Gov. Mark Dayton's aggressive plans to boost water quality by requiring buffer strips along Minnesota waterways took a step back Friday when the governor acknowledged he's ordered state conservation officials to stop mapping "private ditches."

Dayton's made water quality and buffer strips a key part of his intended legacy in his last years in office. The Legislature last year backed a scaled down effort to require the buffers. While there was consensus on the plan for public waterways, farmers and farm groups remained concerned about the law's intentions when it came to ditches on private land.

The new law requires strips on ditches in areas that would benefit public waterways, but farm groups say private ditches were never meant to be part of the deal.

On Friday, Dayton said he pulled back on the private ditch efforts and ordered the Minnesota Department of Natural Resources to stop mapping them after Republicans threatened to torpedo water quality projects Dayton's seeking in a public works spending bill in the coming session.

Dayton said he wouldn't put those public works projects at risk, but he continued to argue that private ditch buffers would make a difference in the state's water quality.

"If private ditches are contaminated they flow into public ditches. Sometimes they flow directly into waterways," he said.

Buffers can be grasses, trees or shrubs. They drink up some of the pollutants — like nitrates from fertilizer — that wash off farm fields and end up in waterways. They also help keep stream banks and riverbanks in place.

The DNR was charged with producing maps of public waters and ditch systems that require permanent vegetation buffers. It's set to produce the maps by July.

Minnesota House Republicans on Friday said Dayton's retreat from private ditch mapping was simply the governor agreeing to "uphold the legislative intent of the new buffer law, which was supported by House Republicans and the Senate DFL."

Farmers support land management practices that boost water quality, but "last fall it became clear the DNR was misinterpreting the new law and greatly expanding its scope," state Rep. Paul Torkelson, R-Hanska, said in a statement.

Dayton didn't see it that way, saying he was "deeply disappointed" in the decision he felt compelled to make.

"I thought that we had achieved a modest agreement in the last legislative session about the urgent need to improve the quality of Minnesota's waters by limiting their pollution from runoffs from private and public ditches," he said in the statement.

He called the "fierce opposition" by House Republican leadership "evidence that we are a very long ways from bipartisan agreements even on the severity of our state's water quality problems, much less on the need to take serious steps to improve it."

The environmental group Conservation Minnesota called Dayton's move disappointing.

"There is broad, bipartisan support and urgency among all Minnesotans for cleaning up polluted waters, Paul Austin, the group's executive director, said in a statement. "The fact that politics was injected into an issue that has no real partisan home shows that once again political theater was allowed to trump the will of the people of Minnesota."