STEVE INSKEEP, HOST:
Here's a bit of science - flooding comes about when the soil, the ground can't absorb all the rain, and this happens more often because of climate change. In Iowa, some farmers are experimenting with a way to grow crops that could keep more rainfall in the fields and out of streams. Here's Harvest Public Media's Rachel Cramer.
RACHEL CRAMER, BYLINE: The average annual precipitation in much of the Midwest has been ticking up, and the number of extreme precipitation days has increased by around 45% since the 1950s. Similar to Texas, extreme rainfall across several Midwestern states over several days in June of last year led to catastrophic flooding. There were fatalities and the flooding caused over a billion dollars in damage. Melissa Roberts directs the American Flood Coalition, which works on policies to help communities adapt to rising sea levels and more intense rainfall. She says farmers can help.
MELISSA ROBERTS: Half the land in this country is agriculture and farmland, and we cannot have solutions to flooding and disasters if we don't think about making that part of the solution and think about empowering farmers.
CRAMER: In Iowa, where 85% of the land is used for agriculture, some farmers are experimenting with a practice that could hold more water in their fields. It's called relay intercropping. Ross Evelsizer is leading a research project to develop best practices. He's with the nonprofit Northeast Iowa Resource Conservation and Development.
ROSS EVELSIZER: It's easier to stop the raindrop where it falls, and that means improving the soil health and keeping that ground covered.
CRAMER: In the spring, Evelsizer walked through a field of cereal rye with Mike Bretz, a farmer in East Central Iowa, who had planted the cold-loving crop last October, and he will harvest it this summer. There were also tidy rows of soybeans that he'll harvest in the fall. Evelsizer says a double harvest is rare. Some farmers use a cover crop like cereal rye to hold soil in place, add nutrients, and suppress weeds. But then they typically kill the cover crop with herbicides to plant corn and soybeans in the spring.
EVELSIZER: When there's the most opportunity for a heavy rainfall, which could create a flood event.
CRAMER: With relay intercropping, farmers don't kill the cereal rye. Instead, they work to keep more living roots in the ground year-round, which helps the soil absorb and release water like a sponge.
EVELSIZER: You could probably have a pretty good rainfall and walk out here and not have muddy shoes.
CRAMER: And that could have some big benefits downstream. One of the studies Evelsizer worked on with researchers at Iowa State University and the University of Iowa estimated 500 buildings could have been saved from a devastating 2016 flood in Cedar Rapids if relay intercropping had been used across a watershed. Another benefit with relay intercropping is that farmers can sell two crops instead of one. But there are challenges. Evelsizer says farmers need at least one good rain in the second half of summer for this practice to be profitable. Add to that, a potential lack of markets for cereal rye and extra hurdles getting crop insurance for soybeans. But Mike Bretz is open to experimenting with relay intercropping. He's already using cover crops and other conservation strategies like no-till farming to adapt to shorter, heavier bursts of rain and longer periods of drought.
MIKE BRETZ: It sure seems to me like it's different than it was when I was growing up as a kid, for sure, the weather patterns. But I think hopefully we can agree that whatever direction it goes, whether dryer, wetter or just more inconsistent, that it's going to be different.
CRAMER: Bretz says because the weather is changing, farming may need to change, as well. The hope is that relay intercropping may boost profits and prevent some of the damage that can come from excessive rains.
For NPR News, I'm Rachel Cramer in Des Moines, Iowa.
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