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Strips Of Native Prairie Plants Could Reduce Pollution Runoff From Farm Fields

Emerging prairie strips on Iowa farms.

A new study says small patches of native prairie plants provide a range of conservation benefits to Iowa’s landscape and could reduce water pollution from farm fields.

So-called “prairie strips” are patches of land strategically planted to native, perennial mixes of grasses and flowers on the edges of crop fields.

“What we've been able to document over a decade worth of research on prairie strips,” says Iowa State University professor Lisa Schulte Moore, “is that by converting just a little bit of that crop area to prairie strips we get very substantial benefits.”

Those include:

  • reducing soil loss by 95 percent
  • reducing phosphorus runoff by 77 percent
  • reducing overall nitrogen loss by 70 percent
  • attracting pollinators
  • increasing the number and diversity of birds.

The new study, published in Proceedings of the National Academy of Sciences, also included a survey to assess attitudes toward conservation and prairie strips in particular. It found strong support for the practice.

“There's really not that much difference between farming and non-farming populations in Iowa in terms of supporting these benefits,” Schulte Moore says.

Improving water quality and preventing soil loss top the list of reasons farmers and non-farmers support prairie strips, she says. Farmers have come under increasing pressure to prevent nutrients such as nitrogen and phosphorus, which they apply to fields to enhance crops, from washing off their fields and into streams and rivers. Water flowing into the Des Moines Water Works, for example, has required treatment due to unacceptable levels of nitrates. The size of the Gulf of Mexico dead zone, an oxygen-starved area where much aquatic life cannot survive, relates to the amount of farmland nutrients flushing down the Mississippi River from the upper Midwest.  

The premise of prairie strips is that by planting these diverse mixes of native plants on slightly sloping areas, water flowing by will be slowed, preventing soil and nutrients from washing away.

“We're basically treating every single drop of water that's coming across their farm field,” Schulte Moore says, “while also being attentive to areas that may be lower-producing to begin with.”

Schulte Moore says prairie strips show a greater ability to achieve conservation goals than single-species, cool season grass buffers or waterways that are common on Midwest crop fields.

The 10-year-old practice of prairie strips has expanded from research plots at the Neal Smith National Wildlife Refuge in Prairie City, Iowa, to 47 commercial farm sites in Iowa, Missouri, Illinois and other states. Schulte Moore says preliminary data from those locations suggest their results will be similar, but the research team still has to analyze those data more closely before they are published.