LOCATION ALLDOWN UT

Established Series
Rev. HKS/RLT/SJJ
10/2020

ALLDOWN SERIES

The Alldown series consists of very deep, well drained soils formed in alluvium from basic and intermediate extrusive igneous rocks on fan terraces and valley plains. Slopes range from 1 to 5 percent. Mean annual temperature is about 43 degrees F. and the average annual precipitation is about 11 inches.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Ustic Haplocambids

TYPICAL PEDON: Alldown clay loam--cropland. (Colors are for air-dry soil unless otherwise stated.)

Ap--0 to 10 inches; pinkish gray (7.5YR 6/2) clay loam, brown (7.5YR 4/2) moist; moderate, medium granular structure; very hard, firm, moderately sticky and moderately plastic; many fine, medium and few coarse roots; common fine and medium tubular pores; strongly calcareous; moderately alkaline (pH 8.0); clear smooth boundary. (7 to 10 inches thick)

Bw--10 to 28 inches; light gray (10YR 7/2) clay loam, brown (10YR 5/3) moist; weak, medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; many fine and medium roots; common very fine and fine tubular pores; strongly calcareous; moderately alkaline (pH 8.4); clear smooth boundary. (6 to 26 inches thick)

C1--28 to 48 inches; light gray (10YR 7/2) silt loam, brown (10YR 5/3) moist; massive; hard, friable, moderately sticky and moderately plastic; common fine roots; few fine tubular pores; strongly calcareous; moderately alkaline (pH 8.0); gradual wavy boundary. (10 to 21 inches thick)

C2--48 to 54 inches; light gray (10YR 7/2) clay loam, brown (10YR 5/3) moist; massive; very hard, firm, moderately sticky and moderately plastic; few fine roots; few very fine and fine tubular pores; strongly calcareous; moderately alkaline (pH 8.0); gradual wavy boundary. (4 to 18 inches thick)

C3--54 to 60 inches; light gray (10YR 7/2) very fine sandy loam, brown (10YR 5/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; few very fine and fine tubular pores; strongly calcareous; moderately alkaline (pH 8.0).

TYPE LOCATION: Garfield County, Utah; about 2 miles north of Panguitch; in the southwest 1/4 of sec. 16, T. 34 S., R. 5 W. .; Panguitch USGS quad; approximate coordinates: lat. 37 degrees 51 minutes 05 seconds N. and long. 112 degrees 25 minutes 45 seconds W., NAD WGS84.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 42 to 45 degrees F.
Mean summer soil temperature: 60 to 63 degrees F.
Soil moisture: The soil is dry in parts of the moisture control section for 75 to 90 days during the winter months, and dry in all parts of the moisture control section 40 to 50 percent of the time when the soil temperature at a 20 inch depth is more than 41 degrees F. Soil moisture subclass: ustic-aridic.
Thickness of the ochric epipedon and depth to the cambic horizon: 3 to 11 inches.

Particle-size control section (weighted averages)
Clay content: 18 to 35 percent
Fine and coarser sand content: more than 15 percent (estimated 25 to 50 percent)

A horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3, dry or moist
Effervescence: moderately calcareous or strongly calcareous

C horizons:
Hue: 7.5YR or 10YR
Value: 6 or 7 dry and 4 or 5 moist
Chroma: 2 or 3, dry or moist
Texture: silt loam, loam, sandy clay loam and clay loam with sandy loam and very fine sandy loam below 40 inches
Effervescence: mildly calcareous or strongly calcareous
Sodium Adsorption Ratio: 0 to 13 (estimated)
Reaction: moderately alkaline to very strongly alkaline

COMPETING SERIES: These are the Chaperton, Piceance, Poposhia, Rickman, and Yamo series. Chaperton and Rickman soils have a paralithic contact. Piceance soils have a lithic contact. Poposhia and Yamo soils have horizons of secondary carbonate accumulation.

GEOGRAPHIC SETTING: Alldown soils are on fan terraces and valley plains. Slopes range from 1 to 5 percent. The soils formed in alluvium from basic and intermediate extrusive igneous rocks, and to a lesser-extent sedimentary rocks. The mean annual temperature is 40 to 45 degrees F. Average annual precipitation is 9 to 12 inches, and is distributed fairly evenly throughout the year, with about 55 percent falling between April and September. July, August and September are the wettest months, with December and January being the driest. Elevation is 6,500 to 7,500 feet. The freeze-free period is 70 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Greenhalgh, Jodero, Notter, and Tebbs soils. Greenhalgh soils are fine-silty. Jodero soils have a mollic epipedon thicker than 16 inches. Both soils are on alluvial fans. Notter soils have an argillic horizon and are on stable alluvial fans. Tebbs soils are coarse-loamy, and are on similar landscape positions.

DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.

USE AND VEGETATION: Alldown soils are used for irrigated cropland, rangeland and wildlife habitat. Principal crops are alfalfa and small grains. Potential vegetation is Indian ricegrass, blue grama, basin big sagebrush, winterfat, and Nevada bluegrass.

DISTRIBUTION AND EXTENT: Alldown soils are of limited extent. They are mapped in the Panguitch and John's Valley areas of Garfield County. MLRA 47.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Garfield County (Panguitch Soil Survey Area), Utah, 1984.

REMARKS: Alldown soils were previously classified as Torrifluvents, but they occur on relatively stable, non-flooding landscapes, and lack the irregular decrease in organic matter needed for that classification.

Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface of the soil to a depth of 10 inches. (Ap horizon).
Cambic horizon - from 10 to 28 inches (Bw horizon) based on structure and the higher color value than the Ap horizon. Because there is a lack of fine stratification below this depth, the cambic horizon could be extended deeper. At the present time there is reluctance deepen the cambic without field investigation.

The 04/2012 revision recognizes a cambic horizon in this soil and changes the classification from Ustic Torriorthents to Ustic Haplocambids. The cambic horizon is based on the lack of fine stratification and a color change. Although weakly expressed, a cambic horizon in this soil is consistent with the presumed late-Pleistocene or early-Holocene age of the geomorphic surfaces. The 04/2012 revision also restricts the series to ustic-aridic only; the previous definition included mountain big sage plant communities that are now believed to be in an aridic-ustic regime. Those plant communities and their corresponding 12 to 14 inch annual precipitation are now excluded from the series.

It is assumed the SAR for this soil does not meet the criteria for the Sodic subgroup, despite the strongly alkaline reaction allowed within the upper 100 cm. This needs further investigation.

National Cooperative Soil Survey
U.S.A.