Extending saturated buffers to additional landscape positions

Issue

Nitrate loss from artificial subsurface drainage tiles underlying agricultural fields is a major source of reactive nitrogen, especially nitrate (N03), in surface waters. A novel approach for reducing NO3 loss is to intercept a field tile where it crosses a riparian buffer and divert a fraction of the flow as shallow groundwater within the buffer. This practice is called a saturated buffer, and comprehensive monitoring at a network of sites has demonstrated its utility as an edge-of-field nitrate reduction practice. To date, all saturated buffer establishment has been within the riparian zone, either within existing buffers or in conjunction with filter strip planting. However, saturated buffer establishment may be able to be extended to other landscape positions with sufficient soil organic carbon where it would be possible to intercept a field tile and divert a fraction of the flow as shallow groundwater. Two potential locations would be in combination with grass waterways and prairie strips. We predict that soils within grass waterways and prairie strips contain sufficient organic carbon to facilitate nitrate loss and that they could be modified to act as saturated buffers for the removal of nitrate from tile drainage.

Objective

This project seeks to extend the utility of saturated buffers through establishment in additional landscape positions, in combination with existing grass waterways and prairie strips. If successful, this would dramatically increase possible sites for saturated buffer establishment and increase the potential of the practice for nitrate removal. Additional objectives will be to translate this information into site evaluation and design criteria to optimize the public investment in saturated buffers and provide feedback to NRCS for modifications to the federal practice standard for saturated buffers (CPS #604) where needed.

Approach

To achieve the objectives, the team will monitor NO3 loss and groundwater flow within a grass waterway and a prairie strip modified to function as saturated buffers. Locations planned are in Blackhawk County and Grundy County, Iowa. The team plans to work on private land with interested, innovative landowners and will also coordinate with another INRC-funded project, Evaluating the Potential for Drainageways to Serve as Test Sites for Innovative Grass Waterway Designs to assess soil hydraulic properties within the waterway.