Soil series profile
Keomah soil series
Keomah is a somewhat poorly drained soil with a silt loam surface, mapped on 301,119 acres in 63 counties across 2 states. Hydrologic group C/D.
- Drainage class
- Somewhat poorly drained 100% of mapped acres
- Hydrologic group
- C/D >99% of mapped acres
- Typical topsoil pH
- 6.5 slightly acidic · range 6.2–7.2
- Mapped area
- 301k acres in 63 counties, 2 states
Typical Keomah profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–6 in (Ap) | Silt loam | 6.5 | 16% | 4% | 2% |
| 6–13 in (E) | Silt loam | 5.7 | 20% | 4% | 0.65% |
| 13–28 in (Bt) | Silty clay loam | 5.2 | 38% | 2% | 0.5% |
| 28–48 in (Btg) | Silty clay loam | 6.0 | 35% | 1% | 0.3% |
| 48–60 in (Cg) | Silt loam | 6.5 | 24% | 3% | 0.1% |

What this means
What Keomah soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Keomah soils is slightly acidic: pH 6.5 (most land between 6.2 and 7.2), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers >99% of mapped Keomah acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (>99% of mapped Keomah acres).
100% of mapped Keomah 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 100% 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 Keomah soils very limited, 0% somewhat limited and 0% not limited.
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.
Where Keomah soil is found
Mapped acres
Keomah is mapped in Illinois and Iowa. The 60 counties with the most Keomah acres:
| County | Acres | Share of county land |
|---|---|---|
| Adams County, IL | 28,700 | 5.5% |
| Schuyler County, IL | 25,731 | 9.5% |
| Macoupin County, IL | 23,310 | 4.2% |
| Fulton County, IL | 22,342 | 4.2% |
| Peoria County, IL | 21,904 | 5.7% |
| Greene County, IL | 19,926 | 5.8% |
| McDonough County, IL | 18,790 | 5.0% |
| Hancock County, IL | 17,904 | 3.6% |
| Brown County, IL | 16,687 | 8.8% |
| Woodford County, IL | 9,718 | 2.9% |
| Sangamon County, IL | 9,675 | 1.8% |
| Morgan County, IL | 8,600 | 2.4% |
| Des Moines County, IA | 7,733 | 2.9% |
| Knox County, IL | 6,524 | 1.4% |
| Christian County, IL | 4,737 | 1.0% |
| Logan County, IL | 4,729 | 1.2% |
| Scott County, IL | 4,469 | 2.9% |
| Lee County, IA | 4,384 | 1.3% |
| Cass County, IL | 3,340 | 1.4% |
| Marshall County, IL | 3,241 | 1.3% |
| Pike County, IL | 3,143 | 0.6% |
| De Witt County, IL | 3,076 | 1.2% |
| Warren County, IL | 2,650 | 0.8% |
| Menard County, IL | 2,572 | 1.3% |
| Vermilion County, IL | 2,164 | 0.4% |
| Louisa County, IA | 2,137 | 0.8% |
| Stark County, IL | 2,001 | 1.1% |
| McLean County, IL | 1,903 | 0.3% |
| Washington County, IA | 1,821 | 0.5% |
| Mercer County, IL | 1,792 | 0.5% |
| Henry County, IA | 1,744 | 0.6% |
| Rock Island County, IL | 1,728 | 0.7% |
| Jersey County, IL | 1,721 | 0.7% |
| Tazewell County, IL | 1,498 | 0.4% |
| Stephenson County, IL | 1,117 | 0.3% |
| Henry County, IL | 1,038 | 0.2% |
| Ogle County, IL | 863 | 0.2% |
| Bureau County, IL | 785 | 0.1% |
| Jo Daviess County, IL | 695 | 0.2% |
| Jefferson County, IA | 694 | 0.2% |
| Whiteside County, IL | 518 | 0.1% |
| Keokuk County, IA | 513 | 0.1% |
| Henderson County, IL | 362 | 0.2% |
| Carroll County, IL | 346 | 0.1% |
| Winnebago County, IL | 318 | 0.1% |
| Lee County, IL | 200 | 0.0% |
| Iowa County, IA | 187 | 0.1% |
| Putnam County, IL | 181 | 0.2% |
| Mahaska County, IA | 165 | 0.0% |
| Johnson County, IA | 105 | 0.0% |
| Marion County, IA | 101 | 0.0% |
| Mason County, IL | 100 | 0.0% |
| Madison County, IA | 89 | 0.0% |
| Boone County, IL | 74 | 0.0% |
| LaSalle County, IL | 71 | 0.0% |
| Van Buren County, IA | 59 | 0.0% |
| Wapello County, IA | 38 | 0.0% |
| Warren County, IA | 30 | 0.0% |
| Dallas County, IA | 30 | 0.0% |
| Davis County, IA | 18 | 0.0% |
Septic absorption fields
NRCS rating, share of Keomah acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 99.9% |
| Not rated | 0.1% |
Drainage, water table and flooding
Share of Keomah acres
- Depth to seasonal high water table
- About 1.2 feet (14 in) (median where reported); within 18 inches on 100% of acres.
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 1–4% (median 1%).
- Topsoil organic matter
- Median 2%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 0.0% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 100.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 0.0% |
| C: slow infiltration | 0.0% |
| D: very slow infiltration (clayey, shallow or wet) | 0.0% |
| A/D: D as is, A if drained | 0.0% |
| B/D: D as is, B if drained | 0.0% |
| C/D: D as is, C if drained | 99.9% |
| Not rated | 0.1% |
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 Keomah (component kind "Series") in SSURGO: 301,119 acres.
- Method
- Shares are by mapped acres of Keomah components. The profile comes from the single largest Keomah component. Full methodology.