State soil summary
Soil types in Idaho
The most widespread soil series in Idaho are Portneuf, Pancheri, Ririe. Pick a county below, or enter a ZIP code for the county you live in.
- Well or moderately well drained
- 88% of mapped land
- Typical topsoil pH
- 6.7 neutral · most land 5.6–7.9
- Septic fields very limited
- 86% 1% not limited
- Subject to flooding
- 3% of land, any frequency
Idaho counties
4 county reports, by population
| County | Most common soil | Well drained | Topsoil pH | Septic very limited |
|---|---|---|---|---|
| Ada County | Chilcott | 92% | 7.2 | 89% |
| Canyon County | Power | 83% | 7.5 | 71% |
| Kootenai County | Vassar | 94% | 6.5 | 97% |
| Bonneville County | Pancheri | 79% | 7.0 | 64% |
What this means
What Idaho soils mean for gardens, lawns and septic systems
For gardens
Typical topsoil in Idaho is neutral: pH 6.7 (most land between 5.6 and 7.9), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 88% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (20% of the land).
88% of the land 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 septic systems
For conventional septic absorption fields, NRCS rates 86% of the land in Idaho very limited, 7% somewhat limited and 1% not limited (6% not rated, such as urban land, pits or water).
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.
Statewide mix
Share of all mapped land
Drainage
Show as a table
| Category | Share of land |
|---|---|
| Excessively drained | 1.0% |
| Somewhat excessively drained | 6.2% |
| Well drained | 77.5% |
| Moderately well drained | 3.3% |
| Somewhat poorly drained | 1.5% |
| Poorly drained | 1.5% |
| Very poorly drained | 0.6% |
| Not rated | 8.3% |
Septic absorption fields
Show as a table
| Category | Share of land |
|---|---|
| Not limited | 1.4% |
| Somewhat limited | 7.0% |
| Very limited | 85.5% |
| Not rated | 6.2% |
Topsoil pH
Show as a table
| Category | Share of land |
|---|---|
| Strongly acidic (below 5.5) | 3.4% |
| Moderately to slightly acidic (5.5–6.4) | 26.8% |
| Near neutral (6.5–7.3) | 41.3% |
| Alkaline (7.4 and up) | 20.1% |
| Not reported | 8.4% |
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
- Idaho: 47,946,892 acres of mapped land in 44 counties, pooled (not an average of county figures).
- Method
- Shares are by mapped land area: each map unit’s acres in the county times each soil component’s percentage. Open water is excluded. Topsoil values use the first mineral horizon of each component. Full methodology.