precipitation is mostly 12 to 15 inches, but some is as high as 20 inches. Average January temperature is 29 to 32 degrees F, average July temperature is 69 to 73 degrees F, and mean annual temperature is 47 to 52 degrees F. Frost-free season is 110 to 165 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Asotin, Athena, Chard, Kuhl, Nims, Oliphant, Tucannon, Walla Walla, and Weissenfels soils. All of these soils lack a natric horizon except Weissenfels soils. Weissenfels soils have a lithic contact at a depth of 20 to 40 inches.

DRAINAGE AND PERMEABILITY: Moderately well drained, very slow to rapid runoff; slow permeability.

USE AND VEGETATION: Used mainly for range. A few areas are used for dryland cropland. Winter wheat, barley, and spring wheat are common crops. Vegetation is mainly bluebunch wheatgrass, Idaho fescue, and Sandberg bluegrass.

DISTRIBUTION AND EXTENT: Southeastern and Northcentral Washington. The series is of small extent.


SERIES ESTABLISHED: Walla Walla County, Washington, 1960.

REMARKS: Diagnostic horizons and features recognized in this pedon are a mollic epipedon from the surface to 12 inches, a natric horizon from 12 to 25 inches, and a calcic horizon from 25 to 60 inches.

National Cooperative Soil Survey