Farm fields or lawns? New report on water pollution

The quantity of nitrogen and phosphorus fertilizers that are applied to corn and soybean fields dwarfs that of lawns and golf courses.

Will Hoyer
Will Hoyer

How many of you have been in a conversation about Iowa’s water quality that went something like this?

  • Person 1:  Iowa’s waters really are filthy.
  • Person 2: They sure are. I know a lot of that is because of our state’s agriculture and all the fertilizers that farmers use.
  • Person 1: That’s probably true, but you know what is really a problem?  The fertilizers my neighbors are always putting on their grass. They put so much on all the time and sometimes even in the rain. Why? For a lawn that they never use?
  • Person 2: You’re probably right. I just drove across the river downtown and it was so gross. And I saw several lawn chemical companies out this morning.

If you’re anything like me you’ve probably heard people downplay the role of agriculture in degrading our waters and shift the focus to our urban areas. I recently had dinner with a small group of environmentally aware citizens and a conversation much like the above occurred.

I asked the group what percentage of the applied fertilizers in Iowa are put on farm fields and got responses ranging from 50 to 80 percent. It just so happened that I knew the real answer and it was way higher than the guesses I heard.

IPP’s latest report focuses only on the chemical fertilizers that are applied to the state’s farm fields, lawns and golf courses. It conclusively shows that the quantity of nitrogen and phosphorus fertilizers that are applied to corn and soybean fields dwarfs that of lawns and golf courses. It isn’t even close. Roughly 98% of the nitrogen and phosphorus applied in fertilizers goes on the state’s farm fields.

On average the pounds applied per acre of these fertilizers are higher on lawns and golf courses but the total area that receives treatments is so miniscule relative to the acres of corn and beans in this state. In addition, these fertilizers are applied to areas that have plants that can immediately use the nutrients, whereas many fertilizers are applied to crop fields that do not.

This is not to say that lawn fertilizers in urban areas are blameless. Indeed, in some urban watersheds they may be a significant source of the nutrient pollution entering Iowa’s waters, but overall it’s safe to say that agriculture is where the vast majority of the nutrients that start as applied fertilizers originate. Throw in manure applications and the relative contribution of agriculture gets even larger.

Can that be changed? With cover crops, perennial crops, better cropping practices, and improved nutrient management plans among other things, that gap can be narrowed.  Narrowing that gap will bring with it improved water quality. That is something we can all celebrate.

Posted by Will Hoyer, Research Associate

Author: iowapolicypoints

Iowa Policy Points is a blog of Common Good Iowa, a new organization built on a collective 50 years of experience of two respected Iowa organizations — the Child and Family Policy Center and the Iowa Policy Project. Learn more at

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