Iowa farmers are experimenting with new ways to keep groundwater clean. What’s called a "bio-reactor" was installed recently near Webster City as a way to keep nutrients that run off fields from entering the waterways. Roger Wolf is the environmental programs director of the Iowa Soybean Association.

Wolf says the tile bio-reactor is installed at the outlet of a tile line to reduce nitrate levels in the discharge. The bio-filter that’s now operating on the Arlo Van Diest  farm in Hamilton County is only the second one of its kind in the state. Wolf explains what it is and how it works.

"It’s a large hole in the ground that’s filled full of wood chips and we flood those wood chips with water," Wolf says. "The wood chips allow microbial activity to occur and that’s how the process works." He says this is the second of what will eventually be five of the bio-reactors to be built in Iowa.

The first one was installed last fall near Jefferson. Wolf says they’re carefully monitoring the water going into and out of the system and they’re seeing a dramatic reduction in nitrate levels — up to 70%. Other bio-filters are in the planning stages for farms near Corwith, Fort Dodge and Lake City. Wolf explains why north-central Iowa was chosen for the installation of first bio-filters.

"That’s some of our most productive cropland that you’ll find really in the country for raising corn and soybeans," he says, "and unfortunately it’s also an area where we discharge a lot of nitrogen that leaks out of the system." Learn more at the association’s website: "" and click on Environmental Programs.