LOCATION HELDT WY+CO MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Ustertic Haplocambids
TYPICAL PEDON: Heldt silty clay loam-on a nearly level alluvial terrace under native vegetation. (Colors are for dry soil unless otherwise stated.)
A--0 to 6 inches; light brownish gray (2.5Y 6/2) silty clay loam, grayish brown (2.5Y 5/2) moist; strong very fine granular structure; soft, very friable, sticky and plastic; slightly effervescent, calcium carbonate disseminated; moderately alkaline (pH 8.2); clear smooth boundary. (5 to 10 inches thick)
Bw--6 to 40 inches; light brownish gray (2.5Y 6/2) silty clay, grayish brown (2.5Y 5/2) moist; moderate coarse prismatic structure parting to moderate coarse angular blocky; extremely hard, friable, very sticky and very plastic; common distinct slickensides; slightly effervescent, calcium carbonate occurs as few prominent seams; strongly alkaline (pH 8.5); gradual wavy boundary. (15 to 40 inches thick)
Bk--40 to 60 inches; light gray (2.5Y 7/2) silty clay, grayish brown (2.5Y 5/2) moist; few distinct reddish brown (5YR 5/4) redox concentrations; massive, extremely hard, firm, very sticky and very plastic; strongly effervescent, calcium carbonate occurs as common prominent soft masses and seams; few distinct gypsum crystals; moderately alkaline (pH 8.3); gradual smooth boundary. (6 to 12 inches thick)
TYPE LOCATION: Goshen County, Wyoming; 517 feet east and 187 feet north of the east abutment of the bridge over Cherry Creek on the road to Veteran, SW1/4, SE1/4, SW1/4 of sec. 25, T. 24 N., R. 62 W. 42 degrees 1 minute 2 seconds north latitude and 104 degrees 15 minutes 32 seconds west longitude.
RANGE IN CHARACTERISTICS: Organic content of the A1 horizon averages .6 to 2 percent and decreases uniformly with depth. Conductivity typically ranges from 0 to about 12 millimhos in the upper 40 inches. The soils are usually calcareous throughout, but depth to calcareous material ranges from 0 to 15 inches. Exchangeable sodium percentage usually ranges from less than 1 to 5 percent in the upper part of the control section but commonly increases with increasing depth. The particle size control section is usually clay or silty clay but ranges in clay from 35 to 50 percent, in silt from 10 to 50 percent, and in sand from 10 to 45 percent. Coarse fragments are typically less than 5 percent but range from 0 to 15 percent. Cracks more than .4 inch wide and 12 inches long occur in the upper 20 inches when the soils are dry. 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.
The A horizon has hue of 5Y through 7.5YR, value of 5 through 7 dry, 3 through 6 moist, and chroma of 1 through 4. Surface horizons having value as dark as 5 dry and 3 moist are too thin or contain too little organic matter to be mollic epipedons. Reaction is mildly alkaline through strongly alkaline.
The Bw horizon has hue of 5Y through 7.5YR, value of 5 through 7 dry, 4 through 6 moist, and chroma of 2 through 5. It is usually clay or silty clay but is silty clay loam in some pedons. Reaction is moderately alkaline or strongly alkaline.
The Bk or C horizon has hue of 5Y through 7.5YR, value of 5 through 7 dry, 4 through 6 moist, and chroma of 2 through 5. Reaction is moderately or strongly alkaline. It has 3 to 10 percent calcium carbonate equivalent.
COMPETING SERIES: These are the Denby, Dominguez, Littlenan, and Lockerby series. The Denby soils do not contain visible carbonates within the soil profile. The Dominguez soils have hue of 5YR or redder. The Littlenan and Lockerby soils are underlain by shale at depths of 20 to 40 inches and, in addition, the Lockerby soils do not have a cambic horizon.
GEOGRAPHIC SETTING: The Heldt soils are on fan remnants terraces, hillslopes and alluvial fans. Slopes range from 0 to 25 percent. The soils formed in fine textured alluvial sediments derived primarily from sedimentary rock. The average annual precipitation is 10 to 15 inches with over half falling in the months of April, May, and June. The average annual temperature is 44 to 48 degrees F. The frost-free season is 110 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Orella and Samday soils. Orella and Samday soils have bedrock at depths of less than 20 inches.
DRAINAGE AND PERMEABILITY: Well or moderately well drained; slow or very slow runoff; slow to moderately slow permeability.
USE AND VEGETATION: These soils are used principally as native pastureland, although they may be tilled to both dryland and irrigated crops in some localities. Native vegetation is primarily western wheatgrass, green needlegrass, blue grama, and basin wildrye.
DISTRIBUTION AND EXTENT: Central and northern Wyoming, southern Montana, and northern Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Big Horn County (Big Horn Area), Montana; 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 6 inches (A)
Cambic horizon - 6 to 40 inches (Bw)
SIR- WY1141
LRR- G