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Michigan Phosphorus Data: The Fertilizer Ban is Working

Citing data that shows a 17 percent reduction in phosphorus runoff in a local river, a University of Michigan professor told SafeLawns.org that three years of studies indicate a ban on phosphorus in lawn fertilizers is working as intended.

Bans of phosphorus in lawn fertilizer have become hugely controversial across the United States in the past four years. Opponents of the bans say that the major sources of phosphorus in lakes, rivers and streams do not come from lawns, but rather from leaves, pollen, agricultural runoff and housing developments among others.

Phosphorus in fresh water bodies is of major concern because the nutrient encourages blooms of algae, which sucks up oxygen and other resources and makes life otherwise difficult for marine life.

Professor John Lehman, who had been studying nutrient concentrations in Huron River for several years prior to the city of Ann Arbor enacting a phosphorus ban in fertilizers in 2007, issued a landmark study a year ago that gave the nation its first true data points about whether or not bans of phosphorus in lawn fertilizer affect runoff into bodies of water. Because he held the data prior to the ban, he was in a unique position to conduct the study.

Although the third-year numbers have not been published, he told us: “Year 3 results (2010) to date remain consistent with the hypothesis that river phosphorus is lower in the part of the catchment affected by the ban.”

In a report that Lehman submitted to the city of Ann Arbor, obtained by SafeLawns, he concluded that at the control site of his experiment — upstream from the phosphorus ban — no reduction in phosphorus was seen in the water. That led to the conclusion that the reduction in phosphorus levels in the area impacted by the ban was due to the legislation.

Several media outlets in New York and New Jersey have contacted us in the past month since legislation in both of those states has addressed the phosphorus issue. Based on Lehman’s ongoing three-year study, a phosphorus reduction in lawn fertilizers does appear to be justified.

That would leave two primary questions: 1) What will be the impact on the lack of phosphorus in lawn fertilizers on the health of lawns?; and 2) Should that matter either way? One could easily argue that the health of a lake or river is far more important than the collective health of lawns.

Opponents of the no-phosphorus bills will argue that phosphorus is necessary for lawns to be healthy and that is true. They’ll also point out that a lush lawn reduces soil erosion and therefore keeps phosphorus out of water, which is also true.

But the reality is that lawns are not likely to die outright if phosphorus is taken out of the fertilizers. If data shows, down the road, that the impact on overall lawn health is unreasonable, then perhaps a compromise can be struck that allows some small percentage of phosphorus to be added back into the bags.

In the meantime, we need to rely on the science and stand in favor of reasonable phosphorus restrictions.

About The Author

Paul Tukey

An international leader of the green movement, Mr. Tukey is a journalist, author, filmmaker, TV host, activist and award-winning public speaker, who is widely recognized as North America's leading advocate for landscape sustainability and toxic pesticide reduction strategies.

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