LOCATION STILLMAN                UT

Established Series
Rev. LHS/RJL/JWB/JBF
07/2014

STILLMAN SERIES

The Stillman series consists of very deep, somewhat excessively drained soils that formed in alluvium derived from sandstone and limestone. Stillman soils occur on inset fans, fan skirts and alluvial fans and have slopes of 1 to 10 percent. The average annual precipitation is about 230 mm, and the mean annual air temperature is about 9 degrees C.

TAXONOMIC CLASS: Sandy-skeletal, carbonatic, mesic Xeric Torriorthents

TYPICAL PEDON: Stillman gravelly fine sandy loam, rangeland. (Colors are for air dry soil unless otherwise noted.)

A1--0 to 8 cm; light reddish brown (5YR 6/4) gravelly fine sandy loam, reddish brown (5YR 5/4) moist; weak thin platy structure; soft, very friable, slightly sticky and slightly plastic; few fine roots; few fine and medium pores; 20 percent gravel and 5 percent cobbles; violently effervescent; strongly alkaline (pH 8.8); clear smooth boundary. (8 to 15 cm)

A2--8 to 38 cm; light reddish brown (2.5YR 6/4) very gravelly fine sandy loam, reddish brown (2.5YR 5/4) moist; weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; common fine and few medium roots; few fine pores; 35 percent gravel and 5 percent cobbles; violently effervescent; strongly alkaline (pH 8.5); gradual wavy boundary. (0 to 30 cm)

C--38 to 152 cm; light reddish brown (5YR 6/4) extremely gravelly sand, reddish brown (5YR 5/4) moist; single grained; loose; few fine roots; interstitial pores; 55 percent gravel and 15 percent cobbles; violently effervescent; strongly alkaline (pH 8.5).

TYPE LOCATION: Sevier County, Utah; 0.5 mile west of Vermillion, 150 feet east and 1,700 feet north of the southwest corner of sec. 25 T. 22 S., R. 2 W.; USGS Sigurd 7.5 minute quadrangle; latitude 38 degrees 51 minutes 29 seconds N and longitude 111 degrees 58 minutes 44 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry; moist in winter and spring and for brief periods in late summer due to convection storms; aridic bordering on xeric soil moisture regime.
Mean annual soil temperature: 9.0 to 12.0 degrees C.
Calcium carbonate equivalent: 40 to 60 percent

Particle-size control section - Rock fragments: 35 to 70 percent

A horizon
Hue: 2.5YR or 5YR.
Value: 5 through 7 dry, 4 or 5 moist.
Chroma: 3 through 5.
Reaction: Moderately alkaline or strongly alkaline.

C horizon
Hue: 5YR through 10R.
Value: 6 or 7 dry, 4 through 6 moist.
Chroma: 4 through 6.
Texture: Very gravelly sand, very gravelly loamy sand or extremely gravelly sand with some strata of gravelly or very gravelly sandy loam.
Rock fragments: 35 to 75 percent.
Reaction: Moderately alkaline to strongly alkaline.

COMPETING SERIES: There are no competing series

GEOGRAPHIC SETTING: The Stillman soils are at elevations of 1,585 to 1,770 meters. Slopes are 1 to 10 percent. These soils occur on alluvial fans, fan skirts and inset fans. These soils formed in alluvium derived from sandstone and limestone. The climate is semiarid. The average annual precipitation is 200 to 300 mm. The mean annual air temperature is 8.0 to 10.5 degrees C., and the frost-free period is 100 to 140 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kapture, Redfield, Sanpete and Sigurd series. Kapture soils are coarse-loamy and are on fan skirts. Redfield soils are fine-silty and are on alluvial flats. Both of the soils have less than 35 percent rock fragments in the control section and are under basin big sagebrush. Sanpete and Sigurd soils are loamy-skeletal in the control section. Sanpete soils have a calcic horizon and are on fan remnants under black sagebrush. Sigurd soils are on fan skirts under basin big sagebrush.

DRAINAGE AND PERMEABILITY: Somewhat excessively drained; low or moderate runoff; rapid permeability below depth of about 38 cm; high saturated hydraulic conductivity.

USE AND VEGETATION: These soils are used for irrigated cropland and livestock grazing. The vegetation is shadscale, budsage, horsebrush, winterfat, Indian ricegrass and galleta. Irrigated crops include alfalfa, corn, barley and oats. Some areas are used for gravel pits. These soils are correlated to semidesert ecological sites in Utah.

DISTRIBUTION AND EXTENT: Central Utah, western Sevier County. MLRA 28A. The series is inextensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona

SERIES ESTABLISHED: Richfield Area, Sevier County, Utah, 1947.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from the surface of the soil to 18 cm (A1 and part of the A2 horizon).
Particle-size control section: The zone from 25 to 100 cm (part of A2 and C horizons). .

Taxonomic Version: Tenth Edition, 2006.

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National Cooperative Soil Survey
U.S.A.