For the City Times
CENTRAL WISCONSIN – A two-year project funded through the University of Wisconsin Water Resources Institute is investigating an interseeding cultivation method for potato cropping that shows early promise to reduce nitrate leaching.
“When you look at impacts on the groundwater system from typical cropping systems in the Central Sands, they tend to leach nitrate,” said Kevin Masarik. “Potatoes are particularly challenging because the hill and furrow system tends to promote both (water) recharge, as well as nitrate leaching loss due to the high nitrogen demand of that particular crop.”
The researcher from the University of Wisconsin-Stevens Point and University of Wisconsin-Madison Division of Extension is pursuing what he termed an outside-the-box idea—interseeding rye, oat and millet between the rows of potatoes to create biomass to take up excess nitrates.
In children six months and younger, nitrate promotes the oxidation of hemoglobin to methemoglobin that limits blood’s ability to bind and transport oxygen, depriving the infant of oxygen. Nitrate has also been linked to cancer, thyroid disorders, birth defects and hypertension. Both state health and agricultural officials name nitrate as the most widespread groundwater contaminant in Wisconsin affecting both municipal and private water systems. Because groundwater also makes its way to surface waters, rivers, lakes, streams and wetlands can see higher nitrate levels with one result being increased algae growth, disrupting ecosystems.
Masarik said for the last 20-30 years, when the cause and extent of nitrate in groundwater has been documented, there’s been a simultaneous gap. “We’ve been good at pointing out that there’s a problem, but we haven’t been good at pointing out what the solution is.”
“In the last five years, I’ve been trying to switch the questions that I’m interested in devoting my time and attention to, investigating potential solutions that significantly improve water quality. And that’s what this project was born out of.”
The project also needs to ensure that the potato harvest isn’t hindered nor yield significantly reduced by the additional vegetation between rows. Masarik is grateful for the cooperation of Portage County farmer Justin Isherwood who in 2020 provided a test plot.
“It’s (the study) giving me the book,” Isherwood said. “We know a lot of things in agriculture. There are a few things in agriculture we don’t know. Kevin is giving me those letters and the alphabet. He’s giving me the language of the landscape.”
Isherwood is game to again participate in the study this year.
“It’s exciting to be a part of the science and to be involved in the discovery,” he said.
Discoveries of last year will be applied. For example, rye is likely to be removed from the seed mix because it put early energy into root growth, resulting in slow above-ground growth. The rye was then shaded out by potato plants.
Oat and millet though, “(did) have some success. I think it showed that the amount of biomass accumulation and the amount of nitrogen that the interplanting, or that cover crop, was able to capture is significant enough that this could be viable,” Masarik said.