LOCATION BONE WY+MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, mesic Ustic Torriorthents
TYPICAL PEDON: Bone loam-rangeland. (Colors are for dry soil unless otherwise stated)
E--0 to 2 inches; light gray (10YR 7/2) loam, grayish brown (10YR 5/2) moist; vesicular crust; hard, friable, slightly sticky, slightly plastic; few medium roots; neutral (pH 7.2); abrupt smooth boundary. (0 to 2 inches thick)
Btk--2 to 5 inches; brown (10YR 5/3) heavy clay loam, brown (10YR 4/3) moist; weak fine columnar structure parting to weak fine angular blocky; hard, firm, sticky and plastic; few medium roots; common moderately thick clay films on faces of peds, slightly effervescent, common fine and medium soft masses of calcium carbonates; moderately alkaline (pH 8.2); clear smooth boundary. (1 to 3 inches thick)
C1--5 to 21 inches; brown (10YR 5/3) heavy clay loam, olive brown (2.5Y 4/4) moist; weak medium subangular blocky fragments; hard, firm, sticky and plastic; strongly effervescent, lime disseminated; common nests of sulfates few of more soluble salts; moderately alkaline (pH 8.4); clear smooth boundary.
C2--21 to 44 inches; light olive brown (2.5Y 5/4) clay loam; olive brown (2.5Y 4/4) moist; massive, platelets of rock structure about 60 percent of horizon that are disorientated; hard, firm, sticky and plastic; violently effervescent, lime disseminated; common nests of sulfates and a few of more soluble salts on faces of platelets; moderately alkaline (pH 8.4); clear smooth boundary.
C3--44 to 60 inches; grayish brown (10YR 5/2) silty clay loam, dark grayish brown (10YR 4/2) moist; massive with 60 percent platelets of rock structure which are disoriented; common nests of sulfates and a few of more soluble salts; strongly alkaline (pH 8.8).
TYPE LOCATION: Campbell County, Wyoming; SW1/4, SW1/4, Sec. 36, T. 48 N., R. 72 W.
RANGE IN CHARACTERISTICS: These soils are usually leached free of carbonates through the E and upper Bt horizon but may be calcareous to the surface through recharge. They are always calcareous at a depth of 5 inches. Depth to the base of the Bt horizon is 2 to 5 inches. The Exchangeable Sodium Percentage is always greater than 15 in all horizons except the thin surface E horizon. ESP ranges from 15 to 35. Coarse fragments of soft shale range from 0 to 5 percent. The concentrations of carbonates and gypsum appear to be inherited from the parent materials in the C horizons with only minor illuvial concentrations in the horizon immediately below the thin Bt horizon in some pedons. The EC typically increases with depth. The soil is dry in the moisture control section more than half the time cumulative that the soil temperature at a depth of 20 inches is 41 degrees F. and is never moist in some or all parts for as long as 60 consecutive days when the soil temperature at a depth of 20 inches is 41 degrees F., which occurs about April 21-27, but is dry in all parts of the moisture control section for at least 60 consecutive days from July 15 to October 25 and for at least 90 cumulative days during this period. The mean annual soil temperature is 47 to 53 degrees F., and the soil temperature at a depth of 20 inches is 41 degrees F. or more for 175 to 192 days. Bedrock is deeper than 60 inches.
The E horizon has hue of 10YR, 2.5Y or 5Y, value of 6 to 8 dry and 4 to 6 moist, and chroma of 2 or 3. Texture is typically a loam or fine sandy loam but may be light clay loam in some pedons. Reaction is neutral or slightly alkaline. EC is 0 to 2 mmhos. Some pedons may have A horizons. When present, they have similar properties to the E horizon.
The Bt or Btk horizon has hue of 10YR, 2.5Y or 5Y, value of 5 or 6 dry and 3 or 4 moist, and chroma of 2 or 3. Texture is heavy clay loam or clay with 35 to 50 percent clay. The Bt and Btk horizons are less than 3 inches thick and are diagnostic only at the series level. Reaction ranges from moderately alkaline to very strongly alkaline and are usually buffered with salts when moderately alkaline. EC ranges from 2 to 8 mmhos. ESP is 15 to 35.
The C horizon has hue of 10YR, 2.5Y or 5Y, value of 5 to 7 dry and 4 to 6 moist, and chroma of 2 to 4. Texture is typically heavy clay loam or clay but may be silty clay loam or silty clay in some pedons. Carbonates and gypsum are about equally dispersed throughout this horizon with some local accumulation. Salts more soluble than gypsum are common. EC ranges from 4 to 16 mmhos depending upon landscape position. ESP is 15 to 35 percent. Reaction is moderately alkaline to very strongly alkaline. Bk horizons may occur immediately below the Bt and have the properties as defined for the C.
COMPETING SERIES: These are the Befar, Biedsaw, Gayhart and Gaynor series. None of these soils have a thin Bt horizon or an exchangeable sodium content of more than 15 percent.
GEOGRAPHIC SETTING: Bone soils occur as slick spots on fan aprons, alluvial fans, fan piedmonts, and hill backslope positions. They are usually less than a half acre in size but may be 5 to 10 acres in size in some areas. They dominate the landscape in many places. Slopes are 0 to 20 percent but are normally 0 to 3 percent since the surface, under natural conditions, tends to level itself. Elevations range from 4,500 to 6,000 feet. The average annual precipitation is 13 inches with over half of the annual precipitation falling in April, May, and June and less than one inch falling in each month of July, August, September, and October. Precipitation ranges from 10 to 14 inches. The mean annual air temperature is about 46 degrees F., but ranges from 43 to 51 degrees F. The frost-free season is about 110 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Absted, Arvada, Bidman, and Wyarno soils. The Arvada and Absted soils have natric Bt horizons. Bidman and Wyarno soils have argillic Bt horizons and lack the high ESP. Bone soils can occur intermixed on almost any landscape where sodic shales furnish parent materials.
DRAINAGE AND PERMEABILITY: Typically, these soils are well drained, but some puddling does occur when the soils are eroded and have concave surfaces; very slow permeability; runoff is slow in microdepressions and moderate to rapid depending on slope. These soils "seal up" under natural conditions.
USE AND VEGETATION: The soils are normally barren under native conditions but may support sparse vegetation. When present, native vegetation consists of western wheatgrass, saltgrass, and salt-tolerant forbs.
DISTRIBUTION AND EXTENT: Semiarid areas of Wyoming, Colorado, and South Dakota. Bone soils are extensive in their collective areas, but locally they are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Big Horn County (Big Horn Area), Montana; 1970.