County soil summary
Soil types in Linn County, Iowa
The most widespread soils are Kenyon, Fayette and Clyde; the most common drainage class is well drained (30% of the land), and typical topsoil pH is 6.4.
- Well or moderately well drained
- 59% of land · state 55%
- Typical topsoil pH
- 6.4 slightly acidic · state 6.3
- Septic fields very limited
- 91% of land · state 91%
- Subject to flooding
- 14% of land, any frequency · state 15%
Most common soils in Linn County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 46% of the mapped land; 89 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Kenyon | 8.8% | Moderately well drained | 5.8 |
| Fayette | 8.5% | Well drained | 6.2 |
| Clyde | 6.2% | Poorly drained | 6.7 |
| Dinsdale | 5.6% | Moderately well drained | 6.4 |
| Dickinson | 5.0% | Well drained | 6.5 |
| Sparta | 4.4% | Excessively drained | 6.2 |
| Floyd | 3.9% | Somewhat poorly drained | 6.7 |
| Klinger | 3.7% | Somewhat poorly drained | 6.2 |
What this means
What the soils in Linn County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Linn County is slightly acidic: pH 6.4 (most land between 5.8 and 6.7), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 89% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (33% of the land).
For your lawn and yard
On 73% 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 38% 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 91% of the land in Linn County very limited, 6% somewhat limited and 0% not limited (3% not rated, such as urban land, pits or water).
That is close to the state as a whole (91% very 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 14% of the land (5% occasional, 4% 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 well drained (30%). 59% of the land is moderately well drained or better, compared with 55% across Iowa.
Show as a table
| Category | Linn County | Iowa |
|---|---|---|
| Excessively drained | 8.1% | 1.2% |
| Somewhat excessively drained | 1.2% | 0.7% |
| Well drained | 30.4% | 35.5% |
| Moderately well drained | 19.6% | 17.2% |
| Somewhat poorly drained | 23.6% | 19.9% |
| Poorly drained | 13.7% | 21.9% |
| Very poorly drained | 0.6% | 2.7% |
| Not rated | 2.7% | 0.9% |
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 | Linn County | Iowa |
|---|---|---|
| Not limited | 0.0% | 0.0% |
| Somewhat limited | 6.1% | 8.0% |
| Very limited | 91.1% | 91.2% |
| Not rated | 2.9% | 0.8% |
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 | Linn County | Iowa |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 14.9% | 2.4% |
| B: moderate infiltration | 9.3% | 13.2% |
| C: slow infiltration | 34.4% | 36.9% |
| D: very slow infiltration (clayey, shallow or wet) | 1.2% | 11.4% |
| A/D: D as is, A if drained | 0.1% | 0.2% |
| B/D: D as is, B if drained | 11.2% | 4.9% |
| C/D: D as is, C if drained | 25.9% | 30.0% |
| Not rated | 2.9% | 1.0% |
Flooding
Show as a table
| Category | Linn County | Iowa |
|---|---|---|
| No flooding | 85.4% | 84.5% |
| Rare or very rare | 4.4% | 3.2% |
| Occasional | 4.9% | 9.8% |
| Frequent or very frequent | 4.3% | 2.2% |
| Not reported | 1.1% | 0.3% |
Seasonal high water table
Show as a table
| Category | Linn County | Iowa |
|---|---|---|
| Within 18 inches at some time of year | 37.9% | 43.3% |
| 18 inches to 3.3 feet | 0.0% | 6.5% |
| Deeper than 3.3 feet or none reported | 61.0% | 49.9% |
| Not reported | 1.1% | 0.3% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 6.4 (slightly acidic); 80% of rated land falls between 5.8 and 6.7. Median topsoil organic matter is 3.2%.
Show as a table
| Category | Linn County | Iowa |
|---|---|---|
| Strongly acidic (below 5.5) | 0.4% | 0.3% |
| Moderately to slightly acidic (5.5–6.4) | 54.6% | 52.6% |
| Near neutral (6.5–7.3) | 41.6% | 37.3% |
| Alkaline (7.4 and up) | 0.0% | 8.6% |
| Not reported | 3.4% | 1.2% |
Texture
Show as a table
| Category | Linn County | Iowa |
|---|---|---|
| Sandy | 7.9% | 1.1% |
| Loamy (loam, silt loam and similar) | 88.6% | 96.5% |
| Clayey (40%+ clay) | 0.0% | 1.1% |
| Organic (muck or peat) | 0.5% | 0.3% |
| Not reported (rock, urban land, etc.) | 2.9% | 1.0% |
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
- Linn County, Iowa (FIPS 19113): 457,783 acres of mapped land, 5,917 acres of open water excluded. State comparisons pool all mapped land in Iowa.
- 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.