August 18, 2009

Lawn fertilizer bans boost water quality

A U.S. study shows banning or restricting the use of lawn fertilizers containing phosphorus can help reduce such pollution in lakes and streams.

Until now there has been no evidence local ordinances banning or restricting the use of lawn fertilizers helped reduce phosphorus pollution, University of Michigan Professor John Lehman said.

It's one of those things where political organizations take the action because they believe it's the environmentally conscious thing to do, but there's been no evidence offered in peer-reviewed literature that these ordinances actually have a salutary effect, Lehman said.

Now, such evidence exists because of a study published by Lehman and students Douglas Bell and Kahli McDonald. The study shows phosphorus levels in the Huron River dropped an average of 28 percent after Ann Arbor, Mich., adopted an ordinance in 2006 that curtailed the use of phosphorus on lawns.

Phosphorus is naturally plentiful in southeast Michigan soils, so fertilizing established lawns with the nutrient is generally unnecessary, Lehman said.

Although the science wasn't difficult, its ramifications in a political sense and in an environmental sense will not be insignificant, Lehman said.

The research -- funded by the Environmental Protection Agency, the U.S. Department of Agriculture and the city of Ann Arbor -- appears online in the journal Lake and Reservoir Management.