The Agricultural Drainage Management Coalition (ADMC), Agricultural Drainage Management Systems Task Force and Dr. Dan Jaynes with the National Laboratory for Agricultural & The Environment collaborated to demonstrate and evaluate saturated buffers at field scale to reduce nitrates and phosphorus from subsurface field drainage systems.
With many of the row-crop agriculture fields in the Midwest being located adjacent to ditches, streams, rivers and lakes, it is no surprise that 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.
To accomplish the goals of this demonstration project, fifteen monitoring sites were selected in four different states (IA, IL, IN, and MN). A variety of site characteristics, not all considered “ideal”, were chosen to demonstrate the effectiveness of the practice if implemented at a large scale. This also afforded the opportunity to explore why some sites had SB systems that were more effective at removing nutrients than others. Water flow rates from the subsurface drainage systems were monitored, and water samples for nitrate and phosphorous analysis were taken from September 2012 through September 2015.
The data from this study confirm that, when proper site conditions and design considerations are met, the SB practice can be an effective method for reducing nitrate transport from subsurface drainage systems. Phosphorus loads, however, appear to be generally unaffected by this practice.
Source: www.agnewscenter.com