Mahaska County, Iowa
The most common soil here is Ladoga, on about 14% of the land: a silt loam, smooth, like flour. Otley and Clinton come next.
About 11% of the land drains well, and 33% stays wet for long stretches; groundwater comes within two feet of the surface under 37% of it.
USDA rates 98% of the land very limited for a standard septic drain field, and 70% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 16% of the land floods occasionally or more.
Soils change over short distances, so look up an address below for the soil at that exact spot and the reasons behind each rating.
The soils you're most likely standing on
The biggest named soils in Mahaska County, Iowa, each drawn five feet deep from its official USDA description, in its recorded colors.
Dots mark gravel; white flecks mark lime. Shares are by acres across the survey area, and each mapped patch usually mixes several of these soils.
The biggest mapped areas
The dominant drainage class is Moderately well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Alfisols — moderately leached forest soils with a clay-enriched subsoil. 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 Mahaska County, Iowa. Search your address to find the exact soil composition, drainage, and series details at your specific location.
| Soil Map Unit | Acres | Drainage | Hydro Group | Dwellings | Septic |
|---|---|---|---|---|---|
| Otley silty clay loam, 2 to 5 percent slopes | 28K | Moderately well drained | C | Very limited | Very limited |
| Ladoga silt loam, 5 to 9 percent slopes, eroded | 19K | Moderately well drained | C | Somewhat limited | Very limited |
| Mahaska silty clay loam, 0 to 2 percent slopes | 19K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Colo-Ely complex, 0 to 5 percent slopes | 18K | Poorly drained | C/D | Very limited | Very limited |
| Taintor silty clay loam, 0 to 2 percent slopes | 16K | Poorly drained | D | Very limited | Very limited |
| Ladoga silt loam, 2 to 5 percent slopes | 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 |
| Otley silty clay loam, 5 to 9 percent slopes, eroded | 13K | Moderately well drained | C | Very limited | Very limited |
| Clinton silt loam, 9 to 14 percent slopes, eroded | 12K | Moderately well drained | C | Somewhat limited | Very limited |
| Clinton silt loam, 5 to 9 percent slopes, eroded | 11K | Moderately well drained | C | Somewhat limited | Very limited |
| Mahaska silty clay loam, 2 to 5 percent slopes | 10K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Nodaway silt loam, 0 to 2 percent slopes | 8K | Moderately well drained | B | Very limited | Very limited |
| Zook silty clay loam, 0 to 2 percent slopes, occasionally flooded | 8K | Poorly drained | D | Very limited | Very limited |
| Otley silty clay loam, 5 to 9 percent slopes | 7K | Moderately well drained | C | Very limited | Very limited |
| Ladoga silt loam, 5 to 9 percent slopes | 7K | Moderately well drained | C | Somewhat limited | Very limited |
| Nira silty clay loam, 5 to 9 percent slopes, moderately eroded | 6K | Moderately well drained | C | Very limited | Very limited |
| Lindley-Keswick complex, 14 to 18 percent slopes, moderately eroded | 6K | Well drained | C | Very limited | Very limited |
| Colo silty clay loam, 0 to 2 percent slopes, occasionally flooded | 6K | Poorly drained | C/D | Very limited | Very limited |
| Nodaway-Vesser silt loams, 2 to 5 percent slopes | 5K | Moderately well drained | B | Very limited | Very limited |
| Clinton silt loam, 14 to 18 percent slopes, eroded | 5K | Moderately well drained | C | Very limited | Very limited |
Soil Orders in This Area
The USDA classifies every soil into one of 12 soil orders. Here are the dominant orders found in this survey area.
What This Means
Building & Foundations
About 70% of soils are rated "very limited" for dwellings with basements. Specific challenges include steep slopes, poor drainage in some areas, flood-prone areas. A geotechnical assessment is recommended before building.
Septic Systems
About 98% 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.