LOCATION SILKTASSEL         NM
Inactive Series
Rev. DGS/RLB
09/2007

SILKTASSEL SERIES


The Silktassel series consists of shallow, well drained, moderately slowly permeable soils that formed in colluvium derived from tuff. These steep to very steep soils are on mountain tops and flanks. Slope ranges from 35 to 95 percent. Mean annual precipitation is about 14 inches and the mean annual temperature is about 60 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Aridic Lithic Argiustolls

TYPICAL PEDON: Silktassel very gravelly loam - rangeland. (Colors are for dry soil unless otherwise stated).

A1--0 to 3 inches; brown (7.5YR 4/3) crushed, very gravelly loam, dark brown (7.5YR 3/3) crushed, moist; 24 percent clay; weak fine granular structure; loose; slightly sticky and slightly plastic; common fine roots throughout; 40 percent nonflat angular 0.1-to 3-inch tuff gravel; noneffervescent by HCl, 1 normal; neutral; clear smooth boundary. (0 to 7 inches thick)

A2--3 to 7 inches; brown (7.5YR 4/2) crushed, very gravelly loam, dark brown (7.5YR 3/2) crushed, moist; 22 percent clay; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots throughout; few fine dendritic tubular pores; 40 percent nonflat angular 0.1-to 3-inch tuff gravel, 10 percent nonflat angular 3-to 10-inch tuff cobbles; noneffervescent by HCl, 1 normal; neutral; clear smooth boundary. (0 to 7 inches thick)

Bt1--7 to 12 inches; brown (7.5YR 5/4) crushed, very gravelly clay loam, dark brown (7.5YR 3/4) crushed, moist; 32 percent clay; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots throughout; few fine dendritic tubular pores; 15 percent patchy faint clay films on faces of peds; 40 percent nonflat subangular 0.1-to 3-inch tuff gravel, 15 percent nonflat subangular 3-to 10-inch tuff cobbles; noneffervescent by HCl, 1 normal; neutral; gradual smooth boundary. (5 to 10 inches thick)

Bt2--12 to 17 inches; strong brown (7.5YR 4/6) crushed, extremely gravelly clay loam, dark brown (7.5YR 3/4) crushed, moist; 28 percent clay; moderate fine subangular blocky structure; moderately hard, friable, moderately sticky and moderately plastic; few fine roots throughout; few fine dendritic tubular pores; 15 percent patchy faint clay films on faces of peds; 50 percent nonflat angular 0.1-to 3-inch tuff gravel, 20 percent nonflat angular 3-to 10-inch tuff cobbles; noneffervescent by HCl, 1 normal; neutral. (5 to 10 inches thick)

R--17 inches; thickly bedded massive tuff.

TYPE LOCATION: Dona Ana County, New Mexico; approximately 5.6 miles west and 6 miles south of White Sands; 2,590 feet west and 210 feet south of the northeast corner of sec. 30, T. 23 S., R. 4 E. USGS Organ Peak topographic quadrangle; latitude 32 degrees 17 minutes 8.55 seconds north and longitude 106 degrees 34 minutes 16.1 seconds west. UTM zone 13S, 352048E, 3573000N; NAD 27"

RANGE IN CHARACTERISTICS:

Soil Moisture: usually dry in some or in all parts for six-tenths or more of the time that the soil temperature exceeds 41 degrees F. Some part of the epipedon is moist for more than 90 cumulative days in most years when the soil temperature exceeds 41 degrees F. Aridic ustic moisture regime.

Mean annual soil temperature: 59 to 62 degrees F.

Depth to lithic contact: 10 to 20 inches

Thickness of mollic epipedon: 7 to 14 inches

Particle-size control section (weighted average):

Clay content: 27 to 35 percent

Coarse fragment content: 60 to 75 percent

Reaction: slightly acid to neutral

A horizon:
Hue: 5YR or 7.5YR
Value: 3 to 5 dry, 1 to 3 moist
Chroma: 1 to 3, dry or moist
Coarse fragment content: tuff fragments; 45 to 65 percent gravel size fragments; 0 to 15 percent cobbles

Bt horizons:
Hue: 5YR or 7.5YR
Value: 4 or 5 dry, 3 to 5 moist
Chroma: 4 to 6, dry or moist
Texture modifier: very gravelly or extremely gravelly
Coarse fragment content: tuff fragments; 40 to 75 percent total coarse fragments. 30 to 60 percent gravel, 10 to 15 percent cobbles.
Texture: loam, clay loam

COMPETING SERIES: These are the Atascosa (AZ), Costavar (AZ), Guaynaka (AZ), and Woodcutter (AZ) series. Atascosa soils have hue yellower than 7.5YR and formed on rhyolitic conglomerate and rhyolitic tuff. Costavar soils formed in dacitic volcanic breccia and are calcareous and moderately alkaline. Guaynaka soils have hue of 2.5YR. Woodcutter soils contain less than 60 percent rock fragments in the particle size control section, and the upper part of argillic horizon is included in mollic epipedon.

GEOGRAPHIC SETTING:
Parent material: Colluvium from tuff
Landform: Mountain tops and flanks
Slope: 35 to 65 percent
Mean annual temperature: 58 to 61 degrees
Mean annual precipitation: 13 to 15 inches
Precipitation pattern: Precipitation falls mostly during the months of July through September. The driest months are March and April. Precipitation during the months of January, February, and March is less than 13 percent of the total.
Frost-free period: 140 to 180 days
Elevation: 4,700 to 6,300 feet

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Thaad, Tuftuff, and Arbol soils.
Thaad and Tuftuff soils are greater than 20 inches to bedrock and are on mountain flanks and bases.
Arbol soils do not have argillic horizons and are on mountain tops and flanks.

DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderately slow. Runoff is very high.

USE AND VEGETATION: Used for livestock grazing. Vegetation is of the montane shrubland type consisting of metcalf muhly, blue grama, sideoats grama, bull muhly, wolftail, shrub live-oak, and Wright's silktassel.

DISTRIBUTION AND EXTENT: Southern New Mexico; LRR D, MLRA 42. The series is of minor extent.

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

SERIES ESTABLISHED: Dona Ana County, New Mexico; 2001.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Particle-size control section: The zone from 7 to 17 inches. (Bt1 and Bt2 horizons)

Mollic epipedon: The zone from 0 to 7 inches. (A1, and A2 horizons)

Argillic horizon: The zone from 7 to 17 inches. (Bt1, and Bt2 horizons)

Lithic contact: The contact with bedrock at 17 inches. (R horizon)

The assignment of the cation exchange capacity is inferred from lab data from similar soils in the surrounding area.


National Cooperative Soil Survey
U.S.A.