Michigan legislators have banned lawn fertilizers containing phosphorus, which in large amounts can cause algae blooms in waterways while encouraging growth of nuisance aquatic plants.
The measure was enacted last week and takes effect Jan. 1, 2012. The ban will exclude farms, which are working with the state Department of Agriculture to reduce phosphorus use. Also exempt are golf courses, new lawns and homes whose owners can prove through soil tests that their lawns need phosphorus, a naturally occurring soil nutrient that helps grow strong plant roots.
Lawn companies and retailers say compliance won't be a problem because many of the state's local governments already prohibit fertilizes with phosphorus.
"We stopped selling phosphorus fertilizers about two years ago," Bill Young, assistant manager of a Home Depot store in Troy, told the Detroit Free Press for a Sunday story.
Troy is in Oakland County, which has imposed a ban, as have neighboring Macomb and Wayne counties.
Similar policies around the nation have led fertilizer manufacturers to rid their products of phosphorus. They sometimes replace it with potash, Young said.
Among Great Lakes states that restrict phosphorus fertilizers are Minnesota, Wisconsin, New York and Illinois. Phosphorus overloading is a concern in the region because algae blooms can rob the water of oxygen. In Lake Erie, they have created "dead zones" with so little oxygen that virtually nothing can survive.
Manufacturers also have dropped phosphorus from dishwasher detergents after 15 states, including Michigan, imposed bans this year. Decades ago, bans on phosphorus in laundry detergents helped reduce algae in the Great Lakes and other waterways.
The Michigan Nursery and Landscape Association supported the fertilizer legislation, said Amy Frankmann, the group's executive director, although she said the group is disappointed that the measure allows local ordinances more restrictive than the state law.
Environmental groups worked for eight years to get the ban, Elizabeth Riggs of the Huron River Watershed Council told the Free Press. Some cities, counties and townships have enacted their own prohibitions.
Testing has shown a 30 percent drop in phosphorus levels in the Huron River since Ann Arbor banned fertilizers with phosphorus in 2007, Riggs said.
Farms will remain the primary source of phosphorus in waterways. But the new law will bring about a significant drop-off because homeowners often use too much fertilizer, said James Clift, policy director for the Michigan Environmental Council.
"There are a lot of uses of phosphorus, so we have to focus on the ones we can eliminate," he said.