Soil series profile
Zook soil series
Zook is a poorly drained soil with a silty clay loam surface, mapped on 966,469 acres in 189 counties across 7 states. Hydrologic group D.
- Drainage class
- Poorly drained >99% of mapped acres
- Hydrologic group
- D 63% of mapped acres
- Typical topsoil pH
- 6.1 slightly acidic · range 5.7–6.5
- Mapped area
- 966k acres in 189 counties, 7 states
Typical Zook profile
Texture and pH by depth
Show as a table
| Depth | Texture | pH | Clay | Sand | Organic matter |
|---|---|---|---|---|---|
| 0–4 in (A1) | Silty clay loam | 5.7 | 32% | 16% | 4.3% |
| 4–40 in (A2) | Silty clay loam | 6.6 | 35% | 16% | 2.6% |
| 40–60 in (Bg) | Silty clay loam | 6.7 | 35% | 15% | 2.2% |

What this means
What Zook soil means for gardens, lawns and septic systems
For gardens
Typical topsoil in Zook soils is slightly acidic: pH 6.1 (most land between 5.7 and 6.5), the range most vegetables, flowers and lawn grasses prefer.
Loamy topsoil (loam, silt loam and similar) covers 95% of mapped Zook acres: generally the easiest soil to garden, holding moisture without staying waterlogged. The most common surface texture is silty clay loam (83% of mapped Zook acres).
100% of mapped Zook 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 100% 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 93% 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 100% of the acres in mapped Zook soils very limited, 0% somewhat limited and 0% not limited.
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 98% of the acres (78% occasional, 19% frequent).
Only a licensed site evaluation or perc test at the actual lot decides whether a system is allowed and which design.
Where Zook soil is found
Mapped acres
Zook is mapped in Missouri, Iowa, Nebraska, Illinois, Kansas, Minnesota and South Dakota. The 60 counties with the most Zook acres:
| County | Acres | Share of county land |
|---|---|---|
| DeKalb County, MO | 45,015 | 16.6% |
| Daviess County, MO | 43,692 | 12.1% |
| Harrison County, MO | 42,375 | 9.2% |
| Adams County, IA | 30,131 | 11.2% |
| Wayne County, IA | 23,827 | 7.1% |
| Grundy County, MO | 23,319 | 8.4% |
| Caldwell County, MO | 23,138 | 8.4% |
| Ringgold County, IA | 21,210 | 6.2% |
| Dodge County, NE | 21,032 | 6.2% |
| Johnson County, MO | 20,829 | 3.9% |
| Warren County, IA | 20,781 | 5.7% |
| Lucas County, IA | 19,860 | 7.2% |
| Nodaway County, MO | 19,392 | 3.5% |
| Putnam County, MO | 17,531 | 5.3% |
| Richardson County, NE | 17,048 | 4.8% |
| Cass County, IA | 16,941 | 4.7% |
| Otoe County, NE | 15,850 | 4.1% |
| Sullivan County, MO | 15,371 | 3.7% |
| Schuyler County, MO | 14,822 | 7.5% |
| Decatur County, IA | 13,758 | 4.1% |
| Mercer County, MO | 13,543 | 4.7% |
| Mahaska County, IA | 13,516 | 3.7% |
| Cuming County, NE | 12,515 | 3.4% |
| Gentry County, MO | 12,390 | 4.0% |
| Johnson County, NE | 12,272 | 5.1% |
| Clark County, MO | 12,113 | 3.7% |
| Colfax County, NE | 12,071 | 4.6% |
| Jasper County, IA | 11,236 | 2.4% |
| Audubon County, IA | 11,195 | 3.9% |
| Madison County, IA | 10,933 | 3.1% |
| Livingston County, MO | 10,829 | 3.2% |
| Adair County, MO | 10,294 | 2.8% |
| Clarke County, IA | 10,273 | 3.7% |
| Davis County, IA | 10,138 | 3.2% |
| Adair County, IA | 10,125 | 2.8% |
| Pottawattamie County, IA | 10,005 | 1.6% |
| Cass County, MO | 9,895 | 2.2% |
| Macon County, MO | 9,813 | 1.9% |
| Carroll County, MO | 9,733 | 2.2% |
| Nemaha County, NE | 9,217 | 3.5% |
| Lancaster County, NE | 8,968 | 1.7% |
| Burt County, NE | 8,480 | 2.7% |
| Keokuk County, IA | 8,418 | 2.3% |
| Ray County, MO | 8,329 | 2.3% |
| Montgomery County, IA | 8,324 | 3.1% |
| Shelby County, IA | 8,234 | 2.2% |
| Marion County, IA | 7,956 | 2.3% |
| Jackson County, KS | 7,866 | 1.9% |
| Chariton County, MO | 7,225 | 1.5% |
| Andrew County, MO | 7,084 | 2.5% |
| Iroquois County, IL | 6,613 | 0.9% |
| Guthrie County, IA | 6,576 | 1.7% |
| Iowa County, IA | 6,392 | 1.7% |
| Page County, IA | 6,109 | 1.8% |
| Butler County, NE | 6,059 | 1.6% |
| Linn County, MO | 5,491 | 1.4% |
| Mills County, IA | 5,020 | 1.8% |
| Washington County, IA | 4,897 | 1.4% |
| Monroe County, IA | 4,814 | 1.7% |
| Buchanan County, MO | 4,684 | 1.8% |
Septic absorption fields
NRCS rating, share of Zook acres
Show as a table
| Category | Share of acres |
|---|---|
| Not limited | 0.0% |
| Somewhat limited | 0.0% |
| Very limited | 100.0% |
Drainage, water table and flooding
Share of Zook acres
- Depth to seasonal high water table
- About 0 inches (median where reported); within 18 inches on 93% of acres.
- Flooding
- Mapped as flooding on 98% of acres (78% occasional, 19% frequent).
- Slope
- Typically 1–2% (median 1%).
- Topsoil organic matter
- Median 4.5%.
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 | 0.0% |
| Poorly drained | 99.2% |
| Very poorly drained | 0.8% |
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 | 3.6% |
| D: very slow infiltration (clayey, shallow or wet) | 63.3% |
| 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 | 33.1% |
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 Zook (component kind "Series") in SSURGO: 966,469 acres.
- Method
- Shares are by mapped acres of Zook components. The profile comes from the single largest Zook component. Full methodology.