LOCATION OTA ID

Established Series
Rev. ALH/RWL
07/2012

OTA SERIES

The Ota series consists of very deep, well drained soils that formed in loess and volcanic ash mixed with colluvium over residuum from cinders and pumice. Slopes range from 15 to 50 percent on lava plains. The average annual precipitation is about 200 millimeters and the average annual temperature is about 11.5 degrees C.

TAXONOMIC CLASS: Loamy-skeletal over cindery, isotic over glassy, mesic Vitrixerandic Haplocalcids

TYPICAL PEDON: Ota gravelly ashy loam -- on a 43 percent convex northwest-facing slope at 1,028 meters elevation in rangeland. The surface has about 1 percent stone cover. When described on August 19, 1999, the soil was dry throughout. (Colors are for air-dry soil unless otherwise noted.)

A--0 to 10 cm; yellowish brown (10YR 5/4) gravelly ashy loam, dark yellowish brown (10YR 3/4) moist; moderate fine and medium platy structure parting to weak fine subangular blocky; soft, very friable, nonsticky and nonplastic; many very fine and fine, few medium and coarse roots; many very fine and fine, few medium irregular pores; 15 percent gravel, 5 percent cobbles; neutral (pH 7.3); clear smooth boundary. (5 to 13 cm thick)

Bw1--10 to 28 cm; light yellowish brown (10YR 6/4) gravelly ashy loam, dark yellowish brown (10YR 4/4) moist; moderate fine and medium subangular structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; common very fine and fine, few medium tubular pores; 20 percent gravel, 5 percent cobbles; slightly alkaline (pH 7.5); clear smooth boundary.

Bw2--28 to 48 cm; light yellowish brown (10YR 6/4) very gravelly ashy loam, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; few very fine, fine and medium tubular pores; 35 percent gravel, 5 percent cobbles; slightly alkaline (pH 7.6); clear wavy boundary.

2Bw3--48 to 58 cm; light yellowish brown (10YR 6/4) extremely gravelly ashy fine sandy loam, dark yellowish brown (10YR 4/4) moist; weak fine subangular structure; soft, very friable, nonsticky and nonplastic; few very fine, fine and medium roots; few fine, medium and coarse irregular pores; 75 percent gravel, 5 percent cobbles; 2 percent voids of 2 to 5 mm; slightly alkaline (pH 7.6); clear wavy boundary. (combined Bw horizon - 25 to 50 cm thick)

2Bkq1--58 to 75 cm; pale brown (10YR 6/3) extremely gravelly ashy loamy sand, brown (10YR 4/3) moist; massive; loose, nonsticky and nonplastic; few very fine, fine and medium roots; few fine, medium and coarse irregular pores; slightly effervescent (about 5 percent disseminated CaC03); common thin to moderately thick coats of calcium carbonate and silica in vesicles and on all sides of rock fragments; 80 percent gravel, 5 percent cobbles; 5 percent voids of 2 to 5 mm; moderately alkaline (pH 7.9); clear wavy boundary. (0 to 18 cm thick)

2Bkq2--75 to 97 cm; very pale brown (10YR 7/3) discontinuous moderately cemented extremely gravelly ashy sand, brown (10YR 5/3) moist; massive; loose, nonsticky and nonplastic; few very fine and fine roots in voids; violently effervescent (about 10 percent disseminated CaC03); common thin to moderately thick coats of calcium carbonate and silica in vesicles and on all sides of rock fragments; 80 percent gravel, 5 percent cobbles; 10 percent voids of 2 to 25 mm; moderately alkaline (pH 8.0); clear wavy boundary. (10 to 38 cm thick)

2Bkq3--97 to 180 cm; gravel (cinders and pumice); fragmental; common thin to thick coats of calcium carbonate and silica in vesicles and on undersides of rock fragments; 85 percent gravel, 5 percent cobbles; 10 percent voids of 2 to 50 mm.

TYPE LOCATION: Ada County, Idaho; about 17 miles north of Grandview; 275 meters east and 730 meters north of the southwest corner of section 28, T.2 S., R.4 E.; USGS Cinder Cone Butte Quadrangle; Latitude - 43 degrees, 13 minutes, 18.1 seconds N. and Longitude - 115 degrees, 59 minutes, 35.5 seconds W., NAD83.

RANGE IN CHARACTERISTICS:
Depth to calcium carbonate - 36 to 64 cm
Depth to cindery particle-size class - 36 to 64 cm
Depth to bedrock - greater than 150 cm
Particle-size control section (upper part) - 14 to 20 percent clay; 35 to 50 percent rock fragments; (lower part) - 0 to 5 percent clay; 80 to 95 percent rock fragments (5 to 10 percent coarse or very coarse voids)
Moisture control section - moist less than 90 consecutive days when the soil temperature is greater than 8 degrees C.
Average annual soil temperature - 12 to 13 degrees C.

A horizon
Hue - 7.5YR or 10YR
Value - 5 or 6 dry, 3 or 4 moist
Clay content - 8 to 18 percent
Rock fragments (cinders/pumice) - 15 to 30 percent gravel, 0 to 5 percent cobble, 0 to 5 percent stones and 15 to 35 percent total
Reaction - neutral or slightly alkaline
Volcanic glass content - 10 to 20 percent
Acid oxalate extract Al + 1/2 Fe - 0.3 to 0.5 percent

Bw horizon
Hue - 7.5YR or 10YR
Chroma - 3 or 4 dry or moist
Texture L or FSL
Clay content - 10 to 20 percent
Rock fragments (cinders/pumice) - 20 to 45 percent gravel, 0 to 10 percent cobbles, 0 to 5 percent stones and 25 to 50 percent total
Reaction - neutral or slightly alkaline
Volcanic glass content - 15 to 30 percent
Acid oxalate extract Al + 1/2 Fe - 0.1 to 0.4 percent

Bkq horizon
Hue - 7.5YR or 10YR
Value - 6 or 7 dry, 4 or 5 moist
Chroma - 3 or 4 dry or moist
Texture - LFS, LS, FS or S
Clay content - 0 to 5 percent
Rock fragments (cinders/pumice) - 60 to 85 percent gravel, 5 to 15 percent cobbles, 5 to 15 percent stones and boulders and 75 to 95 percent total
Voids (2-50mm) 5 to 15 percent
Calcium carbonate content - 5 to 15 percent
Reaction - slightly alkaline or moderately alkaline
Volcanic glass content - 30 to 50 percent

COMPETING SERIES: There are no competing series. The Suppah soils are similar, but do not have calcic horizons.

GEOGRAPHIC SETTING: Ota soils are on cinder cones and shield volcanoes on lava plains at elevations of 935 to 1,075 meters. Slopes range from 15 to 50 percent. These soils formed in loess and volcanic ash mixed with colluvium over residuum from cinders and pumice. Average annual precipitation is 200 to 230 cm. Average annual temperature is 11 to 12 degrees C. Frost-free period is 140 to 155 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Montezuma soils which are ashy and on footslopes of cinder cones.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; moderate over very rapid saturated hydraulic conductivity.

USE AND VEGETATION: Ota soils are used mainly for wildlife habitat. Native vegetation is Wyoming big sagebrush, spiny hopsage, and Thurber's needlegrass. Some areas are mined for gravel.

DISTRIBUTION AND EXTENT: Ada County, Idaho. MLRA 11. Ota soils are of small extent.

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

SERIES ESTABLISHED: Ada County, Idaho, 2012.

REMARKS: Diagnostic horizons and features recognized in this pedon:
Ochric epipedon - zone from 0 to 10 cm (A horizon)
Cambic horizon - zone from 10 to 58 cm (Bw1, Bw2 and 2Bw3 horizons)
Calcic horizon - zone from 58 to 97 cm (2Bkq1 and 2Bkq2 horizons)
Vitrandic features zone 0 to 75 cm has ashy textures and zone from 28 to 75 cm has greater than 35 percent cinders, pumice and pumicelike fragments
Particle-size control section - zone from 25 to 100 cm with 25 to 48 cm qualifying as loamy-skeletal and 58 to 100 cm qualifying as cindery (less than two-thirds pumice vs. cinders is assumed).
Soil moisture regime - aridic bordering xeric

ADDITIONAL DATA: Reference sample no. - S99ID-001-002 (NSSL pedon 00P0207)

National Cooperative Soil Survey
U.S.A.