County soil summary
Soil types in Mercer County, New Jersey
The most widespread soils are Sassafras, Bucks and Matapeake; the most common drainage class is well drained (46% of the land), and typical topsoil pH is 5.0.
- Well or moderately well drained
- 69% of land · state 62%
- Typical topsoil pH
- 5.0 very strongly acidic · state 5.0
- Septic fields very limited
- 86% of land · state 90%
- Subject to flooding
- 5% of land, any frequency · state 18%
Most common soils in Mercer County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 48% of the mapped land; 68 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Sassafras | 11.1% | Well drained | 6.0 |
| Bucks | 9.3% | Well drained | 5.0 |
| UdorthentsGeneral soil group, not a named series | 5.8% | — | — |
| Matapeake | 4.8% | Well drained | 6.0 |
| Othello | 4.6% | Poorly drained | 5.0 |
| Urban landLand type, not a soil series | 4.1% | — | — |
| Penn | 4.0% | Well drained | 6.4 |
| Quakertown | 3.8% | Well drained | 5.6 |
What this means
What the soils in Mercer County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Mercer County is very strongly acidic: pH 5.0 (most land between 4.6 and 6.3). Most vegetables and lawn grasses do best around 6.0 to 7.0, so lime is often needed; blueberries, azaleas and rhododendrons like it as it is.
Loamy topsoil (loam, silt loam and similar) covers 83% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (41% of the land).
69% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
On 52% of the land, 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.
A seasonal high water table comes within 18 inches of the surface on 27% of the land, often in spring. Basements, sump pumps and lawns in low spots feel it first.
For a septic system
For conventional septic absorption fields, NRCS rates 86% of the land in Mercer County very limited, 9% somewhat limited and 0% not limited (4% not rated, such as urban land, pits or water).
That is close to the state as a whole (90% very 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.
Flooding is mapped on 5% of the land (1% occasional, 4% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Drainage
How long the soil stays wet
The most common drainage class is well drained (46%). 69% of the land is moderately well drained or better, compared with 62% across New Jersey.
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| Excessively drained | 2.2% | 5.3% |
| Somewhat excessively drained | 3.0% | 4.5% |
| Well drained | 46.4% | 36.6% |
| Moderately well drained | 17.8% | 15.4% |
| Somewhat poorly drained | 9.7% | 5.9% |
| Poorly drained | 14.8% | 9.5% |
| Very poorly drained | 2.1% | 13.6% |
| Not rated | 4.1% | 9.0% |
Septic absorption fields
NRCS rating for conventional drain fields
The rating looks at the soil from 24 to 60 inches deep: permeability, depth to a seasonal water table or bedrock, flooding and slope. “Very limited” means at least one feature is unfavorable enough that a conventional field is hard to make work.
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| Not limited | 0.0% | 1.2% |
| Somewhat limited | 9.4% | 2.9% |
| Very limited | 86.2% | 89.7% |
| Not rated | 4.4% | 6.1% |
Rain, runoff and water table
Hydrologic soil group, flooding, seasonal water table
Hydrologic soil group
How fast rain soaks in when the soil is already wet. Group A soaks in fastest, D slowest.
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 7.1% | 19.9% |
| B: moderate infiltration | 35.9% | 21.5% |
| C: slow infiltration | 25.6% | 17.8% |
| D: very slow infiltration (clayey, shallow or wet) | 11.2% | 10.6% |
| A/D: D as is, A if drained | 2.7% | 15.9% |
| B/D: D as is, B if drained | 5.5% | 4.7% |
| C/D: D as is, C if drained | 7.3% | 2.8% |
| Not rated | 4.7% | 6.8% |
Flooding
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| No flooding | 94.5% | 82.0% |
| Rare or very rare | 0.2% | 2.4% |
| Occasional | 1.0% | 2.1% |
| Frequent or very frequent | 4.2% | 13.4% |
| Not reported | 0.0% | 0.1% |
Seasonal high water table
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| Within 18 inches at some time of year | 27.4% | 32.1% |
| 18 inches to 3.3 feet | 17.6% | 15.8% |
| Deeper than 3.3 feet or none reported | 55.0% | 52.1% |
| Not reported | 0.0% | 0.1% |
Topsoil pH and texture
First mineral layer of each soil
Typical topsoil pH is 5.0 (very strongly acidic); 80% of rated land falls between 4.6 and 6.3. Median topsoil organic matter is 2.2%.
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| Strongly acidic (below 5.5) | 62.9% | 62.1% |
| Moderately to slightly acidic (5.5–6.4) | 32.5% | 22.5% |
| Near neutral (6.5–7.3) | 0.1% | 2.9% |
| Alkaline (7.4 and up) | 0.0% | 1.1% |
| Not reported | 4.4% | 11.4% |
Texture
Show as a table
| Category | Mercer County | New Jersey |
|---|---|---|
| Sandy | 8.7% | 24.8% |
| Loamy (loam, silt loam and similar) | 83.3% | 53.1% |
| Clayey (40%+ clay) | 0.1% | 0.1% |
| Organic (muck or peat) | 3.4% | 13.7% |
| Not reported (rock, urban land, etc.) | 4.4% | 8.2% |
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
- Mercer County, New Jersey (FIPS 34021): 141,625 acres of mapped land, 4,875 acres of open water excluded. State comparisons pool all mapped land in New Jersey.
- 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.