LOCATION NAFF WA+IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Typic Argixerolls
TYPICAL PEDON: Naff silt loam, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 8 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak thick platy and moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many roots; neutral (pH 6.6); abrupt smooth boundary. (6 to 10 inches thick)
A--8 to 17 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak coarse prismatic and moderate fine granular structure; hard, friable, slightly sticky and plastic; many roots; many very fine pores; slightly acid (pH 6.4); clear wavy boundary. (5 to 10 inches thick)
BA--17 to 16 inches; brown (10YR 5/3) heavy silt loam, dark brown (10YR 4/3) moist; moderate fine prismatic structure; hard, firm, sticky and plastic; many roots; many very fine pores; peds and pores coated with clean very fine sand and silt grains; few thin clay films visible below coatings on peds; neutral (pH 6.6); gradual wavy boundary. (8 to 20 inches thick)
Bt1--26 to 61 inches; pale brown (10YR 6/3) light silty clay loam, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate fine angular blocks; very hard, firm, very sticky and very plastic; common fine roots; many very fine pores; thin clay films on blocks and in some pores; coating of clean silt or very fine sand on prism faces, few black stains and very fine concretions; neutral (pH 6.8); gradual wavy boundary. (25 to 40 inches thick)
Bt2--61 to 80 inches; pale brown (10YR 6/3) light silty clay loam, brown (10YR 5/3) moist; moderate medium prismatic structure parting to moderate fine angular blocks; hard, firm, sticky and plastic; few roots; many very fine pores; thin continuous clay films on peds and in pores; common black stains and very fine concretions; neutral (pH 6.8). (20 to 30 inches thick)
TYPE LOCATION: Spokane County, Washington; 75 feet west of the center of Latah Cutoff Road; 800 feet south of the northeast corner of section 2, T.21N., R.45E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 47 to 52 degrees F. These soils are usually moist but are dry in all parts between depths of 4 and 12 inches for 60 to 75 consecutive days in summer and early fall. The solum is more than 40 inches thick. Depth to bedrock is more than 5 feet. The mollic epipedon ranges from 10 to 20 inches. The particle-size control section averages from 30 to 35 percent clay.
The BA horizon has value of 5 or 6 dry, 3 or 4 moist, and chroma of 2 to 4 moist and dry. Texture is silt loam or silty clay loam. Reaction is slightly acid or neutral.
The A horizon has value of 4 or 5 dry, 1 to 3 moist, and chroma of 1 or 2 moist or dry. Reaction is moderately acid to neutral.
The Bt horizon has hue of 10YR or 7.5YR, value of 5 or 6 dry, 3 to 5 moist, and chroma of 3 to 6 moist or dry. some pedons, the peds in the upper part of the Bt horizon are coated with light gray very fine sand and silts in amounts from a few grains to 1 mm thick. Texture is silt loam or silty clay loam. Reaction is slightly acid to slightly alkaline.
COMPETING SERIES: These are the Hillsboro, Larkin, and Zehlorn series. Larkin soils are silt loam throughout. Hillsboro soils are strongly acid throughout the A and B horizons. Palouse soils are silt loam or heavy silt loam throughout and have a mollic epipedon 20 to 30 inches thick.
GEOGRAPHIC SETTING: These soils are on nearly level to very steep uplands, including hills and plateaus. The dominant slope range is 2 to 40 percent. The soils formed in layered loess dating back to early Wisconsin. They occur at elevations between 1,800 to 3,200 feet. The annual precipitation is 18 to 22 inches. Summers are warm and dry and winters are cool and moist. The average annual temperature ranges from 47 to 50 degrees F. and the frost free season is about 145 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Caldwell, Garfield, Latah, Latahco, Palouse, and Thatuna soils and the competing Larkin soils. Caldwell, Latah, and Latahco soils are on bottomlands. Garfield soils have an ochric epipedon and are on eroded ridgetops. Palouse soils lack an argillic horizon and have a mollic epipedon more than 20 inches thick.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Used for production of small grains, dry peas and lentils, hay and pasture. Original vegetation was Idaho fescue, bluebunch wheatgrass, Sandberg bluegrass, arrowleaf balsamroot, common snowberry, and wild roses.
DISTRIBUTION AND EXTENT: Spokane County, Washington, 1961.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
REMARKS: Diagnostic horizons and feature recognized in this pedon are a mollic epipedon for the surface to 17 inches and an argillic horizon from 26 to 80 inches.