LOCATION ROUND BUTTE MTEstablished Series
TAXONOMIC CLASS: Fine, illitic, frigid Typic Natrixeralfs
TYPICAL PEDON: Round Butte silty clay loam, cultivated (colors are for dry soil unless otherwise noted).
Ap--0 to 7 inches; light brownish gray (10YR 6/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; weak thick platy structure; very hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine tubular pores; many clear unstained sand grains; neutral (pH 6.7); abrupt wavy boundary. (4 to 10 inches thick)
Btn1--7 to 11 inches; pale brown (10YR 6/3) clay, brown (10YR 5/3) moist; strong medium prismatic structure parting to strong medium subangular blocky; very hard, firm, sticky and very plastic; many very fine and fine roots along faces of peds; common very fine and fine tubular pores; continuous moderately thick brown (10YR 4/3) clay films on faces of peds and in pores; few thick very dark grayish brown (10YR 3/2) organic films on faces of peds; moderately alkaline (pH 7.9); gradual wavy boundary.
Btn2--11 to 14 inches; light yellowish brown (10YR 6/4) clay, brown (10YR 5/3) moist; weak coarse prismatic structure parting to moderate medium subangular blocky; very hard, firm, sticky and very plastic; many fine roots along faces of peds; few very fine and fine tubular pores; common moderately thick dark grayish brown (10YR 4/2) clay films on faces of peds and in pores; few moderately thick very dark brown (10YR 2/2) organic film on faces of peds; slightly effervescent; moderately alkaline (pH 8.1); clear wavy boundary. (Bt Horizons are 6 to 15 inches thick)
Bkn--14 to 21 inches; very pale brown (10YR 7/3) silty clay, brown (10YR 5/3) moist; massive; 1/8- to 1/4-inch thick weathered varves; very hard, firm, sticky and very plastic; few fine roots in widely spaced vertical cracks; few very fine and fine pores; strongly effervescent with disseminated and common soft medium lime masses and common fine seams of line between varves; strongly alkaline (pH 8.6); gradual wavy boundary. (5 to 8 inches thick)
C1--21 to 44 inches; very pale brown (10YR 7/3) silty clay, brown (10YR 5/3) moist; massive; 1/4- to 1/2-inch thick, unweathered varves; very hard, firm, sticky and very plastic; alternating varves of very pale brown (10YR 7/3) clay and white (10YR 8/2) silt loam; few fine and very fine roots in widely spaced vertical cracks; slightly effervescent; strongly alkaline (pH 8.8); abrupt smooth boundary. (12 to 21 inches thick)
C2--44 to 60 inches; very pale brown (10YR 7/3) alternating thick strata of silty clay and silt, brown (10YR 5/3) moist; massive; alternating strata of 1/4- to 1/2-inch thick unweathered varves of silty clay and 8-inch thick varves of silt; hard and soft, firm, very friable, sticky and nonsticky and very plastic and nonplastic; slightly effervescent; very strongly alkaline (pH 9.3)
TYPE LOCATION: Lake County, Montana; 1,430 feet west and 500 feet north of the SE corner of sec. 27, T. 22 N., R. 21 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches; dry in all parts more than half the time (cumulative) during April through September and never moist in some or all parts for as long as 90 consecutive days during May through August.
Depth to Bkn horizon - 10 to 20 inches.
Depth to varves - weathered, 10 to 20 inches; unweathered, 15 to 30 inches.
Ap horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 3, 4, or 5 moist
Chroma: 2 or 3
Texture: silty clay loam or silt loam
Clay content: 22 to 35 percent
EC: 0 to 2 mmhos/cm
SAR: 3 to 13
Reaction: pH 6.6 to 9.6
Btn1 horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay, silty clay, or silty clay loam
Clay content: 35 to 60 percent
EC: 0 to 4 mmhos/cm
SAR: 13 to 40
Reaction: pH 7.9 to 9.6
Btn2 horizon - Hue: 10YR or 2.5Y
Value: 6, or 7 dry; 4 or 5 moist
Chroma: 3 or 4
Texture: clay, silty clay, or silty clay loam
Clay content: 35 to 60 percent
EC: 0 to 4 mmhos/cm
SAR: 13 to 60
Reaction: pH 7.9 to 9.6
Bkn horizon - Hue: 10YR or 2.5Y
Value: 7 or 8 dry; 5 or 6 moist
Chroma: 3 or 4
Texture: clay, silty clay or silty clay loam
Clay content: 35 to 55 percent
Calcium Carbonate equivalent: 8 to 15 percent
EC: 0 to 4 mmhos/cm
SAR: 13 to 60
Reaction: pH 7.9 to 9.6
C1 horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3 or 4
Texture: clay, silty clay , or silty clay loam
Clay content: 35 to 55 percent
EC: 0 to 4 mmhos/cm
SAR: 13 to 60
Reaction: pH 7.9 to 9.6
C2 horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3 or 4
Texture: strata of silty clay and clay varves and strata of silt and silt loam
Clay content: 30 to 50 percent--35 to 55 percent clay in the varved strata; 5 to 12 percent clay in the silt strata
EC: 0 to 4 mmhos/cm
SAR: 13 to 60
Reaction: pH 7.9 to 9.6
COMPETING SERIES:
Esteslake (MT) - have EC greater than 8 mmhos/cm throughout; have SARs greater than 40 above a depth of 11 inches; depth to unweathered varves is greater than 40 inches.
GEOGRAPHIC SETTING:
Landform - alluvial fans, stream terraces, and lake plains and terraces.
Elevation - 2,500 to 3,000 feet.
Slope- 0 to 15 percent.
Parent material - strongly alkaline lacustrine or glaciolacustrine deposits.
Climate - long, cold winter; moist springs; warm, dry summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual temperature - 40 to 45 degrees F.
Frost-free period - 105 to 130 days.
DRAINAGE AND PERMEABILITY: Well drained; very slow permeability.
USE AND VEGETATION: Round Butte soils are used mainly for irrigated crops, dryland crops, pastureland, and rangeland. Potential native vegetation is bluebunch wheatgrass, western wheatgrass, green needlegrass, and sedges.
DISTRIBUTION AND EXTENT: Round Butte soils are of moderate extent in the mountain valleys of northwestern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lake County, Montana, 1929 soils report "Soil Survey of the Lower Flathead Valley Area Montana."
REMARKS: Soil interpretations records: MT0423; MT9051. Laboratory Data: S65MT-047-001; S65MT-47-2; S65MT-47-8. Memo dated May 8, 1969, Lincoln Lab assignment of illitic mineralogy. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 7 inches (Ap horizon); a natric horizon from 7 to 21 inches (Btn1, Btn2 and Bkn horizons). a particle-size control section from 7 to 14 inches (Btn1 and Btn2 horizons). Round Butte soils have a frigid temperature regime and a xeric moisture regime bordering on aridic.