Saturated Buffers in Northwest Ohio: Reducing Field Drainage for Improved Water Quality

Across Ohio, farmers are taking up the call to work together to improve water quality for our families and communities. One particular ongoing conservation program, the Blanchard River Demonstration Farms Network, continues to expand its focus on advancing research and showcasing real-world examples of the best land management practices by partnering with farmers in northwest Ohio.

A saturated buffer is an area of perennial vegetation between agricultural fields and waterways where tile outlets drain. Tile lines connect to a water control structure, which directs a portion of the water into the tile under the buffer rather than discharging directly into a stream or ditch. As water drains into the buffer, the living roots of vegetation absorb water and nutrients, potentially removing nitrate from the water that is diverted through the buffer.

The Demonstration Farms Network specifically addresses critical water quality issues through innovative conservation practices. A relatively new conservation practice being evaluated by the program is a saturated buffer. 

A saturated buffer is an edge-of-field conservation practice that is intended to remove nitrate and other potential nutrients from subsurface field tile drainage in farm fields before it enters ditches, streams, and other surface waters. It’s a critical conservation practice that’s capable of reducing nutrient runoff with little annual maintenance by the farmer to ensure effective operation.

While this practice has been studied across the Midwest, there is limited research about how this practice performs in Ohio. As a result, the Demonstration Farms Network partnered with researchers Dr. Stephen Jacquemin, Professor of Biology at Wright State University Lake Campus, and Theresa Dirksen, Agriculture and Natural Resources Director in Mercer County, to address the benefits and costs of this practice within the topography and soil characteristics of northwest Ohio.

“Saturated buffers are an underutilized tool in northwest Ohio that could help us continue to make progress towards sustainable long-term nutrient reductions,” says Jacquemin. “They offer a unique combination of riparian management and controlled drainage to help reduce nutrient loads leaving fields.”

To demonstrate a saturated buffer’s ability to reduce nutrient loss, a dedicated research site, known as the St. Charles saturated buffer, was constructed within the agricultural landscape of the Grand Lake St. Marys watershed in Mercer County, Ohio. 

Installed along an open ditch within a 30-acre subwatershed area, the saturated buffer has an approximately 40-foot vegetative buffer zone planted with cool-season grasses. Not only does this vegetative zone provide uptake of lost nutrients but it also serves as a habitat for wildlife. “Saturated buffers not only help to reduce nutrient runoff but the restoration of a riparian edge can be great for wildlife too – enhancing the biological diversity potential of an area,” says Jacquemin.

When there is subsurface tile drainage flow, a three-chambered water control structure regulates water flow to the buffer. The water control structure utilizes two sets of stop logs, wherein the initial stop log acts as a controlled drainage mechanism for the field. Once the water table is high enough to leave the field, the water flows into a central portion of the control structure where it is distributed along the length of the 1,200-foot distribution tile. Any water that does not percolate through the soil can leave the central chamber of the control structure to continue flowing out the third chamber and into the stream. 

A look inside the three-chambered water control structure.

Comparing the drainage water outflow to a paired monitoring site without a vegetative buffer zone or water control structure, researchers monitored the volume of water reduced over a year at the St. Charles saturated buffer site. 

During the initial monitoring period from December 13, 2020 to December 12, 2021, researchers noted that conditions were extremely dry over the first half of the year. However, the total annual precipitation during the study period was 33.1 inches and approximately 11 distinct rain events occurred to raise the water table in the field enough to initiate active tile runoff from the field into the buffer. 

As a result, researchers found that the field exhibited a 70% reduction in outflow volume as an effect of the first stop log in the water control structure. Flow volume was further reduced through the buffer’s vegetation by processing approximately 35% of flow leaving the field. Once infiltrated, abiotic and biotic processes facilitated significant nutrient reductions of dissolved nitrogen and phosphorus.

This project is scheduled to complete water quality monitoring in 2022 to generate a full two years of data from which to draw conclusions. 

Saturated buffers exhibit a strong potential to find their way into farmers’ conservation tool bags as they work together with researchers to reduce nutrient runoff across the region.

To learn more about the conservation practices improving agriculture’s impact on downstream water quality in Ohio, please visit the Conservation Practice page.

Saturated Buffers in Northwest Ohio

Saturated Buffers in Northwest Ohio:

Reducing Drainage Water Volume for Improved Water Quality


saturated-bufferA saturated buffer is an innovative conservation practice with positive impacts on downstream water quality. While this practice has been studied across the Midwest, there is limited research about how this practice performs in northwest Ohio. As a result, Ohio researchers are addressing the benefits, costs, and other related issues of this practice within the topography and soil characteristics of northwest Ohio.

Download Saturated Buffer Fact Sheet

Reducing Nutrient and Sediment Loss: Part 4

Research being done at the Blanchard River Demonstration Farms and other related sites around the state is helping researchers determine what practices work best for reducing nutrient and sediment loss. Over the last five years, on-farm research has shown that three practices in particular help reduce nutrient and sediment loss:

  • Following the 4R approach
  • Reducing soil erosion
  • Developing a water management plan

Research shows that phosphorus is leaving the farm via water, through both surface and subsurface runoff. Implementing practices that slow, stop and/or treat water before it exits the farm can greatly reduce phosphorus discharge downstream. However, the unpredictability of the weather can make this difficult. In fact, the frequency of rainfall events totaling 1 inch or more has almost doubled in most northwest Ohio towns. These intense rainfall events drive a majority of nutrients downstream each year.

By developing a water management plan, you can begin to identify where nutrients are potentially escaping your farm and determine appropriate solutions, such as drainage water management structures, phosphorus removal beds, two-stage ditches, reconstructed wetlands and filter strips.

Saturated Buffer

What is it: Saturated buffers are a new practice that redirects a portion of field tile drainage water into riparian zones rather than into surface waters like traditional tile outlets. Riparian zones are areas adjacent to streams. Diverted waters then filter through the soil in the riparian zone before entering surface water/streams. Research on saturated buffers is ongoing.

How it helps: The goal of the saturated buffer is to use the riparian zone as a sponge to treat the tile water leaving the field. Once the riparian zone is full of water, or saturated, the water is slowly released through the soil and the nutrients are removed. This process is most effective at reducing nitrogen by causing it to turn into a gas, or denitrify. Phosphorus removal is still highly variable and needs to be studied further.

Drainage Water Management

What is it: Drainage Water Management (DWM) is an NRCS-approved conservation engineering practice that manages water discharge from surface and/or subsurface agricultural drainage systems. A DWM structure holds water in root zones when crops need it and drains it when there’s too much.

How it helps: By adjusting the tile outlet elevation, a DWM structure manages the timing and amount of water discharged from agricultural drainage systems. From a water quality standpoint, DWM provides the most benefit by raising the tile outlet elevation immediately after harvest until early spring. A DWM structure can impact nutrient movement, primarily reducing nitrogen loss.

“If we can get by with free-flowing drainage only three or four months a year we can show that constant drip from the tile going into the steams. We will spend about $4,000 for 50 more acres of controlled drainage structures. If we would get a 5% yield increase in a couple of dry years, it pays for itself.” – Duane Stateler

Sites should be evaluated by SWCD and NRCS professionals to determine if this practice can address the resource concern of the producer. If reduction of phosphorus is the primary resource concern, then the producer should look to other practices that are more efficient at removing phosphorus.


This article was featured in the September/October 2021 edition of Our Ohio Magazine

After fall field work is complete, the structures are closed until mid-March. Then the structures are opened, allowing drainage water to flow freely to the outlet. After spring field work is completed (planting and sidedressing corn), the structures are closed again until two weeks prior to harvest. This allows the soil to once again drain freely so harvest equipment can enter the field. Once fall field work is complete, the structures are closed.

Saturated Buffer Conservation

Dr. Stephen Jacquemin of Wright State University introduces Saturated Buffer research in Ohio. There are only a few dozen Saturated Buffers across the U.S. This conservation method helps reduce nitrogen and phosphorus-rich water from fields.

How it works: Below the field, nutrient-rich water is collected in perforated drain pipes. Inside the structure, this water is diverted into a lateral ↔️ distribution line, or saturated soil area, where vegetation at the ground level naturally removes the nutrients in the water. Essentially, this practice acts as a sponge to store water leaving the field.