Saturated Buffers
Remove nitrogen naturally from subsurface drainage
Where Microbes Stand Up to Nitrates
An edge-of-field saturated buffer is a water quality and conservation practice that focuses on cleansing tile drainage water of nitrates before it hits your local waterways.
In a saturated buffer, an area of perennial vegetation lies between your agricultural fields and the waterways where tile outlets drain. Tile lines flow into a water level control structure, which distributes water into the perennial vegetation “buffer,” where the living roots of the plants absorb water and nutrients. Throughout the process, nitrates are either absorbed or turned into harmless nitrogen gas.
The result? Cleaner water for your community.
Benefits at a Glace
Up to 50% nitrate-nitrogen removal from water diverted through the buffer
Removal of sediment, phosphorous and pesticides
5% streamflow reduction
Provides wildlife habitat
How It’s Done
Most of the time, saturated buffers are installed through a local “batch and build.” Batch and build is exactly like it sounds – local conservation professionals batch construction of several saturated buffers for efficiency. They’re 100% paid for and landowners may even receive a small payment. The group organizing the program does all the behind-the-scenes work so it takes very little landowner time – often just an afternoon to sign paperwork.
Saturated Buffer Components
- Excess water drains to laterals
- Water moves through tile main
- Water control structure diverts water to edge-of-field buffer
- Water seeps into root zone. Microbes remove nitrates, transforming them into nitrogen gas
- In heavy rain, excess water moves directly to bypass flow, preventing backups
If a saturated buffer isn’t the right fit, the next best choice is a bioreactor. Read more about bioreactors here.
Myth vs Fact
Myth or fact? saturated buffers cause wet spots.
Myth!
The name of this structure is misleading, because they don’t cause wet spots! In the case of heavy rain, there is a bypass pipe that allows water to flow straight to an outlet so water doesn’t back up into the field.
MYTH or fact? saturated buffers are ineffective because of bypass flow.
Myth!
Saturated buffers still treat 40-60% of a drainage area’s water! That’s because peak flow doesn’t happen every day. Saturated buffers are one of the most cost effective tools in the Iowa NRS.
Cost-Share Options
This practice has considerable potential due to its reliability, effectiveness and low cost. The best way to get an edge-of-field practice installed is to sign up during a “batch and build” process. Learn more about batch and build in the link below. .
Getting Started
A great place to start if you’d like an edge of field practice installed in your field is to talk with your local NRCS office or the Iowa Department of Agriculture.
More Resources
Here are more helpful resources on saturated buffers:
Cleaning Iowa’s Waters with Saturated Buffers in Iowa Watersheds (Iowa State University) provides a helpful overview of how saturated buffers work
Agricultural Drainage Management Coalition looks at the cost, scalability and potential impact of saturated buffers
Transforming Drainage collects research and use cases from around the Midwest
Questions and Answers About Saturated Buffers for the Midwest (Iowa State University) addresses FAQs about installation, cost and more
Clean Water Iowa shares saturated buffer success stories
Already have a bioreactor of saturated buffer? Check out this booklet that’s a straightforward guide to keeping your edge of field practice operating as designed.