Results from the first saturated-buffer research site at Bear Creek, Iowa, show significant improvements in subsurface drainage water quality, says Dan Jaynes, a soil scientist at the National Laboratory for Agriculture and the Environment in Ames, Iowa, which developed the technique.

From 2011 to 2013, an average of 50% of total tile flow from a 25-acre field was diverted into the 1,000-foot Bear Creek buffer, Jaynes says. During high flow periods, some water bypasses the buffer and flows directly into the stream to maintain drainage efficiency. “The higher the percentage of water through the buffer, the more nitrogen is removed,” Utt says.

The N load in the diverted flow at Bear Creek ranged from 240 lbs. to 336 lbs. nitrate-N. “All of the nitrate diverted into the buffer was removed in the shallow groundwater under the buffer before it reached the stream,” Jaynes says (see table).

The cost to remove the N: about $1.02 per pound, “comparable to the nitrate-removal cost of constructed wetlands,” Jaynes says. Eventually, saturated buffers might be eligible for conservation payments, Utt says.

There’s “tremendous potential for broad implementation” of this practice, he adds.

“All the producers we are working with are very conservation-minded,” Utt says. “They are excited about the potential of this practice.” Says Cain, “This is a great opportunity to take conservation to the next level.”