LOCATION FRANKLIN IAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Udollic Endoaqualfs
TYPICAL PEDON: Franklin silt loam, on a slope of about 1 percent, in a cultivated field. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 15 centimeters; black (10YR 2/1) silt loam, very dark gray (10YR 3/1) dry; weak fine subangular blocky structure; friable; neutral; abrupt smooth boundary. (15 to 23 centimeters thick)
E--15 to 33 centimeters; dark grayish brown (10YR 4/2) silt loam; weak fine subangular blocky structure; friable; strongly acid; clear smooth boundary. (10 to 20 centimeters thick)
Bt1--33 to 46 centimeters; dark grayish brown (2.5Y 4/2) silty clay loam; weak fine subangular blocky structure; friable; few distinct very dark grayish brown (10YR 3/2) organoargillans on all faces of peds; common fine distinct yellowish brown (10YR 5/4) masses of oxidized iron on faces of peds; moderately acid; gradual smooth boundary.
Bt2--46 to 71 centimeters; dark grayish brown (2.5Y 4/2) and grayish brown (2.5Y 5/2) silty clay loam; moderate fine subangular blocky structure; friable; few distinct very dark grayish brown (10YR 3/2) organoargillans on all faces of peds; moderately acid; abrupt smooth boundary. (Combined thickness of the Bt horizon is 20 to 60 centimeters thick.)
2Bt3--71 to 94 centimeters; yellowish brown (10YR 5/6) and light brownish gray (2.5Y 6/2) loam; moderate medium prismatic structure; firm; common distinct very dark grayish brown (10YR 3/2) organoargillans on all faces of peds; pebble band at 71 centimeters; about 2 percent rock fragments; moderately acid; gradual wavy boundary. (15 to 40 centimeters thick)
2Bw--94 to 117 centimeters; yellowish brown (10YR 5/6) loam; moderate coarse prismatic structure; firm; few fine prominent black (10YR 2/1) manganese masses; many fine prominent gray (10YR 5/1) iron depletions; about 5 percent rock fragments; moderately acid; gradual wavy boundary. (0 to 30 centimeters thick)
2BC1--117 to 173 centimeters; light olive brown (2.5Y 5/6) loam; moderate coarse prismatic structure; firm; few fine prominent black (10YR 2/1) manganese masses; common fine prominent light brownish gray (2.5Y 6/2) iron depletions; about 5 percent rock fragments; neutral; gradual wavy boundary.
2BC2--173 to 203 centimeters; yellowish brown (10YR 5/6) loam; moderate coarse prismatic structure dissected by few oblique fractures; firm; few fine prominent grayish brown (2.5Y 5/2) iron depletions; strongly effervescent; about 5 percent rock fragments; moderately alkaline.
TYPE LOCATION: Major Land Resource Area (MLRA) 104-Eastern Iowa and Minnesota Till Prairies, Linn County, Iowa subset; located about 4 miles south of Alburnett; located about 240 feet west and 1,450 feet south of the northeast corner of section 14, T. 84 N., R. 7 W.; USGS Marion topographic quadrangle; lat. 42 degrees 5 minutes 26 seconds N. and long. 91 degrees 37 seconds 12 minutes W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to till--50 to 100 centimeters
Depth to carbonates--more than 120 centimeters
Clay content of the particle-size control section (weighted average)--27 to 35 percent
Sand content of the particle-size control section (weighted average)--10 to 15 percent
Special feature--some pedons have a stone line or thin layer, 2 to 13 centimeters thick, of gravelly and sandy materials at the base of the silty sediments
A or Ap horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silt loam
Clay content--15 to 25 percent
Sand content--less than 10 percent
Reaction--moderately acid to neutral
E horizon:
Hue--10YR
Value--3 to 5
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--15 to 30 percent
Sand content--less than 10 percent
Reaction--strongly acid to slightly acid
BE, EB, or Bt horizon:
Hue--10YR or 2.5Y
Value--4 or 5
Chroma--2 to 4
Texture--silty clay loam
Clay content--28 to 35 percent
Sand content--10 to 20 percent
Reaction--strongly acid to slightly acid
2Bt and 2Bw (when present) horizon:
Hue--7.5YR, 10YR, or 2.5Y
Value--4 to 6
Chroma--2 to 8
Texture--loam, clay loam, or sandy clay loam
Clay content--20 to 35 percent
Sand content--40 to 65 percent
Reaction--moderately acid to neutral
Rock fragment content--2 to 12 percent
2BC and 2C (when present) horizon:
Hue--7.5YR to 2.5Y
Value--4 to 6
Chroma--1 to 8
Texture--loam
Clay content--18 to 27 percent, mean of 22 percent
Sand content--35 to 50 percent, mean of 44 percent
Reaction--slightly acid to moderately alkaline
Rock fragment content--2 to 12 percent
Moist bulk density--1.75 to 1.9 g/cc
COMPETING SERIES: These are the
Atterberry,
Bethalto,
Canoe,
Curran,
Emery,
Koszta,
Millbrook,
Mulvey,
Virgil, and
Wauconda series.
Atterberry--have a sand content of less than 7 percent in the lower third of the series control section
Bethalto--have a sand content of less than 7 percent in the lower third of the series control section
Canoe--have a sand content of 10 to 20 percent in the lower third of the series control section
Curran--have a sand content of more than 70 percent in the lower third of the series control section
Emery--have a rock fragment content of less than 1 percent in the lower third of the series control section
Koszta--have a sand content of less than 15 percent in the lower third of the series control section
Millbrook--have a moist bulk density of less than 1.75 g/cc in the lower third of the series control section
Mulvey--have a sand content of more than 75 percent in the lower third of the series control section
Virgil--have a moist bulk density of less than 1.75 g/cc in the lower third of the series control section
Wauconda--have carbonates within a depth of 100 centimeters
GEOGRAPHIC SETTING:
Parent material--50 to 100 centimeters of loess and the underlying till
Landform--interfluves, head slopes, and side slopes on dissected till plains
Slope--0 to 5 percent
Elevation--155 to 400 meters above sea level
Mean annual air temperature--7 to 11 degrees C
Mean annual precipitation--735 to 965 millimeters
Frost-free period--160 to 205 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Aredale,
Kenyon,
Maxfield, and
Olin soils.
Aredale--are on lower landscape positions on convex side slopes and have a sand content that averages 25 to 45 percent in particle-size control section
Kenyon--are on lower landscape positions on interfluves and side slopes and have a sand content that averages 30 to 70 percent in particle-size control section
Maxfield--are on lower landscape positions on interfluves and head slopes of broad, shallow drainageways and are frequently saturated from the soil surface to a depth of 0.3 meters during the wettest periods of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation
Olin--are on landscape positions similar to those of the Franklin series and have a sand content that averages 60 to 85 percent in particle-size control section
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs at a depth between 0.3 and 1 meter during the wettest periods of years when precipitation is within one standard deviation of the 30 year mean of annual precipitation, this saturation is considered and both perched and apparent and can occur on this soil based on the season and intensity of rainfall during a given period of time
Saturated hydraulic conductivity--1.0 to 10 micrometers per second in the loess and 0.01 to 1.0 micrometers per second in the till
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, and legume hay. The native vegetation is big bluestem, little bluestem, switchgrass, other grasses of the tall grass prairie and mixed deciduous trees.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic section--Dissected till plains
MLRAs--Eastern Iowa and Minnesota Till Prairies (104) and Illinois and Iowa Deep Loess and Drift, West-Central Part (108C)
Local physiographic area--Iowa Erosion Surface
LRR M; northeastern Iowa
Extent--moderately extensive
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Bremer County, Iowa, 1965.
REMARKS:
Particle-size control section--the zone from a depth of 33 to 83 centimeters;
series control section--the zone from the surface to a depth of 150 centimeters.
Diagnostic horizons and features recognized in this pedon include:
ochric epipedon--the zone from the surface to a depth of 33 centimeters (Ap and E horizons);
argillic horizon--the zone from a depth of 33 to 94 centimeters (Bt1, Bt2 and 2Bt3 horizons;
aquic moisture regime.
Some question exists as to whether the Franklin soils meet the saturation requirements for Aqualfs, but until further study is made it seems best to classify them as Aqualfs on the basis of morphology. Some evidence indicates that that proportion of montmorillonite in the loess decreases from Iowa to Indiana and illite increases in proportion.
Classification to the fine-silty particle-size family is questionable. Further study is needed to resolve this issue.
Cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Some pedons have vertical seams or wedges of sand or loamy sand about 5 to 15 centimeters wide and about 0.9 to 1.2 meters deep extending downward from the stone line into the till.
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.