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Removing tile water nutrients aims to improve nearby lakes

The Hammer Kavazanjian Farm installs an edge-of-field phosphorus removal system.

May 26, 2021

7 Min Read
Charlie Hammer and Nancy Kavazanjian gather a water sample
WATER SAMPLE: Nancy Kavazanjian and Charlie Hammer gather a water sample for lab analysis of phosphorus and nitrates in their tile water.Photos courtesy of American Soybean Association

Decades before soil health became a recognized valuable science, Charlie Hammer and Nancy Kavazanjian launched their Wisconsin family farm in 1980 with the motto, “Our Soil, Our Strength.”

“We dedicated ourselves to doing what’s best for our soils and our crops 41 years ago,” Kavazanjian says. “All of our conservation and agronomic efforts to build healthier soils continue to pay benefits. And we’ve always been very involved in water quality because we have many lakes here in Wisconsin. Now we’ve installed an innovative proof-of-concept system to remove phosphorus from tile water and keep nutrients on the land.”

Hammer has continued the innovator legacy on the fourth-generation farm that’s been in the family since his great-grandparents immigrated from Germany in 1866, buying 173 acres near Beaver Dam.

“We’ve added small grains and cover crops to our crop rotation, along with variable-rate nutrients to improve crop fertility and water quality, but we wanted to take the next step of filtering our tile water,” he says.

Mining-water filter technology

It was a dinner table discussion with Kavazanjian’s brother that brought Arizona mining water reclamation technology to its first on-farm trial in a 70-acre Wisconsin field.

Hammer and Kavazanjian were discussing the merits of an edge-of-field bioreactor to remove nitrates. “My brother Ed Kavazanjian Jr., a geotechnical engineer at Arizona State University, asked why we weren’t considering phosphorus removal, which neither of us knew existed,” she recalls.

The innovative phosphorus-removal technology using slag, a steel byproduct, was lab-tested at ASU for more than a year.

“Once we had proof-of-concept that it removed phosphorus from water in the lab, while allowing for the use of a downstream bioreactor to manage nitrogen, our next step was a field demonstration. And Nancy and Charlie agreed to host the field site,” explains Nasser Hamdan, a senior investigator on the project for ASU’s Center for Bio-mediated and Bio-inspired Geotechnics.

To further assist with this water quality effort, the Hammer Kavazanjian Farm received a Conservation Demonstration Grant from the American Soybean Association and the Walton Family Foundation. They were one of three farm operations to receive a cost-share grant to demonstrate new next-level conservation practices. ASA and Walton Family Foundation Conservation Champions and ASA’s Conservation Legacy Award winners from the past five years were eligible to apply for the grant.

Install gravity-fed system

One of ASU’s industry contacts supplied slag for the project for the cost of transporting it to the site. Kunkel Engineering Group in Beaver Dam, the local office of another ASU industry partner, provided design and field supervision last fall at no cost to the project. They selected the edge of a 70-acre field that tile-drains into a wetland and then into a nearby recreational lake.

The phosphorus filter design includes a smaller geomembrane-lined, rock-covered filter pit that contains steel slag. Field tile lines, with shutoff valves, feed the water into this slag filter and then into a larger open holding pond, where the P precipitates out.

“Once the soluble phosphorus in the water hits the steel slag, a chemical reaction begins to remove the phosphorus out of the water,” Hammer says. “We see positive phosphorus reduction already, but the engineers want at least six months of data.”


Hamdan likes the current progress with this phosphorus removal system. “We’ve seen near-complete removal, which is impressive to achieve because it’s more difficult to remove P in tile water that already has a low P level,” Hamdan says.

Local community and municipality support

The two lake associations surrounding the lake on the other side of the wetland want to help by providing funds. Kavazanjian says they’re so excited, they want five or six more filters installed. “We’ve had to rein them in until we have proof-of-concept,” she says.

She also notes that watershed groups and several area sewer districts are interested in the results because they need to reduce phosphorus in sewage treatment plants. “If they can buy or swap credits, that could be something that they pay us for, which is a win-win for everybody.”

Like his dad and grandparents, Hammer is proud of their farm’s innovative practices over the decades. “What’s even more important is to demonstrate the technology value to a wider network of farmers, watershed and conservation groups, and our lake association neighbors,” he says. “We plan to host a field day in 2021 to showcase the results.”

There are many phosphorus sources — from soil and rocks to farm fields, fertilized lawns, wastewater treatment plants, animal manure and commercial cleaning products — so it’s a challenge across many industries.

Bioreactor addition in 2nd phase

ASU, Kunkle Engineering and Hammer Kavazanjian Farm plan to attempt another innovation: adding a bioreactor to this system to remove nitrates and phosphorus from the tile water.

“We’d love to perfect a combination system that brings us clean water so we can show the community that we are part of the solution,” Kavazanjian says.

Hamdan says they initially conducted lab research to remove phosphorus and nitrates simultaneously — a bioreactor system using wood chips and slag. “Since nitrate removal takes longer than phosphorus, this process was not very efficient. But we learned that while the chemistry from the slag imparted changes to pH and alkalinity changes in the water, it had no significant impact on the microbes needed for denitrification to remove nitrate,” he adds. “So, we can attach a bioreactor to our phosphorus removal system.”

“One thing we’ve already learned from this project is that our current agronomic and cover crop practices show a reduced level of phosphorus,” Kavazanjian adds. “Now, with help from the Walton Family Foundation, we can help fund the bioreactor to reduce our nitrate levels.”

Big innovation, conservation history

Winners of the ASA Conservation Legacy Award in 2020, Hammer and Kavazanjian have worked hard to leave a legacy of healthier soil, reduced erosion, energy conservation, habitat for pollinators and wildlife, and precision technology investment to reduce inputs.


“Along with my parents, I give credit to my buddy, Illinois farmer Jim Kinsella, as a valuable early mentor,” Hammer says. “He taught me the importance of no-till and paying attention to soil biology, compaction, crop residue — not trash — and keeping living crops growing on set-aside acres back in the 1980s and ’90s.”

Hammer and Kavazanjian love to incorporate innovative conservation practices beyond agronomics. They are renewable-energy advocates, adding a wind turbine in 2009 that spins their electric meter backward on windy days to pay for itself. Three years ago, they added a solar array that powers their farm shop on sunny days. And they use ethanol and biodiesel to power their vehicles and equipment.

Network and support agriculture

While innovation has its share of pitfalls, the couple emphasizes the importance of starting small and seeking help from family, friends and business partners to survive and thrive. “Your commodity organizations like ASA offer great resources to network and learn,” Kavazanjian says. “We’ve had great partnerships on projects with Natural Resources Conservation Service, our local Farm Service Agency, local watershed and other groups that have helped us with various practices.”

Hammer loves to connect with a network of like-minded farmer-friends in a social media group that shares innovative successes and failures.

“Both Nancy and I encourage young farmers to find their network of people to share ideas that can help improve your business and your conservation practices,” Hammer says.

ASA is proud of its conservation legacy and partnership with the Walton Family Foundation. The Walton family has a long legacy of love for the outdoors. The foundation works with organizations like ASA to align policy and market incentives to encourage farmers to adopt practices that improve water quality, enhance soil health and reduce pollution across the Mississippi River basin.

Source: American Soybean Association, which is responsible for the information provided and is wholly owned by the source. Informa Business Media and its subsidiaries aren’t responsible for any of the content contained in this information asset.

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