Soil series profile
Zahill soil series
Zahill is a well drained soil with a loam surface, mapped on 1,570,215 acres in 39 counties across 3 states. Hydrologic group C.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- C 71% of mapped acres
- Typical topsoil pH
- 7.9 moderately alkaline · range 7.9–8.0
- Mapped area
- 1.6M acres in 39 counties, 3 states
Typical Zahill profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–5 in (Ap) | Loam | 7.9 | 24% | 36% | 1.5% |
| 5–31 in (Bk) | Loam | 8.3 | 25% | 36% | 1% |
| 31–51 in (BCk) | Loam | 8.6 | 26% | 38% | 0.5% |
| 51–79 in (C) | Loam | 8.6 | 26% | 38% | 0.5% |
What this means
What Zahill soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Zahill soils is moderately alkaline: pH 7.9 (most land between 7.9 and 8.0). Acid-loving plants such as blueberries and azaleas struggle without amended beds, and some trees and shrubs show iron chlorosis (yellow leaves with green veins).
Loamy topsoil (loam, silt loam and similar) covers 100% of mapped Zahill acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is loam (65% of mapped Zahill acres).
100% of mapped Zahill acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 71% 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 71% of the acres in mapped Zahill soils very limited, 29% 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 Zahill soil is found
Mapped acres
Zahill is mapped in Montana, North Dakota and South Dakota.
| County | Acres | Share of county land |
|---|---|---|
| Roosevelt County, MT | 329,006 | 21.7% |
| Sheridan County, MT | 255,225 | 24.0% |
| Richland County, MT | 177,517 | 13.0% |
| Williams County, ND | 111,495 | 8.4% |
| McCone County, MT | 103,143 | 6.1% |
| Daniels County, MT | 91,860 | 10.1% |
| Mountrail County, ND | 63,782 | 5.4% |
| McLean County, ND | 43,786 | 3.3% |
| Dawson County, MT | 43,658 | 2.9% |
| Divide County, ND | 34,085 | 4.1% |
| Burleigh County, ND | 29,968 | 2.9% |
| Logan County, ND | 29,250 | 4.7% |
| Stutsman County, ND | 27,772 | 2.0% |
| Sheridan County, ND | 23,024 | 3.7% |
| Ward County, ND | 22,002 | 1.7% |
| McIntosh County, ND | 20,301 | 3.4% |
| Edmunds County, SD | 17,837 | 2.4% |
| Faulk County, SD | 16,598 | 2.6% |
| Burke County, ND | 15,994 | 2.2% |
| Kidder County, ND | 15,557 | 1.8% |
| Campbell County, SD | 13,431 | 2.8% |
| McPherson County, SD | 13,063 | 1.8% |
| Hill County, MT | 10,907 | 0.6% |
| Wells County, ND | 10,308 | 1.3% |
| Emmons County, ND | 7,549 | 0.8% |
| Chouteau County, MT | 6,603 | 0.3% |
| Toole County, MT | 6,516 | 0.6% |
| LaMoure County, ND | 5,075 | 0.7% |
| Walworth County, SD | 4,935 | 1.1% |
| Dickey County, ND | 4,674 | 0.6% |
| Blaine County, MT | 4,157 | 0.2% |
| Liberty County, MT | 3,199 | 0.4% |
| Potter County, SD | 2,796 | 0.5% |
| Brown County, SD | 2,108 | 0.2% |
| Valley County, MT | 1,343 | 0.0% |
| McHenry County, ND | 751 | 0.1% |
| Spink County, SD | 530 | 0.1% |
| McKenzie County, ND | 245 | 0.0% |
| Foster County, ND | 164 | 0.0% |
Septic absorption fields
NRCS rating, share of Zahill acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 28.8% |
| Very limited | 71.2% |
Drainage, water table and flooding
Share of Zahill 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 5–38% (median 10%).
- Topsoil organic matter
- Median 1.5%.
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 | 28.9% |
| C: slow infiltration | 71.1% |
| 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 Zahill (component kind "Series") in SSURGO: 1,570,215 acres.
- Method
- Shares are by mapped acres of Zahill components. The profile comes from the single largest Zahill component. Full methodology.