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Saturated buffers a new tool to improve water quality

saturated bufferNick Meier takes a proactive approach to protecting water quality and reducing soil loss on his farm near La Porte City in Black Hawk County. And like a growing number of Iowa farmers, he is exploring a range of new technologies to help him reach his environmental goals.

That’s why Meier was eager to participate when researchers were on the lookout for a farm in the Miller Creek watershed to install a saturated buffer. It’s a new type of conservation structure that has shown promise in removing nitrates and other nutrients from tile-drained water.

"I really wanted to learn more about this technology. I wanted to see how it will work on my farm," Meier, a Black Hawk County Farm Bureau member, said as he watched technicians install the saturated buffer on his farm earlier this spring. "It goes beyond the filter strips we put in about eight to 10 years ago, and I think it can really make a difference in improving water quality."

Research on saturated buffers bears that out, according to Dan Jaynes, a soil scientist at the U.S. Department of Agriculture’s (USDA) National Laboratory for Agriculture and the Environment, which is located on the Iowa State University (ISU) campus. He’s helped to install several saturated buffer research projects around the Midwest, including a pioneering one installed in 2010 at Bear Creek in Story County. That project was funded by a grant from the Leopold Center at ISU.

A saturated buffer, Jaynes said, is designed to enhance the performance of a buffer strip by reworking it so it can intercept and treat tile drainage, as well as surface water. "We’ve found that they work very well. For the tile water that’s flowing through the buffer, it’s taking the nitrate level down to zero," Jaynes said.

He and other researchers be­­lieve that saturated buffers could be a valuable tool for farmers as they ramp up their efforts to reduce nutrient loss and continue to improve Iowa’s water quality.

No drainage restrictions

While it enhances the buffer strip by treating a portion of the tile water drainage, the saturated buffer doesn’t restrict drainage or adversely affect field work by making fields too wet, Jaynes emphasized. "The idea with the saturated buffer is that you can put them in and forget them and they will keep doing their job by removing nitrates for years and years. There really are no moving parts."

Another advantage is that the system can be installed quickly and fairly inexpensively, Jaynes said. He estimated the installation of the saturated buffer, with equipment and tile work, will cost a farmer about $2,000 and require only a few hours to install.

To install the saturated buffer on the Meier farm, tiling technicians first dug a hole in a well-established buffer strip and dropped in a drainage control box. The box, once buried, was connected to an existing tile line that moves water collected from the pattern tile of a nearby field.

The technicians then bury a perforated tile line laterally under the buffer strip for several hundred feet, parallel to the stream. One outlet on the control box is then connected to the line of perforated tile and the other is to the line that goes to the stream.

Diverting drainage

The control box will divert a portion of the tile drainage water through the perforated tile and into the soil beneath the buffer strip. The water will saturate the root zone of the buffer strip, where high-organic soils and deeply-rooted grasses will work to remove nitrates and other nutrients.

Jaynes, along with Tom Isen­hart, an associate professor in ISU’s Natural Resource Ecology and Management program, are installing saturated buffers in targeted watersheds around the state as part of a project funded through the Iowa Nutrient Research Center. The center, part of the state’s water quality initiative, is designed to promote research into new practices that show promise in reducing nutrient loss and improving water quality.

With each saturated buffer, the researchers are installing a series of monitoring wells so they can determine how well the structure is working at removing nitrates and other nutrients. They are also installing rain gauges and other monitoring systems to see how the saturated buffer performs in varying weather conditions.

In normal conditions, the saturated buffer is designed to intercept and divert 30 to 50 percent of the water coming from the tile line, Jayne said. "It’s a pretty significant percentage and should definitely make a difference."

Many technologies

The saturated buffer is just one of the technologies that Meier is looking into on his farm. Working with Shane Wulf, coordinator of the Miller Creek Water Quality Improvement Project, he’s planning to install a bioreactor on this farm after soybean planting is complete. Meier has also experimented with no-till and strip tillage on his farm.

"It’s really important to try all of these different technologies that are available for conservation and water quality. That way, we can see which ones work the best for us," Meier said. "I don’t want to lose any nutrients at all from my fields, if I can help it."



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