Soil series profile
Farnuf soil series
Farnuf is a well drained soil with a loam surface, mapped on 688,583 acres in 72 counties across 5 states. Hydrologic group B.
- Drainage class
- Well drained >99% of mapped acres
- Hydrologic group
- B 99% of mapped acres
- Typical topsoil pH
- 7.0 neutral · range 6.7–7.2
- Mapped area
- 689k acres in 72 counties, 5 states
Typical Farnuf profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–6 in (Ap) | Loam | 7.0 | 21% | 42% | 3% |
| 6–18 in (Bt) | Clay loam | 7.0 | 30% | 34% | 2% |
| 18–36 in (Btk) | Silt loam | 7.9 | 25% | 21% | 0.75% |
| 36–60 in (C) | Stratified gravelly sandy loam to silty clay loam | 8.0 | 23% | 60% | 0.25% |
What this means
What Farnuf soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Farnuf soils is neutral: pH 7.0 (most land between 6.7 and 7.2), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers >99% of mapped Farnuf acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (90% of mapped Farnuf acres).
>99% of mapped Farnuf acres 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 a septic system
For conventional septic absorption fields, NRCS rates 6% of the acres in mapped Farnuf soils very limited, 94% somewhat limited and 0% not limited.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Farnuf soil is found
Mapped acres
Farnuf is mapped in Montana, North Dakota, South Dakota, Wyoming and Colorado. The 60 counties with the most Farnuf acres:
| County | Acres | Share of county land |
|---|---|---|
| Valley County, MT | 73,274 | 2.3% |
| Roosevelt County, MT | 63,001 | 4.2% |
| Daniels County, MT | 46,111 | 5.1% |
| McKenzie County, ND | 37,353 | 2.1% |
| Big Horn County, MT | 35,604 | 0.8% |
| Perkins County, SD | 35,199 | 1.9% |
| Glacier County, MT | 32,810 | 2.1% |
| Sheridan County, MT | 30,656 | 2.9% |
| Lewis and Clark County, MT | 28,552 | 1.4% |
| Sioux County, ND | 25,048 | 3.6% |
| Corson County, SD | 21,916 | 1.4% |
| Chouteau County, MT | 16,965 | 0.7% |
| Blaine County, MT | 13,668 | 0.5% |
| Ravalli County, MT | 13,454 | 0.9% |
| Morton County, ND | 11,152 | 0.9% |
| Larimer County, CO | 11,134 | 0.7% |
| Toole County, MT | 11,077 | 1.0% |
| Fergus County, MT | 10,422 | 0.4% |
| Richland County, MT | 10,327 | 0.8% |
| Dunn County, ND | 10,315 | 0.8% |
| Bowman County, ND | 9,058 | 1.2% |
| Harding County, SD | 8,015 | 0.5% |
| Divide County, ND | 7,903 | 1.0% |
| Sweet Grass County, MT | 7,184 | 0.6% |
| Sheridan County, WY | 6,748 | 0.4% |
| Slope County, ND | 6,712 | 0.9% |
| Burke County, ND | 6,408 | 0.9% |
| Emmons County, ND | 6,372 | 0.7% |
| Custer County, MT | 6,316 | 0.3% |
| Stark County, ND | 6,294 | 0.7% |
| Cascade County, MT | 6,059 | 0.4% |
| Fallon County, MT | 5,890 | 0.6% |
| Hettinger County, ND | 5,578 | 0.8% |
| Campbell County, SD | 5,489 | 1.2% |
| McCone County, MT | 4,902 | 0.3% |
| Park County, WY | 4,417 | 0.3% |
| Meagher County, MT | 3,943 | 0.2% |
| Park County, MT | 3,632 | 0.2% |
| Adams County, ND | 3,554 | 0.6% |
| Grant County, ND | 3,508 | 0.3% |
| Jefferson County, MT | 3,254 | 0.3% |
| Mercer County, ND | 3,156 | 0.5% |
| Williams County, ND | 3,081 | 0.2% |
| Gallatin County, MT | 2,971 | 0.2% |
| Phillips County, MT | 2,896 | 0.1% |
| Wheatland County, MT | 2,789 | 0.3% |
| Logan County, ND | 2,433 | 0.4% |
| Oliver County, ND | 2,226 | 0.5% |
| Liberty County, MT | 2,027 | 0.2% |
| Hill County, MT | 1,586 | 0.1% |
| McLean County, ND | 1,114 | 0.1% |
| McIntosh County, ND | 1,067 | 0.2% |
| Prairie County, MT | 947 | 0.1% |
| Golden Valley County, ND | 550 | 0.1% |
| Billings County, ND | 546 | 0.1% |
| Mountrail County, ND | 487 | 0.0% |
| Missoula County, MT | 265 | 0.0% |
| Silver Bow County, MT | 241 | 0.1% |
| Broadwater County, MT | 203 | 0.0% |
| Walworth County, SD | 181 | 0.0% |
Septic absorption fields
NRCS rating, share of Farnuf acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 93.6% |
| Very limited | 6.2% |
| Not rated | 0.2% |
Drainage, water table and flooding
Share of Farnuf acres
- Depth to seasonal high water table
- About 3.9 feet (47 in) (median where reported).
- Flooding
- Mapped as flooding on <1% of acres (0% occasional, <1% frequent).
- Slope
- Typically 1–10% (median 4%).
- 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 | 99.7% |
| Moderately well drained | 0.1% |
| Somewhat poorly drained | 0.0% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
| Not rated | 0.2% |
Hydrologic soil group
Show as a table
| Category | Share of acres |
|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 0.0% |
| B: moderate infiltration | 98.5% |
| C: slow infiltration | 1.3% |
| 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% |
| Not rated | 0.2% |
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 Farnuf (component kind "Series") in SSURGO: 688,583 acres.
- Method
- Shares are by mapped acres of Farnuf components. The profile comes from the single largest Farnuf component. Full methodology.