County soil summary
Soil types in Marion County, Indiana
The most widespread soils are Miami, Brookston and Treaty; the most common drainage class is somewhat poorly drained (22% of the land), and typical topsoil pH is 6.5.
- Well or moderately well drained
- 34% of land · state 52%
- Typical topsoil pH
- 6.5 slightly acidic · state 6.3
- Septic fields very limited
- 67% of land · state 92%
- Subject to flooding
- 8% of land, any frequency · state 10%
Most common soils in Marion County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 85% of the mapped land; 27 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Urban landLand type, not a soil series | 26.6% | — | — |
| CrosbyGeneral soil group, not a named series | 18.2% | — | — |
| Miami | 12.9% | Moderately well drained | 6.5 |
| Brookston | 7.8% | Poorly drained | 6.5 |
| Treaty | 5.8% | Poorly drained | 6.5 |
| Udorthents, Cut and filledGeneral soil group, not a named series | 5.5% | — | — |
| Fox | 5.1% | Well drained | 6.2 |
| Gessie | 3.3% | Well drained | 7.9 |
What this means
What the soils in Marion County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Marion County 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 67% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (45% of the land).
For your lawn and yard
On 56% of the land, 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 40% of the land, 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 67% of the land in Marion County very limited, 0% somewhat limited and 0% not limited (33% not rated, such as urban land, pits or water).
Statewide, 92% of the land is very limited, so Marion County is less restrictive than typical.
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.
Flooding is mapped on 8% of the land (<1% occasional, 8% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Drainage
How long the soil stays wet
The most common drainage class is somewhat poorly drained (22%). 34% of the land is moderately well drained or better, compared with 52% across Indiana.
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| Excessively drained | 0.0% | 1.3% |
| Somewhat excessively drained | 0.0% | 2.0% |
| Well drained | 18.9% | 29.6% |
| Moderately well drained | 15.2% | 18.8% |
| Somewhat poorly drained | 22.1% | 22.4% |
| Poorly drained | 15.3% | 16.6% |
| Very poorly drained | 1.1% | 6.9% |
| Not rated | 27.3% | 2.3% |
Septic absorption fields
NRCS rating for conventional drain fields
The rating looks at the soil from 24 to 60 inches deep: permeability, depth to a seasonal water table or bedrock, flooding and slope. “Very limited” means at least one feature is unfavorable enough that a conventional field is hard to make work.
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| Not limited | 0.0% | 0.1% |
| Somewhat limited | 0.0% | 5.2% |
| Very limited | 67.1% | 91.7% |
| Not rated | 32.8% | 3.1% |
Rain, runoff and water table
Hydrologic soil group, flooding, seasonal water table
Hydrologic soil group
How fast rain soaks in when the soil is already wet. Group A soaks in fastest, D slowest.
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.1% | 5.5% |
| B: moderate infiltration | 11.4% | 15.9% |
| C: slow infiltration | 14.8% | 17.6% |
| D: very slow infiltration (clayey, shallow or wet) | 0.2% | 9.5% |
| A/D: D as is, A if drained | 0.5% | 5.0% |
| B/D: D as is, B if drained | 17.6% | 21.2% |
| C/D: D as is, C if drained | 22.6% | 22.0% |
| Not rated | 32.8% | 3.3% |
Flooding
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| No flooding | 60.1% | 87.8% |
| Rare or very rare | 0.0% | 1.0% |
| Occasional | 0.2% | 2.1% |
| Frequent or very frequent | 7.5% | 6.9% |
| Not reported | 32.2% | 2.2% |
Seasonal high water table
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| Within 18 inches at some time of year | 40.1% | 53.6% |
| 18 inches to 3.3 feet | 13.7% | 12.7% |
| Deeper than 3.3 feet or none reported | 14.3% | 32.3% |
| Not reported | 32.0% | 1.4% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 6.5 (slightly acidic); 80% of rated land falls between 6.2 and 7.2. Median topsoil organic matter is 2.5%.
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| Strongly acidic (below 5.5) | 0.9% | 6.2% |
| Moderately to slightly acidic (5.5–6.4) | 11.6% | 50.7% |
| Near neutral (6.5–7.3) | 54.6% | 37.9% |
| Alkaline (7.4 and up) | 0.1% | 0.9% |
| Not reported | 32.8% | 4.3% |
Texture
Show as a table
| Category | Marion County | Indiana |
|---|---|---|
| Sandy | 0.0% | 7.6% |
| Loamy (loam, silt loam and similar) | 67.2% | 86.2% |
| Clayey (40%+ clay) | 0.0% | 1.6% |
| Organic (muck or peat) | 0.0% | 1.5% |
| Not reported (rock, urban land, etc.) | 32.8% | 3.1% |
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
- Marion County, Indiana (FIPS 18097): 248,221 acres of mapped land, 7,603 acres of open water excluded. State comparisons pool all mapped land in Indiana.
- Method
- Shares are by mapped land area: each map unit’s acres in the county times each soil component’s percentage. Open water is excluded. Topsoil values use the first mineral horizon of each component. Full methodology.