LOCATION NISHNA IA+MN NEEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, mesic Vertic Endoaquolls
TYPICAL PEDON: Nishna silty clay, with a slope of less than 1 percent, on flood plain, at elevation of about 960 feet above mean sea level, in a cultivated field. (All colors are for moist soil unless otherwise stated.)
Ap--0 to 18 centimeters; black (10YR 2/1) silty clay, very dark gray (10YR 3/1) dry; moderate medium subangular blocky structure parting to weak fine granular; friable; very few silt coats of grayish brown (10YR 5/2) dry; many roots; many pores; neutral; clear smooth boundary.
A1--18 to 41 centimeters; black (N 2/0) silty clay, very dark gray (N 3/0) dry; moderate fine subangular blocky structure; firm; sheen on faces of peds; many roots; many fine pores; slightly effervescent; slightly alkaline; clear smooth boundary.
A2--41 to 66 centimeters; black (10YR 2/1) silty clay, very dark gray (10YR 3/1) dry; moderate medium and fine subangular blocky structure; firm; few roots; few fine pores; gray lime flecks and small lime concretions; slightly effervescent; moderately alkaline; clear smooth boundary. (Combined thickness of the A horizon is 46 to 76 centimeters.)
Bkg--66 to 91 centimeters; very dark gray (N 3/0) silty clay, dark gray (N 4/0) dry; moderate fine subangular blocky structure; firm; few roots; few fine pores; many soft and hard small lime accumulations; slightly effervescent; moderately alkaline; clear smooth boundary. (15 to 56 centimeters thick)
Cg--91 to 152 centimeters; dark gray (5Y 4/1) silty clay; very weak fine subangular blocky structure grading to massive; firm; few fine roots; few fine pores; many soft and hard lime accumulations; strongly effervescent; moderately alkaline.
TYPE LOCATION: Major Land Resource Area (MLRA) 107 - Iowa and Missouri Deep Loess Hills; Fremont County, Iowa subset; about 1 1/2 miles west and 1 mile north of Randolph; located about 1,320 feet east and 1,320 feet north of the southwest corner of section 5, T. 70 N., R. 41 W.; USGS Tabor NE topographic quadrangle; lat. 40 degrees 53 minutes 30 seconds N. and long. 95 degrees 35 minutes 23 seconds W., NAD 83.
RANGE IN CHARACTERISTICS: The mollic epipedon commonly is 60 to 91 centimeters thick, but it ranges to more than 152 centimeters thick. The content of sand typically is about 5 percent or less, but pedons with up to 15 percent sand are within the range. Typically, the soil is slightly alkaline or moderately alkaline and has carbonates throughout, except the Ap horizon is leached of carbonates and is neutral in many pedons. The 25 to 100 centimeter particle-size control section averages between 38 and 46 percent clay. Some pedons have snail shell fragments from the surface to depths of 70 centimeters.
The A horizon typically has hue of 10YR or is neutral, value of 2 or 3, and chroma of 0 or 1. It is silty clay loam or silty clay with 36 to 44 percent clay.
Overwash phases are recognized in some pedons and are silt loam with 20 to 27 percent clay.
In most pedons the Bkg horizon is weakly expressed. It has hue of 10YR, 5Y or is neutral, value of 3 and chroma of 0 or 1. It contains 38 to 46 percent clay.
The Cg horizon has value of 4, and chroma of 0 or 1. In some pedons redoximorphic features with high value and chroma are present below a depth of 91 centimeters.
COMPETING SERIES: These are the Knoke soils in the same family. Other closely related soils are Clamo, Okoboji, Shiloh, Wabash, Zoe and Zook soils. Knoke soils contain more than 15 percent sand in the particle size control section. Clamo, Okoboji, Shiloh, Wabash, Zoe, and Zook do not have calcic horizons and are not in the calcareous family class. In addition, Clamo and Zoe soils are in areas that have less than 660 millimeters of precipitation. Okoboji and Shiloh soils do not have secondary carbonation in upper 1/3 of the series control section. Wabash soils average more than 46 percent clay in the particle size control section.
GEOGRAPHIC SETTING: Nishna soils are on low, flat (backswamp) low flood plains and often are some distance from the main stream channel. Slope gradients typically are 1 percent or less. Slope ranges from 0 to 2 percent. These soils formed in alluvial sediments low in sand content (less than 15 percent). They lack silt or sand stratification above a depth of 1.2 meters. Mean annual air temperature is about 7 to 13 degrees C. Mean annual precipitation ranges from 660 to 860 millimeters. Frost-free period ranges from 160 to 185 days. Elevation ranges from 290 to 335 meters above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bremer, Calco, Colo, Nevin, Nodaway and Zook soils. Nishna soils typically are on lower elevations and wetter than all but the Calco soils. Bremer and Nevin soils are noncalcareous; and, in addition, the Nevin soils have thinner A horizons and are lower in clay. Nodaway soils are coarser textured, lighter colored, and are stratified.
DRAINAGE AND PERMEABILITY: Poorly drained and very poorly drained; runoff is slow. Runoff accumulates on this soil from adjacent soils. Permeability is slow. Depth to the seasonal high water table is 0 to 30 centimeters for poorly drained soils and +30 centimeters for very poorly drained soils.
USE AND VEGETATION: Native vegetation was sedges and swamp grasses. Corn and soybeans are the principal crops when adequate drainage is possible. Some small grain and hay is also grown.
DISTRIBUTION AND EXTENT: MLRA 107 (Iowa and Missouri Deep Loess Hills), MLRA 103 (Central Iowa and Minnesota Till Plains), and MLRA 106 (Nebraska and Kansas Loess-Drift Hills); along the Missouri River and Minnesota River tributaries. These soils are moderately extensive.
MLRA OFFICE RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Fremont County, Iowa, 1974.
REMARKS: Diagnostic horizons and features recognized in this pedon include: mollic epipedon--the zone from the surface to a depth of 91 centimeters (Ap, A1, A2 and Bkg horizons); Aquic moisture regime.