LOCATION STAIRCASE IDEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Cumulic Ultic Haploxerolls
TYPICAL PEDON: Staircase sandy loam -- on a nearly level stream flood plain step, in hayland/pasture at 3,080 feet elevation. When described on December 3, 1997, the soil was moist to 30 inches, dry between 30 and 40 inches and slightly moist below. (Colors are for air-dry soil unless otherwise stated.)
Ap--0 to 4 inches; dark grayish brown (10YR 4/2) sandy loam, very dark brown (10YR 2/2) moist; weak thin and medium platy structure parting to moderate fine and medium subangular blocky; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine, few medium roots; common very fine and fine, few medium irregular pores; 10 percent fine gravel; moderately acid (pH 6.0); clear smooth boundary.
A1--4 to 14 inches; dark grayish brown (10YR 4/2) fine gravelly sandy loam, very dark brown (10YR 2/2) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine, few medium roots; many very fine and fine, few medium irregular pores; 20 percent fine gravel; slightly acid (pH 6.1); clear smooth boundary.
A2--14 to 22 inches; grayish brown (10YR 5/2) fine gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common very fine and fine, few medium roots; common very fine and fine, few medium irregular pores; 20 percent fine gravel; slightly acid (pH 6.1); clear smooth boundary.
A3--22 to 32 inches; brown (10YR 5/3) fine gravelly sandy loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common very fine and fine roots; few very fine and fine irregular pores; 20 percent fine gravel; moderately acid (pH 5.8); clear smooth boundary.
A4--32 to 42 inches; grayish brown (10YR 5/2) fine gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common very fine and fine roots; few very fine and fine irregular pores; 25 percent fine gravel; moderately acid (pH 6.0); clear smooth boundary. (combined A horizon - 18 to 48 inches)
AB--42 to 50 inches; pale brown (10YR 6/3) fine gravelly sandy loam, brown (10YR 4/3) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; few very fine and fine roots; few very fine and fine irregular pores; 25 percent fine gravel; moderately acid (pH 6.0); clear wavy boundary. (0 to 18 inches thick)
Bw1--50 to 58 inches; very pale brown (10YR 7/3) fine gravelly sandy loam, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; few very fine and fine irregular pores; few fine faint brown (10YR 4/3) moist iron masses; 25 percent fine gravel; slightly acid (pH 6.3); clear smooth boundary. (0 to 24 inches thick)
Bw2--58 to 72 inches; very pale brown (10YR 7/3) gravelly loamy sand, brown (10YR 5/3) moist; single grain; loose, nonsticky and nonplastic; few very fine and fine irregular pores; few fine and medium distinct yellowish brown (10YR 5/6) moist iron masses; 30 percent gravel; slightly acid (pH 6.5).
TYPE LOCATION: Boise County, Idaho; about 4 1/2 miles north of Crouch; 1,300 feet north and 2,000 feet east of the southwest corner of section 23, T.10 N., R.4 E.; USGS Pyle Creek Quadrangle; Latitude - 44 degrees, 10 minutes, 54 seconds N. and Longitude - 115 degrees, 57 minutes, 01 seconds W.; NAD 83
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness - 24 to 48 inches
Depth to redoximorphic features - 40 to 60 inches
Depth to bedrock - 60 inches or more
Reaction - moderately acid through neutral
Base saturation in some part between 10 to 30 inches - 50 to 75 percent
Particle-size control section - 8 to 18 percent clay; 5 to 25 percent rock fragments
Moisture control section - dry 60 to 90 consecutive days following the summer solstice
Average annual soil temperature - 47 to 50 degrees F.
Ap or A horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 1 through 3 dry or moist
Texture - SL or L
Clay content - 8 to 18 percent
Rock fragments - 0 to 25 percent gravel
AB and Bw horizon
Hue - 2.5Y or 10YR
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 2 or 3 dry or moist
Organic matter content - 0 to 1 percent with irregular decrease
Texture - SL, COSL, LS or LCOS
Clay content - 4 to 12 percent
Rock fragments - 5 to 35 percent gravel
Redox concentrations - few or common, distinct or prominent soft masses
Buried A horizons and/or sand lenses occur in some pedons
COMPETING SERIES: These are the Boise and Cloudyway series. Boise soils do not have redox features within 60 inches (somewhat excessively drained) and are moist less than 90 consecutive days when the soil temperature is greater than 47 degrees F. (aridic bordering on xeric). Cloudyway soils do not have redox features within 60 inches (well drained).
GEOGRAPHIC SETTING: Staircase soils are nearly level or gently sloping on river and stream flood-plain steps and on drainageways on relict lake terraces at elevations of 3,000 to 4,500 feet. Slopes range from 0 to 4 percent. These soils formed in alluvium from granitic rocks. Average annual precipitation is dominantly 20 to 26 inches, but ranges to 16 inches in foothills. Average annual temperature ranges from 45 to 48 degrees F. Frost-free period is 90 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brownlee and Hellake soils. These soils are on adjacent uplands and have argillic horizons.
DRAINAGE AND PERMEABILITY: Moderately well drained with a high water table at 40 to 60 inches below the surface at some time during April through June; very slow or slow runoff; moderately rapid permeability. Staircase soils are subject to rare flooding for brief or very brief periods in December through June. On some areas all or part of the pedon is commonly saturated during the growing season due to flood irrigation.
USE AND VEGETATION: Staircase soils are used mainly for hayland/pasture (irrigated and non-irrigated). Some areas are used for rangeland or homesites. Native vegetation is very rare, but is considered to have been ponderosa pine and Lemon needlegrass in mountain valleys. Where mapped in foothills the native vegetation is basin big sagebrush and basin wildrye.
DISTRIBUTION AND EXTENT: West-central Idaho. MLRA 10 and 43B. Staircase soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Boise County Area, Idaho, Parts of Ada and Boise Counties, 2005.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - zone from 0 to 42 inches (Ap, A1, A2, A3 and A4 horizons)
Particle-size control section - zone from 10 to 40 inches
Soil moisture regime - xeric
Significant Fe concentrations present in some pedons are due to continuous flood irrigation during the growing season and not related to natural drainage conditions.
The Type Location is located in a converted woodland site that is consistent with the dominant concept of this series. The dry phase under sagebrush (native rangeland) is less extensive.