By Greg McGlinch, CCA, PhD, assistant professor, Wright State University Lake Campus and Stephen J. Jacquemin, PhD, professor, Wright State University Lake Campus
Driving across the rural Ohio landscape, you might occasionally see little gray objects with black caps poking their heads up around fields adjacent to streams and rivers. These gray box-like structures hold an opportunity for farmers and landowners to increase their ability to reduce nutrient loading while conserving precious water in their fields. The name of these little boxes are controlled drainage structures and they can be part of a bigger conservation practice called saturated buffers.
Saturated buffers utilize water control structures to divert subsurface tile water from agricultural fields into the riparian buffer by redirecting drainage through perforated tiles feeding these edge- of-stream vegetated transitional habitats. This edge-of-field conservation practice takes up minimal room, requiring only a 30-foot-wide vegetative buffer, and offers the farmer an opportunity to not only hold water in the buffer but also back water up into the field (USDA-ARS, 2018). The control structure has the ability to raise the water table to just about 1.5 foot below the soil surface, allowing for adequate crop production and water storage in times of drought conditions. The stated purpose of these conservation practices is to reduce nitrate loading but, as ongoing research in Ohio has found, may also reduce dissolved reactive phosphorus (DRP). Suitable sites for saturated buffers require a field tile that intersects a stream side vegetated buffer that sits below the average field elevation, soils that exhibit at least 1.2+% organic matter and are composed of material that promote gradual water transfer, and be situated on a relatively stable stream bank.
Success in Mercer County
Agricultural and Water Quality Researchers at Wright State University Lake Campus had begun monitoring a vegetative saturated buffer, which drains about 20+ field acres of a 135-acre field, during the 2018 through 2019 seasons. The project was in collaboration with VanTilburg Farms, Ohio EPA, Pheasants Forever and Mercer County Ag Solutions. The saturated buffer and field site was located in the Northwest part of Mercer County in the Lake Erie Watershed. Soils in the area consisted of poorly drained clays with an average slope of 1.4%. Cropping practices were a corn-soybean rotation with an annual rye, clover and radish cover crop mix inter-seeded into standing corn. During the study period it was documented that almost 25% of the subsurface flow was directed into the saturated buffer, allowing for almost 1,000,000 gallons of water to infiltrate. Nitrate reductions averaged 75% with DRP reductions of 80%, relating to roughly 13 pounds of N per acre and a 0.25 pound of DRP per acre. The success of the saturated buffer has led to further interest among conservation groups to install additional buffers in the county. Recently, a saturated buffer research project has concluded in the southern portion of Mercer County, in the Grand Lake St Marys Watershed, with positive results forthcoming in the upcoming months.
While the water infiltration and nutrient reduction benefits are of significant importance, there are many other potential benefits of a saturated buffer.
- Using controlled drainage can potentially lead to yield increases for farmers. Studies in northern Ohio have found that corn and soybean yields had increased by 3.3% and 2.1%, respectively, with the adoption of controlled drainage.
- The use of perennial cool season grasses and forbs in the vegetative buffers provide significant habitat for wildlife. These areas are also important for the implementation of pollinator habitats that prove beneficial for agricultural crop production.
Increasing the buffers effectiveness and longevity
The longevity of a saturated buffer is unknown and undoubtedly varies from site to site but to enhance their effectiveness, farmers can implement a variety of conservation techniques:
- Utilize cover crops as a practice to allow for greater retention of nitrogen and phosphorus, further reducing nutrient losses before any edge of field practice is needed. The establishment of a cereal rye or small grain cover crop after corn can also capture residual nitrogen and mineralize it for future availability.
- Apply nutrients when crops are actively growing to reduce the potential loss into the buffer and or adjacent stream.
- Haying or the removal of vegetation from the buffer area would be a practical method to harvest nutrients that would be sequestered in the soil. Be sure to double check your specific conservation program to ensure this is feasible.
The cost and installation could range from $2,000 to $5,000 depending on the equipment, supplies, installation, and topography. It would be advisable to contact your local SWCD or NRCS office about EQIP, H2Ohio or other potential cost-share opportunities to offset expenses related to the installation and management of the practice.
Recently, the USDA-FSA is offering landowners in the Lake Erie and Scioto River watersheds cost share opportunities to install saturated buffers, CP21S, through CREP. Not only will the FSA potentially provide cost share for the installation and land rental payments, but the state will provide an additional incentive payment per practice installed.
The capability of saturated buffers could not only improve yields but also reduce nutrients and flow to local watersheds, making them an appealing practice to farmers and conservationists. The continued interest will make them a great addition to our conservation toolbox to enhance current practices like nutrient management and cover crops.
Remember the next time you’re cruising through the Ohio countryside, those little gray control structures with the black cap are doing more than conserving water, they’re protecting the environment.