Soil series profile
Naff soil series
Naff is a well drained soil with a silt loam surface, mapped on 156,787 acres in 7 counties across 2 states. Hydrologic group C.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- C 100% of mapped acres
- Typical topsoil pH
- 6.6 neutral · range 6.5–6.7
- Mapped area
- 157k acres in 7 counties, 2 states
Typical Naff profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–9 in (H1) | Silt loam | 6.7 | 20% | 11% | 4% |
| 9–47 in (H2) | Silty clay loam | 7.0 | 30% | 7% | 1.5% |
| 47–60 in (H3) | Silty clay loam | 7.0 | 30% | 7% | 0.75% |
What this means
What Naff soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Naff soils is neutral: pH 6.6 (most land between 6.5 and 6.7), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Naff acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (100% of mapped Naff acres).
100% of mapped Naff acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 100% 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 97% of the acres in mapped Naff soils very limited, 3% 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 Naff soil is found
Mapped acres
Naff is mapped in Washington and Idaho.
| County | Acres | Share of county land |
|---|---|---|
| Spokane County, WA | 64,655 | 5.7% |
| Whitman County, WA | 40,610 | 3.0% |
| Nez Perce County, ID | 27,141 | 5.9% |
| Latah County, ID | 19,838 | 3.5% |
| Benewah County, ID | 4,353 | 1.0% |
| Lewis County, ID | 190 | 0.1% |
| Lincoln County, WA | 0 | 0.0% |
Septic absorption fields
NRCS rating, share of Naff acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 2.9% |
| Very limited | 97.1% |
Drainage, water table and flooding
Share of Naff acres
- Depth to seasonal high water table
- None reported within about 6.5 feet (median where reported).
- Flooding
- Not mapped as flooding on most acres.
- Slope
- Typically 9–20% (median 15%).
- Topsoil organic matter
- Median 3%.
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 | 0.0% |
| C: slow infiltration | 100.0% |
| 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 Naff (component kind "Series") in SSURGO: 156,787 acres.
- Method
- Shares are by mapped acres of Naff components. The profile comes from the single largest Naff component. Full methodology.