LOCATION POMAN CAEstablished Series
TAXONOMIC CLASS: Sandy, mixed, mesic Xeric Haplodurids
TYPICAL PEDON: Poman loamy sand - on a 1 percent slope under cheatgrass and rabbitbrush at 4,240 feet elevation. (When described on October 20, 1982, the soil was dry throughout.)
A1--0 to 2 inches; light brownish gray (10YR 6/2) loamy sand, dark brown (10YR 3/3) moist, single grain; loose, nonsticky and nonplastic; few very fine and fine roots; many very fine interstitial pores; mildly alkaline (pH 7.5); clear smooth boundary. (1 to 3 inches thick)
A2--2 to 10 inches; light brownish gray (10YR 6/2) loamy sand, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine, few medium roots; many very fine interstitial, few very fine tubular pores; moderately alkaline (pH 8.0); clear smooth boundary. (7 to 9 inches thick)
Bk1--10 to 18 inches; light brownish gray (10YR 6/2) loamy sand, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; few very fine, fine and medium roots; many very fine interstitial, common very fine tubular pores; strongly effervescent with disseminated lime; moderately alkaline (pH 8.0); clear wavy boundary. (7 to 9 inches thick)
Bk2--18 to 29 inches; light brownish gray (10YR 6/2) loamy sand, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; few very fine and fine roots; many very fine interstitial, common very fine tubular pores; strongly effervescent with disseminated lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (10 to 12 inches thick)
2Ckqm--29 to 32 inches; pale brown (10YR 6/3) duripan, brown (10YR 4/3) moist; massive; very hard, very firm and brittle; has opal laminar cap 1 to 2 mm thick; violently effervescent with disseminated lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (2 to 4 inches thick)
2Ckq--32 to 39 inches; light yellowish brown (10YR 6/4) duripan, dark yellowish brown (10YR 4/4) moist; massive; hard, very firm and brittle when wet; strongly effervescent with disseminated lime; moderately alkaline (pH 8.0); abrupt wavy boundary. (6 to 8 inches thick)
3C1--39 to 45 inches; pale brown (10YR 6/3) sand, dark grayish brown (10YR 4/2) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; many very fine interstitial pores; moderately alkaline (pH 8.0); clear wavy boundary. (5 to 7 inches thick)
3C2--45 to 60 inches; light brownish gray (10YR 6/2) sand, grayish brown (10YR 5/2) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; many very fine interstitial pores; moderately alkaline (pH 8.0).
TYPE LOCATION: Siskiyou County, California; about 1.2 miles north of the town of Macdoel, 0.5 mile west of Highway 97; about 2,100 feet east, 1,200 feet south of the northwest corner of section 8, T. 46 N., R. 1 W.
RANGE IN CHARACTERISTICS: The thickness of the solum and depth to the duripan ranges from 20 to 40 inches. The mean annual soil temperature ranges from 48 degrees F to 52 degrees F. The soil temperature at a depth of 20 inches is above 41 degrees F from about March 15 to December 1 (255 days) and is above 47 degrees F from about April 15 to November 15 (210 days). The soil between depths of 12 and 36 inches or to the duripan is dry in all parts from June 10 to November 15 (155 days). Moisture control section is dry more than one half the time the soil temperature is greater than 41 degrees F.
The A horizon has dry color of 10YR 6/2 or 6/3 and moist color of 10YR 3/2, 3/3. Reaction ranges from neutral to moderately alkaline. Texture ranges from loamy sand to loamy fine sand. Clay content ranges from 0 to 5 percent.
The B horizon has dry color of 10YR 6/2, 6/3, 6/4, 7/2 and moist color of 10YR 3/3, 4/3, or 4/4. Reaction is mildly alkaline or moderately alkaline. Texture ranges from loamy sand to loamy fine sand. Clay content ranges from 0 to 5 percent.
The duripan ranges from 8 to 12 inches in thickness and has an indurated opal cap with silica and calcium cementation.
The 3C horizon has dry color of 10YR 6/2, 6/3, 6/4, 7/1, 7/2, 7/3, 7/4 and moist color of 10YR 4/2, 4/3, 5/2, 5/3, or 5/4. Reaction is mildly alkaline or moderately alkaline. Clay content ranges from 0 to 2 percent.
COMPETING SERIES: This is the Koehler series in the same family and the Prineville and Taunton series. Koehler soils have an inudrated duripan, and average between 5 to 35 percent lime-silica fragments in the particle-size control section. Prineville and Taunton soils are coarse-loamy.
GEOGRAPHIC SETTING: Poman soils are on alluvial plains. Slopes are 0 to 2 percent. The soils formed in alluvium and lacustrine sediments weathered from extrusive igneous rock. Elevations are 4,035 to 4,300 feet. The climate is semiarid with warm dry summers and cool moist winters. The average annual precipitation is about 10 to 12 inches. Snowfall is 20 to 30 inches. The average annual temperature is about 46 degrees F. The average January temperature is about 28 degrees F and the average July temperature is about 63 degrees F. Frost-free season is about 30 to 50 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Doel (T), Fordney, Modoc, Leavers (T) and Rojo (T) soils. Doel, Leavers and Rojo soils are coarse-loamy. Modoc soils are fine-loamy. Fordney soils are deep.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained, slow runoff; rapid permeability.
USE AND VEGETATION: Cropland, hay and pasture and rangeland. Vegetation is Indian ricegrass, thurber needlegrass, rabbitbrush and big sagebrush.
DISTRIBUTION AND EXTENT: North central California. These soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Siskiyou County, California, Butte Valley-Tule Lake Soil Survey 1984.
REMARKS: Diagnostic horizons and features recognized in the pedon are:
Ochric epipedon: The zone from the surface of the soil to a depth of 10 inches (A1, A2).
Aridic moisture: Zone from 12 inches to the duripan. It is dry throughout (155 days).
Textural control: Zone from a depth of 10 inches to the pan. It has sandy particle-size class.