Researchers: Prairie strips can reduce nutrient loss

The first year that prairie strips were strategically planted in corn and soybean fields near the Neal Smith National Wildlife Refuge, they worked to reduce loss of nutrients that can impair water quality, says Matt Helmers, an agricultural and biosystems engineer at Iowa State University.

"Things like plant diversity — the diversity of the prairie — have changed over time, evolved and enhanced," Helmers said. "But water quality, we saw real benefits right from the beginning. It was surprising. We weren't sure we'd see dramatic benefits."

Those dramatic benefits Helmers and other researchers discovered: Converting just 10 percent of a crop field into prairie could reduce by 95 percent the soil and sediment leaving the field. Phosphorus loss decreased by 90 percent, and nitrogen loss by 85 percent. And the prairie created a habitat for pollinators, birds and animals.

What happens is that the "thick-stemmed vegetation" that comes with a prairie's native grasses, flowers and other plants "slows down the flow of water and allows the water to infiltrate."

Researchers are looking at four different row crop and prairie configurations in 12 sloping fields. One treatment is all corn or soybeans, another is 10 percent prairie at the foot of the slope, another adds a few prairie strips to the field with prairie at the foot, totaling 10 percent prairie, and the last adds strips to the foot slope, totaling 20 percent prairie.

About a dozen state and federal conservation and agricultural agencies are participating in the project, including the Leopold Center for Sustainable Agriculture.

With Iowa under pressure to reduce the amount of nitrogen and phosphorus that enters the state's waterways and eventually contributes to the Gulf of Mexico's dead zone, Helmers talked about how the research program — officially called Science-based Trials of Row-crops Integrated with Prairie Strips — fits into the state's plan to reduce water pollution.

Q. How did the research project begin?

A. About 10 years ago, some folks were interested in what we could do within the agricultural landscape to reduce, on the water quality side, some of the nutrient and sediment exported from that land, as well as enhance the biodiversity on the landscape. ... We wondered: Can we convert a small part of the landscape into a prairie cover and see disproportionate benefits?

Q. Was it an immediate success, or did it require some tweaking?

A. Our field sites are in Jasper County, near the Neal Smith National Wildlife Refuge on land owned by the refuge. We implemented the treatments in 2007 and then in 2008 we had a lot of rain, but we still saw dramatic benefits from a water quality standpoint in that first year.

Q. That first year, what kind of vegetation did you have?

A. That's where it would depend, each site would be different. We had some clover and blue grass and probably a little bromegrass that was there from before. But you still some small stands of switchgrass, Indian grass, bluestem, there would have been some annual weeds in their, too, that would have provided some resistance to that water flow.

Q. How many rows are taken out of production?

A. Some strips might have been 20-foot wide, 25-foot wide. Some might have taken 10 rows out of production for an individual strip.

Q. Has it been a cost-effective way to improve water quality?

A. It's quite cost-effective. We're talking $24 to $35 an acre. We're taking 10 percent of the land out of production.

Q. How does that compare to cover crops, which a lot of people are considering? Are the benefits similar?

A. We're getting similar benefits. There are advantages and disadvantages to each one. Cover crops may be similar in costs per acre.

Q. What do you hear from farmers about the project? What do they like — and don't like?

A. One of the factors is still the cost. It's a cost to the producer, even if they get into federal incentive-type programs. And there's a hassle factor. ... Why are they interested? It definitely provides water quality benefits and other environmental benefits as well — aesthetic benefits, some habitat for wildlife, birds, pollinators, plant diversity. It's not just the water-quality benefit but other benefits, too, to that landowner and society at large.

Q. Do you have to be an organic farmer to use prairie strips?

A. No, no. At our research site, many of the farmers that have implemented the strips to date are not organic farms. They spray next to the prairie strip, but they are able to spray and keep from killing the prairie. It's been implemented on organic and non-organic operations.

Q. How does this project fit into the state's nutrient reduction strategy?

A. I think it's another tool, another option that farmers have to help reduce nutrients leaving their fields. It specifically does a good job with phosphorus and sediment in runoff. Nitrates that are moving primarily with water that's moving through the root zone and through shallow groundwater or tile, it may not be as effective in that, but it's very effective for reducing surface water runoff, reducing sediment loss in the field, and phosphorus loss in the field. To me it's another practice that farmers can think about and evaluate for their operation to help us meet the goals in the Iowa Nutrient Reduction Strategy.

Q. The project was recently written about in the New York Times. Why are are so many people interested in project?

A. There is a growing interest in what can we do on our agricultural lands to reduce nutrient loss, to provide environmental benefits. People see this as one of the options that farmers can use. People are engaged and interested in practices that can put on the land that can have a measurable and substantial impact on providing water quality benefits, other environmental benefits. And people who have been involved have seen the results. They've been out there. They've seen how we've monitored it, they've seen how we're evaluating it, and have confidence in that.

Q. What's next for the project?

A. Phase One was at Neal Smith. Phase Two is to go out on producers' fields. ... With that, we're trying to evaluate the project under a wider range of conditions — some flatter, some steeper sites. We will have added 15 to 20 farmer sites by the end of the year, early next year. ... Certainly, there is a lot more outreach to do, but we're pretty excited about how many farmers are interested.

FOR MORE

For more information, go to: www.nrem.iastate.edu/research/STRIPs