Soil series profile
Sylvan soil series
Sylvan is a well drained soil with a silt loam surface, mapped on 236,619 acres in 28 counties across 2 states. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B 100% of mapped acres
- Typical topsoil pH
- 6.5 slightly acidic · range 6.2–6.5
- Mapped area
- 237k acres in 28 counties, 2 states
Typical Sylvan profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–6 in (Ap) | Silt loam | 6.2 | 18% | 6% | 2% |
| 6–26 in (Bt) | Silty clay loam | 6.0 | 29% | 4% | 0.75% |
| 26–60 in (C) | Silt | 7.9 | 10% | 5% | 0.25% |
What this means
What Sylvan soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Sylvan soils is slightly acidic: pH 6.5 (most land between 6.2 and 6.5), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Sylvan acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (54% of mapped Sylvan acres).
100% of mapped Sylvan 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 32% of the acres in mapped Sylvan soils very limited, 68% 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 Sylvan soil is found
Mapped acres
Sylvan is mapped in Illinois and Indiana.
| County | Acres | Share of county land |
|---|---|---|
| Knox County, IN | 27,262 | 8.3% |
| Rock Island County, IL | 26,340 | 10.1% |
| Henry County, IL | 26,171 | 5.1% |
| Peoria County, IL | 19,265 | 5.0% |
| Posey County, IN | 17,273 | 6.7% |
| Morgan County, IL | 15,204 | 4.2% |
| Mercer County, IL | 14,775 | 4.2% |
| Cass County, IL | 13,192 | 5.7% |
| Menard County, IL | 10,568 | 5.4% |
| Gibson County, IN | 9,962 | 3.2% |
| Scott County, IL | 8,934 | 5.7% |
| Fulton County, IL | 5,698 | 1.1% |
| Calhoun County, IL | 4,540 | 3.1% |
| Jersey County, IL | 4,422 | 1.9% |
| Greene County, IL | 4,342 | 1.3% |
| Stark County, IL | 3,932 | 2.2% |
| Brown County, IL | 3,776 | 2.0% |
| St. Clair County, IL | 3,624 | 0.9% |
| Madison County, IL | 3,249 | 0.7% |
| Bureau County, IL | 3,215 | 0.6% |
| Knox County, IL | 2,640 | 0.6% |
| Tazewell County, IL | 1,940 | 0.5% |
| Pike County, IN | 1,896 | 0.9% |
| White County, IL | 1,524 | 0.5% |
| Pike County, IL | 1,339 | 0.3% |
| Schuyler County, IL | 1,198 | 0.4% |
| Logan County, IL | 316 | 0.1% |
| Marshall County, IL | 21 | 0.0% |
Septic absorption fields
NRCS rating, share of Sylvan acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 67.8% |
| Very limited | 32.2% |
Drainage, water table and flooding
Share of Sylvan 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 8–30% (median 14%).
- Topsoil organic matter
- Median 1.5%.
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 | 100.0% |
| C: slow infiltration | 0.0% |
| 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 Sylvan (component kind "Series") in SSURGO: 236,619 acres.
- Method
- Shares are by mapped acres of Sylvan components. The profile comes from the single largest Sylvan component. Full methodology.