CELINA, Ohio – A saturated buffer is a relatively new tool to help farmers keep nutrients out of the water. It’s an edge-of-field conservation practice that effectively routes a portion of the subsurface tile through a riparian area prior to that drainage water entering surface waters such as a creek or stream.

“By routing a portion of the volume of water from the edge-of-field tile through the riparian buffer, it reduces the amount of volume leaving the field,” said Dr. Stephen Jacquemin, professor of biology at Wright State University Lake Campus. “What water does make it through the saturated buffer will have a significant reduction in nutrients – specifically dissolved nitrogen like nitrate as well as dissolved phosphorous.”

Jacquemin has been involved in constructing several saturated buffers in Northwest Ohio in the Grand Lake St. Marys watershed. In that area, scientists have seen that these buffers, on average, can take up about a third of the annual tile flow leaving the field. They must be appropriately sized and the installer needs to follow the recommendations for implementation.

“By monitoring the volume that makes it into the buffer, we’ve seen nutrient reduction well in excess of 75 percent of nitrogen and phosphorous,” Jacquemin said. “A saturated buffer is extremely low-tech. It is just natural vegetation between the field and the stream.”

The buffer takes the tile main that would have gone straight into the stream, then uses a control structure to route a portion of that field tile water parallel to the stream, routing it through another tile, Jacquemin explained. That tile is gravity fed between the elevation of that tile and the actual stream.

“The riparian zone would have been bypassed by the tile; the saturated buffer kind of forces the water to go through that riparian, and it allows the riparian zone to take up water and those nutrients,” Jacquemin said.

Theresa Dirksen, agriculture and natural resources director in Mercer County, has been involved with installing two saturated buffers, one of which she designed. That one drains 25 to 30 acres.

“It’s pretty simple where we’re rerouting all of the drainage tile into an Agri Drain three chamber control box,” Dirksen said. “We route that 25 to 30 acres into that box. It then has the opportunity to spill over a series of blades. 

They can back water up into the field to a specific elevation if it’s a time when the crop field is too dry. A portion of those tiles will hold the water which becomes available moisture for growing crops. When the field doesn’t have a crop, it can keep water back in the field instead of discharging during rain events. Once the water spills over, they attached, in this case, an 8-inch perforated tile so the water can be distributed from the field into that tile.

That tile runs adjacent to the grass or riparian buffer, Dirksen said. It acts like a leach field similar to what would be on a home septic system. That water can leach out of the tile and then move laterally through the buffer area alongside the creek. It enters back into the creek after it is filtered through the ground.

“During high flows, it is going to push as much water into the buffer as it can, and then the rest will just bypass it and discharge into that open ditch as it historically would,” she explained.

Dirksen was able to use two cost-share programs to build the buffer. The soil and water district was awarded a 319 grant from Ohio EPA to fund the installation of the structure and the tile. The riparian buffer was seeded through the Conservation Reserve Program.

“The few saturated buffers we have seem to be working really well,” Dirksen said. “It is a practice that doesn’t take a whole lot of land out of production, and it is not a huge cost.”

Anyone interested should visit their Natural Resources Conservation Service or soil and water district.