LOCATION MCPAN IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Xeric Argidurids
TYPICAL PEDON: McPan silt loam -- in irrigated cropland on a 3 percent southwest-facing slope at an elevation of 3,580 feet. (Colors are for air-dry soil unless otherwise noted.)
Ap--0 to 6 inches; brown (10YR 5/3) silt loam, dark yellowish brown (10YR 3/4) moist; weak very fine, fine and medium subangular blocky structure parting to medium fine and medium granular; hard, very friable, nonsticky and nonplastic, common very fine and few fine roots; many very fine and common fine and medium irregular pores; 5 percent cobbles; slightly acid (pH 6.4); abrupt wavy boundary. (4 to 7 inches thick)
Bt--6 to 10 inches; brown (10YR 4/3) silty clay loam, dark yellowish brown (10YR 3/4) moist; weak, fine and medium prismatic structure parting to strong fine, medium and coarse subangular blocky; hard, friable, moderately sticky and moderately plastic; common very fine and few fine, medium, and coarse roots; common very fine tubular, and few very fine irregular pores; 5 percent cobbles; few faint clay films on faces of peds and in pores; neutral (pH 7.0); clear wavy boundary. (4 to 29 inches thick)
Btk--10 to 20 inches; dark yellowish brown (10YR 4/4) silty clay loam, dark yellowish brown (10YR 3/4) moist; very pale brown (10YR 8/3) lime veins, very pale brown (10YR 7/3) moist; moderate very fine, fine and medium subangular blocky structure; hard, very friable, moderately sticky and moderately plastic; common very fine and few fine roots; common very fine tubular and few very fine irregular pores; slightly effervescent (about 10 percent calcium carbonate equivalent); 5 percent cobbles; few faint clay films on faces of peds and in pores; slightly alkaline (pH 7.5); clear wavy boundary. (0 to 15 inches thick)
Bkq1--20 to 24 inches; very pale brown (10YR 7/3) cobbly loam, light yellowish brown (10YR 6/4) moist; weak fine and medium subangular blocky structure; hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and few fine tubular pores; violently effervescent (about 25 percent calcium carbonate equivalent); 5 percent gravel and 10 percent cobbles; lime and silica coatings 1 to 2 mm thick on sides and undersides of rock fragments; slightly alkaline (pH 7.7); abrupt wavy boundary.
Bkq2--24 to 27 inches; very pale brown (10YR 7/3) cobbly loam, yellowish brown (10YR 5/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine tubular pores; violently effervescent (about 25 percent calcium carbonate equivalent); 5 percent gravel and 10 percent cobbles; lime and silica coatings 1 to 2 mm thick on sides and undersides of rock fragments; slightly alkaline (pH 7.7); abrupt wavy boundary. (combined thickness of Bkq horizons - 6 to 14 inches)
Bkqm--27 to 29 inches; white (10YR 8/2) lime and silica cemented continuous, indurated duripan; silica cap less than 1 mm thick at 32 inches; 15 percent gravel, 15 percent cobbles; violently effervescent (about 25 percent calcium carbonate equivalent; abrupt wavy boundary. (1/8 inch to 2 inches thick)
2R--29 inches; basalt; lime-silica coating completely fills all fractures in the basalt bedrock.
TYPE LOCATION: Gooding County, Idaho; about 5 miles northwest of Gooding; 400 feet east and 1650 feet north of the southwest corner of section 14, T. 5 S., R. 14 E.; USGS Gooding Butte Quadrangle.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 47 to 56 degrees F.
Depth to carbonates - 10 to 25 inches
Depth to calcic horizon - 15 to 33 inches
Thickness of duripan - 1/8 to 2 inches
Depth to duripan - 20 to 39 inches
Depth to bedrock - 21 to 40 inches
Clay (control section average) - 22 to 32 percent
A or Ap horizon
Value - 5 or 6 dry, 3 through 5 moist
Chroma - 2 through 4 dry or moist
Clay content -= 16 to 25 percent
Reaction - Neutral or slightly alkaline
Bt horizon
Value - 4 through 6 dry, 3 through 5 moist
Chroma - 3 or 4 dry or moist
Texture - SIL or SICL
Clay content - 24 to 32 percent
Rock fragments - 0 to 5 percent cobbles
Reaction - neutral or slightly alkaline
Btk or Btkq horizon (when present)
Value - 4 through 8 dry, 3 through 6 moist
Chroma - 3 or 4 dry or moist
Texture - SIL or SICL
Clay content - 21 to 30 percent
Rock fragments - 0 to 5 percent cobbles
Calcium carbonate equivalent - 5 to 15 percent
Reaction - neutral or slightly alkaline
Bkq horizon
Value - 5 to 7 dry, 4 through 6 moist
Chroma - 2 through 4 dry or moist
Texture - L or SIL
Rock fragments - 0 to 15 percent gravel, 0 to 15 percent cobbles and 0 to 25 percent total
Clay content - 18 to 27 percent
Calcium carbonate equivalent - 15 to 30 percent
Reaction - slightly alkaline or moderately alkaline
Bkqm horizon
Thickness of laminar caps - .5 to 4 mm
Distance between laminar caps - 0 to 2 inches
COMPETING SERIES: These are the Elijah and Virtue soils. Elijah and Virtue soils lack bedrock above 40 inches.
GEOGRAPHIC SETTING: McPan soils are on plug domes (buttes) and lava flow lobes on shield volcanoes and lava plains. McPan soils are underlain by basalt and formed in silty alluvium from weathered volcanic ash mixed with colluvium from basalt. Slopes are 1 to 20 percent. Elevation is 3,000 to 4,700 feet. The average annual precipitation is 8 to 12 inches. The average annual temperature is 45 to 54 degrees F. The frost-free period is 100 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Power, Gooding, Elijah, and Catchell soils. Power and Gooding soils have bedrock below 40 inches. Catchell and Gooding soils have fine, smectitic control sections.
DRAINAGE AND PERMEABILITY: Well drained; runoff is slow to rapid; permeability is moderately slow.
USE AND VEGETATION: McPan soils are used maily for rangeland and irrigated crops. Potential native vegetation is Wyoming big sagebrush and Thurber needlegrass.
DISTRIBUTION AND EXTENT: McPan soils are of small extent in south-central and southwestern, Idaho; MLRA 11.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Gooding County, Idaho, 1993.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the soil surface to 6 inches (Ap horizon)
Argillic horizon - the zone from 6 to 20 inches (Bt and Btk horizons)
Calcic horizon - the zone from 20 to 29 inches (Bkq1,Bkq2 and Bkqm horizons)
Duripan - the zone from 27 to 29 inches (Bkqm horizon)
Particle-size control section - the zone from 6 to 20 inches
Soil moisture regime - aridic bordering xeric
Geographic setting - terms used throughout MLRA 11 to identify the setting of this soil are quite varied although all equate to the same landscape. There will be further investigation from an MLRA project level as to the accepted terms for use.
The term silty alluvium used in this series concept infers a localized influence on the mixed loess and weathered volcanic ash soil mantle by overland flow of running water.