LOCATION RUSTICO UTEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Cumulic Haploxerolls
TYPICAL PEDON: Rustico silty clay loam-irrigated cropland. (Colors are for air-dry soil unless otherwise noted.)
Ap--0 to 23 cm; brown (7.5YR 5/3) silty clay loam, dark brown (7.5YR 3/2) moist; weak coarse subangular blocky structure parting to weak fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few medium, fine and very fine roots; few fine and common very fine random tubular pores; slightly effervescent; moderately alkaline (pH 8.3); clear smooth boundary. (18 to 25 cm thick)
A1--23 to 46 cm; brown (7.5YR 5/3) silty clay loam, dark brown (7.5YR 3/2) moist; weak medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few medium, fine and very fine roots; few fine and common very fine random tubular pores; slightly effervescent; carbonates are disseminated but also occurs in filaments; moderately alkaline (pH 8.3); clear smooth boundary. (15 to 25 cm thick)
A2--46 to 64 cm; brown (7.5YR 5/2) silty clay loam, very dark brown (7.5YR 2/2) moist; weak medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; common very fine random tubular pores; slightly effervescent; carbonates are disseminated and also occurs in filaments; moderately alkaline (pH 8.4); abrupt smooth boundary. (18 to 28 cm thick)
C1--64 to 86 cm; brown (7.5YR 5/3) clay loam, dark brown (7.5YR 3/3) moist; massive; hard, friable, moderately sticky and moderately plastic; few very fine roots; few very fine random tubular pores; noneffervescent matrix with carbonates in thin filaments; moderately alkaline (pH 8.2); gradual smooth boundary. (0 to 30 cm thick)
C2--86 to 127 cm; brown (7.5YR 5/3) silty clay loam, dark brown (7.5YR 3/3) moist; few fine faint strong brown (7.5YR 5/6) redoximorphic features; massive; hard, firm, moderately sticky and moderately plastic; few very fine roots; few very fine random tubular pores; noneffervescent matrix with carbonates in thin filaments; moderately alkaline (pH 8.3); gradual smooth boundary. (0 to 23 cm thick)
Ab--127 to 152 cm; brown (7.5YR 5/2) silty clay loam, dark brown (7.5YR 3/2) moist; few fine faint strong brown (7.5YR 4/6) redoximorphic features; weak medium subangular blocky structure, parting to weak fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few very fine roots; few fine and very fine tubular pores; noneffervescent; moderately alkaline (pH 8.2)
TYPE LOCATION: Beaver County, Utah; about 850 feet west and 530 feet south of the northeast corner of sec. 6, T. 29 S., R. 10 W; Milford Flat USGS Quad; lat. 38 degrees 19 minutes 22 seconds N. and long. 113 degrees 0 minutes 43 seconds W., NAD27.
RANGE IN CHARACTERISTICS:
Soil moisture: These soils are dry for 50 to 60 percent of the time the soil temperature at a depth of 50 cm is above 5 degrees C. They are usually dry in some part of the moisture control section for 60 to 75 days out of the 120 days after 21st of June. The soil moisture regime is aridic bordering on xeric.
Mean annual soil temperature: 9 to 11 degrees C.
Mean summer soil temperature: 19 to 22 degrees C.
Mollic epipedon thickness: 50 to 75 cm.
Other features: Organic matter decreases irregularly with depth or remains above 0.5 percent within the depth of 127 cm. Buried A horizons within or below the C horizon are common, and may have few fine faint redoximorphic features.
Particle-size control section (weighted average):
Clay content: 27 to 35 percent.
Sand content: Less than 15 percent of fine sand or coarser.
Effervescence: The upper part of the control section is effervescent and the lower part is noneffervescent.
Calcium carbonate: the control section contains filaments of calcium carbonate.
A horizon:
Hue: 7.5YR or 10YR.
Value: 2 or 3 moist and 4 or 5 dry.
Reaction: Moderately alkaline or strongly alkaline.
C horizon:
Hue: 7.5YR or 10YR.
Value: 2 to 4 moist and 4 to 6 dry.
Chroma: 2 to 4.
Mottles: Few fine faint relic redoximorphic features occur in many pedons.
Texture: Silty clay loam or clay loam, with some pedons having subhorizons of loam.
Reaction: Slightly alkaline to strongly alkaline.
COMPETING SERIES: These are the Caldwell (WA), Harana (OR), Jett (OR), Keigley (UT), Loupence (ID), Red Rock (UT) and Snow (WA). Caldwell, Loupence and Snow soils are noneffervescent throughout. Harana soils have noneffervescent A horizons, chroma of 1 in the control section and chroma of 1 or less below 100 cm. Jett and Red Rock soils have silt loam control sections averaging 18 to 27 percent clay. Keigley soils are effervescent throughout and carbonates are disseminated. Keigley soils also have a xeric soil moisture regime.
GEOGRAPHIC SETTING: Rustico soils occur on stream terraces and alluvial flats at elevations of 1,460 to 1,600 meters. Slopes range from 0 to 2 percent. These soils formed in alluvium derived from mixed rocks. The mean annual air temperature is 7 to 10 degrees C. Average annual precipitation is 200 to 310 mm. The freeze-free period in 100 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Decca and Uvada soils. These soils lack mollic epipedons. Decca soils have argillic horizons and strongly contrasting textures within a 100 cm depth. Uvada soils have fine-textured natric horizons.
DRAINAGE AND PERMEABILITY: Well drained; low runoff; moderately slow and slow permeability.
USE AND VEGETATION: These soils are used principally for irrigated crops of alfalfa, small grains and corn. Present vegetation is basin big sagebrush, rabbitbrush, bottlebrush squirreltail and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Southwestern Utah. MLRA 28A. These soils are inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Iron County, Utah, Iron-Washington Area, 1997. The name is taken from San Rustico, the name given to the area by Father Escalante.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon (cumulic): The zone from the surface to 64 cm. (Ap, A1, and A2 horizons)
Cumulic feature: A mollic epipedon thicker than 50 cm with an irregular decrease in organic carbon.
Particle-size control section: The zone from 25 to 100 cm (A1, A2, C1, C2 horizons).
Classification is based on the "Keys to Soil Taxonomy, Tenth Edition, 2006".