WORTHINGTON, Minn. (AP) -

As Minnesota communities spend millions of dollars to remove nitrate contamination from their drinking water, state officials say it's time for farmers to do more to prevent the problem.

The Minnesota Department of Agriculture plans to use new rules to be more aggressive in getting farmers to limit the amount of fertilizer chemicals leaching into groundwater.

"We could restrict the timing, the source, the placement of those products. We could also require certain best management practices be put in place," Assistant Commissioner Matt Wohlman told Minnesota Public Radio for a story that aired Monday.

But Kris Sigford, water quality director at the Minnesota Center for Environmental Advocacy, said the department hasn't moved fast or forcefully enough.

"Unfortunately, we have a bigger environmental problem than we had a quarter of a century ago," Sigford said. "It's time to move from purely voluntary to regulatory, to develop some practices that actually work and require them to be employed in certain regions of the state."

Hastings, St. Peter, Lincoln Pipestone Rural Water and other public and private entities have spent tens of millions of dollars installing equipment to remove nitrates. At high concentrations in drinking water, nitrates can pose health problems, particularly for babies. Consumers typically pay the cleanup costs through higher water bills.

The agriculture department estimates about 280 townships making up one-tenth of the state's surface area have problems with nitrates.

Sigford points to department data that show increasing nitrate contamination in six of seven testing regions. From 1985 to 1999, two-thirds of water tests in those areas showed nitrates; from 2000 to 2010, nine out of 10 did. Unsafe concentrations rose as well. She said that's a clear signal of policy failure.

Wohlman disagreed. While the data suggest an increase, he said, the department's findings aren't detailed enough to draw a firm conclusion.

"We do believe that nitrogen in groundwater is a major issue for the state," he said. "The data is not deep."

Tim Figge, who lives outside of Hastings, once had little concern about his water, drinking it straight from the well. But that changed two years ago. He knew some of his neighbors were having troubles, and his pregnant daughter came one for a visit. So he had his well tested. The results showed unsafe nitrate levels.

"We're edging towards the precipice right now," Figge said. "With high, high levels of nitrates that need to be addressed."