LOCATION DECAN NVEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Argiduridic Durixerolls
TYPICAL PEDON: Decan gravelly clay loam, woodland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches; grayish brown (10YR 5/2) gravelly clay loam, very dark grayish brown (10YR 3/2) moist; moderate thick platy structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine interstitial pores; 20 percent pebbles; slightly acid (pH 6.2); abrupt smooth boundary. (2 to 3 inches thick)
A2--2 to 3 inches; dark grayish brown (10YR 4/2) gravelly clay loam, very dark grayish brown (10YR 3/2) moist; strong very fine granular structure; slightly hard, friable, sticky and plastic; common very fine roots; many very fine interstitial and few very fine tubular pores; 20 percent pebbles; slightly acid (pH 6.2); abrupt smooth boundary. (1 to 4 inches thick)
Bt1--3 to 8 inches; brown (7.5YR 4/2) clay, dark brown (7.5YR 3/2) moist; moderate medium prismatic structure; hard, firm, sticky and very plastic; common very fine and few fine and medium roots; common very fine tubular pores; many pressure faces and thin clay films in pores; 10 percent pebbles; slightly acid (pH 6.3); clear wavy boundary. (3 to 7 inches thick)
Bt2--8 to 17 inches; brown (7.5YR 4/4) clay, dark brown (7.5YR 3/4) moist; moderate medium prismatic structure; hard, firm, very sticky and very plastic; common very fine and few fine and medium roots; common very fine tubular pores; many pressure faces; 10 percent pebbles; neutral (pH 6.6); abrupt wavy boundary. (7 to 12 inches thick)
Btk--17 to 23 inches; pink (7.5YR 7/4) clay loam, brown (7.5YR 5/4) moist; weak medium prismatic structure; slightly hard, friable, sticky and plastic; few very fine through medium roots; many very fine interstitial pores; few thin clay films on faces of peds and lining pores; matrix noneffervescent but violently effervescent in many fine and medium prominent white (10YR 8/2) lime masses; 10 percent pebbles; mildly alkaline (pH 7.6); abrupt wavy boundary. (5 to 8 inches thick)
Bqkm--23 inches; light brown (7.5YR 6/4) indurated duripan with thin (1 to 2 millimeter) continuous silica laminae capping light brown (7.5YR 6/4) strongly silica-cemented materials stratified with sandy loam that is weakly silica-cemented; massive; extremely hard, extremely firm, brittle; few fine roots in weakly cemented material between strongly lime and silica cemented plates; common fine interstitial pores in weakly cemented material; strongly effervescent; strongly alkaline (pH 8.8).
TYPE LOCATION: Lincoln County, Nevada; about 1200 feet north of the southeast corner of section 6, T. 4 S., R. 71 E.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry, but are moist in winter and spring and for 10 to 20 days cumulative during the period July through October due to summer convection storms.
Soil temperature - 47 to 53 degrees F.
Mollic epipedon thickness - 7 to 12 inches.
Depth to duripan - 20 to 40 inches.
Control section - Clay content: Average 35 to 45 percent.
Rock fragments: Averages 10 to 30 percent, predominantly pebbles.
A horizons - Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3.
Reaction: Slightly acid or neutral.
Bt1 horizon - Hue: 10YR or 7.5YR.
Value: 4 or 5 dry, 3 or 4 moist.
Chroma: 2 or 3.
Clay content: 40 to 50 percent
Rock fragments: 10 to 35 percent.
Structure: Moderate or strong, medium or fine prismatic, subangular blocky, or angular blocky.
Consistence: Hard or very hard.
Reaction: Slightly acid or neutral.
Bt2 horizon - Hue: 10YR or 7.5YR.
Value: 4 or 5 dry, 3 or 4 moist.
Chroma: 2 through 4.
Clay content: 40 to 50 percent
Rock fragment: 10 to 35 percent.
Structure: Moderate or strong, medium or fine prismatic or angular blocky.
Consistence: Hard or very hard.
Reaction: Slightly acid or neutral.
Btk horizon - Hue: 10YR or 7.5YR
Value: 6 through 8 dry, 5 or 6 moist.
Chroma: 4 or 5.
Texture: Clay loam and loam
Clay content: 25 to 35 percent
Structure: Prismatic or subangular blocky.
Rock fragments: 5 to 15 percent pebbles.
Reaction: Mildly alkaline to strongly alkaline.
Other features: Matrix noneffervescent through effervescent with common or many violently effervescent fine and medium lime masses.
Bk horizon (when present) - Hue: 10YR or 7.5YR
Value: 6 through 8 dry, 5 or 6 moist.
Chroma: 4 or 5.
Clay content: 25 to 35 percent
Structure: Prismatic or subangular blocky.
Rock fragments: 5 to 15 percent pebbles.
Other features: Matrix noneffervescent to effervescent with common or many violently effervescent fine and medium lime masses.
Bqkm horizon - Hue: 10YR or 7.5YR
Value: 6 through 8 dry, 5 through 7 moist.
Chroma: 1 through 6.
Cementation: 1 to 10 millimeters thick continuously indurated silica cap, with strongly silica cemented material within common to many discontinuous silica laminae below.
COMPETING SERIES: These are the Adios(ID), Barnard(OR), Fleischmann(NV), Ollierivas(T CA) and Xerta(NV) series. The Adios, Ollierivas and Xerta soil have bedrock at 26 to 40 inches. The Barnard soils contain less than 5 percent coarse fragments in the particle-size control section. Barnard and Fleischmann soils do not receive the 10 to 20 days of summer precipitation.
GEOGRAPHIC SETTING: Decan soils are on fan piedmonts and old valley fill terraces. These soils formed in alluvium from ignimbrites and volcanic tuffs. Elevations are 5800 to 6600 feet. Slopes are 2 to 30 percent. The climate is cool, semiarid. The mean annual precipitation is 12 to 16 inches; the mean annual temperature is 45 to 50 degrees F., and the frost-free season is 110 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Acoma, Cath, Cedaran, Fanu, and Tica soils. Acoma soils lack a duripan. Cath soils lack a duripan and have a fine-loamy control section. Cedaran, Fanu, and Tica soils have mean annual soil temperatures less than 47 degrees F.
DRAINAGE AND PERMEABILITY: Well drained, slow or medium runoff; slow permeability.
USE AND VEGETATION: Woodland and wildlife habitat. The vegetation is principally Utah juniper, Wyoming big sagebrush, cliffrose, bottlebrush squirreltail, and Indian ricegrass.
DISTRIBUTION AND EXTENT: East central Nevada. Decan soils are moderately extensive. MLRA 28A,28B.
MLRA OFFICE RESPONSIBLE: Reno, Nevada
SERIES ESTABLISHED: Lincoln County, Nevada (Meadow Valley Area), 1971.
REMARKS: Decan was reclassified from frigid to mesic in 1990 to better represent the series concept.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 8 inches (A1, A2 and Bt1 horizons).
Particle-size control section - The zone from 3 to 23 inches (Bt1, Bt2 and Btk horizons).
Duripan - At about 23 inches (Bqkm horizon).