SPRINGFIELD, Ill. – Water quality is an important theme in agriculture, more specifically maintaining the quality of waterways and streams. Many groups see buffers as the solution, but buffers may not be enough. The Agricultural Drainage Management Coalition (ADMC) has been working on and researching the effectiveness of saturated buffers to stop excess nutrients from reaching waterways.
“We have a lot of great buffers installed throughout the Midwest and they do a really good job at trapping nutrients that move across the surface,” said Keegan Kult, with the ADMC, during a recent phone interview. “But, with a tile drain landscape, a lot of the nutrients actually flow underneath the ground in the tile lines themselves.”
The challenge facing the ADMC was to find a way to trap the nutrients moving through the subsurface tile lines, without compromising the effectives of the tile drainage system or the production of the adjacent field.
“Saturated buffers are one of the conservation drainage practices that are aimed to remove nitrogen from tile lines before that water reaches the stream,” said Kult. “We basically tap into a tile line before it outlets with a control structure and we divert a portion of that tile flow laterally through the filter strip or buffer that's in place.”
Using a series of water stops or baffles, a control structure diverts tile water from going directly out of a tile outlet into a waterway. Instead the water is moved laterally through the buffer in tile lines that run parallel to the stream.
“We install lateral tile lines within the filter strip itself, typically those are 500-1,000 feet long,” he said. “Then, that water will redistribute back out into the soil profile of the filter strip.”
This allows the vegetation of the buffer strip to trap nitrogen or other nutrients that potentially could be in that tile water.
The ADMC is an industry led coalition. It includes many tile line manufactures, distributors, tile installers and other related organizations. Throughout the Midwest, they have established seven of these saturated buffer sites that they are able to monitor and test.
“We had a recent contract with the Farm Services Agency, FSA, to continue monitoring on seven of these sites,” he said. “Last year, we were about 33 percent of the nitrate load was removed on average over the seven sites.”
The Iowa State University Agriculture Research Service in Ames has also been monitoring and testing their own saturated buffer sites. According to Kult, they reported a 44 percent reduction in nitrate levels across multiple sites and years.
This is a comparison of the tile drainage water going into the saturated buffer versus coming out of the buffer and into the water way. The saturated buffer was able to trap between 33 and 44 percent of the nitrate load over the course of a growing season.
The system will not stop all water moving through the lines, particularly during extremely wet conditions. The tile lines still need to function and drain the field.
The amount of the tile water being diverted will be dependent on the amount of tile flow.
The control mechanism that diverts the tile water uses gravity flow. There is no mechanical pump, electricity requirement or equipment to maintain. Once it is installed, there is nothing else the grower has to do with it.
Average cost to install a saturated buffer system is $3,600.
“All the benefits of these saturated buffers are realized downstream and that is why there are really good financial assistance opportunities for these saturated buffers right now,” he said.
The local NRCS offices will be able to assist growers who want to establish these buffer systems. They can help with the financial assistant programs through EQIP or CRP.
“There is also quite a few state led initiatives in the Midwest that will help finance these systems,” he said. “The installation itself generally only takes half of a day for a drainage contractor to do and if you have the right site, you can pretty much set these out there and forget about them.”
When compared to other forms of removing nitrogen from the water, these saturated buffers are among the most cost effective. Over the course of 40 years, total cost per pound of nitrogen removed is approximately $1.22.
For growers interested in learning more about saturated buffers and including them in their operation, they can reach out to the ADMC directly. They can also go to their local NRCS or SWCD offices.
“When these get designed, they get designed with the fields drainage system in mind,” said Kult. “The more slope we have to work with in your field, the more aggressive we can be with how much water we are going to push through the buffer.”