Soil series profile
Colyell soil series
Colyell is a somewhat poorly drained soil with a silt loam surface, mapped on 39,512 acres in 2 counties in LA. Hydrologic group C/D.
- Drainage class
- Somewhat poorly drained >99% of mapped acres
- Hydrologic group
- C/D 92% of mapped acres
- Typical topsoil pH
- 5.3 strongly acidic · range 5.3–5.3
- Mapped area
- 40k acres in 2 counties, 1 state
Typical Colyell profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–3 in (A) | Silt loam | 5.3 | 7% | 34% | 2.25% |
| 3–8 in (E) | Silt | 5.3 | 9% | 11% | 0.75% |
| 8–12 in (EB) | Silt loam | 5.3 | 11% | 31% | 0.25% |
| 12–15 in (2Bt/E) | Silty clay | 5.9 | 47% | 6% | 0.25% |
| 15–39 in (2Bt) | Silty clay | 5.9 | 47% | 6% | 0.25% |
| 39–60 in (3Btn) | Silty clay loam | 6.8 | 29% | 18% | 0.25% |
What this means
What Colyell soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Colyell soils is strongly acidic: pH 5.3. 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 92% of mapped Colyell acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silt loam (92% of mapped Colyell acres).
>99% of mapped Colyell acres is somewhat poorly to very poorly drained, so soil stays soggy for long spells after rain and in wet seasons. Raised beds, plants that tolerate wet feet, and not working the soil while wet all help.
For lawns and yards
On 92% 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.
A seasonal high water table comes within 18 inches of the surface on >99% of mapped acres, 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 92% of the acres in mapped Colyell soils very limited, 0% somewhat limited and 0% not limited (8% not rated, such as urban land, pits or water).
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 >99% of the acres (0% occasional, 26% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Colyell soil is found
Mapped acres
Colyell is mapped in Louisiana.
| County | Acres | Share of county land |
|---|---|---|
| Livingston Parish, LA | 37,893 | 9.2% |
| East Baton Rouge Parish, LA | 1,619 | 0.6% |
Septic absorption fields
NRCS rating, share of Colyell acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 91.8% |
| Not rated | 8.2% |
Drainage, water table and flooding
Share of Colyell acres
- Depth to seasonal high water table
- About 1.0 feet (12 in) (median where reported); within 18 inches on >99% of acres.
- Flooding
- Mapped as flooding on >99% of acres (0% occasional, 26% frequent).
- Slope
- Typically 1–2% (median 2%).
- Topsoil organic matter
- Median 2.2%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 0.0% |
| Somewhat excessively drained | 0.0% |
| Well drained | 0.0% |
| Moderately well drained | 0.0% |
| Somewhat poorly drained | 99.3% |
| Poorly drained | 0.0% |
| Very poorly drained | 0.0% |
| Not rated | 0.7% |
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 | 0.0% |
| 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 | 91.8% |
| Not rated | 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
- All map unit components named Colyell (component kind "Series") in SSURGO: 39,512 acres.
- Method
- Shares are by mapped acres of Colyell components. The profile comes from the single largest Colyell component. Full methodology.