Soil series profile
Sonsac soil series
Sonsac is a well drained soil with a gravelly silt loam surface, mapped on 238,542 acres in 37 counties across 2 states. Hydrologic group D.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- D 75% of mapped acres
- Typical topsoil pH
- 6.0 moderately acidic · range 5.7–6.1
- Mapped area
- 239k acres in 37 counties, 2 states
Typical Sonsac profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–1 in (Oi) | Slightly decomposed plant material | 4.3 | Not reported | Not reported | 69% |
| 1–3 in (A) | Gravelly silt loam | 6.0 | 22% | 14% | 3% |
| 3–6 in (E) | Very gravelly silt loam | 5.9 | 18% | 22% | 2% |
| 6–10 in (Bt1) | Very gravelly silty clay loam | 6.8 | 27% | 19% | 1.28% |
| 10–32 in (2Bt2) | Very gravelly clay | 7.0 | 74% | 6% | 0.96% |
| 32–79 in (2R) | Bedrock | Not reported | Not reported | Not reported | Not reported |
What this means
What Sonsac soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Sonsac soils is moderately acidic: pH 6.0 (most land between 5.7 and 6.1). 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 Sonsac acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is gravelly silt loam (66% of mapped Sonsac acres).
100% of mapped Sonsac acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 95% 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 Sonsac 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 Sonsac soil is found
Mapped acres
Sonsac is mapped in Missouri and Illinois.
| County | Acres | Share of county land |
|---|---|---|
| Jefferson County, MO | 78,019 | 18.7% |
| Washington County, MO | 64,346 | 13.2% |
| Stone County, MO | 20,703 | 7.0% |
| Crawford County, MO | 19,074 | 4.0% |
| McDonald County, MO | 15,747 | 4.6% |
| Dade County, MO | 14,445 | 4.6% |
| Cedar County, MO | 14,049 | 4.6% |
| Monroe County, IL | 4,490 | 1.9% |
| Ste. Genevieve County, MO | 1,314 | 0.4% |
| Franklin County, MO | 1,188 | 0.2% |
| St. Louis County, MO | 731 | 0.2% |
| Barry County, MO | 728 | 0.1% |
| St. Francois County, MO | 497 | 0.2% |
| Taney County, MO | 392 | 0.1% |
| Osage County, MO | 384 | 0.1% |
| Dent County, MO | 372 | 0.1% |
| Maries County, MO | 364 | 0.1% |
| Newton County, MO | 320 | 0.1% |
| Henry County, MO | 249 | 0.1% |
| Gasconade County, MO | 247 | 0.1% |
| Camden County, MO | 208 | 0.0% |
| Greene County, MO | 180 | 0.0% |
| Pulaski County, MO | 94 | 0.0% |
| St. Clair County, MO | 69 | 0.0% |
| Cooper County, MO | 68 | 0.0% |
| Miller County, MO | 62 | 0.0% |
| Pettis County, MO | 57 | 0.0% |
| Lawrence County, MO | 55 | 0.0% |
| Morgan County, MO | 26 | 0.0% |
| Cole County, MO | 16 | 0.0% |
| Saline County, MO | 15 | 0.0% |
| Phelps County, MO | 12 | 0.0% |
| Iron County, MO | 9 | 0.0% |
| Douglas County, MO | 5 | 0.0% |
| Perry County, MO | 4 | 0.0% |
| Laclede County, MO | 3 | 0.0% |
| Jasper County, MO | 1 | 0.0% |
Septic absorption fields
NRCS rating, share of Sonsac 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 Sonsac acres
- Depth to seasonal high water table
- None reported within about 6.5 feet (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 9–33% (median 28%).
- Topsoil organic matter
- Median 3%.
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 | 5.1% |
| C: slow infiltration | 19.6% |
| D: very slow infiltration (clayey, shallow or wet) | 75.3% |
| 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 Sonsac (component kind "Series") in SSURGO: 238,542 acres.
- Method
- Shares are by mapped acres of Sonsac components. The profile comes from the single largest Sonsac component. Full methodology.