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The purple and green areas on the map show where farmers are barred from applying fertilizer in the fall or on frozen ground.

Many Minnesota farmers, including some in the Mankato region, will be barred from applying fertilizer in the fall or applying it on frozen ground as the state tries to reduce nitrates in drinking water.

Minnesota’s Groundwater Protection Rule was finalized last spring and is being implemented this year. The Department of Agriculture posted a final map on its website (mda.state.mn.us/nfr) this week showing which areas of land are under the restrictions.

In general, farmers in central Minnesota and all along the eastern and southeastern border are under the restrictions because the soils are more vulnerable to allowing nitrates to leach. But there are pockets in this region, including along much of the Minnesota River, where farmers will be under the new restrictions.

Beyond vulnerable soils, there are also spots around the state (marked in green on the map) where the restrictions apply because high levels of nitrates have been identified in drinking water, often in municipal water systems.

Warren Formo, executive director of the Minnesota Agricultural Water Resource Center, which was formed by the major farm groups, said when the rules were first being discussed farmers thought they were being punished. But he said that as the discussion and rules have focused more on the water quality aspect, farmers have been more receptive.

“We all want safe drinking water and farmers are working hard to keep water safe in their areas. This has been under development and talked about for several years. I think now that the rule is final, farmers are aware of it.”

Formo said that municipal water supplies that have elevated nitrate levels treat them to safe levels for all residents. He said he hopes the ag department will put more focus on working with farmers and other rural residents who have private wells to ensure nitrates are measured and removed through methods such as a reverse-osmosis system.

“The department should inform and educate people,” he said.

Brink of a crisis

The new regulations come as the Environmental Working Group released a report this month saying an estimated half a million Minnesotans — or one in eight residents — draw from groundwater contaminated with elevated levels of nitrate, a toxic pollutant that is linked to cancer and is especially dangerous for infants, causing “blue baby syndrome.”

The group’s one-in-eight count includes water where nitrate levels were above 3 milligrams per liter. That’s a level where health officials deem that the nitrate came from human, not natural, sources.

But the state and federal health limit for nitrate is 10 milligrams per liter, or 10 parts per million. The EWG argues the 10 milligrams level should be lowered, saying it is dangerous at much lower levels. They cite research that even as low as 1 milligram per liter, nitrates may increase the risk of colorectal cancer.

The EWG, other environmental groups and some ag experts criticize the new fertilizer rules for not addressing manure, for not covering more cropland and for not working to cut down on farm fertilizer use in general.

“We think it’s a move in the right direction, but we definitely think the rule falls short for several reasons,” said Sarah Porter, senior GIS analyst with EWG.

“It doesn’t address how much nitrogen goes down. And it only affects 13% of the cropland in the state, so it’s not that much.”

Studies show that farmers continue to use more nitrogen than needed. A 2014 survey by the state agriculture department and USDA found that statewide 61 percent of fields received more nitrogen fertilizer and 71 percent of fields more manure nitrogen than recommended by the University of Minnesota.

Porter said they also believe the Groundwater Protection Rule lacks teeth. The rule is largely voluntarily in the first years and becomes mandatory later. “It could be several years and that’s too slow.”

Anne Weir Schechinger, senior economic analyst with EWG, said another big shortfall of the rule is that it doesn’t put fertilizer restrictions around private wells that have tested high for nitrates. The restrictions are only around towns where high nitrates have been found in municipal water supplies.

“The private well is a big issue. In our analysis we learned that a majority of wells in the state aren’t even being tested for nitrates,” Schechinger said.

The analysis found that 3,300 private wells had tested at 10 or above for nitrates at some point in the past decade. There are an estimated 200,000 private wells in the state, she said.

The state requires a test of every well for nitrates and other contaminants when it’s constructed, but after that there are no requirements for retesting a well. “A lot of these wells are decades old and maybe haven’t been tested since they were put in,” Schechinger said.

The state ag department does have a small program that pays for well testing in a few townships. When entire townships are tested, the results are often startling, Porter said. “In certain areas of the state this is really becoming a problem. In some townships where they test, 30% or 40% of the wells are testing above the legal limit.”