LOCATION LETHA                   ID+OR

Established Series
Rev. TWP/WJL/CWT/GHL
08/2021

LETHA SERIES

The Letha series consists of very deep, somewhat poorly drained soils on low terraces. They formed in alluvium from acid igneous rocks. Permeability is moderate. Slopes are 0 to about 3 percent. The average annual precipitation is about 250 millimeters, and the average annual air temperature is about 9 degrees C.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, calcareous, mesic Aeric Halaquepts

TYPICAL PEDON: Letha fine sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)

A--0 to 15 cm; light gray (2.5Y 7/2) fine sandy loam, light olive brown (2.5Y 5/3) moist; moderate very thin platy and weak very fine granular structure; friable, slightly sticky; many roots; many very fine and fine pores; slightly effervescent; very strongly alkaline (pH 9.4); clear smooth boundary. (8 to 20 cm thick)

Bk1--15 to 28 cm; light yellowish brown (2.5Y 6/3) fine sandy loam, light olive brown (2.5Y 5/3) moist; weak coarse and medium subangular blocky structure; hard, friable, slightly sticky; common roots; common very fine pores; strongly effervescent; very strongly alkaline (pH 9.7); clear smooth boundary. ( 5 to 18 cm thick)

Bk2--28 to 69 cm; light yellowish brown (2.5Y 6/3) fine sandy loam, light olive brown (2.5Y 5/3) moist; weak medium subangular blocky structure; very hard, firm, slightly sticky and slightly plastic; common roots; few very fine pores; few thin dark grayish brown (10YR 4/2) films on ped faces; strongly effervescent; very strongly alkaline (pH 10.4); gradual smooth boundary. (25 to 56 cm thick)

Bn--69 to 89 cm; light yellowish brown (2.5Y 6/3) fine sandy loam, light olive brown (2.5Y 5/3) moist; massive; very hard, very friable, slightly sticky; common roots; few very fine pores; slightly effervescent; very strongly alkaline (pH 10.2); abrupt smooth boundary. (15 to 25 inches thick)

C1--89 to 109 cm; pale yellow (2.5Y 7/3) fine sandy loam, olive brown (2.5Y 4/3) and grayish brown (2.5Y 5/2) moist; few medium faint light olive brown (2.5Y 5/3) and dark grayish brown (10YR 4/2) mottles; massive; friable, slightly sticky and slightly plastic; few roots; few very fine pores; slightly effervescent; very strongly alkaline; abrupt smooth boundary. (8 to 23 cm thick)

2C2--109 to 150 cm; very gravelly coarse sand; single grain; loose; slightly effervescent in places; strongly alkaline. (over a meter thick)

TYPE LOCATION: Gem County, Idaho; about 11.2 km west of Emmett; 150 meters north and 18 meters east of the southwest corner of the NW section 8, T.6N., R.2W.

RANGE IN CHARACTERISTICS:

Average annual soil temperature - 9 to 12 degrees C
Depth to mottles - 50 to 100 cm
Depth to water table - 90 to 120 cm; May through September
Sodium saturation - greater than 50 percent in some part of the upper 50 cm
Texture of control section - SL, FSL
Clay content of control section - 5 to 15 percent
Reaction - moderately to very strongly alkaline

A horizon
Hue - 10YR or 2.5Y
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 2 or 3

COMPETING SERIES: These are the Argenta, Dunphy and Wabuska soils. Argenta soils have 20 percent or more durinodes in a friable matrix above a depth of 100 cm. Dunphy soils have weak silica cementation within 100 cm of the surface. Wabaska soils have average annual soil temperatures of 12 to 15 degrees C.

GEOGRAPHIC SETTING: Letha soils are on low terraces at elevations of 610 to 1070 meters. Slopes range from 0 to about 3 percent. The soils formed in moderately coarse textured alluvium derived from coarse grained acid igneous rocks. The average annual precipitation is 200 to 300 millimeters, including 300 to 910 mm of snow. Average annual temperature is 8 to 11 degrees C. Frost-free period is 140 to 160 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Baldock soils and the Falk and Moulton soils. Falk and Moulton soils are noncalcareous. These soils are on landscape positions similar to Letha soils.

DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; moderate permeability. A fluctuating water table is at depths of about 90 to 120 cm in summer.

USE AND VEGETATION: Chiefly irrigated pasture or rangeland. Vegetation in the potential natural plant community is greasewood, saltgrass, and basin wildrye.

DISTRIBUTION AND EXTENT: Southwestern Idaho and southeastern Oregon. Moderately extensive.

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

SERIES ESTABLISHED: Gem County, Idaho, 1949.

REMARKS:

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National Cooperative Soil Survey
U.S.A.