LOCATION YAHMORE NMEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Pachic Argiustolls
TYPICAL PEDON: Yahmore fine sandy loam -- on a plane toeslope sloping 4 percent to the southeast at 7,680 feet elevation -- forest. (Colors are for dry soil unless otherwise noted. When described, the soil was dry from 0 to 21 inches and moist from 21 to 64 inches.) Soil surface is covered with 1 inch of pine needles, twigs, and cones.
A--0 to 5 inches; brown (7.5YR 5/2) fine sandy loam, dark brown (7.5YR 3/2) moist; moderate thick platy structure parting to moderate medium granular; soft, very friable, slightly sticky and nonplastic; few fine and common very fine roots; few very fine irregularly shaped pores; neutral (pH 6.6); clear smooth boundary. (5 to 10 inches thick)
BA--5 to 21 inches; brown (7.5YR 5/3) fine sandy loam, dark brown (7.5YR 3/3) moist; weak coarse subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; few coarse and medium and common fine and very fine roots; few fine and common very fine tubular pores; neutral (pH 7.0); clear wavy boundary. (0 to 16 inches thick)
Bt1--21 to 33 inches; brown (7.5YR 5/4) fine sandy loam, brown (7.5YR 4/4) moist; moderate coarse subangular blocky structure; hard, friable, slightly sticky and nonplastic; few coarse, medium and fine and common very fine roots; few fine and common very fine tubular pores; few thin clay films on faces of peds and lining pores; neutral (pH 7.0); clear wavy boundary. (7 to 18 inches thick)
Bt2--33 to 44 inches; reddish brown (5YR 5/4) sandy clay loam, reddish brown (5YR 4/4) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, slightly sticky and slightly plastic; few coarse and very fine roots; few fine and very fine tubular pores; common moderately thick clay films on faces of peds and lining pores; neutral (pH 7.2); gradual smooth boundary. (10 to 15 inches thick)
Bt3--44 to 64 inches; yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist; moderate medium prismatic structure parting to weak medium subangular blocky; hard, firm, slightly sticky and slightly plastic; few fine and very fine roots; few fine and very fine tubular pores; common moderately thick clay films on faces of peds and lining pores; neutral (pH 7.2).
TYPE LOCATION: San Juan County, New Mexico; on the Navajo Indian Reservation about 7 miles west of Sheep Springs; 100 feet east and 100 feet south of the northwest corner of sec. 25, T.22N., R.19W; Latitude 36 degrees 7 minutes 7 seconds N and Longitude 108 degrees 49 minutes 35 seconds W.
RANGE IN CHARACTERISTICS:
Soil moisture - Typically, the soil moisture control section (SMCS) is moist in all parts from January to May and intermittently moist in some part from June to December. The SMCS is moist in all parts less than 40 percent of the time (cumulative), when the soil temperature at 20 inches is 41 degrees F or higher. Typic ustic moisture regime.
Soil temperature - 43 to 47 degrees F.
Reaction - ranges from slightly acid in the surface to neutral in the subsoil.
Silicate clay content, control section weighted average - 10 to 18 percent
Rock fragments - less than 5 percent
Depth to base of Mollic epipedon - 16 to 29 inches
Depth to base of Argillic horizon - 40 to 60 inches or more
A horizon - Hue: 7.5YR or 10YR
Value: 4 or 5 dry
Chroma: 1 or 2
Organic carbon content: 1 to 2 percent
Texture: fine sandy loam, sandy loam, or loam
BA horizon - Value: 3 through 5 dry, 2 or 3 moist
Chroma: 1 through 3
Organic carbon content: 1 to 2 percent
Texture: fine sandy loam or sandy loam
upper Bt horizons - Value: 4 through 6 dry, 3 or 4 moist
Chroma: 2 through 4
Organic carbon content: 0.5 to 1 percent
Clay content: 14 to 18 percent
Texture: fine sandy loam or sandy loam
lower Bt horizons - Hue: 5YR through 10YR
Value: 5 through 7 dry, 4 through 6 moist
Chroma: 3 through 6
Organic carbon content: 0.3 to 0.5 percent
Clay content: 12 to 27 percent
Texture: sandy clay loam or sandy loam
Other features: some pedons have relict redox concentrations, soft shale fragments, or minor amounts of secondary calcium carbonates
COMPETING SERIES: This is the Dempsey series. Dempsey soils have yellower (2.5Y & 5Y) hues.
GEOGRAPHIC SETTING: Yahmore soils are on toeslopes and footslopes. They formed in alluvium derived from Tertiary sandstone and basalt and Cretaceous shale. Slopes range from 1 to 15 percent. Elevation ranges from 7,400 to 8,600 feet. The mean annual precipitation is 16 to 20 inches with more than 50 percent falling as snow from winter storms. The mean annual temperature is 41 to 45 degrees F. The average frost-free period is 90 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kunz, Sandark, Tunitcha, and Tuntsa soils. Kunz and Tunitcha soils are fine-loamy, lack mollic epipedons and occur on adjacent knolls, footslopes and backslopes. Sandark soils are sandy and occur in more heavily wooded areas. Tuntsa soils lack argillic horizons and occur on adjacent non-wooded areas.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability.
USE AND VEGETATION: Yahmore soils are used for livestock grazing and timber production. Present vegetation is ponderosa pine forest with an understory of Gambel oak, Rocky Mountain juniper, blue grama, bottlebrush squirreltail, needleandthread, pingue and silvery lupine.
DISTRIBUTION AND EXTENT: Yahmore soils are of small extent on the Defiance Uplift-Chuska Mountains portion of the Colorado Plateau province in northwest New Mexico and northeast Arizona. MLRA 39.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Shiprock Area Soil Survey, Western San Juan County, New Mexico, 1993. Yahmore is a coined name.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to a depth of about 21 inches. (A and BA horizons)
Pachic subgroup - The presence of a mollic epipedon that is greater than 16 inches thick. (A and BA horizons)
Argillic horizon - The zone from 21 to 64 inches. (Bt1, Bt2, and Bt3 horizons)
Classified according to Soil Taxonomy Second Edition, 1999; Keys to Soil Taxonomy Tenth Edition, 2006.
ADDITIONAL DATA: Organic carbon values are estimated.