Planting just 10 to 20 percent of a crop field with patches of prairie can reduce erosion by 95 percent and runoff by 90 percent.
Gary Van Ryswyk's concern for how his farming methods impact the landscape is obvious. A practitioner of a no-till system that avoids disturbing a field's surface as much as possible, he is particularly focused on keeping soil in place.
"None of us who farm want the soil to move—we care," Van Ryswyk told me one summer afternoon while standing in a central Iowa soybean field he no-tills. "I was one of these guys who didn't think we were losing that much soil. I was shocked at how much was being lost."
He was referring to a waist-high pile of eroded real estate next to a collection flume at the bottom of the field. It was a reminder that even a cutting edge conservation system can't always prevent land from slipping away.
On the other hand, the researchers Van Ryswyk works with have been somewhat surprised at the lack of eroded soil being collected by a flume just a few hundred feet away. The soybeans above that particular collector are also being grown under no-till and the field slope is the same. But growing in strategic spots on the second field plot are patches of native prairie.
Van Ryswk is raising crops on the Neal Smith National Wildlife Refuge and the prairie plantings are part of a study coordinated by Iowa State University's Leopold Center for Sustainable Agriculture. Called STRIPs (Science-based Trials of Rowcrops Integrated with Prairie), the study has produced impressive results: planting just 10 to 20 percent of a crop field to native prairie “strips” (some of the plantings look more like ragged slices of pie) consistently cuts erosion by an astounding 95 percent. The plantings, which have been in place since 2007, can reduce phosphorus and nitrogen runoff by as much as 90 percent.
“It's hard to improve on 95 percent,” Matt Helmers, an ISU engineer and one of the STRIPs coordinators, said to me. It seems the thick stems of prairie plants are effective at slowing water, and anything along for the ride, via a kind of pinball effect. This works particularly well during extreme rain events, which are increasingly common in Midwestern fields.
Tallgrass prairies once covered 10 percent of the contiguous U.S., and its replacement by annual crops is considered the most substantial decline of any major ecosystem in North America. But when environmentalists suggest returning more prairie grasses and other perennials to the landscape, reaction from the agricultural community is often outright hostile. Farmers envision a “Buffalo Commons” scenario where rowcrops are replaced with thousands of square miles of nature preserves—leaving no room for food production or the people involved with it.
What’s so exciting about the STRIPs research is that it proves the value of targeting conservation to critical, relatively small, areas, providing outsized environmental benefits in regions where working farmland is a key part of the economy.
Pauline Drobney, a U.S. Fish and Wildlife Service prairie biologist who is working on the STRIPs initiative, said while patches of prairie are not as optimal as having grasslands extending to the horizon, targeted plantings of natural habitat do provide key ecological services. For example, numerous pollinators and grassland birds use the strips.
"It won't be all of the solution—we still need big blocks of grassland landscape. But these diverse prairies in these strips can providesome of the birds places to fledge; it can be a place for a whole host of invertebrates and other things we know that we depend on," said Drobney while standing in a prairie patch literally abuzz with insect life.
This is no silver bullet. For one thing, the strips keep soil from leaving a field and making its way into waterways, but erosion within fields still occurs.
"We really need a systems approach and think about how we protect that land all the way from the top of that slope to the bottom," said Helmers, adding that a systems approach could include cover cropping and no-till production, with the prairie strips serving as a "polisher."
That's an important message as the STRIPs team takes the next step: getting farmers beyond the refuge to establish prairie within crop fields. One potential barrier to adaption is that, as with many conservation measures, the strips have the potential to produce more benefits off the farm—cleaner water for example—than on. Van Ryswyk argues that even the most conscientious farmers aren't likely to notice the difference on their land given that erosion can creep by unnoticed.
In other words, prairie strips in rowcropped fields are mostly a public good, and getting them established may require public support to prime the pump. A STRIPs economic analysis concluded that while the technique is cost-effective, federal conservation initiatives like the Environmental Quality Incentives Program or the Conservation Reserve Program may be needed to provide the financial incentives farmers require to actually implement them. Such incentives could be particularly attractive at a time when cost-conscious conservationists seek techniques that deliver proven results.
Paying for such a public good would help, says Van Ryswyk. But it also wouldn't hurt if more farmers were aware of how much runoff occurs in even well-managed fields. "One of the big barriers is, like me, most farmers truly believe they aren't losing as much soil as they really are."
Brian DeVore works for the Land Stewardship Project, a nonprofit organization fostering sustainable agriculture since 1982. DeVore writes for and edits the group's publication, The Land Stewardship Letter.