Soil series profile
Dallam soil series
Dallam is a well drained soil with a loamy fine sand surface, mapped on 853,187 acres in 7 counties across 2 states. Hydrologic group B.
- Drainage class
- Well drained 100% of mapped acres
- Hydrologic group
- B 100% of mapped acres
- Typical topsoil pH
- 7.2 neutral · range 7.2–7.2
- Mapped area
- 853k acres in 7 counties, 2 states
Typical Dallam profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–9 in (A) | Loamy fine sand | 7.2 | 8% | 84% | 0.7% |
| 9–36 in (Bt) | Sandy clay loam | 7.7 | 28% | 60% | 0.3% |
| 36–57 in (Btk1) | Sandy clay loam | 8.2 | 31% | 55% | 0.3% |
| 57–80 in (2Btk2) | Clay loam | 8.0 | 34% | 40% | 0.3% |
What this means
What Dallam soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Dallam soils is neutral: pH 7.2, the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 54% of mapped Dallam acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is fine sandy loam (53% of mapped Dallam acres).
100% of mapped Dallam 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 Dallam soils very limited, 100% somewhat limited and 0% not limited.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Dallam soil is found
Mapped acres
Dallam is mapped in Texas and New Mexico.
| County | Acres | Share of county land |
|---|---|---|
| Dallam County, TX | 304,682 | 31.6% |
| Hartley County, TX | 265,109 | 28.3% |
| Union County, NM | 158,533 | 6.0% |
| Quay County, NM | 85,855 | 4.6% |
| Harding County, NM | 19,237 | 1.3% |
| Colfax County, NM | 18,649 | 0.7% |
| Hutchinson County, TX | 1,123 | 0.2% |
Septic absorption fields
NRCS rating, share of Dallam acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 100.0% |
| Very limited | 0.0% |
Drainage, water table and flooding
Share of Dallam 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 0–3% (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 | 100.0% |
| 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 | 0.0% |
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 Dallam (component kind "Series") in SSURGO: 853,187 acres.
- Method
- Shares are by mapped acres of Dallam components. The profile comes from the single largest Dallam component. Full methodology.