LOCATION SWEAGERT CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Typic Durixerolls
TYPICAL PEDON: Sweagert gravelly sandy loam on a south facing 3 percent slope under a cover of needlegrass, bluebunch wheatgrass and low sagebrush at an elevation of 4270 feet. (Colors are for dry soil unless otherwise stated. When described May 20, 1986, the soil was moist below 3 inches.)
A1--0 to 3 inches; grayish brown (10YR 5/2) gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; moderate very thin platy structure; slightly hard, very friable, nonsticky and slightly plastic; many very fine roots; common very fine tubular pores; 30 percent very fine gravel; slightly acid (pH 6.5); abrupt smooth boundary. (3 to 4 inches thick)
A2--3 to 6 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate very thin platy structure; slightly hard, very friable, nonsticky and slightly plastic; common very fine and fine roots; common very fine tubular pores; 5 percent very fine gravel; slightly acid (pH 6.5); abrupt smooth boundary. (3 to 4 inches thick).
Bt1--6 to 12 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; common very fine tubular pores; few thin clay films in pores; 5 percent gravel; neutral (pH 6.8); clear smooth boundary.
Bt2--12 to 16 inches; brown (10YR 5/3) clay loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; common very fine and few fine tubular pores; common thin clay films on peds and in pores; 5 percent gravel; neutral (pH 7.0); clear smooth boundary. (Combined thickness of the Bt1 and Bt2 horizons is 8 to 24 inches)
Bt3--16 to 24 inches; pale brown (10YR 6/3) clay loam, dark brown (10YR 3/3) moist; moderate medium angular blocky structure; hard, firm, slightly sticky and plastic; few very fine roots; common very fine and few fine tubular pores; many moderately thick clay films on peds and in pores; 5 percent gravel; neutral (pH 7.0); abrupt wavy boundary. (4 to 6 inches thick)
2Bt4--24 to 26 inches; light yellowish brown (10YR 6/4) gravelly clay, yellowish brown (10YR 5/4) moist; strong medium angular blocky structure; hard, firm, slightly sticky and very plastic; common very fine matted roots; few very fine tubular pores; many thick clay films on ped faces and pores; 30 percent fine gravel; neutral (pH 7.0); abrupt smooth boundary. (2 to 4 inches thick)
2Bqm--26 to 33 inches; very pale brown (10YR 7/4) continuously strongly cemented duripan, dark yellowish brown (10YR 4/4) moist; strong thin platy structure; with 1/4 to 1/8 inch thick indurated, continuous silica and manganese capping; 30 percent gravel, 20 percent cobbles; slightly alkaline (pH 7.5); clear wavy boundary. (7 to 10 inches thick)
2Bqkm--33 to 60 inches; very pale brown (10YR 7/4) strongly cemented duripan, dark yellowish brown (10YR 4/4) moist; strong thin platy structure; 60 percent gravel and 10 percent cobbles; slightly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Modoc County, California; about 4 miles north of Adin, about 4 miles north of Adin, 300 feet south of dirt road, 40 feet east of BLM boundary fence; 1,300 feet west and 1,800 feet north of the southeast corner of sec. 4, T. 39 N., R. 9 E., Adin NW (Adin) quadrangle (7.5 minute series).
RANGE IN CHARACTERISTICS: Mollic epipedon is 14 to 20 inches thick. Depth to duripan is 20 to 40 inches. The mean annual soil temperature is 47 to 52 degrees F. The soil temperature exceeds 41 degrees F. from mid March to mid November (250 days) and exceeds 47 degrees F. from mid May to early November. The soil moisture control section (8 to 20 inches) is dry in all parts from early July to mid September (75 days) and is moist in all parts from mid November to early May. The particle size control section (6 to 26 inches) averages 27 to 35 percent clay and 5 to 30 percent rock fragments, mostly gravel. Base saturation by sum of cations ranges from 90 to 100 percent.
The A horizon color is 10YR 5/1, 5/2, or 5/3. Moist color is 10YR 3/2, or 3/3. Organic matter ranges from 1 to 4 percent. Texture is gravelly sandy loam or loam. Clay content ranges from 12 to 25 percent. Rock fragments, mostly gravel, range from 5 to 30 percent. Reaction is slightly acid or neutral.
The Bt1 and Bt2 horizon color is 10YR 4/1, 4/2, 4/3, 4/4, 5/1, 5/2, 5/3, or 7.5YR 5/2. Moist color is 10YR 2/1, 2/2, 3/1, 3/2, 3/3, 4/2, or 7.5YR 3/2. Organic matter ranges from 1 to 2 percent. Texture is loam or clay loam. Clay content ranges from 25 to 30 percent. Rock fragments, mostly gravel, range from 0 to 15 percent. Reaction is slightly acid or neutral.
The Bt3 horizon color is 10YR 6/1, 6/3, 7/4 or 7.5YR 5/4. Moist color is 10YR 3/3, 3/4, 4/2, 4/4; 7.5YR 3/2, 4/2, or 4/4. Organic matter ranges from 0.5 to 2 percent. Texture is clay loam or sandy clay loam. Clay content ranges from 30 to 35 percent. Rock fragments, mostly gravel range from 5 to 15 percent. Reaction is slightly acid or neutral.
The 2Bt4 horizon color is 10YR 5/4 or 6/4. Moist color is 10YR 3/4 or 5/4. Organic matter ranges from 0.3 to 0.8 percent. Texture is gravelly clay, clay or gravelly clay loam. Clay content ranges from 30 to 45 percent. Rock fragments, mostly gravel, range from 10 to 30 percent.
The 2Btqkm horizon. Rock fragments, mostly gravel or cobbles, range from 35 to 60 percent in the upper part and 60 to 80 percent in the lower part. Reaction is slightly alkaline or moderately alkaline.
COMPETING SERIES: These are Drewsgap (OR) and Milldam (OR)?????
GEOGRAPHIC SETTING: Sweagert soils are on terraces. Slopes are 0 to 9 percent. These soils formed in alluvium from extrusive igneous rock. Elevation is 4200 to 4800 feet. The climate is semiarid with warm dry summers and cold moist winters. Mean annual precipitation is 14 to 16 inches. Snowfall is 12 to 24 inches. The mean annual temperature is 45 to 50 degrees F. The mean January temperature is about 32 degrees F. The mean July temperature is about 67 degrees F. Frost free season is 80 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adinot (T), Bieber, and Oxendine (T) soils. Adin soils are on fans and hills, are less than 20 inches deep to bedrock. Bieber soils are on mounds, are less than 20 inches deep to duripan and are clayey. Oxendine soils are on intermounds, are less than 20 inches deep to a gravelly duripan and are loamy.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to ponded runoff; moderately slow permeability in the upper part of the Bt horizon and slow in the lower part, in some pedons it is moderately slow throughout.
USE AND VEGETATION: This soil is used for livestock grazing. Small areas are used as cropland. The natural vegetation is needlegrass, bluebunch wheatgrass, sandberg bluegrass, bottlebrush squireltail, and low sagebrush. Soils are cropped to barley, wheat, oats, and some alfalfa.
DISTRIBUTION AND EXTENT: Northeastern California. The soils are not extensive. MLRA is 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Modoc County, Intermountain Soil Survey Area, California 1994. Source of name is Sweagert Flat.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Rock fragments, mostly gravel, on the soil surface, range from 0 to 15 percent.
Mollic epipedon - 0 to 16 inches (A1, A2, Bt1, Bt2)
Base saturation by Hach Kit ranges from 90 to 100 percent to a depth of 16 inches.
Argillic horizon - 6 to 26 inches (Bt1, Bt2, Bt3, 2Bt4)
Organic matter by Walkley-Black ranges from 0.2 to 2 percent to a depth of 26 inches. Base saturation by Hach Kit ranges from 90 to 100 percent to a depth of 26 inches.
Other Diagnostic Horizons and Soil Characteristics:
Duripan - 26 to 60 inches (2Bqm, 2Bqkm)
Moisture Regime - Xeric