Soil series profile
Knox soil series
Knox is a well drained soil with a silt loam surface, mapped on 270,031 acres in 27 counties across 3 states. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B 66% of mapped acres
- Typical topsoil pH
- 6.5 slightly acidic · range 5.6–6.5
- Mapped area
- 270k acres in 27 counties, 3 states
Typical Knox profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–6 in (Ap) | Silt loam | 6.5 | 23% | 4% | 2% |
| 6–36 in (Bt) | Silty clay loam | 6.5 | 30% | 4% | 0.75% |
| 36–60 in (C) | Silt loam | 6.7 | 23% | 4% | 0.25% |
What this means
What Knox soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Knox soils is slightly acidic: pH 6.5 (most land between 5.6 and 6.5), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Knox acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (94% of mapped Knox acres).
100% of mapped Knox acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
Most land is in hydrologic groups B and C, where rain soaks in at a moderate pace.
For a septic system
For conventional septic absorption fields, NRCS rates 42% of the acres in mapped Knox soils very limited, 58% somewhat limited and 0% not limited.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Knox soil is found
Mapped acres
Knox is mapped in Missouri, Kansas and Iowa.
| County | Acres | Share of county land |
|---|---|---|
| Buchanan County, MO | 35,993 | 13.8% |
| Lafayette County, MO | 33,138 | 8.2% |
| Andrew County, MO | 22,295 | 8.0% |
| Jackson County, MO | 21,248 | 5.5% |
| Wyandotte County, KS | 20,151 | 20.8% |
| Platte County, MO | 19,988 | 7.4% |
| Saline County, MO | 16,722 | 3.5% |
| Clay County, MO | 16,030 | 6.3% |
| Ray County, MO | 12,070 | 3.3% |
| Holt County, MO | 10,574 | 3.6% |
| Doniphan County, KS | 10,513 | 4.2% |
| Leavenworth County, KS | 10,329 | 3.5% |
| Carroll County, MO | 10,189 | 2.3% |
| Atchison County, KS | 9,547 | 3.5% |
| Cooper County, MO | 6,432 | 1.8% |
| Howard County, MO | 4,738 | 1.6% |
| Chariton County, MO | 4,024 | 0.8% |
| Crawford County, IA | 1,775 | 0.4% |
| Carroll County, IA | 1,675 | 0.5% |
| Audubon County, IA | 1,652 | 0.6% |
| Fremont County, IA | 450 | 0.1% |
| Pettis County, MO | 378 | 0.1% |
| Brown County, KS | 74 | 0.0% |
| Worth County, MO | 18 | 0.0% |
| Clinton County, MO | 16 | 0.0% |
| Jefferson County, KS | 8 | 0.0% |
| Pottawatomie County, KS | 5 | 0.0% |
Septic absorption fields
NRCS rating, share of Knox acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 57.8% |
| Very limited | 42.2% |
Drainage, water table and flooding
Share of Knox acres
- Depth to seasonal high water table
- About 1.0 feet (12 in) (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 7–23% (median 12%).
- Topsoil organic matter
- Median 2%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 100.0% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 66.3% |
| C: slow infiltration | 33.7% |
| D: very slow infiltration (clayey, shallow or wet) | 0.0% |
| A/D: D as is, A if drained | 0.0% |
| B/D: D as is, B if drained | 0.0% |
| C/D: D as is, C if drained | 0.0% |
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
- All map unit components named Knox (component kind "Series") in SSURGO: 270,031 acres.
- Method
- Shares are by mapped acres of Knox components. The profile comes from the single largest Knox component. Full methodology.