LOCATION ST. GEORGE UT
Established Series
Rev. VLM/AJE/WWJ
12/2015
ST. GEORGE SERIES
The St. George series consists of very deep, well drained, moderately slowly permeable soils that formed in alluvium from sandstone, siltstone, and shale. These soils are on river flood plains and alluvial fans. Slopes are 0 to 5 percent. The mean annual temperature is about 63 degrees F., and the average annual precipitation is about 9 inches.
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, calcareous, thermic Typic Torrifluvents
TYPICAL PEDON: St. George silt loam, cultivated. (Colors are for air dry soils unless otherwise noted.)
Ap--0 to 9 inches; light brown (7.5YR 6/4) silt loam; reddish brown (5YR 4/4) moist; moderate medium subangular blocky structure; hard, very friable, slightly sticky, slightly plastic; common fine, few medium and coarse roots; strongly effervescent, lime is disseminated; moderately alkaline (pH 8.0); diffuse smooth boundary. (3 to 15 inches thick)
Cy1--9 to 20 inches; strong brown (7.5YR 5/6) silt loam, yellowish red (5YR 4/6) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky, moderately plastic; common fine, few medium and coarse roots; many fine tubular pores; common fine gypsum granules; strongly effervescent, lime is disseminated; moderately alkaline (pH 8.1); clear smooth boundary. (4 to 22 inches thick)
Cy2--20 to 29 inches; light reddish brown (5YR 6/4) silt loam; reddish brown (5YR 4/4) moist; massive; slightly hard, friable, slightly sticky, moderately plastic; common fine and few medium roots; many fine and few medium tubular pores; common fine gypsum granules; strongly effervescent, lime is disseminated; moderately alkaline (pH 8.2); gradual smooth boundary. (4 to 22 inches thick)
Cy3--29 to 38 inches; light reddish brown (5YR 6/4) silt loam; yellowish red (5YR 4/6) moist; massive; soft, very friable, slightly sticky, slightly plastic; common fine roots; many fine and very fine tubular pores; common fine gypsum granules; strongly effervescent, lime is disseminated; moderately alkaline (pH 8.0); gradual smooth boundary. (O to 20 inches thick)
Cy4--38 to 60 inches; reddish yellow (5YR 6/6) very fine sandy loam; yellowish red (5YR 4/6) moist; massive; slightly hard, very friable, slightly sticky, slightly plastic; few fine roots; many fine and very fine tubular pores; common fine gypsum granules; strongly effervescent, lime is disseminated; moderately alkaline (pH 8.0).
TYPE LOCATION: Washington County, Utah; one mile southwest of the Hurricane Airport; near the center of sec. 16, T.42S., R.13W.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in the soil moisture control section during December-January. Typic aridic soil moisture regime.
Mean annual soil temperature: 59 to 67 degrees F.
Mean summer soil temperature:77 to 82 degrees F.
Texture PSCS: stratified with silt loam, fine sandy loam, very fine sandy loam (loam) and light silty clay loam but averages loam or silt loam
Clay content PSCS: 14 to 18 percent
Soft to hard granules and crystals of gypsum, ranging from about 0.05 to 3mm. in diameter, comprise 8 to 30 percent by volume of the soil.
Al horizon
Hue:7.5YR or 5YR
Value: 4 through 6 dry, 3 through 5 moist
Chroma: 2 through 6
Texture: silt loam or loam to silty clay loam. The layer of silty clay loam on the surface was deposited by silty irrigation water. It ranges from 2 to 15 inches thick.
C horizon
Hue:7.5YR, 5YR or 2.5YR
Value:5 through 7 dry, 3 through 5 moist
Chroma: 3 through 8.
COMPETING SERIES: This is the
Harkey series.Harkey soils do not have gypsum in the control sectionand have hues 7.5YR and yellower.
GEOGRAPHIC SETTING: St. George soils are on river flood plains and alluvial fans at elevations of 2,450 to 3,400 feet. Slopes range from 0 to 5 percent. These soils formed in alluvium from sandstone, siltstone, and shale. The mean annual temperature is 57 to 65 degrees F., and the mean summer temperature is 80 to 84 degrees F. The average annual precipitation is 8 to 11 inches. The frost-free period is 190 to 195 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Hantz,
Junction, and
Tobler soils and the competing
Leeds soils Hantz soils have silty clay or clay control sections. Junction and Tobler soils have fine sandy loam control sections and Tobler soils lack gypsum in the profile.
DRAINAGE AND PERMEABILITY: Well and moderately well-drained; slow runoff; moderately slow permeability.
USE AND VEGETATION: Irrigated cropland of alfalfa, small grains, improved pasture, corn and sugar beets for seed. Some areas are used for rangeland. Vegetation is galleta, creosote bush, cholla cactus, filaree, and salt grass.
DISTRIBUTION AND EXTENT: Southwestern Utah. This soil occurs in LRR-D, MLRA 30. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA
SERIES ESTABLISHED: Washington County (Virgin River Valley Area), Utah, l937
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 9 inches (Ap horizon)
Entisol feature - The absence of diagnostic subsurface horizons
Fluvial feature - Irregular decrease in organic carbon in the zone from 9 to 60 inches (C1, C2, C3, C4 horizons)
The St. George soils were formerly classified as Alluvial soils.
OSED scanned by NSSQA. Last revised by state 3/72.
Classified according to Soil Taxonomy Second Edition, 1999.
When the competing series section was updated in September 2001, questions were raised about the description and/or the classification of this series. It was suggested that this soil should classify in the suborder of Gypsids. A field study of the type location is recommended to resolve the questions.
Responsibility for this series was transferred from Davis to Phoenix 12/2015. The last revision to the series was 6/2005. ET
National Cooperative Soil Survey
U.S.A.