Private water wells soaking up fertilizers, University research says

The study predicts that over the next 20 years, there will be a 45 percent spike in nitrate well contamination.

by Lyra Fontaine

From 2007 to 2012, more than a quarter of southeastern Minnesota’s grassland disappeared as fertilized farmland expanded — a shift in land use that’s contaminating the region’s private drinking water wells.

The switch from grass to crops — a trend across the Midwest that’s spurred by rising crop prices — could lead to a 45 percent increase in the number of wells in the region contaminated with potentially dangerous nitrate, according to recently published University of Minnesota research.

Though the link between agriculture and water contamination is well established, said the study’s lead researcher, Bonnie Keeler of the University’s Institute on the Environment, the recent study of southeastern Minnesota is one of the first attempts to understand the cost of nitrate pollution.

“We know there’s some private benefits and income generated from converting grass to corn,” Keeler said, “but there’s much less information on the societal costs.”

For the 70 percent of Minnesotans who rely on groundwater for drinking and the 1 million people who drink from private wells, there are both financial burdens and health risks.

Excess nitrate in well water, a majority of which comes from agricultural fertilizers, is potentially dangerous for infants, according to the Minnesota Department of Health. Nitrate is also associated with some cancer risks, according to the paper published in late June in the journal “Environmental Research Letters.”

A majority of southeastern Minnesota residents depend on groundwater for drinking, Keeler said.

“Many households are unaware of nitrate contamination in their wells,” Keeler said. “If they decide to do something about it, they’re on their own.”

To cope with contamination, she said, residents can choose to dig a new well, buy bottled water or install a treatment system — as did geologist Jeff Broberg, a resident of the region who owns a farm and works as an environmental consultant.

To counteract the nitrate pollution in his well, which Broberg said is twice the federal threshold, he uses a reverse osmosis system for drinking water. And on top of that system’s up-front and annual costs, Broberg said he’ll have to pay even more in the future because of his polluted well.

“If I had to sell my property, I’d have to disclose that my well is contaminated,” Broberg said, “which would be a $25,000 deduction off of my property.”

Keeler’s study estimates that over 20 years, it could cost anywhere from $700,000 to $12 million to address the issue of nitrate contamination.

Broberg said he thinks the government should better regulate the use of crops and contaminants and farmers should be held financially responsible for the pollution they incur when overapplying nitrates to their fields.

“There seems to be no abatement for the desire to use more and more fertilizer to contaminate more and more groundwater,” he said. “We put more value on crops than we do on our water.”

The Minnesota Department of Agriculture is currently revising its management plan for nitrate contamination, according to a statement from the department. The new plan, which is “largely based on years of research” by the University, is set to be released this fall.

Over the next six years, the agriculture department will test private wells at more than 70,000 households in agricultural townships across Minnesota, the statement said.

Though the plan will include restrictions on fertilizer use in vulnerable areas, it will largely make voluntary suggestions for farmers.

Southeastern Minnesota largely sits atop fractured and dissolved bedrock, which provides passageways for nitrate, making it particularly vulnerable to groundwater contamination, Broberg said.

In the region, researchers noticed a significant shift in land use between 2007 and 2012, as grassland decreased by 26 percent while corn and soybean acreage rose by about the same percentage during the time period, the study said.

Farmers are clearing the land to plant corn, a crop that requires nitrogen, Broberg said.

“In our southeast region, the overapplication just percolates into the ground,” he said.

The research is being expanded statewide, Keeler said, and will examine public water supplies and provide a fuller assessment of the cost of nitrate pollution in Minnesota. Keeler said she expects to have preliminary findings by the fall.

Broberg, who called the initial study’s results “disturbing,” said he’s not optimistic about the future of Minnesota’s groundwater.

“If I’m looking forward 50 years, I’m very discouraged,” he said. “I think that everyone in this part of the state will be drinking treated water.”