Stripped down: How ecosystems could help farmland weather climate change
One of the likely consequences of climate change in the Midwest is more frequent, intense rainstorms, particularly in the spring — a time that's already ripe for soil erosion.
That's one of the reasons Iowa State University researchers are experimenting with how to reduce soil loss.
"The potential for increased rainfall events or increased intensity of rainfall makes it even more critical that we protect our soil," said Matt Helmers, a professor of ag & biosystems engineering at Iowa State who is leading research at the Neal Smith Wildlife Refuge in central Iowa.
Helmers and his team have set up small 1-acre plots of corn and soybean rotations on the undulating hills. Then they planted strips of prairie grass in parts of the fields to see if the long roots that remain in the ground year-round help hold soil in place.
On a recent blustery rainy day, I visited the Neal Smith Wildlife Refuge with research project manager Chris Witte and farmer Gary Van Ryswyk. First, we checked out control plots with 100 percent corn and soybeans and no prairie grass strips.
As we wound our way through last year's corn stalks, Witte pointed to the bottom of the slope where the scientists had set up plastic flumes to direct the water to flow past the measuring equipment.
"You can see where it drains a part of the field, and you can see the catchments are kind of funnel- shaped, where they focus water into an area," said Witte. At the base of the catchment was a box that looked like an over-sized birdhouse; it held water- and soil-run-off-measuring equipment, which is triggered to turn on when there’s a big rain.
This sloping field is already no-till, which helps with erosion because it limits soil churning and leaves some residual crop roots in the ground. Yet there were still wet smears of mud that had oozed down the slope into the flumes:
"Yeah, this is actually nothing," said Witte. "In some major runoff events can have this six inches deep full of sediment.”
In the four years of the experiment, the prairie strips have reduced soil loss by 90 percent in wet seasons. For example, in rainy 2008 the thin prairie grass strips saved about nine tons of soil per acre — that's the weight of about four Honda Civics.
Making room for prairie
The early evidence that these prairie grass strips save soil is compelling, but would any farmer actually try this system?
I asked Van Ryswyk, who is farming these trial plots, if he'd be willing to implement something like this on his own farm. It would mean taking some of the field out of crop production — up to 10 percent depending on how much of the farmland is sloping.
"It wouldn't be practical for me to put big toes at the bottom (of a hill), because that would take too much ground out," said Van Ryswyk. But he said some of the narrower strips that slice across the field in the middle of the slope might work. "That's why I'm kind of waiting to see how plots turn out to know which ones work well, and still leave most amount crop ground in field."
We did some quick math and determined that for every acre a farmer takes out of production, that's over a thousand dollars lost in income (assuming 175 bushels of corn an acre at $7 a bushel).
But Van Ryswyk said he'd also consider planting strips of something other than prairie grass, like alfalfa, which could serve a similar purpose, but he could harvest and feed to his cattle.
Witte pointed out that even though the strips do cost money in the sense that a farmer is giving up some cropland, the long-term benefits could be well worth it:
"As far as measuring the benefits of these strips, you might not find out until, if you incorporated this for say 50 years or something," said Witte. "Because in 50 years when have the 100 percent crop watersheds and most of the topsoil is gone, you've got these where it's saved a lot of it, your productivity could be a lot higher in these, down the line. So it's kind of an immediate benefit versus a benefit down in the future."
Boost for the good guys
Scientists think the prairie grasses could provide other benefits, too. Iowa State entomologist Matt O'Neal said some of his grad students are studying what type of insect communities the prairie grasses foster.
Warmer, wetter growing seasons in the Midwest have led to some problems with increased crop pests and diseases; O'Neal said boosting the populations of beneficial insects could help control the pesky insects that eat crops.
"Ecologists think about how aspects of the ecosystem provide services that we would pay for in other ways — like pest suppression. Yeah, you can use insecticides, you can pay for that to be sprayed on your crop, or you might supplement that with beneficial insects like lady beetles that feed on things like aphids. That can provide a natural control."
As another example, O'Neal said, many studies have shown that soybean fields already have insect predators living there, and they do kill a fair amount of aphids — which is great news for farmers. And O'Neal said that's prompted another question: Would you be able to kill off more aphids — and stop outbreaks — if you improved habitat for these good guy insect predators?
O'Neal said the Neal Smith Wildlife Refuge prairie strips project is an important effort to get a big-picture look at how natural ecosystems interact with farming.
"We're exploring how there could be multiple ecosystem services delivered to agriculture by incorporating prairie into the landscape. And then the question is how much, and where?" O'Neal said. "You don't want to take away from production by growing prairie, but is there a sweet spot somewhere in there where you get the most out of prairie by using least amount of lands.