Soil series profile
Knoco soil series
Knoco is a well drained soil with a clay surface, mapped on 859,562 acres in 54 counties across 3 states. Hydrologic group D.
- Drainage class
- Well drained 96% of mapped acres
- Hydrologic group
- D 95% of mapped acres
- Typical topsoil pH
- 8.2 moderately alkaline · range 7.9–8.2
- Mapped area
- 860k acres in 54 counties, 3 states
Typical Knoco profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–9 in (A) | Clay | 8.2 | 50% | 22% | 0.75% |
| 9–19 in (C) | Clay | 8.2 | 50% | 22% | 0.25% |
| 19–60 in (Cd) | Clay | 8.2 | 50% | 22% | 0.15% |
What this means
What Knoco soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Knoco soils is moderately alkaline: pH 8.2 (most land between 7.9 and 8.2). Acid-loving plants such as blueberries and azaleas struggle without amended beds, and some trees and shrubs show iron chlorosis (yellow leaves with green veins).
Clayey topsoil covers 87% of mapped Knoco acres. Clay holds water and nutrients but drains slowly and compacts if worked wet: add compost, avoid tilling soggy soil and consider raised beds. The most common surface texture is clay (82% of mapped Knoco acres).
100% of mapped Knoco acres is moderately well to excessively drained, which suits most garden plants.
For lawns and yards
On 95% 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.
For a septic system
For conventional septic absorption fields, NRCS rates 95% of the acres in mapped Knoco soils very limited, 0% somewhat limited and 0% not limited (5% 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.
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Knoco soil is found
Mapped acres
Knoco is mapped in Texas, Oklahoma and Kansas.
| County | Acres | Share of county land |
|---|---|---|
| Foard County, TX | 76,681 | 14.0% |
| Knox County, TX | 72,916 | 13.4% |
| Baylor County, TX | 53,550 | 9.5% |
| King County, TX | 50,589 | 8.7% |
| Woods County, OK | 46,203 | 5.6% |
| Stonewall County, TX | 37,508 | 6.4% |
| Cottle County, TX | 35,511 | 6.2% |
| Barber County, KS | 35,167 | 4.9% |
| Woodward County, OK | 33,128 | 4.0% |
| Blaine County, OK | 27,899 | 4.7% |
| Archer County, TX | 26,507 | 4.6% |
| Childress County, TX | 25,369 | 5.6% |
| Major County, OK | 25,122 | 4.1% |
| Hardeman County, TX | 23,497 | 5.3% |
| Greer County, OK | 23,241 | 5.7% |
| Wilbarger County, TX | 21,338 | 3.5% |
| Harmon County, OK | 18,758 | 5.6% |
| Beckham County, OK | 16,879 | 2.9% |
| Cotton County, OK | 15,296 | 3.7% |
| Wichita County, TX | 15,026 | 3.9% |
| Haskell County, TX | 14,577 | 2.5% |
| Oldham County, TX | 14,259 | 1.5% |
| Comanche County, OK | 13,984 | 2.1% |
| Borden County, TX | 12,753 | 2.2% |
| Tillman County, OK | 11,649 | 2.1% |
| Fisher County, TX | 11,072 | 1.9% |
| Crosby County, TX | 10,949 | 1.9% |
| Mitchell County, TX | 10,297 | 1.8% |
| Kiowa County, OK | 8,237 | 1.3% |
| Jackson County, OK | 7,551 | 1.5% |
| Potter County, TX | 6,571 | 1.1% |
| Armstrong County, TX | 6,558 | 1.1% |
| Taylor County, TX | 6,353 | 1.1% |
| Howard County, TX | 6,113 | 1.1% |
| Jones County, TX | 5,507 | 0.9% |
| Young County, TX | 5,222 | 0.9% |
| Clay County, TX | 4,753 | 0.7% |
| Nolan County, TX | 4,002 | 0.7% |
| Scurry County, TX | 3,879 | 0.7% |
| Randall County, TX | 3,646 | 0.6% |
| Montague County, TX | 2,864 | 0.5% |
| Garza County, TX | 2,643 | 0.5% |
| Throckmorton County, TX | 1,008 | 0.2% |
| Hartley County, TX | 940 | 0.1% |
| Dawson County, TX | 934 | 0.2% |
| Harper County, OK | 688 | 0.1% |
| Dickens County, TX | 534 | 0.1% |
| Kent County, TX | 497 | 0.1% |
| Coke County, TX | 447 | 0.1% |
| Caddo County, OK | 362 | 0.0% |
| Washita County, OK | 310 | 0.0% |
| Tom Green County, TX | 158 | 0.0% |
| Runnels County, TX | 53 | 0.0% |
| Sterling County, TX | 8 | 0.0% |
Septic absorption fields
NRCS rating, share of Knoco acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 94.8% |
| Not rated | 5.2% |
Drainage, water table and flooding
Share of Knoco 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 5–26% (median 9%).
- Topsoil organic matter
- Median 0.8%.
Drainage class
Show as a table
| Category | Share of acres |
|---|---|
| Excessively drained | 4.1% |
| Somewhat excessively drained | 0.0% |
| Well drained | 95.9% |
| 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 | 0.0% |
| C: slow infiltration | 0.0% |
| D: very slow infiltration (clayey, shallow or wet) | 94.9% |
| 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 | 5.1% |
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
- All map unit components named Knoco (component kind "Series") in SSURGO: 859,562 acres.
- Method
- Shares are by mapped acres of Knoco components. The profile comes from the single largest Knoco component. Full methodology.