Soil series profile
Promise soil series
Promise is a well drained soil with a clay surface, mapped on 844,657 acres in 27 counties across 3 states. Hydrologic group D.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- D >99% of mapped acres
- Typical topsoil pH
- 7.0 neutral · range 7.0–7.0
- Mapped area
- 845k acres in 27 counties, 3 states
Typical Promise profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–8 in (Ap) | Clay | 7.0 | 57% | 4% | 4% |
| 8–16 in (Bss) | Clay | 7.7 | 63% | 3% | 2.3% |
| 16–36 in (Bkss) | Clay | 8.0 | 63% | 3% | 1.4% |
| 36–47 in (Cy) | Clay | 7.9 | 61% | 3% | 1.1% |
| 47–79 in (C) | Clay | 7.9 | 60% | 4% | 0.7% |
What this means
What Promise soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Promise soils is neutral: pH 7.0, the range most vegetables, flowers and lawn grasses prefer.
Clayey topsoil covers 100% of mapped Promise acres. Clay holds water and nutrients but drains slowly and compacts if worked wet: add compost, avoid tilling soggy soil and consider raised beds. The most common surface texture is clay (99% of mapped Promise acres).
100% of mapped Promise 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 100% of the acres in mapped Promise soils very limited, 0% 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 Promise soil is found
Mapped acres
Promise is mapped in South Dakota, Montana and Nebraska.
| County | Acres | Share of county land |
|---|---|---|
| Stanley County, SD | 167,239 | 18.0% |
| Lyman County, SD | 117,697 | 11.3% |
| Dewey County, SD | 78,935 | 5.4% |
| Jones County, SD | 74,930 | 12.2% |
| Brule County, SD | 59,761 | 7.2% |
| Buffalo County, SD | 59,761 | 7.2% |
| Mellette County, SD | 49,798 | 6.0% |
| Haakon County, SD | 41,250 | 3.6% |
| Jackson County, SD | 28,693 | 2.4% |
| Judith Basin County, MT | 26,889 | 2.9% |
| Gregory County, SD | 24,232 | 3.7% |
| Tripp County, SD | 22,263 | 2.2% |
| Hyde County, SD | 15,569 | 2.8% |
| Ziebach County, SD | 14,505 | 1.2% |
| Walworth County, SD | 13,166 | 3.0% |
| Potter County, SD | 11,835 | 2.1% |
| Corson County, SD | 9,973 | 0.6% |
| Sully County, SD | 6,071 | 1.0% |
| Hughes County, SD | 6,050 | 1.3% |
| Campbell County, SD | 4,886 | 1.0% |
| Charles Mix County, SD | 4,767 | 0.7% |
| Hand County, SD | 3,319 | 0.4% |
| Boyd County, NE | 2,091 | 0.6% |
| Knox County, NE | 524 | 0.1% |
| Treasure County, MT | 338 | 0.1% |
| Keya Paha County, NE | 90 | 0.0% |
| Holt County, NE | 24 | 0.0% |
Septic absorption fields
NRCS rating, share of Promise acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 100.0% |
Drainage, water table and flooding
Share of Promise 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 1–8% (median 4%).
- Topsoil organic matter
- Median 4%.
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 | 0.5% |
| D: very slow infiltration (clayey, shallow or wet) | 99.5% |
| 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 Promise (component kind "Series") in SSURGO: 844,657 acres.
- Method
- Shares are by mapped acres of Promise components. The profile comes from the single largest Promise component. Full methodology.