County soil summary
Soil types in Clay County, Missouri
The most widespread soils are Sharpsburg, Armster and Macksburg; the most common drainage class is moderately well drained (47% of the land), and typical topsoil pH is 6.5.
- Well or moderately well drained
- 63% of land · state 67%
- Typical topsoil pH
- 6.5 slightly acidic · state 6.0
- Septic fields very limited
- 91% of land · state 93%
- Subject to flooding
- 21% of land, any frequency · state 20%
Most common soils in Clay County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 62% of the mapped land; 56 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Sharpsburg | 13.4% | Moderately well drained | 6.2 |
| SharpsburgGeneral soil group, not a named series | 9.4% | — | — |
| Armster | 7.4% | Moderately well drained | 6.0 |
| LagondaGeneral soil group, not a named series | 7.1% | — | — |
| Macksburg | 6.4% | Somewhat poorly drained | 5.9 |
| Knox | 6.3% | Well drained | 6.5 |
| Nodaway | 6.0% | Moderately well drained | 6.7 |
| Ladoga | 5.8% | Moderately well drained | 6.6 |
What this means
What the soils in Clay County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Clay County is slightly acidic: pH 6.5 (most land between 5.9 and 7.3), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 90% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (62% of the land).
63% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
On 80% 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 21% 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 Clay County very limited, 4% somewhat limited and 0% not limited (5% not rated, such as urban land, pits or water).
That is close to the state as a whole (93% 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 21% of the land (18% occasional, 2% 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 moderately well drained (47%). 63% of the land is moderately well drained or better, compared with 67% across Missouri.
Show as a table
| Category | Clay County | Missouri |
|---|---|---|
| Excessively drained | 0.0% | 1.0% |
| Somewhat excessively drained | 0.0% | 7.9% |
| Well drained | 16.0% | 29.2% |
| Moderately well drained | 46.7% | 28.8% |
| Somewhat poorly drained | 25.1% | 18.1% |
| Poorly drained | 6.0% | 13.0% |
| Very poorly drained | 0.5% | 0.6% |
| Not rated | 5.8% | 1.5% |
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 | Clay County | Missouri |
|---|---|---|
| Not limited | 0.0% | 0.0% |
| Somewhat limited | 4.1% | 6.1% |
| Very limited | 91.0% | 92.9% |
| Not rated | 4.9% | 1.0% |
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 | Clay County | Missouri |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% | 3.8% |
| B: moderate infiltration | 14.2% | 15.7% |
| C: slow infiltration | 35.7% | 27.6% |
| D: very slow infiltration (clayey, shallow or wet) | 18.2% | 31.2% |
| A/D: D as is, A if drained | 0.0% | 0.0% |
| B/D: D as is, B if drained | 0.1% | 2.9% |
| C/D: D as is, C if drained | 26.0% | 17.2% |
| Not rated | 5.8% | 1.6% |
Flooding
Show as a table
| Category | Clay County | Missouri |
|---|---|---|
| No flooding | 79.1% | 80.2% |
| Rare or very rare | 1.3% | 4.1% |
| Occasional | 17.5% | 9.4% |
| Frequent or very frequent | 1.9% | 6.1% |
| Not reported | 0.2% | 0.2% |
Seasonal high water table
Show as a table
| Category | Clay County | Missouri |
|---|---|---|
| Within 18 inches at some time of year | 20.7% | 27.8% |
| 18 inches to 3.3 feet | 25.5% | 29.2% |
| Deeper than 3.3 feet or none reported | 53.9% | 42.9% |
| Not reported | 0.0% | 0.1% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 6.5 (slightly acidic); 80% of rated land falls between 5.9 and 7.3. Median topsoil organic matter is 2.8%.
Show as a table
| Category | Clay County | Missouri |
|---|---|---|
| Strongly acidic (below 5.5) | 0.0% | 22.1% |
| Moderately to slightly acidic (5.5–6.4) | 42.1% | 45.6% |
| Near neutral (6.5–7.3) | 45.8% | 28.6% |
| Alkaline (7.4 and up) | 6.3% | 2.1% |
| Not reported | 5.8% | 1.6% |
Texture
Show as a table
| Category | Clay County | Missouri |
|---|---|---|
| Sandy | 0.0% | 1.0% |
| Loamy (loam, silt loam and similar) | 90.0% | 94.6% |
| Clayey (40%+ clay) | 4.2% | 2.8% |
| Organic (muck or peat) | 0.0% | 0.0% |
| Not reported (rock, urban land, etc.) | 5.8% | 1.6% |
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
- Clay County, Missouri (FIPS 29047): 254,088 acres of mapped land, 7,403 acres of open water excluded. State comparisons pool all mapped land in Missouri.
- 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.