Soil Survey of Latah County, Idaho

USDA – NRCS, Soil Survey Office
220 East 5th Street, Room 212C
Moscow, ID 83843
208-882-4960 Ext. 127

Contact: Brian Gardner, SSPL
Email: brian.gardner@id.usda.gov

State survey area: ID057
Soil survey area: 437,500 total acres (684 square miles)
Status: 383,000 acres mapped; database in progress
Completion target: fieldwork complete Sept. 2009; database complete Sept. 2010

GENERAL: The ID057 project area is composed of the MLRA E43A portion of Latah County, Idaho.  This region includes an area of initial mapping (207,500 aces) as well as well as an area that was previously included in the ID610 soil survey project (230,000 acres).  The portion of the survey area that was included in ID610 is being extensively remapped to reflect improved understanding of soil properties and interpretations for forestry in MLRA E43A. 

The survey area is located in the southern part of the Idaho panhandle. The survey area includes the eastern third of Latah County as well as the higher elevation ridges and foothills that extend westward to the border with Whitman County, Washington.  The survey area consists of mountainous terrain with associated foothills, the eastern margin of the Columbia Plateau and the headwaters of the Palouse and Potlatch river drainages.  The survey area includes three mountainous terrains: the Palouse Range, the HooDoo Mountains and the unnamed system of low mountains that forms the northern border of Latah County, including Mary Minerva McCroskey State Park.  Elevation within the survey area ranges from about 1,800 feet in the Potlatch river canyon to 5,340 feet at the summit of Bald Mountain. Annual precipitation ranges from 23 inches at the lowest elevations to 55 inches near the crest of Mica Mountain north of Deary, Idaho. Mean annual air temperature ranges from about 45 degrees F in canyons to 40 degrees F on the higher mountains and in areas of cold air accumulation. Land uses are primarily forestland, hay production, grazing and some limited production of small grains.

SOILS:  The soils of the survey area are derived from a number of different geologic materials. These include low grade metamorphic rocks such as quartzite and siltite of the Pre-Cambrian Belt Series a well as higher grade metamorphics such as mica schist, and phyllite that have also been correlated to the Belt Series. Intrusive igneous rocks of Cretaceous age are also abundant. These are primarily granites and granodiorites. Extrusive igneous rocks are the Columbia River Basalts, older basalts found in the Palouse River Valley and a body of rhyolite immediately north of the town of Deary.  Tertiary age alluvial deposits of silt and clay are widespread on the surface of the Columbia Plateau and form a regional paleoslol that is now blanketed by about one meter of Holocene loess. The loess deposit extends a short way into the foothills and mountains. Most of the soils in these mountains and foothills have a mantle of volcanic ash derived from the Cascade volcanoes that forms the surface horizons. Andisols and andic subgroups dominate the mountain terrain. Floodplain deposits are of limited extent and are dominated by silty material on the Columbia Plateau or by coarser sand and gravel deposits in the mountains. Soils tend to be deep or very deep as the area escaped glaciation.

Major soils of the survey area include the following:

Soils on stream terraces, drainageways, AND floodplains

1.  TENEB-SPACECREEK-AQUANDIC ENDOAQUEPTS 
     Very deep, poorly drained to well drained, nearly level to undulating soils formed in mixed alluvium Soils on canyon sides and benches

2.  KLICKSON-AGATHA
     Deep and very deep, well drained, undulating to very steep soils formed in loess and colluvium and/or residuum from basalt

Soils on basalt plateaus

3.  TANEY-CARLINTON-SANTA-BENEWAH
     Moderately deep to a fragipan and very deep, moderately well to well drained, undulating to steep soils formed in loess and Tertiary alluvial sediments with a minor addition
     of volcanic ash.

4.   THREEBEAR-NORWIDGE 
      Moderately deep to a fragipan and very deep, moderately well and well drained, undulating to steep soils formed in a mantle of volcanic ash over loess and Tertiary alluvial
      sediments

Soils in mountains

5.   KRUSE-NOIL-CARRICO
      Moderately deep to very deep, rolling to very steep soils formed in colluvium and residuum form granitic or metamorphic rocks

6.   JACOT-JUDGETOWN-BOULDERCREEK-LADO 
      Deep and very deep, well drained, undulating to very steep soils formed with a thick mantle of volcanic ash over the following:  loess and residuum from granitic and
      metamorphic rocks or colluvuim and residuum from granitic and metamorphic rocks

7.   GRANDAD-TOWNSHIP-NAKARNA 
      Deep and very deep, well drained, rolling to very steep soils formed in a thick mantle of volcanic ash over material from metamorphic rocks high in mica

8.   VAYWOOD-WEITAS
      Very deep, well drained, rolling to very steep soils formed in a thick mantle of volcanic ash over colluvium and residuum from granitic or metamorphic rocks.

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