The Future Of Soil Under A Changing Climate

IRA FLATOW: This is Science Friday. I’m Ira Flatow, coming to you today from the studios of KURNPR Utah in Salt Lake City. Later in the hour, inside the secret signals plants send from leaf to leaf when danger strikes.

But first, while Hurricane Florence is washing away homes and highways in the south, all that flooding not only devastates property, takes lives, but it severely impacts agriculture. And I’m talking about the soil. A 2011 report put out by Wisconsin Initiative on Climate Change Impacts states if we don’t take action, this rainfall pattern, quote, “could cause soil erosion in Wisconsin to double by 2050 from 1990 rates.”

So what is the impact of changing climate on this soil? And what does this mean for the future of soil health? My next guest calls soil the underdog of natural resources. And she’s here to explain how we should be paying more attention to too much water. Well, Andrea Basche is an agricultural scientist at the University of Nebraska in Lincoln. Welcome to Science Friday.

ANDREA BASCHE: Thanks for having me.

IRA FLATOW: So why do you call the soil the underdog natural resource?

ANDREA BASCHE: That’s a great question, Ira. You know, I feel we give a lot of attention to water pollution and air quality. But infrequently, do you hear about the imperative of soil. So I appreciate you and your team taking a segment to give us the opportunity to promote that. But water and air seem to get a lot more attention than soil.

IRA FLATOW: Yeah. Well, we’re going to talk about it now. You know, it’s really interesting, because when people talk about soil in the Midwest and the west, they look at the 1930s dust bowl drought as a major cause of soil erosion in the plains in the Midwest. But today, out in Nebraska where you are, too much rain is the problem.

ANDREA BASCHE: Well, too much rain isn’t always the problem. It can be sometimes too much of the problem. So just to put some of the soil erosion numbers into context, there have been several articles that summarize erosion rates and soil formation rates.

David Montgomery is a great soils person. He’s written some really wonderful books about soils and society. And he estimates that soil formation rates, so how quickly soil forms, to be happening at a rate of about less than half a ton of soil per acre per year.

And let me just put that into context for you, that research out of Iowa State University, where I went to graduate school, called the Daily Erosion Project, they produce daily estimates of erosion for parts of the Upper Midwest, including parts of Southeast Nebraska.

And I was looking at some of the numbers recently and they estimate that parts of Southeast Nebraska, in 2017, had over 30 tons of soil loss per acre per year. So again, if we’re thinking about formation rates being less than half a ton per acre per year, we’re losing soil in one year that’s going to take decades to replace.

Another example, where I live in Lincoln, we’ve had a lot of rain this year. We’ve had about six inches of rain the beginning of this month. The Daily Erosion Project estimated some areas in the eastern part of the state of losing more than three tons per acre. That’s just over a few days. So it’s going to take several years to replace what was lost in just a few days.

IRA FLATOW: What does all this rain do to the structure of the soil?

ANDREA BASCHE: Right. So the force of rainfall hitting the soil can break up the good aggregation that you have. And those soil aggregates– if you think about soil, it’s kind of a matrix of particles. And those aggregates being really critical to having good space in the soil for roots to grow, for water to infiltrate. As you have that declining structure, you have less opportunity for good crop productivity.

You’re also losing the most nutrient-rich part of the soil when you have that erosion. So the rich topsoil is going away with that. And that’s leading to other problems, like water pollution. So yeah, the degradation being a risk for long-term productivity from an agricultural standpoint.

IRA FLATOW: We hear about planting cover crops as a way to protect soil health. How do cover crops helps soils from these extreme events?

ANDREA BASCHE: So that’s something I’ve done a lot of research on. And I’ll just take a step back for those folks who aren’t familiar with what a cover crop is. It’s basically a plant that you would grow when the soil would otherwise be bare, to protect it.

And so what that means in a place like the Corn Belt, typically, farmers are going to plant corn or soybean in the spring, in April or May. They’re going to harvest in September or October. And that’s another five or six months of the year when the soil is left bare, unprotected, you’re missing an opportunity to do what plants do, which is convert sunlight into carbon.

So what a cover crop does is to cover the soil in that bare period to protect it from things like soil erosion, you’re adding carbon into the system when you’re doing that. Some of the work that I’ve done has showed that cover crops can increase water infiltration. So that’s the rate at which water can enter the soil.

And so you’re getting all of those benefits, in terms of soil protection and really to building resilience and buffering a soil against things like floods and droughts.

IRA FLATOW: I’m want to bring in another guest who’s studying how rising temperatures affect the soil microbiome, all those bacteria and microbes that live in the soil. Kristin DeAngelis is a microbiologist at the University of Massachusetts in Amherst. Welcome to Science Friday.

KRISTEN DEANGELIS: Thank you for having me.

IRA FLATOW: So you’ve been studying an experiment in a forest that’s been going on for 20 years, where the soil has been artificially heated that entire time. You found that there were spikes in how the microbes were responding. Tell us about that.

KRISTEN DEANGELIS: Yeah. So I’ve been working on this long-term climate change manipulation experiment that was established in 1991 by a collaborator of mine, Jerry Melillo. And they are heating the soil five degrees above ambient. This is a forest soil in central Massachusetts. And it’s heated year round.

The way that the heat is through these buried resistance cables. And it’s the same technology that the NFL uses in like the football games in the north to keep the snow from accumulating on the field. But they’re buried thermistors that keep the experimental plots heated five degrees warmer compared to the controls.

And over this 27 years, all of this carbon has been lost as CO2. And of course, that’s a positive feedback to climate. And we’re really interested in how the microbes are responding to this degradation of soil.

IRA FLATOW: And how are they responding?

KRISTEN DEANGELIS: Well, they’re more active. As you would imagine, you heat up a system, it becomes more active. And the biomass has decreased, the microbial biomass. And soils are living. And they’re living because the microbes that live there. And it’s mostly bacteria and fungi.

And what’s interesting, and where I come in as a microbiologist, really interested in bacteria, is that the biomass has decreased in these warm soils, but they’re really decreased because the fungi are declining and the bacteria, in terms of their numbers, seem to be doing OK. And that’s really this next research project of ours, is to try and understand how is it that the bacteria seem to be resilient to this warming and drying effect.

IRA FLATOW: Now, I know that you both spend a lot of time thinking about the soil. What are the questions that we need to be asking when you think about the health of the soil in the next 50 years? And Kristen you can go first.

KRISTEN DEANGELIS: The questions that we need to be asking about soil?

IRA FLATOW: Yeah. What do we need to worry about? What are the questions– I know you’re doing research on it. What’s the long-term prognosis?

KRISTEN DEANGELIS: Right. So keeping soil healthy. And I think there’s a big debate among academics and farmers right now about how to sort of define what makes a healthy soil. But keeping carbon in the soil, promoting practices that promote soil conservation, and really just raising awareness of soil as a limiting natural resource.

So you know, questions to be asking is can you promote planting that will keep erosion at bay, promote soil formation, and supporting people in your community who are doing those sorts of things, like our organic farmers in my community, for example.

IRA FLATOW: Andrea, how do you bring more– you say you thank us for paying attention to this. And we think this is something we should be doing, as a matter of fact. How do you bring more attention to people talking about, hey, you want to eat? You got to have soil. You know?

ANDREA BASCHE: Yeah. I think if everyone who’s listening today goes out and tells three of their friends about the imperative of soil and that we’re losing soil at a rate much faster that we can form it or that it’s naturally formed, go tell your friends, raising awareness about that.

The base of people who live in rural areas and who are farming, every survey that comes up tends to show that those numbers are declining, which I don’t necessarily think is a good thing, because we need to have our urban food eaters– you know, we all sit down to eat three times a day– really thinking about how they can support all of those things.

And you know, I appreciate the organic debate, organic versus conventional. I don’t know that I appreciate it. I think it’s much more nuanced than that. I think there’s a lot of other ways that we can support producers trying to– I think a lot about just getting continuous cover of the soil. So doing things like having more cover crops, more perennial crops, agroforestry, which is getting trees into landscapes.

So what are more of those things that we can do? So we’ve got to move kind of beyond just organic as one option. But I think that consumers being more aware and thinking about how they can support food producers in soil conservation, because we do all need to eat three times a day.

IRA FLATOW: Can they learn anything from their home garden plot about any of this? Andrea or Kristen? I mean, is that a helpful thing to do? Is have a garden, so you’re more aware?

ANDREA BASCHE: I would say so. I mean, I think gardening is a lot of fun. It’s really humbling too. It’s not easy to have to grow your own food. So if you’re thinking about ways that you can use less tillage in your own garden or do things like mulching to keep weeds down or conserve moisture, I mean, I think those are principles that farmers who grow crops on a larger scale are thinking about as well. So I think it’s a humbling experience and they can learn some of the basics of soil management in that way too.

IRA FLATOW: Yeah, we talked about the water. And the next time we talk to you, we’re going to talk about the wildfires happening out west and how they affect the soil and the soil structure. We’ve run out of time about that. But that’s certainly an interesting topic to talk about also.

I would like to thank my guests talk, Dr. Andrea Basche, agriculture scientist at the University of Nebraska in Lincoln, Dr. Kristen DeAngelis, a microbiologist University of Massachusetts at Amherst. After the break, imagine being a plant, you’re minding your own business, and then someone takes a bite out of you. Turns out that plants don’t just sit there and let it happen. I’ll tell you how they fell? Well, you’ll hear. Stay with us. We’ll come back after the break.

Copyright © 2018 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/