Nitrates raise costs of treating drinking water

Farm Forum

ST. PETER, Minn. (AP) – Residents of St. Peter, Minn., pay high rates for drinking water because it takes extra equipment to remove the unhealthy levels of nitrates from its groundwater.

When nitrates from agricultural fertilizer seep into drinking water supplies they pose a risk to infants, pregnant women and others. They’ve made the southern Minnesota city one of at least two dozen communities in the state with unhealthy levels of fertilizer by-products in their groundwater.

Bruce Montgomery, manager of the fertilizer management section for the state Department of Agriculture, told Minnesota Public Radio for a story aired on Sept. 10 that adjusting fertilizer practices can only partially help protect water supplies. Despite farmer cooperation, nitrate levels in one St. Peter city well are still 60 percent above recommended levels.

So St. Peter uses a reverse osmosis water treatment system. It’s one reason customers pay in the top third of municipal water rates in Minnesota, City Administrator Todd Prafke said. The city hasn’t analyzed exactly how much nitrate removal costs an average resident. But state agriculture officials say it can add as much as $200 a year to a typical homeowner’s bill.

“It’s an additional level of treatment that you might not otherwise undertake,” Prafke said. “If you’re doing more stuff there’s an additional cost related to that more stuff that you’re doing.”

Montgomery said there’s a proven solution: growing perennial crops that absorb nitrates, such as alfalfa, strategically placed in wellhead areas. Alfalfa root systems grow as much as eight feet a year. He said the crop is “like a very good Hoover vacuum cleaner. … It does a really, really good job of removing those nitrates.”

Alfalfa can reduce nitrates reaching aquifers by up to 90 percent, he said. The hitch is that farmers are reluctant to switch because they don’t think it’s as profitable as corn.

But they’re not necessarily right, said Mike McDuffy, an extension economist at Iowa State University. He said he knows several farmers that are making good money from alfalfa, partly because it’s in short supply due to drought.

According to Iowa State University data, alfalfa this year could clear as much as $300 an acre. Corn, on the other hand, is fetching lower prices than recent years, and corn farmers may see profits of less than $200 an acre this year.

Duffy said rotating alfalfa with other crops preserves a good share of the environmental benefits while also increasing profitability.