The effectiveness of saturated buffers on buffers enrolled in CRP to reduce nutrient loading from tile drainage waters has proven successful by a group of researchers.
The Agricultural Drainage Management Coalition (ADMC) Member Companies and Dr. Dan Jaynes with the National Laboratory for Agricultural and the Environment partnered for the study.
This demonstration program builds upon this same group of collaborator’s findings from the 2012-2015 project that evaluated the ability for saturated buffers at field scale to reduce nitrate and phosphorus from field drainage systems.
Many of the row-crop agriculture fields in the Midwest are located adjacent to ditches, streams, rivers and lakes, so it is no surprise nutrient transport from agriculture lands is a major concern. Large areas of the Midwest are intensively tile drained and it is assumed that many of the vegetated buffers adjacent to waterways are being under-utilized, because the tile outlets quickly move large amounts of subsurface flow past the buffer and into the receiving waterway without any opportunity for treatment by the buffer.
The project collaborators sought to demonstrate and evaluate the effectiveness of a new conservation practice commonly referred to as a saturated buffer (SB). The goal of a SB system is to hydrologically reconnect a subsurface drainage outlet with an edge-of-field buffer. This practice takes advantage of both the denitrification and plant nutrient uptake opportunities that are known to exist in buffers with perennial vegetation.
This project monitored nine SB’s in Iowa, Illinois, and Minnesota. These sites intentionally included a variety of soil types, buffer vegetation, surface topographies, and ditch/stream channel depths. The monitoring timeline included a period from September 2016 through February 2017, yielding six months of flow and nutrient samples.
All nine sites were consistent in showing nitrate concentration reductions from the main line of the drainage system to the stream side test well. This reinforces data from the previous study where 27 out of 28 field years indicated the same reductions.
Current data collection techniques heavily support the use of saturated buffers as a credible nitrate load reduction practice. The cost per pound of nitrate removed is low compared to other nitrate removal practices.