LOCATION KNIFFIN IA
Established Series
Rev. JDH-JES-TWN
04/2011
KNIFFIN SERIES
The Kniffin series consists of very deep, somewhat poorly drained soils formed in loess. These soils are on summits of interfluves, side slopes, and treads on stream terraces. Slope ranges from 2 to 9 percent. Mean annual air temperature is about 11 degrees C. Mean annual precipitation is about 950 millimeters.
TAXONOMIC CLASS: Fine, smectitic, mesic Vertic Epiaqualfs
TYPICAL PEDON: Kniffin silt loam, on a convex slope of 3 percent, in a hayfield. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 23 centimeters; very dark grayish brown (10YR 3/2) silt loam, dark grayish brown (10YR 4/2) dry; weak fine subangular blocky structure parting to weak fine granular; friable; many medium roots; many fine tubular pores; common distinct very dark brown (10YR 2/2) organic stains on all faces of peds; moderately acid; abrupt smooth boundary.
E--23 to 36 centimeters; dark grayish brown (10YR 4/2) silt loam, grayish brown (10YR 5/2) dry; weak thick platy structure parting to moderate medium granular; friable; many medium roots; common fine tubular pores; few distinct very dark grayish brown (10YR 3/2) organic stains on all faces of peds; moderately acid; clear smooth boundary. (Combined thickness of the A and E horizons is 13 to 40 centimeters.)
Btg1--36 to 48 centimeters; about 50 percent grayish brown (10YR 5/2) and about 50 percent brown (10YR 5/3) silty clay loam; moderate fine subangular blocky structure; friable; common medium roots; common fine tubular pores; few distinct dark gray (10YR 4/1) clay films on all faces of peds; few distinct light gray (10YR 7/2) dry, silt coats on all faces of peds; few fine prominent yellowish brown (10YR 5/6) masses of oxidized iron on all faces of peds; moderately acid; abrupt smooth boundary.
Btg2--48 to 71 centimeters; dark grayish brown (10YR 4/2) silty clay; moderate medium subangular blocky structure; firm; common fine roots; common fine tubular pores; very few distinct dark gray (10YR 4/1) clay films on all faces of peds; few distinct very dark grayish brown (10YR 3/2) organic stains on all faces of peds; common medium prominent yellowish brown (10YR 5/6) masses of oxidized iron; moderately acid; clear smooth boundary.
Btg3--71 to 102 centimeters; grayish brown (10YR 5/2) silty clay; moderate fine angular blocky and subangular blocky structure; firm; common fine roots between peds; few fine tubular pores; common distinct dark gray (10YR 4/1) clay films on all faces of peds; few fine prominent black (N 2.5/0) spherical iron-manganese concretions in matrix; common medium prominent yellowish brown (10YR 5/6) masses of oxidized iron; moderately acid; gradual smooth boundary.
Btg4--102 to 122 centimeters; grayish brown (2.5Y 5/2) silty clay loam; moderate fine angular blocky structure; firm; few fine roots between peds; few fine tubular pores; common distinct gray (2.5Y 5/1) clay films on all faces of peds; few fine prominent black (N 2.5/0) spherical iron-manganese concretions in matrix; common medium prominent brown (7.5YR 4/4) masses of oxidized iron; moderately acid; clear smooth boundary.
Btg5--122 to 152 centimeters; grayish brown (2.5Y 5/2) silty clay loam; weak very fine prismatic structure parting to moderate fine angular blocky; firm; few fine roots between peds; few fine tubular pores; few distinct gray (2.5Y 5/1) clay films on faces of peds; few distinct light gray (10YR 7/2) dry, silt coats on all faces of peds; few medium prominent black (N 2.5/0) spherical iron-manganese concretions in matrix; common medium prominent brown (7.5YR 4/4) masses of oxidized iron; slightly acid; clear smooth boundary.
Btg6--152 to 175 centimeters; grayish brown (2.5Y 5/2) silty clay loam; weak medium prismatic structure; friable; few distinct gray (2.5Y 5/1) clay films on faces of peds; few distinct light gray (10YR 7/2) dry, silt coats on all faces of peds; few medium prominent black (N 2.5/0) spherical iron-manganese concretions in matrix; many medium prominent strong brown (7.5YR 4/6) masses of oxidized iron; slightly acid; gradual smooth boundary. (Combined thickness of the Bt horizons is 50 to 200 centimeters.)
Cg--175 to 200 centimeters; light olive gray 5Y 6/2) silty clay loam; massive; friable; few medium prominent black (N 2.5/0) spherical iron-manganese concretions in matrix; many medium prominent strong brown (7.5YR 4/6) masses of oxidized iron; slightly acid.
TYPE LOCATION: Major Land Resource Area (MLRA) 109-Iowa and Missouri Heavy Till Plain, Wayne County, Iowa subset; about 2 miles south of Confidence; located about 2,475 feet north and 1,381 feet east of the southwest corner of section 35, T. 70 N., R. 20 W.; USGS Confidence topographic quadrangle; lat. 40 degrees 49 minutes 7.8 seconds N. and long. 93 degrees 7 minutes 50.5 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Depth to carbonates--greater than 200 centimeters
Clay content in the particle-size control section (weighted average)--38 to 45 percent
Sand content in the particle-size control section (weighted average)--1 to 4 percent
Special feature--some horizon between the A or Ap horizon and a depth of 75 centimeters has a dominant matrix chroma of more than 2
Ap or A horizon:
Hue--10YR
Value--2 or 3
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--18 to 35 percent
Sand content--less than 5 percent
Reaction--very strongly acid to neutral
E horizon (when present):
Hue--10YR
Value--4 or 5
Chroma--1 or 2
Texture--silt loam or silty clay loam
Clay content--18 to 35 percent
Sand content--less than 5 percent
Reaction--very strongly acid to neutral
In cultivated or eroded areas, the E horizon has been incorporated into the Ap horizon
BE horizon (when present):
Hue--10YR or 2.5Y
Value--4 or 5
Chroma--2 or 3
Texture--silt loam or silty clay loam
Clay content--20 to 35 percent
Sand content--less than 5 percent
Reaction--very strongly acid to neutral
Thickness--0 to 15 centimeters
Btg horizon:
Hue--10YR or 2.5Y
Value--4 to 6
Chroma--2 or 3
Texture--silty clay loam or silty clay
Clay content--30 to 54 percent, at least one subhorizon has a clay content that ranges from 48 to 54 percent
Sand content--1 to 4 percent
Reaction--strongly acid to neutral
Some horizon between the A or Ap horizon and a depth of 75 centimeters has matrix chroma greater than 2 in more than 40 percent of the matrix
Silt coats are commonly oriented as a horizontal band at the top of the Bt horizon
BCg and Cg horizons:
Hue--2.5Y or 5Y
Value--5 or 6
Chroma--1 or 2
Texture--silty clay loam or silt loam
Clay content--22 to 35 percent
Sand content--1 to 4 percent
Reaction--strongly acid to neutral
COMPETING SERIES: These are the
Bucknell,
Gifford,
Kilwinning,
Leonard,
Mexico,
Pershing,
Rathbun,
Rinda,
Shields, and
Stateline series.
Bucknell--have a sand content that averages 15 to 25 percent in the particle-size control section
Gifford--have a sand content of more than 10 percent in the lower third of the series control section
Kilwinning--have a dominant matrix chroma of 2 or less between the bottom of the A or Ap horizon and a depth of 75 centimeters
Leonard--have a dominant matrix chroma of 2 or less between the bottom of the A or Ap horizon and a depth of 75 centimeters
Mexico--have sand content of 4 to 25 percent in the lower half of the series control section
Pershing--do not have a subhorizon within the argillic horizon with a clay content of more than 48 percent
Rathbun--have surface layers that are less than 12 centimeters thick
Rinda--have a dominant matrix chroma of 2 or less between the bottom of the A or Ap horizon and a depth of 75 centimeters
Shields--have carbonates within a depth of 150 centimeters
Stateline--have a sand content of more than 4 percent in the upper third of the series control section
GEOGRAPHIC SETTING:
Parent material--loess
Landform--summits of interfluves, side slopes, and treads on stream terraces
Slope--2 to 9 percent
Elevation--200 to 300 meters above sea level
Mean annual air temperature--9 to 12 degrees C
Mean annual precipitation--865 to 1,040 millimeters
Frost-free period--175 to 210 days
GEOGRAPHICALLY ASSOCIATED SOILS: Near the type location, these are
Armstrong,
Bucknell,
Gara, and
Seymour soils.
Armstrong--are at lower landscape positions and have a sand content that averages 30 to 45 percent in the particle-size control section
Bucknell--are at lower landscape positions and have a sand content that averages 15 to 25 percent in the particle-size control section
Gara--are at lower landscape positions and have a sand content that averages 25 to 45 percent in the particle-size control section
Seymour--are at higher landscape positions and have a mollic epipedon 25 to 46 centimeters thick
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--somewhat poorly drained--a frequently saturated zone occurs within depths of 0.3 to 1.0 meter during March to June in years when precipitation is within one standard deviation of the 30 year mean of annual precipitation, this saturation is considered perched
Saturated hydraulic conductivity--0.01 to 0.10 micrometers per second
USE AND VEGETATION:
Most areas are cultivated. The principal crops are corn, soybeans, small grains, hay, and pasture. A few areas are in woodland. The native vegetation is mixed prairie grasses and deciduous trees.
DISTRIBUTION AND EXTENT:
Physiographic Division--Interior Plains
Physiographic Province--Central Lowland
Physiographic sections--Dissected till plains
MLRA--Iowa and Missouri Heavy Till Plain (109)
LRR M; southern Iowa and northern Missouri
Extent--minor
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Appanoose County, Iowa, 1970.
REMARKS:
Particle-size control section--the zone from a depth of 36 to 86 centimeters;
series control section--the zone from the surface to a depth of 175 centimeters.
Diagnostic horizons and features recognized in the pedon include:
ochric epipedon--the zone from the surface to a depth of 36 centimeters (Ap and E horizons);
argillic horizon--the zone from a depth of 36 to 175 centimeters (Btg1, Btg2, Btg3, Btg4, Btg5, and Btg6 horizons);
aquic moisture regime.
Taxonomy version--Keys to Soil Taxonomy, tenth edition, 2006.
Kniffin soils are the intergrade member of a biosequence that includes the prairie influenced Seymour soils and the forest influenced Rathbun soils.
ADDITIONAL DATA:
Laboratory data--National Soil Survey Laboratory, Lincoln, Nebraska-user pedonid number 69IA007002 (http://ssldata.sc.egov.usda.gov/).
Laboratory data--Iowa State University Lab samples #63958-63966, additional lab data available
National Cooperative Soil Survey
U.S.A.