Plymouth County, Iowa
The most common soil here is Galva, on about 46% of the land: a silty clay loam, smooth and slightly sticky. Ida and Radford come next.
About 75% of the land drains well, and 14% stays wet for long stretches; groundwater comes within two feet of the surface under 20% of it.
USDA rates 83% of the land very limited for a standard septic drain field, and 32% very limited for homes with basements. That means extra cost or special design, not that it can't be done.
Worth knowing: 23% 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 Plymouth 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 Well drained and the dominant hydrologic group is C (slow infiltration, moderate runoff). The most common soil order is Mollisols — grassland soils with a thick, dark, fertile topsoil rich in organic matter. 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 Plymouth 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 |
|---|---|---|---|---|---|
| Galva silty clay loam, 5 to 9 percent slopes, eroded | 129K | Well drained | C | Somewhat limited | Very limited |
| Galva silty clay loam, 2 to 5 percent slopes | 110K | Well drained | C | Somewhat limited | Very limited |
| Radford silty clay loam, 2 to 5 percent slopes | 44K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Ida silt loam, 9 to 14 percent slopes, severely eroded | 43K | Well drained | B | Somewhat limited | Somewhat limited |
| Ida silt loam, 14 to 20 percent slopes, severely eroded | 23K | Well drained | B | Very limited | Very limited |
| Galva silty clay loam, terrace, 2 to 5 percent slopes | 22K | Well drained | C | Somewhat limited | Very limited |
| McPaul-Kennebec silt loams, 2 to 5 percent slopes | 18K | Moderately well drained | B | Very limited | Very limited |
| Ida silt loam, 5 to 9 percent slopes, severely eroded | 16K | Well drained | B | Not limited | Somewhat limited |
| Kennebec silt loam, 0 to 2 percent slopes, occasionally flooded | 14K | Moderately well drained | B | Very limited | Very limited |
| Colo silty clay loam, deep loess, 0 to 2 percent slopes, occasionally flooded | 11K | Poorly drained | C/D | Very limited | Very limited |
| Kennebec-McPaul silt loams, 2 to 5 percent slopes | 11K | Moderately well drained | B | Very limited | Very limited |
| Ida silt loam, 20 to 30 percent slopes, severely eroded | 11K | Well drained | B | Very limited | Very limited |
| Galva silty clay loam, 9 to 14 percent slopes, eroded | 10K | Well drained | C | Somewhat limited | Very limited |
| Monona silt loam, 5 to 9 percent slopes, eroded | 9K | Well drained | B | Not limited | Somewhat limited |
| Primghar silty clay loam, 2 to 5 percent slopes | 9K | Somewhat poorly drained | C/D | Very limited | Very limited |
| McPaul silt loam, 0 to 2 percent slopes | 8K | Moderately well drained | B | Very limited | Very limited |
| Radford silty clay loam, 0 to 2 percent slopes | 8K | Somewhat poorly drained | C/D | Very limited | Very limited |
| Napier silt loam, 5 to 9 percent slopes | 6K | Well drained | B | Not limited | Somewhat limited |
| Monona silt loam, 9 to 14 percent slopes, eroded | 6K | Well drained | B | Somewhat limited | Somewhat limited |
| Napier-Castana silt loams, 9 to 14 percent slopes | 5K | Well drained | B | Somewhat limited | Somewhat 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 32% of soils have significant building limitations, while the rest are generally suitable. Check specific sites carefully — conditions vary across the area.
Septic Systems
About 83% 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.