Soil series profile
Duval soil series
Duval is a well drained soil with a very fine sandy loam surface, mapped on 568,578 acres in 9 counties in TX. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B 99% of mapped acres
- Typical topsoil pH
- 6.5 slightly acidic · range 6.5–6.5
- Mapped area
- 569k acres in 9 counties, 1 state
Typical Duval profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–15 in (A) | Very fine sandy loam | 6.5 | 13% | 78% | 0.75% |
| 15–38 in (Bt) | Sandy clay loam | 7.4 | 26% | 66% | 0.4% |
| 38–50 in (Btk) | Sandy clay loam | 8.0 | 24% | 66% | 0.2% |
| 50–80 in (2Cr) | Bedrock | Not reported | Not reported | Not reported | Not reported |
What this means
What Duval soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Duval soils is slightly acidic: pH 6.5, the range most vegetables, flowers and lawn grasses prefer.
Sandy topsoil covers 97% of mapped Duval acres. It drains fast and warms early in spring, but dries out and loses nutrients quickly: mulch, compost and steady watering help. The most common surface texture is very fine sandy loam (75% of mapped Duval acres).
100% of mapped Duval 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 0% of the acres in mapped Duval soils very limited, 99% 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 Duval soil is found
Mapped acres
Duval is mapped in Texas.
| County | Acres | Share of county land |
|---|---|---|
| Frio County, TX | 159,478 | 22.0% |
| La Salle County, TX | 130,710 | 13.5% |
| Webb County, TX | 94,021 | 4.4% |
| Dimmit County, TX | 79,311 | 9.5% |
| Zavala County, TX | 40,846 | 4.9% |
| Medina County, TX | 31,133 | 3.7% |
| Atascosa County, TX | 22,794 | 2.9% |
| Bexar County, TX | 7,494 | 0.9% |
| Uvalde County, TX | 2,790 | 0.3% |
Septic absorption fields
NRCS rating, share of Duval acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 98.6% |
| Very limited | 0.0% |
| Not rated | 1.4% |
Drainage, water table and flooding
Share of Duval 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 2–2% (median 2%).
- Topsoil organic matter
- Median 0.8%.
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 | 98.6% |
| 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 | 1.4% |
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 Duval (component kind "Series") in SSURGO: 568,578 acres.
- Method
- Shares are by mapped acres of Duval components. The profile comes from the single largest Duval component. Full methodology.