LOCATION CONNAH MT
Established Series
Rev. BDD-JAL-KLS
03/2023
CONNAH SERIES
The Connah series consists of very deep, well drained soils that formed in till derived from glaciolacustrine deposits. These soils are on till plains. Slopes are 0 to 8 percent. Mean annual precipitation is about 510 mm, and mean annual air temperature is about 6 degrees C.
TAXONOMIC CLASS: Fine, illitic, frigid Typic Haploxeralfs
TYPICAL PEDON: Connah silt loam, forested (colors are for dry soil unless otherwise noted).
Oi--0 to 3 cm; undecomposed needles and twigs.
E--3 to 21 cm; very pale brown (10YR 7/3) silt loam, pale brown (10YR 6/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium roots; many very fine and fine tubular pores; 5 percent cobbles, 5 percent gravel; moderately acid (pH 5.6); clear wavy boundary. (15 to 25 cm thick)
Bt/E--21 to 39 cm; B part (70 percent) is light yellowish brown (10YR 6/4) silty clay, brown (10YR 5/3) moist; E part (30 percent) is very pale brown (10YR 7/3) silty clay loam, pale brown (10YR 6/3) moist that interfingers into the B part; color mixed is yellowish brown (10YR 5/4) moist; moderate medium subangular blocky structure; hard, firm, sticky and plastic; many fine and medium roots; many very fine and fine tubular pores; 5 percent cobbles, 5 percent gravel; moderately acid (pH 5.6); clear wavy boundary. (15 to 28 cm thick)
Bt1--39 to 67 cm; light brown (7.5YR 6/4) clay, brown (7.5YR 5/4) moist; weak coarse prismatic structure parting to strong medium subangular blocky; very hard, firm, sticky and plastic; common fine roots; many fine and common medium pores; many continuous distinct clay films in tubular pores and on faces of peds; 5 percent cobbles, 5 percent gravel; moderately acid (pH 5.6); gradual wavy boundary.
Bt2--67 to 90 cm; light brown (7.5YR 6/4) clay, brown (7.5YR 5/4) moist; moderate medium subangular blocky structure; very hard, firm, sticky and plastic; common fine roots; many fine pores and common very fine tubular pores; few distinct clay films in tubular pores and on faces of peds; 5 percent cobbles, 5 percent gravel; neutral (pH 6.8); gradual wavy boundary. (Combined thickness of Bt1, Bt2 horizons - 40 to 55 cm thick)
Bk--90 to 123 cm; light gray (10YR 7/2) silty clay, yellowish brown (10YR 5/4) moist; weak medium subangular blocky structure; hard, firm, sticky and plastic; few fine roots; few very fine tubular pores; common fine soft threads and seams of lime; strongly effervescent; 5 percent cobbles, 5 percent gravel; slightly alkaline (pH 7.8); gradual wavy boundary. (25 to 41 cm thick)
C--123 to 156 cm; very pale brown (10YR 7/3) silty clay, pale brown (10YR 6/3)) moist; massive; hard, firm, sticky and plastic; few fine roots; strongly effervescent; 5 percent cobbles, 5 percent gravel; slightly alkaline (pH 7.8).
TYPE LOCATION: Lake County, Montana; about 395 meters east and 120 meters south of the NW corner of sec. 4, T. l9 N., R. 19 W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature--7 to 8 degrees C
Soil moisture control section--between 10 and 30 cm
Depth to Bk horizon--70 to 100 cm
Some pedons have a thin dark colored A horizon that when mixed to a depth of 18 cm will not meet the requirements for a mollic epipedon.
Particle-size control section:
Clay content--40 to 60 percent
Rock fragment content--0 to 10 percent
E horizon
Value--6 or 7 dry; 5 or 6 moist
Chroma--2 or 3
Texture--silt loam or silty clay loam
Clay content--10 to 35 percent
Rock fragment content--0 to 20 percent--0 to 10 percent cobbles and stones, 0 to 10 percent gravel
Reaction--pH 5.6 to 6.5
Bt/E horizon
Value--B part 5 or 6, E part 6 or 7 dry; B part 4 or 5, E part 4, 5, or 6 moist
Chroma--B part 3 through 5; E part 3 or 4
Texture--B part silty clay or clay; E part silty clay loam or silt loam
Clay content--B part 40 to 50 percent; E part 30 to 40 percent; mixed 35 to 45 percent
Rock fragment content--0 to 10 percent total; 0 to 5 percent cobbles, 0 to 5 percent gravel
Reaction--pH 5.6 to 6.5
Bt horizon
Hue--7.5YR or 10YR
Value--5 or 6 dry; 4 or 5 moist
Chroma--3 or 4
Texture--clay or silty clay
Clay content--40 to 60 percent
Rock fragment gravel--0 to 10 percent--0 to 5 percent cobbles, 0 to 5 percent gravel
Reaction--pH 5.6 to 7.3
Bk horizon
Hue--7.5YR or 10YR
Value--6 or 7 dry; 5 or 6 moist
Chroma--2, 3, or 4
Texture--silty clay or silty clay loam
Clay content--30 to 50 percent
Rock fragment content--0 to 10 percent total; 0 to 5 percent cobbles, 0 to 5 percent gravel
Calcium carbonate equivalent--5 to 15 percent
Reaction--pH 7.4 to 8.4
C horizon
Hue--10YR or 7.5YR
Value--6 or 7 dry; 5 or 6 moist
Chroma--3 or 4
Texture--silty clay loam or silty clay
Clay content--30 to 50 percent
Rock fragment content--0 to 10 percent total; 0 to 5 percent cobbles, 0 to 5 percent gravel
Reaction--pH 7.4 to 8.4
COMPETING SERIES:
Grassvalley (MT) - has a horizon of secondary carbonate accumulation above a depth of 70 cm; does not have a mixed Bt/E horizon.
GEOGRAPHIC SETTING:
Landform--till plains
Elevation--910 to 1075 meters
Slope--0 to 8 percent
Parent material--till derived from glaciolacustrine deposits
Climate--long, cold winters; moist springs; warm, dry summers
Mean annual precipitation--460 to 560 mm
Mean annual air temperature--6 to 7 degrees C
Frost-free period--90 to 105 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained, slow permeability.
USE AND VEGETATION: Connah soils are used mainly for irrigated and nonirrigated crops, pastureland, and timber production. Principal crops are wheat, barley, and alfalfa hay. The potential native vegetation is ponderosa pine and Douglas-fir with an understory of common snowberry, pinegrass, and woods rose.
DISTRIBUTION AND EXTENT: Connah soils are of small extent in the valleys of western Montana; MLRA 44A.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lake County, Montana, 1991; proposed Lake County, Montana, l986. Formerly called Crow series in the 1929, "The Lower Flathead Valley Area, Montana" soil survey.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon--3 to 21 cm (E horizon)
Argillic horizon--21 to 90 cm (Bt/E, Bt1, and Bt2 horizons)
Horizon of secondary calcium carbonate accumulation--90 to 123 cm (Bk horizon)
Particle-size control section--21 to 71 cm (Bt/E, Bt1 horizons and part of the Bt2 horizon)
Connah soils have a frigid temperature regime and a xeric soil moisture regime bordering on ustic.
Converted to metric and O horizons were updated to start at zero. Competing series section was not updated. 01/2023
ADDITIONAL DATA: Soil Interpretation Record: MT1014. August 19, 1985 (RP85-MT104), mineralogy of Bt2 of the S65MT-047-024-9, soil survey laboratory memorandum No. 1, Beltsville, Maryland 1952 profiles 13 and 14.
National Cooperative Soil Survey
U.S.A.