LOCATION BOSTRUM IDEstablished Series
The Bostrum series consists of moderately deep, well drained soils that
formed in residuum derived dominately from basalt. Bostrum soils are
on basalt plains and have slopes of 0 to 20 percent. Permeability is
very slow. The average annual precipitation is about 14 inches, and
the average annual air temperature is about 47 degrees F.
TAXONOMIC CLASS: Fine, smectitic, mesic Typic Palexeralfs
TYPICAL PEDON: Bostrum gravelly silt loam in rangeland. (Colors are
for dry soil unless otherwise noted.)
A--0 to 5 inches; light brownish gray (10YR 6/2) gravelly silt
loam, dark grayish brown (10YR 4/2) moist; moderate medium platy
structure; slightly hard, very friable, slightly sticky and slightly
plastic; many fine roots; many medium vesicular pores; 25 percent
pebbles on surface; neutral (pH 6.8); abrupt smooth boundary. (4 to 6
inches thick)
E--5 to 8 inches; light gray (10YR 7/1) silt loam; dark grayish
brown (10YR 4/2) moist; strong fine subangular blocky structure;
slightly hard, very friable, slightly sticky and slightly plastic; many
fine roots; many very fine tubular pores; neutral (pH 7.2); abrupt
smooth boundary. (0 to 3 inches thick)
Bt1--8 to 13 inches; brown (10YR 5/3) silty clay, brown (10YR 4/3)
moist; strong fine and medium columnar structure parting to strong
medium angular blocky; very hard, firm, very sticky and very plastic;
common fine roots; common very fine tubular pores; continuous thick
dark yellowish brown (10YR 3/4) clay films on all faces of peds and in
the pores; continuous thick bleached white (N 8/) silt capping on top
of columns; mildly alkaline (pH 7.6); clear smooth boundary. (3 to 7
inches thick)
Bt2--13 to 19 inches; brown (10YR 5/3) silty clay, brown (10YR 4/3)
moist; moderate medium prismatic structure parting to strong fine and
medium angular blocky; hard, firm, very sticky and very plastic; common
fine roots; common very fine tubular pores; many moderately thick clay
films on all faces of peds and in the pores; mildly alkaline (pH 7.8);
clear smooth boundary. (4 to 8 inches thick)
Bt3--19 to 29 inches; light yellowish brown (10YR 6/4) silty clay
loam, brown (7.5YR 4/4) moist; strong fine and medium angular blocky
structure; hard, firm, very sticky and very plastic; common fine roots;
common very fine tubular pores; many moderately thick clay films on all
faces of peds and in the pores; moderately alkaline (pH 8.2); abrupt
wavy boundary. (6 to 12 inches thick)
R--29 inches; basalt; lime-coated on surface.
TYPE LOCATION: Camas County, Idaho; about 2.5 miles southwest of Magic
Reservoir; 150 feet east and 2,100 feet south of the northwest corner
of section 25 T. 2 S., R. 17 E.
RANGE IN CHARACTERISTICS:
Depth to bedrock - 20 to 40 inches
Average annual soil temperature - 47 to 52 degrees F.
E horizons - may be absent in some pedons
A horizon
Value- 5 through 7 dry, 3 or 4 moist
Rock fragments - 0 to 30 percent
Chroma- 1 through 3 dry or moist
E horizon
Rock fragments - 0 to 30 percent
Btk- present in some pedons
Bt horizons
Hue- 10YR through 5YR
Value- 4 through 6 dry, 3 through 5 moist
Chroma- 3 or 4 dry or moist
Texture - SIC, C, CL, or SICL
Clay content - 35 to 50
Reaction - neutral to moderately alkaline
Rock fragments - 0 to 10 percent
COMPETING SERIES: There are no other series recognized in this
family. Lostvalley is in a similar family. Lostvalley soils are
frigid.
GEOGRAPHIC SETTING: Bostrum soils are on basalt plains and have slopes
of 0 to 20 percent. Elevation ranges from 4,400 to 5,000 feet. The
soils formed in residuum derived dominately from basalt. The annual
precipitation is 12 to 16 inches, most of which comes as fall and
winter snow and early spring rains. Average annual air temperature is
45 to 50 degrees F. The frost-free season is 60 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adios, Gooding, Hamrub,
and Yutrue soils. Adios soils are 20 to 40 inches deep to a duripan.
Gooding soils have aridic moisture regime and are more than 40 inches
deep. Hamrub soils are deep and have mollic epipedons. Yutrue soils
are clayey to the surface. Adios soils occur on buttes. Gooding,
Hamrub, and Yutrue soils occur on the same landscape. Hamrub soils are
on mounds.
DRAINAGE AND PERMEABILITY: Well drained, slow to rapid runoff; very
slow permeability.
USE AND VEGETATION: Used for range. Vegetation is Sandberg bluegrass,
bluebunch wheatgrass, Idaho fescue, low sagebrush, alkali sagebrush,
and rabbitbrush.
DISTRIBUTION AND EXTENT: South central Idaho. This series is
inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Camas County, Idaho, 1977.
REMARKS: Diagnostic horizons and features recognized in this pedon
are:
Ochric epipedon - occurs from the soil surface to approximately 8
inches (A and E horizons)
Argillic horizon - is the zone from approximately 8 to 29 inches (Bt1,
Bt2, and Bt3 horizons). There is an absolute clay increase of 15
percent within the top 1 inch.
National Cooperative Soil Survey