The hard frost this winter and a late spring have Steve Klotz worried.

The area Department of Natural Resources fisheries supervisor in Lanesboro knows livestock farmers often have full manure-storage pits and are eager to spread some on their fields. In fact, many have already had to apply manure, even though the ground is still frozen.

His fear is that it will lead to fish kills.

"It's a serious issue right now," he said.

According to the Minnesota Pollution Control Agency, someone from the public reported dead trout in Gorman Creek near Kellogg, and an investigation found about a dozen dead fish. But so far, the MPCA and DNR haven't heard of any more fish kills, according to the MPCA. It is continuing to investigate the Gorman fish kill.

Klotz said he's very surprised there haven't been more reports of fish kills. Maybe the sheer volume of water so far has diluted the manure, he said.

But there's still a lot of snow on north-facing bluffs and it could melt soon; there could also be rain. That could be enough to bring more manure into streams.

"I'm not saying it's over with," he said. When he checked Rush Creek north of Rushford Wednesday, it was running dark brown with runoff.

With that dark water, "I don't know how (fish) survive," he said.

The problem started before winter, Klotz said. Many farmers who had grass waterways, terraces and other conservation measures to slow runoff have "plowed up and planted" that land into row crops, he said. "There's a lot of soil moving" now because of the loss of those measures, he said.

Because of the late spring and hard frost, the MPCA issued a news release last Friday reminding the 25,000 livestock farmers in the state about best management practices.

"If possible, farmers should refrain from spreading manure during periods of rapid melt," it said. "This may be even more important in some areas this year because of frozen snow conditions."

The MPCA is asking farmers to not spread manure until snow melts and the ground thaws.

"We have already had several cases where manure was applied in accordance with the rule, but has negatively impacted surface and groundwater a significant distance away," said Wayne Cords, MPCA feedlot program supervisor.

The MPCA also recommends no spreading of solid manure on fields with a slope of more than 6 percent or liquid manure on fields with more than a 2-percent slope or near areas such as waterways that concentrate flow. The MPCA recommends putting manure on fields with crop residue and in low concentrations.