Soil series profile
Osco soil series
Osco is a well drained soil with a silt loam surface, mapped on 731,407 acres in 56 counties across 3 states. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B >99% of mapped acres
- Typical topsoil pH
- 6.0 moderately acidic · range 6.0–6.0
- Mapped area
- 731k acres in 56 counties, 3 states
Typical Osco profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–14 in (Ap) | Silt loam | 6.0 | 24% | 4% | 3.5% |
| 14–55 in (Bt) | Silty clay loam | 5.6 | 31% | 4% | 0.5% |
| 55–60 in (C) | Silt loam | 6.7 | 24% | 4% | 0.25% |
What this means
What Osco soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Osco soils is moderately acidic: pH 6.0. 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 Osco acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (100% of mapped Osco acres).
100% of mapped Osco 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 1% of the acres in mapped Osco soils very limited, 99% 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 Osco soil is found
Mapped acres
Osco is mapped in Illinois, Iowa and Minnesota.
| County | Acres | Share of county land |
|---|---|---|
| Knox County, IL | 60,409 | 13.3% |
| Ogle County, IL | 56,548 | 11.9% |
| Sangamon County, IL | 56,272 | 10.2% |
| Warren County, IL | 54,478 | 15.7% |
| Carroll County, IL | 53,128 | 19.1% |
| Stephenson County, IL | 38,178 | 10.9% |
| Henry County, IL | 38,062 | 7.4% |
| Morgan County, IL | 29,863 | 8.3% |
| Tazewell County, IL | 27,737 | 6.9% |
| McLean County, IL | 26,383 | 3.5% |
| Lee County, IL | 26,191 | 5.8% |
| Stark County, IL | 21,852 | 12.0% |
| Mercer County, IL | 21,479 | 6.2% |
| Peoria County, IL | 20,825 | 5.4% |
| Christian County, IL | 17,667 | 3.9% |
| Logan County, IL | 15,371 | 4.0% |
| Fulton County, IL | 15,155 | 2.8% |
| Winnebago County, IL | 14,953 | 4.8% |
| McDonough County, IL | 13,566 | 3.6% |
| Bureau County, IL | 13,309 | 2.4% |
| Marshall County, IL | 11,492 | 4.7% |
| Henderson County, IL | 10,430 | 4.5% |
| Jo Daviess County, IL | 10,150 | 2.7% |
| LaSalle County, IL | 9,781 | 1.4% |
| Putnam County, IL | 8,846 | 8.9% |
| Whiteside County, IL | 8,414 | 2.0% |
| Cass County, IL | 7,855 | 3.4% |
| Rock Island County, IL | 6,831 | 2.6% |
| Menard County, IL | 5,205 | 2.7% |
| Scott County, IL | 4,236 | 2.7% |
| Jersey County, IL | 4,079 | 1.8% |
| Adams County, IL | 3,629 | 0.7% |
| Hancock County, IL | 2,826 | 0.6% |
| Macon County, IL | 2,617 | 0.7% |
| Marshall County, IA | 2,329 | 0.6% |
| Greene County, IL | 2,192 | 0.6% |
| De Witt County, IL | 2,084 | 0.8% |
| Schuyler County, IL | 1,256 | 0.5% |
| Goodhue County, MN | 944 | 0.2% |
| Cedar County, IA | 826 | 0.2% |
| Tama County, IA | 818 | 0.2% |
| Grundy County, IA | 627 | 0.2% |
| Wabasha County, MN | 420 | 0.1% |
| Scott County, IA | 334 | 0.1% |
| Benton County, IA | 285 | 0.1% |
| Poweshiek County, IA | 266 | 0.1% |
| Linn County, IA | 253 | 0.1% |
| Dodge County, MN | 243 | 0.1% |
| Boone County, IL | 191 | 0.1% |
| Macoupin County, IL | 177 | 0.0% |
| Iowa County, IA | 132 | 0.0% |
| Johnson County, IA | 104 | 0.0% |
| Muscatine County, IA | 65 | 0.0% |
| Hardin County, IA | 23 | 0.0% |
| Woodford County, IL | 14 | 0.0% |
| Clinton County, IA | 9 | 0.0% |
Septic absorption fields
NRCS rating, share of Osco acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 99.0% |
| Very limited | 1.0% |
Drainage, water table and flooding
Share of Osco acres
- Depth to seasonal high water table
- About 4.9 feet (59 in) (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 4–4% (median 4%).
- Topsoil organic matter
- Median 3.5%.
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 | 99.2% |
| C: slow infiltration | 0.8% |
| 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 Osco (component kind "Series") in SSURGO: 731,407 acres.
- Method
- Shares are by mapped acres of Osco components. The profile comes from the single largest Osco component. Full methodology.