LOCATION TILMA ID+WA
Established Series
Rev. CLM/KMS/SHB/SBC
09/2013
TILMA SERIES
The Tilma series consists of very deep, moderately well drained soils that formed in loess. Tilma soils are on loess plains and hills, mainly near drainageways. Slopes are 3 to 25 percent. The mean annual precipitation is about 20 inches and average annual air temperature is about 47 degrees F.
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Xeric Argialbolls
TYPICAL PEDON: Tilma silt loam - on a 7 percent southeast-facing slope in a cultivated field. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 8 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine, few medium roots; many very fine interstitial pores; few uncoated (bleached) silt grains; moderately acid (pH 6.0); abrupt smooth boundary. (6 to 10 inches thick)
A--8 to 14 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and very fine roots; many very fine interstitial pores; slightly acid (pH 6.1); clear smooth boundary. (3 to 7 inches thick)
Bw--14 to 20 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to weak medium subangular blocky; hard, friable, sticky and plastic; many fine and very fine roots; many very fine, common fine tubular pores; some organic stains on faces of peds; many uncoated (bleached) silt grains; slightly acid (pH 6.2); abrupt smooth boundary. (6 to 10 inches thick)
E--20 to 23 inches; light gray (10YR 7/2) silt loam, dark grayish brown (10YR 4/2) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; many fine and very fine roots; few very fine tubular pores; few fine black concretions; slightly acid (pH 6.4); abrupt smooth boundary. (1 to 3 inches thick)
Btb1--23 to 30 inches; brown (7.5YR 5/3) silty clay, light yellowish brown (10YR 6/4) rubbed, brown (7.5YR 4/3) moist; strong medium columnar structure parting to weak medium and coarse subangular blocky structure; extremely hard, extremely firm, very sticky and very plastic; few fine and very fine roots that penetrate peds; many very fine tubular pores; continuous moderately thick clay films on peds; many small and medium black and brown concretions; moderately acid (pH 6.0); abrupt smooth boundary. (5 to 12 inches thick)
Btb2--30 to 34 inches; brown (10YR 5/3) silty clay, light yellowish brown (10YR 6/4) rubbed; brown (7.5YR 5/3) moist; moderate medium prismatic structure; very hard, very firm, very sticky and very plastic; few fine roots; common very fine tubular pores; continuous moderately thick clay films on peds; many black and brown concretions larger than 1 mm.; slightly acid (pH 6.1); abrupt smooth boundary. (4 to 7 inches thick)
Btb3--34 to 42 inches; brown (10YR 5/3) silty clay, light yellowish brown (10YR 6/4) rubbed, brown (7.5YR 4/3) moist, brown (7.5YR 5/3) rubbed moist; strong medium subangular blocky structure; very hard, firm, sticky and plastic; few very fine roots; many very fine tubular pores; continuous moderately thick clay films on peds; slightly acid (pH 6.1); abrupt smooth boundary. (6 to 10 inches thick)
Btb4--42 to 60 inches; light yellowish brown (10YR 6/4) silt loam, very pale brown (10YR 7/3) rubbed, yellowish brown (10YR 5/4) moist, brown (7.5YR 5/3) rubbed moist; weak medium prismatic structure parting to strong medium and fine angular blocky; extremely hard, extremely firm, slightly sticky and slightly plastic; brittle and compact; common very fine tubular pores; continuous moderately thick clay films in pores; many small black concretions and patchy stains on peds; neutral (pH 6.8).
TYPE LOCATION: Benewah County, Idaho; about 560 feet south and 560 feet west of northeast corner of sec. 25, T. 45 N., R. 6 W. Latitude - 47 degrees, 13 minutes, 11.5 seconds North; Longitude - 117 degrees, 1 minute, 31.6 seconds West. NAD 83; USGS Tekoa WA, ID quadrangle.
RANGE IN CHARACTERISTICS:
Thickness of mollic epipedon - 15 to 30 inches
Depth to albic horizon - 15 to 30 inches
Depth to argillic horizon - 18 to 35 inches
Volcanic glass - 1 to 3 percent
Average annual soil temperature - 47 to 56 degrees F
Days continuously moist - 60 to 90 in late winter and spring
Days dry - 45 to 80 consecutive days in late summer
A horizons
Value - 3 to 5 dry, 2 or 3 moist
Chroma - 1 to 3 dry or moist
Reaction - moderately acid to neutral
Bw horizon (Bt or BE in some pedons)
Value - 3 to 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Clay content - less than 1.2 times the amount of clay in the A horizon
Reactions - moderately acid to neutral
E horizon
Value - 4 or 5 moist
Clay content - 5 to 18 percent
Iron-manganese concretions - few to common, ranging from about 1 to 4 mm in diameter
Btb1, Btb2, and Btb3 horizons (Have an abrupt textural change with the overlying E horizon)
Hue - 7.5YR or 10YR
Value - 4 to 6 dry, 3 to 5 moist
Chroma - 2 to 4, dry or moist
Texture - clay, silty clay, silty clay loam
Clay content - 30 to 50 percent, averages greater than 35 percent in particle- size control section
Content of fine and coarser sand- less than 10 percent
Reaction - moderately acid to neutral
Btb4 horizon (resembles a weak fragipan in some pedons)
Texture - silt loam and silty clay loam
Reaction - slightly acid to neutral
Moist consistence - extremely firm to very firm
COMPETING SERIES: These are the
Latah,
Quicksell, and
Setnum series. Latah soils have redoximorphic features in the Bt horizons and are somewhat poorly drained. Quicksell soils have mollic epipedons 10 to 16 inches thick, have 5 percent gravel throughout, and have 20 to 40 percent sand in the particle-size control section. Setnum soils are moderately deep to a lithic contact.
GEOGRAPHIC SETTING: These soils are on plains and hills on plateaus, mainly near drainageways. Slopes range from about 3 to 25 percent. Elevations are 2,300 to 3,200 feet. The soils formed in older loess, probably mostly of the recent or Pinedale surface, Early Bull Lake or Pre Bull Lake. The mean annual precipitation is 18 to 25 inches. The frost-free period is 110 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Garfield,
Palouse,
Naff, and
Thatuna soils. Garfield soils are on convex summits, have an ochric epipedon, and lack an E horizon. Palouse and Naff soils have fine-silty control sections and lack an E horizon, and are on smooth back slopes. Thatuna soils have a fine-silty control section and are on back slopes and foot slopes that are commonly concave.
DRAINAGE AND PERMEABILITY: Moderately well drained; medium to rapid runoff; slow permeability. A seasonally perched water table is present from 18 to 30 inches in the winter to late spring.
USE AND VEGETATION: Most areas are under cultivation. Small grains, hay, pasture, lentils, and peas are the major crops. Principal vegetation of uncultivated areas is Idaho fescue, wild rose, snowberry and small forbs.
DISTRIBUTION AND EXTENT: Loess hills and plains region in the prairies in northern Idaho and eastern Washington. MLRA 9. Moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Whitman County, Washington, 1975.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the surface to 20 inches (Ap, A, and Bw horizons)
Albic horizon - The zone from 20 to 23 inches (E horizon)
Abrupt textural change - at 23 inches (upper boundary of Btb1 horizon)
Argillic horizon - The zone from 23 to 60 inches (Btb1, Btb2, Btb3, and Btb4 horizons)
Particle-size control section - The zone from 23 to 43 inches - (Btb1, Btb2, and part of the Btb3 horizon)
National Cooperative Soil Survey
U.S.A.