County soil summary
Soil types in Mobile County, Alabama
The most widespread soils are Wadley, Heidel and Benndale; the most common drainage class is well drained (28% of the land), and typical topsoil pH is 5.0.
- Well or moderately well drained
- 63% of land · state 81%
- Typical topsoil pH
- 5.0 very strongly acidic · state 5.0
- Septic fields very limited
- 75% of land · state 79%
- Subject to flooding
- 28% of land, any frequency · state 19%
Most common soils in Mobile County
Share of mapped land
A county is a patchwork of many soils. These 8 cover 52% of the mapped land; 64 named soil series are mapped here in all.
| Soil | Share of land | Drainage | Topsoil pH |
|---|---|---|---|
| Wadley | 18.2% | Somewhat excessively drained | 5.2 |
| Heidel | 8.4% | Well drained | 5.0 |
| Urban landLand type, not a soil series | 5.4% | — | — |
| Benndale | 5.2% | Well drained | 5.0 |
| Bibb | 4.0% | Poorly drained | 4.6 |
| Johnston | 3.8% | Very poorly drained | 5.0 |
| Rattlesnake Forks | 3.7% | Somewhat excessively drained | 5.1 |
| Bama | 3.4% | Well drained | 5.3 |
What this means
What the soils in Mobile County mean for gardens, lawns and septic systems
For your garden
Typical topsoil in Mobile County is very strongly acidic: pH 5.0 (most land between 4.5 and 5.2). 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 48% of the land: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is fine sandy loam (45% of the land).
63% of the land is moderately well to excessively drained, which suits most garden plants.
For your lawn and yard
36% of the land is in hydrologic group A, where water soaks in fast. Lawns there dry out quickly; deeper, less frequent watering and organic matter help.
A seasonal high water table comes within 18 inches of the surface on 35% 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 75% of the land in Mobile County very limited, 14% somewhat limited and 8% not limited (3% not rated, such as urban land, pits or water).
That is close to the state as a whole (79% 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 28% of the land (6% occasional, 20% 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 (28%). 63% of the land is moderately well drained or better, compared with 81% across Alabama.
Show as a table
| Category | Mobile County | Alabama |
|---|---|---|
| Excessively drained | 0.7% | 0.8% |
| Somewhat excessively drained | 23.3% | 5.9% |
| Well drained | 28.3% | 60.7% |
| Moderately well drained | 11.1% | 13.8% |
| Somewhat poorly drained | 4.8% | 8.3% |
| Poorly drained | 13.6% | 8.2% |
| Very poorly drained | 12.9% | 1.3% |
| Not rated | 5.4% | 1.0% |
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 | Mobile County | Alabama |
|---|---|---|
| Not limited | 8.1% | 2.9% |
| Somewhat limited | 13.7% | 17.6% |
| Very limited | 74.9% | 78.5% |
| Not rated | 3.3% | 0.9% |
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 | Mobile County | Alabama |
|---|---|---|
| A: fast infiltration (mostly sandy or gravelly) | 36.2% | 13.1% |
| B: moderate infiltration | 10.1% | 27.4% |
| C: slow infiltration | 7.3% | 20.8% |
| D: very slow infiltration (clayey, shallow or wet) | 5.3% | 20.1% |
| A/D: D as is, A if drained | 8.7% | 1.8% |
| B/D: D as is, B if drained | 11.3% | 8.0% |
| C/D: D as is, C if drained | 14.2% | 7.5% |
| Not rated | 6.8% | 1.2% |
Flooding
Show as a table
| Category | Mobile County | Alabama |
|---|---|---|
| No flooding | 71.2% | 80.7% |
| Rare or very rare | 2.1% | 1.9% |
| Occasional | 5.5% | 4.8% |
| Frequent or very frequent | 20.1% | 12.2% |
| Not reported | 1.2% | 0.4% |
Seasonal high water table
Show as a table
| Category | Mobile County | Alabama |
|---|---|---|
| Within 18 inches at some time of year | 35.0% | 19.8% |
| 18 inches to 3.3 feet | 7.5% | 8.3% |
| Deeper than 3.3 feet or none reported | 56.3% | 71.6% |
| Not reported | 1.2% | 0.4% |
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 4.5 and 5.2. Median topsoil organic matter is 1.5%.
Show as a table
| Category | Mobile County | Alabama |
|---|---|---|
| Strongly acidic (below 5.5) | 87.5% | 76.2% |
| Moderately to slightly acidic (5.5–6.4) | 5.0% | 17.1% |
| Near neutral (6.5–7.3) | 0.8% | 2.8% |
| Alkaline (7.4 and up) | 1.3% | 2.4% |
| Not reported | 5.4% | 1.5% |
Texture
Show as a table
| Category | Mobile County | Alabama |
|---|---|---|
| Sandy | 38.2% | 16.5% |
| Loamy (loam, silt loam and similar) | 48.1% | 77.7% |
| Clayey (40%+ clay) | 0.0% | 3.9% |
| Organic (muck or peat) | 8.3% | 0.8% |
| Not reported (rock, urban land, etc.) | 5.4% | 1.1% |
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
- Mobile County, Alabama (FIPS 01097): 699,677 acres of mapped land, 32,492 acres of open water excluded. State comparisons pool all mapped land in Alabama.
- 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.