LOCATION PROMO UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, active, calcareous, mesic Lithic Xeric Torriorthents
TYPICAL PEDON: Promo cobbly silt loam--rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 4 inches; pale brown (10YR 6/3) cobbly silt loam, brown (10YR 4/3) moist; weak medium and thin platy structure; soft, friable, slightly sticky and slightly plastic; few fine roots; many very fine and fine pores; 35 percent angular cobbles and gravel; strongly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (3 to 9 inches thick)
A2--4 to 7 inches; pale brown (10YR 6/3) cobbly silt loam, brown (10YR 4/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; few very fine pores; 35 percent angular gravel and cobbles; strongly effervescent; secondary carbonates are mostly disseminated but are also coats on some pebbles; strongly alkaline (pH 8.6); gradual wavy boundary. (3 to 6 inches thick)
C--7 to 14 inches; pale brown (10YR 6/3) very cobbly loam, brown (10YR 4/3) moist; weak fine and medium angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine and medium roots; 40 percent angular gravel and cobbles; violently effervescent; secondary carbonates segregated as coats on rock fragments; strongly alkaline (pH 8.6); abrupt irregular boundary. (5 to 8 inches thick)
R--14 inches; limestone.
TYPE LOCATION: Box Elder County, Utah; about 14 miles south of Promontory in the Promontory Mountains near the head of Broadmouth Canyon; approximately 650 feet west and 850 feet south of the north quarter corner of section 35, T. 8 N., R. 6 W.; USGS East Promontory 7.5 minute topographic quadrangle; 41 degrees 23 minutes 07 seconds north latitude and 112 degrees 29 minutes 53 seconds west longitude, NAD27; UTM zone 12N 374679E, 4582604N, NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture - The soils are usually dry in all parts of the moisture control section during the period the soil temperature is above 41 degrees F. and are continually dry for 70 to 90 consecutive days during the summer months. They are moist for 60 to 90 consecutive days during the winter months; Aridic moisture regime that borders on xeric.
Mean annual soil temperature - 47 to 49 degrees F.
Mean summer soil temperature - 68 to 71 degrees F.
Ochric epipedon thickness - 7 to 15 inches.
Organic matter content - Averages more than 1.0 percent to a depth of 15 inches.
Depth to bedrock - 10 to 20 inches to a lithic contact.
Particle-size control section - Clay content: Averages 12 to 22 percent; Rock fragments: Averages 35 to 80 percent angular gravel and cobbles and few stones throughout the profile. Lithology of fragments is mainly limestone.
A horizons - Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 2 through 4, dry or moist.
Reaction: Moderately alkaline or strongly alkaline.
Effervescence: Slightly effervescent or strongly effervescent.
Calcium carbonate equivalent: 3 to 15 percent.
C horizon - Value: 6 or 7 dry, 4 or 5 moist.
Chroma: 2 or 3, dry or moist.
Reaction: Moderately alkaline or strongly alkaline.
Calcium carbonate equivalent: 3 to 30 percent.
Other features: Some pedons have identifiable secondary carbonates as coats on bottoms of rock fragments.
COMPETING SERIES: This is the Puffer series.
Puffer soils have ochric epipedons that are 2 to 6 inches thick and average less than 1 percent organic matter content in the epipedon.
GEOGRAPHIC SETTING: Promo soils are on hills and mountains. They typically occur on slightly convex backslope positions with south or west-facing aspect. Slopes are 5 to 60 percent. Elevation ranges from 4,300 to 6,800 feet. These soils formed in colluvium and residuum derived dominantly from limestone with some areas weathered from sandstone and siltstone. The climate is subhumid with cool, moist winters and warm, dry summers. The mean annual precipitation is 12 to 14 inches, the mean annual temperature is 45 to 48 degrees F., the mean summer temperature is about 69 F., and the frost-free period is 100 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Rozlee, Sandall, and Sanpete soils. Rozlee soils are moderately deep to lithic contacts, have mollic epipedons, and have calcic horizons. Sandall are moderately deep to lithic contacts, have calcic horizons, and have carbonatic mineralogy. Sanpete soils are very deep, have calcic horizons, and have carbonatic mineralogy.
DRAINAGE AND PERMEABILITY: Well drained or somewhat excessively drained; high or very high surface runoff; moderately rapid permeability (high saturated hydraulic conductivity).
USE AND VEGETATION: Promo soils are used for rangeland. The native vegetation is black sagebrush, bluebunch wheatgrass, basin wildrye, antelope bitterbrush, Utah juniper, and annual weeds and grasses.
DISTRIBUTION AND EXTENT: Northwestern Utah. These soils are moderately extensive. MLRA 28A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona.
SERIES ESTABLISHED: Box Elder County (East Box Elder Area), Utah, 1969.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 7 inches (A1 and A2 horizons).
Identifiable secondary carbonates - The zone from 4 to 14 inches (A2 and C horizons).
Lithic contact - The boundary at 14 inches to underlying hard bedrock (R layer).
Particle-size control section - The zone from the soil surface to 14 inches (A1, A2, and C horizons).
The active cation exchange activity class was added to the taxonomic classification in December 2002 based on soil property data. Future study is needed to determine whether another series is needed with a xeric moisture regime to represent part of the current series concept.