The problem isn't fertilizer per se, but what critics say has amounted to an overenthusiastic use of it.
Residents may think they're merely fertilizing their lawns, but in reality they're also growing a bumper crop of algae in the nearest body of water.
Every time it rains, the excess nutrients are flushed into streams, lakes, and bays. The algae, in addition to sliming swimmers and looking gross, consume oxygen that is vital to aquatic organisms.
The debate has played out in a half-dozen states from New York to Florida, transforming the once-fallow field of fertilizer law.
Traditionally, laws were aimed at things such as truth in labeling. Now, "it's evolving from consumer protection to environmental protection," said Chris J. Wible, director of environmental stewardship for The Scotts Miracle-Gro Co., a major fertilizer manufacturer, based in Marysville, Ohio.
Pennsylvania has taken no formal action on lawn fertilizers, but some products are changing anyway.
As part of an agreement with advocates for Chesapeake Bay - which drains about half of Pennsylvania - Scotts has voluntarily reduced the phosphorus in the lawn fertilizers it distributes to states in the bay's watershed.
Action on nutrient pollution in Pennsylvania has focused on sewage treatment plants, which are facing tighter discharge restrictions, and agriculture, which has made consistent strides in reduced - and more effective - use of manure and fertilizer.
In most states, discussions about lawn fertilizer "are really in their infancy," said scientist Harry Campbell of the Pennsylvania office of the Chesapeake Bay Foundation. But there is a growing recognition that homeowners and fertilizer are often a recipe for excess, he said.
The problem is "the political palatability of the solutions," Campbell said.
In New Jersey, for example, phosphorus would be pretty much out of the mix, except for new lawns. Nitrogen would also be limited.
