LOCATION ADA IDEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, mesic Typic Argixerolls
TYPICAL PEDON: Ada gravelly loam -- on a 32 percent convex north-facing slope at 3,900 feet elevation in rangeland. (Colors are for air-dry soil unless otherwise noted.)
A--0 to 3 inches; dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; many very fine and fine irregular pores; 15 percent gravel and 5 percent cobbles; neutral (pH 6.6); clear smooth boundary. (2 to 7 inches thick)
BA--3 to 13 inches; brown (10YR 5/3) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine, few medium roots; common very fine and fine tubular pores; 15 percent gravel and 5 percent cobbles; neutral (pH 6.9); clear smooth boundary. (8 to 13 inches thick)
Bt1--13 to 34 inches; yellowish brown (10YR 5/4) very gravelly sandy clay, dark yellowish brown (10YR 4/4) moist; moderate fine subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine and fine tubular pores; common distinct clay films on faces of peds, in pores and bridging sand grains; few distinct bleached silt grains on faces of peds; 35 percent gravel and 10 percent cobbles; neutral (pH 6.8); clear smooth boundary. (13 to 24 inches thick)
Bt2--34 to 46 inches; light brown (7.5YR 6/4) very gravelly clay loam, brown (7.5YR 4/4) moist; strong fine and medium subangular blocky structure; very hard, firm, very sticky and very plastic; few very fine and fine roots; few very fine and fine tubular pores; common prominent clay films on faces of peds, in pores and bridging sand grains; 40 percent gravel and 10 percent cobbles; neutral (pH 7.0); gradual wavy boundary. (10 to 16 inches thick)
Bt3--46 to 60 inches; pink (7.5YR 7/4) extremely gravelly sandy clay loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; hard, friable, sticky and plastic; few very fine and fine roots; few very fine tubular pores; few distinct clay films on faces of ped, in pores and bridging sand grains; 50 percent gravel and 20 percent cobbles; slightly alkaline (pH 7.4).
TYPE LOCATION: Ada County, Idaho; about 1.5 miles north and 0.25 miles west of Lucky Peak Dam; about 2,400 feet south and 2,000 feet west of the northeast corner sec. 35, T. 3 N., R 3 E.; USGS Lucky Peak Quadrangle; (Latitude - 43 degrees, 33 minutes, 09 seconds N. and Longitude - 116 degrees, 03 minutes, 41 seconds W.)
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness - 10 to 20 inches
Average annual soil temperature - 48 to 52 degrees F.
Particle-size control section - averages 35 to 55 percent clay; 35 to 75 percent rock fragments
Reaction - neutral and slightly alkaline
Moisture control section - dry 60 to 90 days following the summer solstice
2C horizons - present in some pedons
A and BA horizons
Value - 3 through 5 dry, 2 or 3 moist
Chroma - 2 or 3 dry or moist
Rock fragments - 0 to 10 percent cobbles
15 to 25 percent gravel
15 to 35 percent total
Bt horizon
Hue - 7.5YR or 10YR
Value - 3 through 7 dry, 3 through 5 moist
Texture - C, SC, SCL, or CL
Clay content - 25 to 55 percent
Rock fragments - 0 to 5 percent stones
0 to 20 percent cobbles
35 to 50 percent gravel
35 to 75 percent total
COMPETING SERIES: These are the Current Spring, Fiddler, Hiibner, Immig and Provig series. Current Spring soils cannot be adequately separated although are formed in alluvium from quartzite, conglomerate and limestone, and in addition, have vegetative indicators (needleandthread) which reflect a drier soil moisture regime. Fiddler soils are 20 to 40 inches deep to bedrock. Hiibner soils are slightly calcareous below 45 inches, have moderate to strong prismatic structure in the Bt horizon, and have angular quartzite and sandstone rock fragments dominating the particle-size control section. Immig soils are 20 to 40 inches deep to bedrock. Provig soils have sola less than 20 inches thick and have a mean annual soil temperature of 54 to 56 degrees F.
GEOGRAPHIC SETTING: Ada soils are on terraces, hill back slopes and fan remnants. These soils formed in slope alluvium, colluvium and residuum from mixed sediments. Slopes are 4 to 65 percent. Elevations range from 2,700 to 4,500 feet. The average annual precipitation is 12 to 18 inches and the average annual temperature is 46 to 50 degrees F. The frost-free period is 100 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brent, Cranegulch, Day, Adelmann, Ladd, and Shawmount soils. Brent soils are on terraces in foothills and mountains and are fine-textured. Cranegulch contain less than 35 percent rock in the particle-size control section. Day soils are on terraces and are very fine-textured. Adelmann and Shawmount soils have an aridic soil moisture regime. Ladd soils are on mountain slopes and are fine-loamy. Adelmann, Cranegulch and Shawmount soils occur on the same landform as the Ada soils.
DRAINAGE AND PERMEABILITY: Well drained; medium to very rapid runoff; slow permeability.
USE AND VEGETATION: Ada soils are used mainly for rangeland. Native vegetation is xeric big sagebrush, basin big sagebrush, bluebunch wheatgrass and Idaho fescue.
DISTRIBUTION AND EXTENT: Southwestern Idaho. MLRA 10 and 11. This series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Ada County, Idaho, 1943.
REMARKS: Diagnostic horizons and features recognized inthis soil are:
Mollic epipedon - the zone from the soil surface to 13 inches (A and BA horizons)
Argillic horizons - the zone from 13 to 60 inches (Bt1, Bt2and Bt3 horizons)
Particle-size control section - the zone from 13 to 33inches (Bt1 horizon)
Soil moisture regime - xeric
The type location of this series was relocated during the Boise Front Project area to better reflect a xeric moisture regime.