Soil guide
Hydric soils, and what they mean for your land
Hydric soils are the ground's memory of being wet. They matter for three practical reasons: they are one of the three factors used to identify a wetland, they signal drainage and workability limits, and they can affect USDA program eligibility if you convert them. This guide explains what hydric soils are, how to check whether your land has them, and where the line to a regulated wetland actually sits.
What a hydric soil is
A hydric soil formed under enough saturation, flooding, or ponding during the growing season to go low on oxygen in its upper layers. Those anaerobic conditions leave physical evidence: gray or bluish colors, mottling, and other features a soil scientist can read. USDA keeps a list of hydric soils and records a hydric rating for each soil map unit in the national survey, so a soil does not have to be wet the day you look at it to be classed hydric; the classification is about how the soil formed.
Hydric soils and drainage class
The soil survey field most closely tied to hydric status is natural drainage class. The wettest classes, poorly and very poorly drained, are where hydric soils concentrate. Because drainage also drives productivity, it carries real weight in how AgriTerra scores a parcel. Here is how each drainage class scores in the productivity index, so you can see how the wet end pulls a score down.
| Drainage class | Sub-score |
|---|---|
| Well or excessively drained | 100 of 100 |
| Moderately well drained | 80 of 100 |
| Somewhat poorly drained | 50 of 100 |
| Poorly drained | 25 of 100 |
| Very poorly drained | 5 of 100 |
Drainage class is read straight from USDA SSURGO and carries 25 percent of the AgriTerra productivity index. The poorly and very poorly drained classes at the bottom are where hydric soils are most common. The scoring is modeled, not a USDA-published rating.
Why hydric soils matter
- Wetland determinations. Hydric soil is one of the three factors, along with wetland plants and wetland hydrology, used to identify a wetland. On its own it is a flag, not a finding. Read the full regulatory picture in wetlands on your land.
- Drainage and workability. Wet soils are harder to work, plant late, and can cost more to farm. Many productive fields on hydric soils are productive because they were tiled; the drainage system is doing real work.
- USDA program eligibility. Converting hydric or wetland ground to cropland can affect farm program eligibility under the wetland conservation (Swampbuster) provisions. A USDA NRCS wetland determination before you drain or clear is the safe path.
How to check a parcel
You have two straightforward routes. In USDA Web Soil Survey, set your Area of Interest, open the Soil Data Explorer, and pull the hydric rating for each map unit. Or read it for a parcel in one step with AgriTerra, which returns the SSURGO drainage and hydric signals alongside the wetlands layer, soil productivity, and every revenue option, free. Either way, treat a hydric flag as a reason to look closer, especially before any drainage or land-use change, and to get a USDA NRCS determination when a wetland conversion is on the table.
For how every figure here is sourced, see how we get our numbers.
Hydric soils: frequently asked questions
- What are hydric soils?
- Hydric soils are soils that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop low-oxygen conditions in their upper layers. That history leaves telltale traits in the soil, such as gray or mottled colors, that soil scientists use to identify them. Hydric soil is one of the three factors used to identify a wetland.
- How do I know if my land has hydric soils?
- The USDA soil survey records a hydric rating for each soil map unit. You can look it up in USDA Web Soil Survey under the Soil Data Explorer, or read it for a parcel in one step with AgriTerra. Drainage class is a strong related clue: very poorly and poorly drained soils are usually hydric or partly hydric.
- Do hydric soils mean I have a regulated wetland?
- Not on their own. A regulated wetland is identified by three factors together, hydric soils, wetland plants, and wetland hydrology, and only the U.S. Army Corps of Engineers can make the jurisdictional determination that a wetland is regulated under the Clean Water Act. Hydric soil is a flag to look closer, not a finding. See our guide to wetlands on your land for the regulatory picture.
- Can you farm hydric soils?
- Often yes, especially where the ground has been drained and is in an established cropping history. But converting new hydric or wetland ground to cropland can affect USDA program eligibility under the wetland conservation (Swampbuster) provisions, so it is worth a USDA NRCS determination before you drain or clear. Wet ground also usually carries a lower productivity score and higher management cost.
Check your parcel's soil and wetlands, free.
AgriTerra reads USDA SSURGO drainage and hydric signals and the USFWS wetlands layer for your parcel, in plain language with the source on every figure.