Janesville64.1°

Law keeps phosphorus off lawns in Wisconsin

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Catherine W. Idzerda
April 12, 2010
— Your lawn needs the N.

It likes to have a little bit of K.


But it probably won’t miss the P.


As of April 1, Wisconsin residents cannot, except in certain limited circumstances, use lawn fertilizer containing phosphorus.


Every fertilizer bag contains three letters: N, P, and K. Those letters stand for nitrogen, phosphorous, and potash and correspond to a set a numbers such as 10-10-10. Those numbers tell you how much of each element you’re getting.


Now, state law says the middle number must be zero on lawn fertilizer bags.


“Phosphorous is helpful for the germination process and is also responsible for fruit and flower development,” said Mike Maddox, horticulture educator for UW Extension and Rotary Botanical Gardens.


If you have an established lawn, you don’t need to worry about fruit and flower development.


And most lawns in this area already have enough phosphorous, Maddox said.


“People probably have ample—if not excessive levels of phosphorous—in their soil,” Maddox said. “Phosphorous really sticks to the soil particles.”


Here’s what happens with excess phosphorous: It runs off into gutters and then into lakes and streams, promoting algae bloom. The law is designed to protect the quality of the state’s waterways, said Charlene Khazae, fertilizer program manager for the Wisconsin Department of Agriculture, Trade and Consumer Protection.


The law applies to homeowners and lawn care companies and does allow some exceptions.


People who are seeding new lawns or laying sod can apply fertilizer with phosphorus when the grass is getting established, Khazae said.


Also, if soil tests show the lawn needs phosphorus, it can be applied.


Here’s where the law gets tricky, especially for retailers. Stores are not allowed to display lawn fertilizer containing phosphorous. Customers have to ask for it.


However, retailers are allowed to sell and display garden fertilizers for vegetables and flowers that contain phosphorus. Also, animal manure sold in bags or finished sewage sludge can be sold or displayed.


Dave Riemer, managing partner of Harris Ace Hardware, said he was able to get rid of his lawn fertilizer containing phosphorus by the April 1 deadline.


His primary challenge comes from a packaging glitch from Scott’s.


The company’s popular “four-step” product looks different than it has in the past. He’s solved the problem by careful labeling.


On the positive side, fertilizer without the phosphorus cost less.


Dave Warren, owner of Dave’s Ace Hardware in Milton and Evansville, wasn’t so lucky. He still has some lawn fertilizer from last year that he’ll have to store somewhere.


He’s also worried about enforcement. How is his staff supposed to know what the fertilizer is being used for?


“Are we supposed to be the phosphorous police?” Warren wondered.


Still, he hasn’t run into any problems yet.


Maddox doesn’t anticipate homeowners will have any problems, either.


“They probably won’t miss it,” Maddox said.



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