Johnson County, Iowa
The dominant drainage class is Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). This report summarizes the major soil map units across the survey area to help you understand what to expect when buying, building, or gardening in Johnson County, Iowa.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Colo-Ely complex, 0 to 5 percent slopes | 27K | Poorly drained | C/D | Very limited | Very limited |
| Tama silt loam, 2 to 5 percent slopes | 20K | Well drained | C | Somewhat limited | Very limited |
| Fayette silt loam, till plain, 5 to 9 percent slopes, eroded | 14K | Well drained | C | Somewhat limited | Very limited |
| Ladoga silt loam, 5 to 9 percent slopes, eroded | 14K | Moderately well drained | C | Somewhat limited | Very limited |
| Ladoga silt loam, 9 to 14 percent slopes, eroded | 13K | Moderately well drained | C | Somewhat limited | Very limited |
| Nodaway-Arenzville silt loams, 1 to 4 percent slopes | 10K | Moderately well drained | B | Very limited | Very limited |
| Tama silt loam, 5 to 9 percent slopes, eroded | 9K | Well drained | C | Somewhat limited | Very limited |
| Fayette silt loam, till plain, 14 to 18 percent slopes, eroded | 9K | Well drained | C | Very limited | Very limited |
| Muscatine silt loam, 0 to 2 percent slopes | 8K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Fayette silty clay loam, till plain, 14 to 18 percent slopes, severely eroded | 7K | Well drained | C | Very limited | Very limited |
| Fayette silt loam, till plain, 2 to 5 percent slopes | 7K | Well drained | C | Somewhat limited | Very limited |
| Garwin silty clay loam, 0 to 2 percent slopes | 7K | Poorly drained | C/D | Very limited | Very limited |
| Ladoga silt loam, 2 to 5 percent slopes | 6K | Moderately well drained | C | Somewhat limited | Very limited |
| Clinton silt loam, 5 to 9 percent slopes, eroded | 6K | Moderately well drained | C | Somewhat limited | Very limited |
| Fayette silt loam, till plain, 25 to 40 percent slopes | 6K | Well drained | C | Very limited | Very limited |
| Water, lakes and reservoirs | 6K | Not rated | Not rated | ||
| Clinton silt loam, 9 to 14 percent slopes, eroded | 6K | Moderately well drained | C | Somewhat limited | Very limited |
| Colo silty clay loam, 0 to 2 percent slopes, ponded, occasionally flooded | 6K | Poorly drained | C/D | Very limited | Very limited |
| Colo silt loam, 0 to 2 percent slopes, occasionally flooded, overwash | 6K | Poorly drained | C/D | Very limited | Very limited |
| Sperry silt loam, depressional, 0 to 1 percent slopes | 6K | Very poorly drained | D | Very limited | Very limited |
What This Means
Building & Foundations
About 47% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 96% of soils are rated "very limited" for septic absorption fields. Despite good drainage overall, limitations may stem from shallow bedrock, steep slopes, or seasonal conditions. Engineered or alternative systems are frequently required. Always get a professional perc test before purchasing land that needs septic.
Gardening & Agriculture
Well-drained soils on sloped terrain — good for most plants but watch for erosion. Terracing, contour planting, and mulching help retain moisture and topsoil. Drip irrigation is more effective than sprinklers on slopes.