LOCATION LENNEP MT

Established Series
Rev. JCM/SHB
01/2023

LENNEP SERIES

The Lennep series consists of deep, well drained soils that formed in alluvium, eolian deposits or residuum weathered from shale. These soils are nearly level to moderately sloping and are mainly on fans, terraces and foot slopes. The mean annual precipitation is about 14 inches, and the mean annual air temperature is 45 degrees F.

TAXONOMIC CLASS: Fine, smectitic, frigid Glossic Vertic Natrustolls

TYPICAL PEDON: Lennep loam, grassland. (Colors are for dry soil unless otherwise noted.)

A2--0 to 2 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; moderate medium platy structure; soft, friable, nonsticky and slightly plastic; many very fine roots; clean silt and sand grains coating the tops of plates; neutral; clear smooth boundary. (2 to 4 inches thick)

AB--2 to 4 inches; grayish brown (10YR 5/2) light silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium platy structure; hard, friable, sticky and plastic; common very fine roots; many very fine pores; clear silt and sand grains coating peds; mildly alkaline; clear wavy boundary. (1 to 3 inches thick)

BA--4 to 8 inches; grayish brown (10YR 5/2) heavy silty clay loam, very dark grayish brown (10YR 3/2) moist; strong medium prismatic structure that separates to moderate thick plates; hard, firm, very sticky and plastic; common very fine roots; many very fine tubular pores; thin patchy clay films on surfaces of peds with thick coatings of clean silt and sand on faces of prisms; mildly alkaline; clear smooth boundary. (3 to 6 inches thick)

B21t--8 to 12 inches; dark grayish brown (10YR 4/2) light clay, dark brown (10YR 3/3) moist; strong medium prismatic structure that separates to strong medium and fine blocks; very hard, very firm, very sticky and very plastic; few very fine roots; common very fine tubular pores; thin continuous clay film on surfaces of peds; mildly alkaline; gradual wavy boundary.

B22t--12 to 16 inches; grayish brown (2.5Y 5/2) clay, olive brown (2.5Y 4/3) moist; strong coarse prismatic structure that separates to strong coarse blocks; extremely hard, very firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; thin continuous clay film on surfaces of peds and coating rims and walls of pores; strongly alkaline; gradual wavy boundary.

B23t--16 to 23 inches; light olive brown (2.5Y 5/3) heavy clay, olive brown (2.5Y 4/3) moist; strong coarse prismatic structure that separates to strong coarse blocks; extremely hard, extremely firm, very sticky and extremely plastic; few very fine roots; few very fine tubular pores; continuous clay film on faces of peds; fine pores partly closed by clayflow; strongly alkaline; clear wavy boundary. (B2t horizon is 6 to 18 inches thick)

B3cacs--23 to 27 inches; light yellowish brown (2.5Y 6/3) clay, light olive brown (2.5Y 5/3) moist; weak coarse blocky structure; extremely hard, very firm, very sticky and very plastic; few very fine roots between blocks; few very fine tubular pores; moderately calcareous; many seams and threads of gypsum crystals and common masses of segregated lime; strongly alkaline; clear wavy boundary. (2 to 6 inches thick)

C1cacs--27 to 32 inches; light yellowish brown (2.5Y 6/3) light clay, light olive brown (2.5Y 5/3) moist; massive; very hard, very firm, very sticky and very plastic; few very fine roots; few very fine tubular pores; strongly calcareous; many seams and threads of gypsum and common lime masses; strongly alkaline; clear wavy boundary.

C2cacs--32 to 41 inches; pale yellow (2.5Y 7/3) heavy silty clay, light yellowish brown (2.5Y 6/3) moist; massive; very hard, firm, sticky and very plastic; strongly calcareous; common crystals of gypsum and mottles of segregated lime; strongly alkaline; clear wavy boundary. (Ccacs horizon is 10 to 20 inches thick)

C3--41 to 73 inches; pale yellow (2.5Y 7/3) heavy silty clay, light yellowish brown (2.5Y 6/3) moist; massive; very hard, firm, sticky and plastic; strongly calcareous; strongly alkaline; few masses of segregated lime.

TYPE LOCATION: Big Horn County, Montana; 600 feet north and 2,100 feet east of the SW corner of sec. 18, T.4S., R.34E.

RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 43 degrees to 46 degrees F. The noncalcareous portion of the solum is 12 to 26 inches thick. The mollic epipedon is 7 to 14 inches thick, and includes the upper part of the argillic horizon. The hue for the whole soil is 10YR through 5Y.

The A2 horizon has value of 5 or 6 dry, 3 or 4 moist and value of 2 or 3. Some pedons lack the thin A2 on the surface and have A1 horizons with granular structure and do not have coatings of clean sand and silt grains on faces of peds.

The A&B horizon has chroma of 2 or 3. Clean sand and silt grains may give crushed soil color value of one-half to one unit lighter. It is loam, clay loam, or silty clay loam. Some pedons lack an A&B horizon but have an A12 horizon that has weak or medium prismatic structure. Some pedons have clean sand and silt coatings on faces of prisms. Some pedons lack a B&A horizon but have a B1t horizon with blocky or prismatic structure with thick coatings of sand and silt grains on vertical faces of peds.

The B2t horizon has value of 4 or 5 dry, 3 through 5 moist, and chroma of 2 or 3. It is clay or silty clay and has 45 to 60 percent clay. The estimated exchangeable sodium ranges from 7 to 10 percent in the upper part to more than 15 percent in the lower part. The structure is medium or strong prismatic and the reaction ranges from mildly to strongly alkaline. Some pedons have thick coatings of silt and sand on the vertical faces of peds in the upper part of the horizon. The B3 horizon has value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 or 3. It is clay or silty clay. Some pedons lack gypsum or other salt crystals in this horizon.

The C horizon ranges from sandy clay loam through clay. Some pedons lack gypsum crystals in the upper part of the C horizon. Some pedons have shale at depths of 40 to 60 inches. The estimated exchangeable sodium is 15 to 25 percent.

COMPETING SERIES: These are the Belfield series in the same family and the related Beckton and Post series. Beckton soils have a mean annual soil temperature of 47 degrees to 59 degrees F. Belfield soils have 35 to 45 percent clay in the argillic horizon. Post soils have more than 60 percent clay in the argillic horizon.

GEOGRAPHIC SETTING: Lennep soils are nearly level to moderate sloping and are on fans, terraces, foot slopes and mantled uplands at elevations of 2,200 to 4,300 feet. They formed in deep water transported sediment or eolian deposits of clay, clay loam and silty clay loam or deep residuum of these textures over shale. Average annual precipitation is 11 to 18 inches, most of which falls in spring and early summer. Mean annual temperature ranges from 40 degrees to 46 degrees F. The (32 degrees F.) growing season is 105 to 135 days.

ASSOCIATED SOILS: These are the Adger, Wyola and Shook soils. Adger soils lack thick coatings of clean sand and silt on the upper part of the argillic horizon. Wyola and Shook soils lack a natric horizon.

DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.

USE AND VEGETATION: Used for dryland farming, irrigated cropland and for range. The major crops for dryland farming are small grains. The native vegetation is green needlegrass, needle-and-thread grass, prairie junegrass and big sagebrush.

DISTRIBUTION AND EXTENT: Widely distributed throughout Montana where it is moderately extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Salina, Kansas

SERIES ESTABLISHED: Big Horn County (Big Horn Area), Montana, 1970.

REMARKS: Lennep soils were formerly classified as Solodized-Solonetz soils.

OSED scanned by SSQA. Last revised by state on 1/75.

National Cooperative Soil Survey
U.S.A.