Soil series profile

Ashkum soil series

Ashkum is a poorly drained soil with a silty clay loam surface, mapped on 592,404 acres in 39 counties across 3 states. Hydrologic group C/D.

#443 by mapped area fine Typic Endoaquolls (Mollisols)

Drainage class
Poorly drained
>99% of mapped acres
Hydrologic group
C/D
99% of mapped acres
Typical topsoil pH
7.0
neutral · range 7.0–7.0
Mapped area
592k
acres in 39 counties, 3 states

Typical Ashkum profile

Texture and pH by depth

Typical Ashkum soil profile by depth 0 in 10 in 20 in 30 in 40 in 50 in 0–12 in · Ap · pH 7.0 · 37% clay Silty clay loam 12–29 in · Bg1 · pH 6.8 · 41% clay Silty clay 29–54 in · 2Bg2 · pH 7.3 · 33% clay Silty clay loam 54–60 in · 2Cg · pH 7.9 · 30% clay Silty clay loam
Depth to scale. More strongly shaded layers hold more clay. Horizon names are the soil survey's (A = topsoil, B = subsoil, C = parent material).
Show as a table
Typical Ashkum horizons (representative values)
Depth Texture pH Clay Sand Organic matter
0–12 in (Ap) Silty clay loam 7.0 37% 8% 5%
12–29 in (Bg1) Silty clay 6.8 41% 8% 1.25%
29–54 in (2Bg2) Silty clay loam 7.3 33% 9% 0.3%
54–60 in (2Cg) Silty clay loam 7.9 30% 9% 0.25%

Representative values from the most extensive Ashkum map unit (Ashkum silty clay loam, 0 to 2 percent slopes, survey area IL105). Other map units of this series vary within the series range.

Hands holding dark garden soil
Stock photo for illustration, not a sample of this soil series. Credit on the Sources & method page.

What this means

What Ashkum soil means for gardens, lawns and septic systems

For gardens

Typical topsoil in Ashkum soils is neutral: pH 7.0, the range most vegetables, flowers and lawn grasses prefer.

Loamy topsoil (loam, silt loam and similar) covers 99% of mapped Ashkum acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (99% of mapped Ashkum acres).

>99% of mapped Ashkum acres is somewhat poorly to very poorly drained, so soil stays soggy for long spells after rain and in wet seasons. Raised beds, plants that tolerate wet feet, and not working the soil while wet all help.

For lawns and yards

On 99% of mapped acres, rain soaks in slowly (hydrologic groups C and D, including dual groups that are D until drained). Expect runoff and puddles after heavy rain: core-aerate compacted lawns and keep ground sloping away from foundations.

A seasonal high water table comes within 18 inches of the surface on >99% of mapped acres, often in spring. Basements, sump pumps and lawns in low spots feel it first.

For a septic system

For conventional septic absorption fields, NRCS rates 99% of the acres in mapped Ashkum soils very limited, 0% somewhat limited and 0% not limited (1% not rated, such as urban land, pits or water).

Where the soil is very limited (slow permeability, a high water table, flooding, shallow bedrock or steep slopes), alternative systems such as mound or sand-filter designs are common and cost more.

Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.

Generated from the mapped numbers above using fixed rules, not a site visit. See how these notes are written.

Where Ashkum soil is found

Mapped acres

Ashkum is mapped in Illinois, Wisconsin and Indiana.

Counties with the most mapped Ashkum soil
County Acres Share of county land
Livingston County, IL 112,826 17.0%
Will County, IL 87,973 16.7%
Vermilion County, IL 63,656 11.2%
Ford County, IL 45,535 14.7%
Cook County, IL 32,989 5.5%
Champaign County, IL 29,231 4.6%
DuPage County, IL 27,507 13.0%
McLean County, IL 25,199 3.3%
Racine County, WI 23,985 11.3%
Grundy County, IL 21,817 8.3%
Lake County, IL 21,186 7.6%
Kankakee County, IL 20,567 4.8%
Kenosha County, WI 18,598 10.8%
Iroquois County, IL 12,258 1.7%
LaSalle County, IL 7,643 1.1%
Milwaukee County, WI 6,995 4.5%
Waukesha County, WI 5,643 1.6%
Kane County, IL 5,320 1.6%
McHenry County, IL 5,314 1.5%
Fond du Lac County, WI 4,417 1.0%
Lake County, IN 3,562 1.1%
Benton County, IN 3,480 1.4%
Porter County, IN 1,671 0.6%
Kendall County, IL 1,427 0.7%
Washington County, WI 1,095 0.4%
Ozaukee County, WI 822 0.6%
LaPorte County, IN 411 0.1%
Warren County, IN 378 0.2%
Jasper County, IN 185 0.1%
White County, IN 179 0.1%
Woodford County, IL 174 0.1%
Winnebago County, IL 121 0.0%
Ogle County, IL 52 0.0%
St. Joseph County, IN 47 0.0%
Boone County, IL 44 0.0%
Bureau County, IL 37 0.0%
Marshall County, IL 22 0.0%
Piatt County, IL 22 0.0%
Putnam County, IL 14 0.0%

Septic absorption fields

NRCS rating, share of Ashkum acres

Not limited 0%
Somewhat limited 0%
Very limited 99%
Not rated 1%
Septic tank absorption field rating across mapped Ashkum acres. Scale 0 to 100% of mapped land.
Show as a table
Septic tank absorption field rating across mapped Ashkum acres.
CategoryShare of acres
Not limited0.0%
Somewhat limited0.0%
Very limited98.8%
Not rated1.2%

Drainage, water table and flooding

Share of Ashkum acres

Depth to seasonal high water table
About 6 inches (median where reported); within 18 inches on >99% of acres.
Flooding
Not mapped as flooding on most acres.
Slope
Typically 0–0% (median 0%).
Topsoil organic matter
Median 5%.

Drainage class

Excessively drained 0%
Somewhat excessively drained 0%
Well drained 0%
Moderately well drained 0%
Somewhat poorly drained 0%
Poorly drained >99%
Very poorly drained 0%
Not rated <1%
Drainage class across mapped Ashkum acres. Scale 0 to 100% of mapped land.
Show as a table
Drainage class across mapped Ashkum acres.
CategoryShare of acres
Excessively drained0.0%
Somewhat excessively drained0.0%
Well drained0.0%
Moderately well drained0.0%
Somewhat poorly drained0.0%
Poorly drained99.9%
Very poorly drained0.0%
Not rated0.1%

Hydrologic soil group

A: fast infiltration (mostly sandy or gravelly) 0%
B: moderate infiltration 0%
C: slow infiltration 0%
D: very slow infiltration (clayey, shallow or wet) 0%
A/D: D as is, A if drained 0%
B/D: D as is, B if drained 0%
C/D: D as is, C if drained 99%
Not rated 1%
Hydrologic soil group across mapped Ashkum acres. Scale 0 to 100% of mapped land.
Show as a table
Hydrologic soil group across mapped Ashkum acres.
CategoryShare of acres
A: fast infiltration (mostly sandy or gravelly)0.0%
B: moderate infiltration0.0%
C: slow infiltration0.0%
D: very slow infiltration (clayey, shallow or wet)0.0%
A/D: D as is, A if drained0.0%
B/D: D as is, B if drained0.0%
C/D: D as is, C if drained98.8%
Not rated1.2%

Sources & data dates

Source
USDA NRCS Soil Survey Geographic Database (SSURGO), queried through Soil Data Access. Public domain.
Data date
SSURGO as published on November 3, 2026 (most recent survey area update October 26, 2026). NRCS refreshes SSURGO each October.
Scope
All map unit components named Ashkum (component kind "Series") in SSURGO: 592,404 acres.
Method
Shares are by mapped acres of Ashkum components. The profile comes from the single largest Ashkum component. Full methodology.

Independent reference site. No government affiliation or endorsement.

Full narrative description: USDA Official Soil Series Description for Ashkum.