Soil series profile
Armster soil series
Armster is a moderately well drained soil with a silt loam surface, mapped on 209,319 acres in 21 counties across 2 states. Hydrologic group D.
- Drainage class
- Moderately well drained 100% of mapped acres
- Hydrologic group
- D 60% of mapped acres
- Typical topsoil pH
- 6.0 moderately acidic · range 5.5–7.3
- Mapped area
- 209k acres in 21 counties, 2 states
Typical Armster profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–6 in (Ap) | Silt loam | 7.3 | 19% | 23% | 2.4% |
| 6–11 in (2Bt1) | Clay loam | 5.3 | 37% | 22% | 1.2% |
| 11–31 in (2Bt2) | Clay | 5.1 | 44% | 17% | 0.51% |
| 31–79 in (2Btg) | Clay loam | 6.3 | 37% | 25% | 0.2% |
What this means
What Armster soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Armster soils is moderately acidic: pH 6.0 (most land between 5.5 and 7.3). Many vegetables grow well here, and some gardens benefit from a little lime. Test before adding any.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Armster acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (33% of mapped Armster acres).
100% of mapped Armster acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 100% of mapped acres, 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.
For a septic system
For conventional septic absorption fields, NRCS rates 100% of the acres in mapped Armster soils very limited, 0% 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.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Armster soil is found
Mapped acres
Armster is mapped in Missouri and Kansas.
| County | Acres | Share of county land |
|---|---|---|
| Carroll County, MO | 30,270 | 6.8% |
| Montgomery County, MO | 28,074 | 8.2% |
| Caldwell County, MO | 25,872 | 9.4% |
| Ray County, MO | 24,221 | 6.7% |
| Clay County, MO | 18,857 | 7.4% |
| Atchison County, KS | 16,908 | 6.1% |
| St. Charles County, MO | 15,746 | 4.4% |
| Platte County, MO | 12,643 | 4.7% |
| Warren County, MO | 11,516 | 4.2% |
| Leavenworth County, KS | 9,367 | 3.2% |
| Callaway County, MO | 7,471 | 1.4% |
| Wyandotte County, KS | 5,150 | 5.3% |
| Buchanan County, MO | 1,305 | 0.5% |
| Clinton County, MO | 635 | 0.2% |
| Cass County, MO | 585 | 0.1% |
| Doniphan County, KS | 392 | 0.2% |
| Daviess County, MO | 220 | 0.1% |
| DeKalb County, MO | 54 | 0.0% |
| Jefferson County, KS | 27 | 0.0% |
| Worth County, MO | 5 | 0.0% |
| Audrain County, MO | 1 | 0.0% |
Septic absorption fields
NRCS rating, share of Armster acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 100.0% |
Drainage, water table and flooding
Share of Armster acres
- Depth to seasonal high water table
- About 2.9 feet (35 in) (median where reported); within 18 inches on <1% of acres.
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 4–12% (median 7%).
- 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 | 0.0% |
| Moderately well drained | 100.0% |
| 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 | 0.0% |
| C: slow infiltration | 40.1% |
| D: very slow infiltration (clayey, shallow or wet) | 59.6% |
| 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 | 0.3% |
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
- All map unit components named Armster (component kind "Series") in SSURGO: 209,319 acres.
- Method
- Shares are by mapped acres of Armster components. The profile comes from the single largest Armster component. Full methodology.