County soil summary
Soil types in Johnson County, Kansas
The most widespread soils are Chillicothe, Woodson and Oska; the most common drainage class is moderately well drained (46% of the land), and typical topsoil pH is 6.1.
- Well or moderately well drained
- 73% of land · state 90%
- Typical topsoil pH
- 6.1 slightly acidic · state 6.5
- Septic fields very limited
- 95% of land · state 77%
- Subject to flooding
- 10% of land, any frequency · state 13%
Most common soils in Johnson County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 67% of the mapped land; 53 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Chillicothe | 15.1% | Moderately well drained | 6.1 |
| Woodson | 13.7% | Somewhat poorly drained | 5.9 |
| Oska | 10.1% | Well drained | 6.1 |
| Martin | 8.2% | Moderately well drained | 6.1 |
| Sharpsburg | 6.2% | Moderately well drained | 6.2 |
| Grundy | 4.8% | Somewhat poorly drained | 6.4 |
| Kennebec | 4.7% | Moderately well drained | 6.2 |
| Vinland | 4.6% | Somewhat excessively drained | 6.7 |
What this means
What the soils in Johnson County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Johnson County is slightly acidic: pH 6.1 (most land between 5.9 and 6.7), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 93% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (56% of the land).
73% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
On 90% 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 29% 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 95% of the land in Johnson County very limited, <1% somewhat limited and 0% not limited (5% not rated, such as urban land, pits or water).
Statewide, 77% of the land is very limited, so Johnson County is more 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 10% of the land (6% occasional, 3% 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 (46%). 73% of the land is moderately well drained or better, compared with 90% across Kansas.
Show as a table
| Category | Johnson County | Kansas |
|---|---|---|
| Excessively drained | 0.1% | 1.5% |
| Somewhat excessively drained | 9.2% | 4.1% |
| Well drained | 17.8% | 66.3% |
| Moderately well drained | 46.4% | 18.3% |
| Somewhat poorly drained | 20.4% | 7.1% |
| Poorly drained | 0.9% | 2.0% |
| Very poorly drained | 0.0% | 0.0% |
| Not rated | 5.3% | 0.7% |
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 | Johnson County | Kansas |
|---|---|---|
| Not limited | 0.0% | 0.9% |
| Somewhat limited | 0.4% | 21.4% |
| Very limited | 94.9% | 76.8% |
| Not rated | 4.7% | 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 | Johnson County | Kansas |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.1% | 6.3% |
| B: moderate infiltration | 4.1% | 24.6% |
| C: slow infiltration | 21.0% | 38.5% |
| D: very slow infiltration (clayey, shallow or wet) | 56.8% | 26.5% |
| A/D: D as is, A if drained | 0.0% | 0.2% |
| B/D: D as is, B if drained | 0.1% | 0.1% |
| C/D: D as is, C if drained | 12.6% | 2.9% |
| Not rated | 5.3% | 1.0% |
Flooding
Show as a table
| Category | Johnson County | Kansas |
|---|---|---|
| No flooding | 84.6% | 86.2% |
| Rare or very rare | 1.6% | 4.8% |
| Occasional | 5.8% | 6.3% |
| Frequent or very frequent | 3.0% | 2.3% |
| Not reported | 5.1% | 0.5% |
Seasonal high water table
Show as a table
| Category | Johnson County | Kansas |
|---|---|---|
| Within 18 inches at some time of year | 28.9% | 7.9% |
| 18 inches to 3.3 feet | 27.5% | 10.1% |
| Deeper than 3.3 feet or none reported | 41.8% | 81.6% |
| Not reported | 1.8% | 0.4% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 6.1 (slightly acidic); 80% of rated land falls between 5.9 and 6.7. Median topsoil organic matter is 3%.
Show as a table
| Category | Johnson County | Kansas |
|---|---|---|
| Strongly acidic (below 5.5) | 0.0% | 0.8% |
| Moderately to slightly acidic (5.5–6.4) | 74.7% | 41.0% |
| Near neutral (6.5–7.3) | 16.6% | 31.7% |
| Alkaline (7.4 and up) | 3.3% | 25.2% |
| Not reported | 5.3% | 1.2% |
Texture
Show as a table
| Category | Johnson County | Kansas |
|---|---|---|
| Sandy | 0.1% | 5.8% |
| Loamy (loam, silt loam and similar) | 93.2% | 89.0% |
| Clayey (40%+ clay) | 1.4% | 3.9% |
| Organic (muck or peat) | 0.0% | 0.0% |
| Not reported (rock, urban land, etc.) | 5.3% | 1.3% |
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
- Johnson County, Kansas (FIPS 20091): 303,972 acres of mapped land, 3,094 acres of open water excluded. State comparisons pool all mapped land in Kansas.
- 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.