Soil series profile
Downs soil series
Downs is a well drained soil with a silt loam surface, mapped on 848,756 acres in 46 counties across 4 states. Hydrologic group C.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- C 91% of mapped acres
- Typical topsoil pH
- 6.2 slightly acidic · range 6.0–6.2
- Mapped area
- 849k acres in 46 counties, 4 states
Typical Downs profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–8 in (Ap) | Silt loam | 6.2 | 21% | 5% | 2.5% |
| 8–17 in (BE) | Silt loam | 6.2 | 21% | 5% | 0.75% |
| 17–33 in (Bt1, Bt2) | Silty clay loam | 5.9 | 28% | 5% | 0.75% |
| 33–39 in (Bt3) | Silt loam | 6.5 | 25% | 5% | 0.25% |
| 39–48 in (BC) | Silt loam | 6.5 | 25% | 5% | 0.25% |
| 48–79 in (C) | Silt loam | 6.5 | 25% | 5% | 0.25% |
What this means
What Downs soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Downs soils is slightly acidic: pH 6.2 (most land between 6.0 and 6.2), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Downs acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (>99% of mapped Downs acres).
100% of mapped Downs acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 91% 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 92% of the acres in mapped Downs soils very limited, 8% 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 Downs soil is found
Mapped acres
Downs is mapped in Iowa, Minnesota, Wisconsin and Illinois.
| County | Acres | Share of county land |
|---|---|---|
| Winneshiek County, IA | 77,209 | 17.6% |
| Olmsted County, MN | 68,735 | 16.5% |
| Clayton County, IA | 55,535 | 11.2% |
| Dubuque County, IA | 52,585 | 13.5% |
| Allamakee County, IA | 51,181 | 12.6% |
| Fillmore County, MN | 45,787 | 8.3% |
| Wabasha County, MN | 45,215 | 13.5% |
| Jasper County, IA | 34,889 | 7.5% |
| Cedar County, IA | 34,379 | 9.3% |
| Jackson County, IA | 29,244 | 7.2% |
| Winona County, MN | 27,340 | 6.8% |
| Clinton County, IA | 26,684 | 6.0% |
| Scott County, IA | 23,777 | 8.1% |
| Fayette County, IA | 23,390 | 5.0% |
| Tama County, IA | 23,284 | 5.1% |
| Jones County, IA | 21,415 | 5.9% |
| Houston County, MN | 21,185 | 6.0% |
| Muscatine County, IA | 18,764 | 6.7% |
| Grant County, WI | 15,726 | 2.1% |
| Delaware County, IA | 15,605 | 4.2% |
| Johnson County, IA | 14,410 | 3.7% |
| Iowa County, IA | 14,035 | 3.8% |
| Marshall County, IA | 12,722 | 3.5% |
| Poweshiek County, IA | 12,588 | 3.4% |
| Goodhue County, MN | 12,363 | 2.5% |
| Dodge County, MN | 8,760 | 3.1% |
| Polk County, IA | 7,203 | 2.0% |
| Warren County, IA | 6,883 | 1.9% |
| Louisa County, IA | 6,509 | 2.5% |
| Howard County, IA | 6,498 | 2.2% |
| Linn County, IA | 6,115 | 1.3% |
| Benton County, IA | 6,028 | 1.3% |
| Green County, WI | 5,758 | 1.5% |
| Marion County, IA | 4,086 | 1.2% |
| Hardin County, IA | 4,062 | 1.1% |
| Lafayette County, WI | 2,263 | 0.6% |
| Butler County, IA | 2,050 | 0.6% |
| Mitchell County, IA | 1,984 | 0.7% |
| Brown County, IL | 656 | 0.3% |
| Mahaska County, IA | 544 | 0.2% |
| Iowa County, WI | 510 | 0.1% |
| Lee County, IA | 444 | 0.1% |
| Jo Daviess County, IL | 286 | 0.1% |
| Carroll County, IL | 47 | 0.0% |
| Stephenson County, IL | 18 | 0.0% |
| Grundy County, IA | 5 | 0.0% |
Septic absorption fields
NRCS rating, share of Downs acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 8.1% |
| Very limited | 91.9% |
Drainage, water table and flooding
Share of Downs acres
- Depth to seasonal high water table
- About 2.0 feet (24 in) (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 4–12% (median 7%).
- Topsoil organic matter
- Median 2.5%.
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 | 9.0% |
| C: slow infiltration | 91.0% |
| 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 Downs (component kind "Series") in SSURGO: 848,756 acres.
- Method
- Shares are by mapped acres of Downs components. The profile comes from the single largest Downs component. Full methodology.