Saturated Success

Tom Isenhart is a catalyst for getting research results to the people who need it most. The professor of natural resource ecology and management has built partnerships with landowners and farmers for decades all with the same goal to improve water quality.

“Dick Schultz (professor, natural resource ecology and management) and I have been partners on a project in Bear Creek Watershed since 1990,” says Isenhart. “There we’ve worked with a significant number of landowners in establishing riparian buffers, for water quality and all the other benefits, such as wildlife habitat, carbon sequestration and biodiversity.”

Riparian buffers are areas of trees, shrubs and grasses planted between crops and streams. Bear Creek has been deemed one of 12 National Showcase Restoration Demonstration Watersheds.

Field plumbing

Isenhart’s most recent work is in partnership with Dan Jaynes, soil scientist for the National Laboratory for Agriculture and Environment. Five years ago Isenhart (’82 botany and environmental studies, ’88 MS water resources, ’92 PhD) and Jaynes came up with a new edge-of-field practice called
saturated buffers.

Saturated buffers address nutrient rich water that would normally bypass riparian buffers and enter streams through outlets in subsurface drainage systems. Those systems, commonly known as field tiles, are a kind of plumbing installed under crop fields meant to prevent ponding. In a saturated buffer, additional plumbing is added under riparian buffer areas to divert some of the water from field tiles into the buffer. As the water moves
through the buffer and towards the stream, microorganisms and plant roots process
the nitrate.

Research results are impressive.

“During the first four years of the study, the amount of water diverted from field tiles into saturated buffers has been 40 to 50 percent. How much water we can divert depends on how much water is moving through the tile—we can’t treat it all. But in the water that has been diverted, all of the nitrate has been removed,” says Isenhart.

Science in practice

Funding for the initial saturated buffer installation came from the Leopold Center for Sustainable Agriculture. Since then, 16 demonstration watersheds have been established through the Iowa Water Quality Initiative, begun in 2013 by the Iowa Legislature to help implement Iowa’s Nutrient Reduction Strategy. Isenhart and others at Iowa State are working with landowners within these watersheds to
implement and assess practices that hold
promise to reduce nitrogen and phosphorus
losses to our waters.

“It was just five years ago when Dan and I put the first saturated buffer on Justin Hanson’s farm up on Bear Creek, and now it’s being considered for approval as a statewide cost-shared, nitrate removal practice. That’s what I really like to see: the science used,” Isenhart says.

Justin Hanson’s father and uncle began exploring nutrient management practices with researchers at Iowa State in 1995, after talking to a neighboring farmer who was working with Iowa State to plant a riparian buffer.

“In 2010, Tom and his team asked what we thought about installing a saturated buffer system and we were really excited about it,” says Hanson (’02 agricultural studies). “We were told this winter by Tom and his team 50 to 70 percent of the nitrate, which would have otherwise gone into our stream, had been removed by the saturated buffer. So we’re pleased.”

Isenhart estimates potentially 32 million pounds of nitrate per year could be prevented from entering Iowa steams using saturated buffers.

Researcher and teacher

Isenhart loves teaching, in and out of the classroom, whether working with students or providing technical assistance to landowners. He is an adviser for the Forestry Club and the student chapters of the Society of American Foresters and Pheasants Forever.

Sara Berges (’09 MS ecology and evolutionary biology) says Isenhart inspires a love of learning through his enthusiasm for natural resource management.

“That excitement rubs off on everyone around him,” says Berges. “Tom also encourages students to dig deeper to gain a better understanding of the underlying principles behind what they are learning.”

Berges says her Iowa State field research experience laid a good foundation for her current work as project coordinator with the Allamakee Soil and Water Conservation District.

Important partners

Isenhart’s graduate students and partners at Iowa State and the University of Iowa are researching stream bank erosion at Onion Creek in Story County and Walnut Creek in Jasper County. Having many partners who bring diverse talents to the table is essential to solving water quality and flooding issues in Iowa, says Isenhart.

“The folks with Hydroscience and Engineering at the University of Iowa bring their expertise in flood mitigation and floodplain management,” says Isenhart. “Our skills here at Iowa State are on the agriculture and water quality side—what we can do to bring more resilience to those flood plains. By reaching across the universities and private colleges and organizations we can bring all the expertise to bear on the issues.”

Isenhart says the most important partners are landowners.

“In Iowa, well over 90 percent of our land is owned by private landowners and these are working lands. In order for us to make improvements in water quality, we really need to work in concert with the objectives of landowners.”

Hanson agrees. “I appreciate Tom’s interest in our operation, not only for what he’s interested in, but what interests us, too. We really appreciate working with him.”