State soil summary
Soil types in Iowa
The most widespread soil series in Iowa are Fayette, Colo, Nicollet. Pick a county below, or enter a ZIP code for the county you live in.
- Well or moderately well drained
- 55% of mapped land
- Typical topsoil pH
- 6.3 slightly acidic · most land 5.8–7.0
- Septic fields very limited
- 91% 0% not limited
- Subject to flooding
- 15% of land, any frequency
Iowa counties
5 county reports, by population
| County | Most common soil | Well drained | Topsoil pH | Septic very limited |
|---|---|---|---|---|
| Polk County | Clarion | 48% | 6.5 | 66% |
| Linn County | Kenyon | 59% | 6.4 | 91% |
| Scott County | Tama | 63% | 6.5 | 93% |
| Johnson County | Fayette | 66% | 6.3 | 99% |
| Black Hawk County | Kenyon | 45% | 6.4 | 93% |
What this means
What Iowa soils mean for gardens, lawns and septic systems
For gardens
Typical topsoil in Iowa is slightly acidic: pH 6.3 (most land between 5.8 and 7.0), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 97% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (35% of the land).
45% of the land 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 83% 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 43% of the land, often in spring. Basements, sump pumps and lawns in low spots feel it first.
For septic systems
For conventional septic absorption fields, NRCS rates 91% of the land in Iowa very limited, 8% 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.
Flooding is mapped on 15% of the land (10% occasional, 2% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Statewide mix
Share of all mapped land
Drainage
Show as a table
| Category | Share of land |
|---|---|
| Excessively drained | 1.2% |
| Somewhat excessively drained | 0.7% |
| Well drained | 35.5% |
| Moderately well drained | 17.2% |
| Somewhat poorly drained | 19.9% |
| Poorly drained | 21.9% |
| Very poorly drained | 2.7% |
| Not rated | 0.9% |
Septic absorption fields
Show as a table
| Category | Share of land |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 8.0% |
| Very limited | 91.2% |
| Not rated | 0.8% |
Topsoil pH
Show as a table
| Category | Share of land |
|---|---|
| Strongly acidic (below 5.5) | 0.3% |
| Moderately to slightly acidic (5.5–6.4) | 52.6% |
| Near neutral (6.5–7.3) | 37.3% |
| Alkaline (7.4 and up) | 8.6% |
| Not reported | 1.2% |
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
- Iowa: 35,622,783 acres of mapped land in 99 counties, pooled (not an average of county figures).
- 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.