Soil series profile
Decatur soil series
Decatur is a well drained soil with a silty clay loam surface, mapped on 395,373 acres in 48 counties across 4 states. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B 99% of mapped acres
- Typical topsoil pH
- 5.3 strongly acidic · range 5.3–6.5
- Mapped area
- 395k acres in 48 counties, 4 states
Typical Decatur profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–7 in (Ap) | Silty clay loam | 6.5 | 32% | 12% | 1% |
| 7–24 in (Bt1) | Silty clay loam | 6.8 | 37% | 13% | 0.75% |
| 24–80 in (Bt2) | Clay | 5.3 | 57% | 9% | 0.25% |
What this means
What Decatur soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Decatur soils is strongly acidic: pH 5.3 (most land between 5.3 and 6.5). 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 90% of mapped Decatur acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (40% of mapped Decatur acres).
100% of mapped Decatur 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 8% of the acres in mapped Decatur soils very limited, 91% somewhat limited and 0% not limited (1% not rated, such as urban land, pits or water).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Decatur soil is found
Mapped acres
Decatur is mapped in Alabama, Tennessee, Georgia and Kentucky.
| County | Acres | Share of county land |
|---|---|---|
| Madison County, AL | 67,713 | 15.3% |
| Colbert County, AL | 49,835 | 15.4% |
| Talladega County, AL | 40,613 | 9.8% |
| Limestone County, AL | 31,277 | 9.8% |
| Lawrence County, AL | 23,926 | 6.2% |
| Lauderdale County, AL | 21,298 | 5.6% |
| Floyd County, GA | 16,755 | 5.4% |
| Monroe County, TN | 14,317 | 3.5% |
| Bartow County, GA | 13,867 | 4.7% |
| Blount County, TN | 12,015 | 3.4% |
| Polk County, GA | 10,796 | 5.7% |
| Shelby County, AL | 9,372 | 2.2% |
| Calhoun County, AL | 9,054 | 2.6% |
| Jefferson County, AL | 6,818 | 1.2% |
| Franklin County, AL | 6,379 | 1.9% |
| Franklin County, TN | 6,250 | 1.8% |
| Chattooga County, GA | 5,793 | 3.0% |
| Loudon County, TN | 5,541 | 3.8% |
| Sevier County, TN | 5,478 | 1.5% |
| Lawrence County, TN | 4,712 | 1.2% |
| Wayne County, KY | 3,850 | 1.3% |
| Morgan County, AL | 3,784 | 1.2% |
| Polk County, TN | 3,502 | 1.3% |
| White County, TN | 2,350 | 1.0% |
| Hawkins County, TN | 2,288 | 0.7% |
| Blount County, AL | 2,260 | 0.6% |
| Tuscaloosa County, AL | 2,149 | 0.3% |
| Cherokee County, AL | 1,979 | 0.6% |
| Jefferson County, TN | 1,859 | 1.0% |
| Coosa County, AL | 1,331 | 0.3% |
| McMinn County, TN | 1,193 | 0.4% |
| Jackson County, AL | 1,144 | 0.2% |
| Catoosa County, GA | 965 | 1.0% |
| Knox County, TN | 785 | 0.2% |
| Coffee County, TN | 671 | 0.2% |
| Cocke County, TN | 651 | 0.2% |
| Hamblen County, TN | 575 | 0.6% |
| Greene County, TN | 386 | 0.1% |
| Bradley County, TN | 361 | 0.2% |
| Grainger County, TN | 329 | 0.2% |
| Roane County, TN | 318 | 0.1% |
| Van Buren County, TN | 317 | 0.2% |
| Hamilton County, TN | 233 | 0.1% |
| Meigs County, TN | 140 | 0.1% |
| Washington County, TN | 46 | 0.0% |
| Rhea County, TN | 42 | 0.0% |
| Union County, TN | 39 | 0.0% |
| Hancock County, TN | 17 | 0.0% |
Septic absorption fields
NRCS rating, share of Decatur acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 91.1% |
| Very limited | 7.6% |
| Not rated | 1.2% |
Drainage, water table and flooding
Share of Decatur 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 4–13% (median 4%).
- Topsoil organic matter
- Median 1.2%.
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 | 98.8% |
| C: slow infiltration | 0.0% |
| 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 | 1.2% |
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 Decatur (component kind "Series") in SSURGO: 395,373 acres.
- Method
- Shares are by mapped acres of Decatur components. The profile comes from the single largest Decatur component. Full methodology.