Unnecessary phosphorus in lawn fertilizers helping fuel algae blooms

Though the algae blooms are being helped by hot and dry weather, they are fed largely by phosphorus, a non-degrading nutrient in many lawn fertilizers, said Chad Cook, watershed educator at the Winnebago County office of the University of Wisconsin-Extension.

Many people don't realize that stormwater drains bypass water treatment facilities and empty out into rivers, lakes, and streams. That means phosphorus runoff from lawns goes directly into surface waters, where it can cause big problems for recreational users and property owners, like algae blooms. Recent toxin-producing blue-green algae blooms on Lake Winnebago have prompted the state Department of Natural Resources to urge people to use caution because contact with the algae can cause illness.

"I think if you talk to people, a lot of them will equate the source of the phosphorus as our farm fields," Cook said. "Actually, our urban residents can have just as big of an impact, if not bigger, depending on what lawn care practices they're using or the other things they are doing," he said. Cook said inexpensive soil tests would reveal that many fertilize their lawns to excess--unwittingly posing harm to surface waters in the process. Cook said soil tests are available for $15 plus $3.50 postage through county extension offices

Oconomowoc bans phosphorus in lawn fertilizer to aid lakes

Concerned about the proliferation of weeds and algae in its chain of lakes, Oconomowoc has banned property owners from using phosphorus to fertilize lawns in what one official said is a regional trend. Common fertilizer contains a combination of phosphorus, nitrogen and potassium.

Lawn care companies have responded to the growing concern over phosphorus in lawn fertilizers. Matt Stroik, service manager for the Milwaukee branch of Scott's Lawn Service, said the company changed last year to phosphorus-free fertilizers. "We were told by our corporate office - they do studies - that they found there is an abundance of phosphorus in our soil and there is no need to put phosphorus back into the soil," said Stroik, referring to the Midwest.

Tom Steinbach, operating manager for Oconomowoc's wastewater utility, said the ban was proposed in 2006 after residents raised concerns about lake quality. Steinbach said phosphorus levels have been increasing in the Oconomowoc River chain of lakes, which include Okauchee, Oconomowoc and Fowler lakes, along with Lac La Belle.

A state Department of Natural Resources spokesman said reducing phosphorus will cut down on algae problems, which have been increasing. "Phosphorus poses a very real concern to area lakes - there's no argument about that," said Carroll Schaal, lake team leader for the DNR. "If phosphorus is being spread very near the lake, every time there's a good rainstorm there's excess phosphorus leaving the shore land to get in the lake."