Established Series


Typically, Toluca soils have dark grayish brown loam A1 horizons, brown prismatic clay loam B2t horizons, light olive brown B3ca horizons and light gray Cca horizons.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Aridic Haplustalfs

TYPICAL PEDON: Toluca clay loam - native grass. (Colors are for dry soil unless otherwise noted.)

A1--0 to 2 inches; dark grayish brown (10YR 4/2) loam, very dark grayish brown (10YR 3/2) moist; weak medium platy separating to weak fine crumb structure; soft, friable; many very fine roots; common clear sand grains; about 10 percent gravel; neutral; clear smooth boundary. (1 to 4 inches thick)

B2t--2 to 7 inches; brown (10YR 5/3) clay loam, dark brown (10YR 4/3) moist; moderate medium prisms separating to moderate medium blocky structure; hard, firm, sticky, plastic; many very fine roots; many very fine tubular pores; distinct continuous varnishlike films on all peds; peds coated grayish brown (10YR 5/2) in the upper part and dark brown (10YR 4/3) in the lower part; mildly alkaline; clear wavy boundary. (3 to 9 inches thick)

B3ca--7 to 9 inches; light olive brown (2.5Y 5/3) clay loam, olive brown (2.5Y 4/3) moist; weak medium prismatic structure separating to weak medium blocky structure; hard, firm, sticky, plastic; many very fine roots; many very fine tubular pores; varnishlike films on walls of root channels and pores and on very small concave surfaces of peds; calcareous with common small white masses of segregated lime; clear wavy boundary. (2 to 4 inches thick)

C1ca--9 to 28 inches; light gray (2.5Y 7/2) heavy loam, light yellowish brown (2.5Y 6/3) moist; massive; slightly hard, friable, sticky, slightly plastic; many grading to few very fine roots; common very fine tubular pores; strongly calcareous with many coarse soft nodular lime segregations.

C2--28 to 60 inches; light yellowish brown (2.5Y 6/3) heavy loam, light olive brown (2.5Y 5/4) moist; massive; slightly hard, friable, sticky, slightly plastic; strongly calcareous with few lime segregations in the upper part.

TYPE LOCATION: Yellowstone County, Montana; 675 feet north and 750 feet east of SW corner of sec. 18, T.2N., R.29E.

RANGE IN CHARACTERISTICS: Toluca soils are usually dry when not frozen unless irrigated. The mean annual soil temperature is 48 to 54 degrees F. The average summer soil temperature is about 64 degrees F. The average organic matter content of the upper 15 inches is 1 to 2 percent. The noncalcareous part of the solum is 6 to 9 inches thick and depth to the Cca horizon is 8 to 11 inches. Under deep cultivation the usual horizon sequence is Ap of clay loam, Cca and C horizons of loam texture; and in many pedons there is a light clay loam Bca horizon 2 to 4 inches thick beneath the Ap horizon. The A1 or Ap horizon has hue of 10YR or 2.5Y, value of 5 or 6 and chroma of 2 or 3. The B horizon has hue of 2.5Y through 7.5YR, value of 5 or 6 and chroma of 2 through 4. It contains 30 to 35 percent clay and 20 to 40 percent fine or coarser sand. The Cca horizon has hue of 7.5YR through 2.5Y, value of 6 through 8 and chroma of 2 or 3. It is loam to light clay loam with 20 to 40 percent fine and medium or coarser sand. It has a CaC03 equivalent of 20 to 30 percent. The substratum may be of very gravelly fine earths or of bedrock below 40 inches.

COMPETING SERIES: These are the Cushman, Fort Collins, Fruita, Keiser, Mack, Mesa, Orchard, and Stoneham series. Cushman soils have a paralithic contact at depths of 20 to 40 inches. Fort Collins soils are noncalcareous to depths of 10 inches or more. Fruita, Mack, Mesa, and Orchard soils have calcareous sola and average less than 1 percent organic matter in the upper 15 inches. Keiser soils have less than 15 percent fine or coarser sands in the control section. Stoneham soils do not have calcic horizons.

GEOGRAPHIC SETTING: Toluca soils are on upland plains or on terraces in valleys. They formed in deep calcareous loamy deposits of mixed mineral origin. The climate is cool semiarid with mean annual temperature of 47 degrees F. and mean summer temperature of about 67 degrees F. Mean annual precipitation is 10 to 14 inches.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hesper, Hopley, Keiser (competing) Treasure and Waneta soils. All of these soils have ochric epipedons. Hopley soils lack argillic horizons. Wanetta soils overlie sand and gravel at depths ranging from 20 to 40 inches.

DRAINAGE AND PERMEABILITY: Well-drained; slow to moderate runoff; moderate permeability.

USE AND VEGETATION: Used for dryland and irrigated grain crop production and for native grass pasture of short and mid grasses, desert shrubs and cacti.

DISTRIBUTION AND EXTENT: Central Montana--moderately extensive.


SERIES ESTABLISHED: Big Horn County (Big Horn Area), Montana, 1970.

REMARKS: The Toluca soils were formerly classified as Brown soils.

OSED scanned by SSQA. Last revised by state on 6/71.

National Cooperative Soil Survey