Dane County Executive Kathleen Falk and Madison Mayor Dave Cieslewicz hosted a presentation Monday night to promote the limitation of phosphorus-based fertilizers, which flow into lakes and grow excessive amounts of algae.

Recent concern about the water quality of Dane County lakes has called attention specifically to the conditions of Lake Mendota. Both Mayor Cieslewicz and Falk have been working together on environmental battles for 15 years and said they have no plans on slowing down now.

“No one step got us to this point while our lakes deteriorated, and no one step will get us out this spot,” Falk said.

Mayor Cieslewicz has been busy constructing several proposals to help control phosphorus runoff into lakes. He has proposed an expansion of the city street-sweeping program to decrease runoff and supported an ordinance to restrict phosphorus in lawn fertilizers.

Mayor Cieslewicz added that he wanted to thank Ald. Gregory Markle for generating the program idea and for his ordinance proposal currently before the City Council that would phase out phosphorus in lawn fertilizer.

Aiding Falk and Cieslewicz, scientist John M. Barten was guest speaker at the presentation. As a Minnesota water-quality manager for the Three Rivers Park District in the Twin Cities area, Barten’s involvement helped create a ban on phosphorus lawn fertilizer in the town of Plymouth, Minn.

Phosphorus, a primary component of fertilizer (along with nitrogen and potash) can leach into lakes. According to Barten, one pound of phosphorus can grow 500 pounds of algae.

In addition, Barten’s study of 181 lawns in the Twin Cities area showed that 80 percent of lawn soils contained very high levels of phosphorus and did not require additional phosphorus. When applied to soils that contain very high levels of phosphorus, he said, the chemical will run off into streets and be carried into the surrounding watershed of ponds, lakes, streams and wetlands.

Barten said banning phosphorus fertilizer is in the best economic interest of any area, especially when removing 25 pounds of phosphorus from lakes can cost more than $5,000 if done through use of street sweeping, management practices and ponds.

“This is a really a win-win situation in my opinion,” Barten said.

Even if phosphorus fertilizer is banned, the chemical can drain into the watershed through other means. Bird droppings, especially those of geese, contain high levels of phosphorus, as well as spring pollen. Urbanization and construction can also flatten and harden soil, causing easy run off during rains.

Despite a potential ban on phosphorus fertilizers, the chemical could find other ways to leach into lakes. In the case of lakes the size of Lake Mendota, the restoration of water quality will be slow.