Sustainable Solutions: Cover Crops: We’ve Got You Covered with Dr. Laura Van Eerd

On this episode of the Sustainable Solutions: From Guelph to Gainesville series on the Streaming Science podcast, Hannah Bokor, second-year undergraduate Environmental Science major at the University of Florida, interviewed Dr. Laura Van Eerd, professor of Sustainable Soil Management at the University of Guelph Ridgetown Campus. Dr. Van Eerd discussed her long-term cover cropping research and explained how cover, or service, crops can benefit sustainable agriculture in the long run for processes such as nutrient cycling, water retention, and overall soil health. Dr. Van Eerd would like to thank her team, specifically Sean Vink, Inderjot Chahal, and Yajun Peng for their hard work. 

Transcript

Bokor Van Eerd Podcast 

Hannah Bokor: [00:00:00] [Music] Hello everyone, and welcome to Sustainable Solutions from Guelph to Gainesville, a podcast brought to you by the Streaming Science Project. Streaming Science is a student-driven program committed to connecting you with leading experts, exploring how science shapes our world, and how we can build a more sustainable future together. 

I'm Hannah Bokor, a second-year undergraduate student studying environmental science at the University of Florida, and I'll be your host for today's episode. 

 In the following interview, I spoke with Dr. Laura Van Eerd about cover cropping and her experience as a professor of sustainable soil management at the University of Guelph, Ridgetown campus. After this episode, I hope you will understand the intersections of soil health with other aspects of the environment and sustainability as a whole through Dr. Van Eerd's long term cover cropping research. So without further ado, let's dive into my conversation with Dr. Van Eerd and bridge the gap from Guelph to Gainesville. 

 Okay. So first [00:01:00] I want the listeners to get to know you. So could you tell us a little bit about your position?  

Dr. Laura Van Eerd: Yeah. So like you said, I'm a professor of sustainable soil management. So I get to do teaching, research and extension work in agriculture, which I really, really enjoy and love. My research centers around sustainable practices about caring for soil. 

One of those things includes cover crops, but also optimizing nitrogen, nitrogen use efficiency. And so that's the basis of my research. I get to teach soil science to our diploma students. I get to talk to farmers about what they do on their farm.  

Hannah Bokor: Awesome. So, where did your interest in that come from?  

Dr. Laura Van Eerd: Oh, so my interest, if we go back, it's, was as a child. So I grew up [00:02:00] on a farm and got to see things grow and watch the soil. I can still remember when the soil- when the puddles dried up, and it all crust, and the earthworms, crops growing. I- really enjoyed that part. And I still enjoy it, right? 

Watching plants grow is, it's a pretty amazing thing.  

Hannah Bokor: I agree. I was also very- my grandparents had a farm when I was younger and I also loved exploring it. Where did you, where was your farm? Like, I know you're in Canada. Have you always been in Canada?  

Dr. Laura Van Eerd: Mm hmm. Yeah, and actually, always here in Ridgetown. 

So, the home farm's just 16 kilometers east over. So that's 10 miles east of Ridgetown campus. So, yeah.  

Hannah Bokor: Oh my gosh.  

Dr. Laura Van Eerd: Yeah, I went to public school, high school, worked as a summer student here at the campus, and [00:03:00] really got to enjoy the research aspect of working at the campus. I didn't know what I wanted to do when I finished high school, but I heard the environment was kind of new and upcoming. 

... I was the first class of environmental science at the University of Guelph and did my undergrad there and knew after completion that I still wanted to be in agriculture and so I, you know, connected with a prof. I was interested in, and I've been at the University of Guelph ever since. 

Hannah Bokor: That's really cool. I didn't know you were the first class of environmental science there– because that's one thing we have in common! Because that's my major too, but I'm definitely not the first class [laughing].  

Dr. Laura Van Eerd: No [laughing], yeah, it was great. So you know, you get, I think with the environmental science, you get to see a very broad aspect of whatever you're interested in. 

And then in terms of my research, now we're focusing [00:04:00] on “what can farmers do in their field to have a positive influence?” Not only on their growing crop, and yields, and economics, but also, “how do you minimize losses to the environment in terms of nutrients or soil, greenhouse gas emissions?” 

So those are kind of the big-scale questions that I'm interested in, in my research program.  

Hannah Bokor: I want to talk more about your research in just a second, but we were talking about you being at Ridgetown. Can you explain how this is unique compared to the main campus for the University of Guelph?  

Dr. Laura Van Eerd: So we're located two hours from main campus, and we are right in the Great Lakes. So our watershed drains into Lake Erie, and because of our soil and warmer climate, we still have a lot of vegetable [00:05:00] production in the area, so processing veg., and that's part of the soil. It's also part of the climate and the facilities to maintain the processing industry. That's probably one of the larger differences in terms of my research and what we do here. 

Hannah Bokor: So is Ridgetown just agriculture-focused because there's so much more to sample?  

Dr. Laura Van Eerd: So, yeah, at our campus we have definitely a focus on agriculture, but also horticulture, environmental management, veterinary, technology, horse handler… So we do have quite a bit of diversity in terms of programs. 

Hannah Bokor: Okay. Awesome. So then circling back to your research, which is obviously soil-focused, and we're discussing cover cropping in this podcast. So could you just explain the term cover [00:06:00] cropping to any listeners who aren't familiar?  

Dr. Laura Van Eerd: Absolutely. So it's right in the name. Right? So we're planting a crop to cover the soil, so it's cover crop. 

Now in terms of cover crop, I like the term “service crop,” right? So we're planting a crop instead of harvesting for food, or fiber, or feed, or fuel, like instead of harvesting, we're planting this crop for a purpose to do a service. So it could be covering the soil as a service or it could be catching nutrients, and sometimes you might see the term catch crop. 

Hannah Bokor: Yeah. I really like that. I've never heard the term service cropping. That makes a lot of sense. I feel like that's a really good way to look at it.  

Dr. Laura Van Eerd: Yeah. Yeah. It's starting to be picked up in the scientific literature and more and more people are using it, but I wouldn't say it's, [00:07:00] it's caught on very heavily. 

Hannah Bokor: Well, we'll spread the new term in this podcast [laughing].  

Dr. Laura Van Eerd: [laughing] Yeah, right on.  

Hannah Bokor: All right. So within your research, can you tell us about how it's set up and what crops you're growing in your plots?  

Dr. Laura Van Eerd: Absolutely. So we have lots of different cover crop experiments that have been- some of them are just you harvest winter wheat and then in August you can plant a cover crop. 

And so we evaluate lots of different cover crops in single species or in mixtures of 2, 4, 8, up to 12 species so we can add biodiversity to the mix. And then we follow that cover crop, so we look at the growth, we look at how much nitrogen and carbon is in the cover crop, and then we plant corn. 

So those are some of the experiments we're looking at right now. But I think [00:08:00] the one experiment that I'm most excited about is our long term cover crop experiment. So here we've planted annual cover crops since 2007 when the experiment started.  

Hannah Bokor: Okay. Awesome. So, with all of this research, what are some of your main hypotheses? What are you trying to figure out with the cover cropping? 

Dr. Laura Van Eerd: Mm hmm. So, in that long term experiment, it really has changed over time. When we first started, what we were trying to figure out was how much nitrogen do these cover crops catch, right? We were looking at them as a catch crop. 

So how much nitrogen do we prevent being lost to the environment? We knew that they captured nitrogen. But the main question was how much is released and is it released in time? The nitrogen is released in time [00:09:00] for the following corn crop. And so those, at the time, those were the questions in 2007 and 2008. 

Hannah Bokor: How do you measure if, how much of that nitrogen is available to the next crop?  

Dr. Laura Van Eerd: Hmm. So there's lots of different ways, but the most direct way is by taking soil samples and plant samples. So throughout that corn growing season, you collect, let's say, every month or maybe more frequently when the corn is small, and so you collect soil samples, and we collected samples up into the three foot depth. 

And we quantified soil mineral nitrogen, so that's nitrate and ammonia. And so we know how much nitrogen is there in the soil. And then we also collect plant samples. So those plants are collected, let's say, depending on the size, five, [00:10:00] about five plants. And we weigh them, and if you want the nitty gritty details, it's you dry them, and you grind them, and then you, you burn them. 

So just like, when you have your campfire and you're measuring or you're looking at the fire, it's the same thing. It just goes into a detector, you burn it at super high temperature under pure oxygen and then you can measure the carbon and nitrogen that was in the plant tissue.  

Hannah Bokor: Okay, that's super cool. 

Because I feel like often we hear, “oh, we're, we're measuring these amounts in the soil or in the plants,” but it's really cool to hear how that actually looks. With the nitrogen specifically then, what exactly have you found in terms of the cover crops' effect on it? 

Dr. Laura Van Eerd: Absolutely. So what we're seeing is that there's up to a hundred pounds of [00:11:00] nitrogen that's in the plants. And if it's in the plants, then it's less susceptible for losses out of the field. Now the cover crop that's grown really makes an influence on will it be available to the next crop and how much will be available to the next crop. So then you have to get into the specifics. And so what we found early on was there wasn't a yield penalty, but there wasn't enough nitrogen credit to the corn crop that we could recommend to farmers if you plant non legume cover crops, you can reduce your fertilizer need to the corn crop.  

Hannah Bokor: So you have found that the cover cropping isn't storing enough nitrogen for the corn?  

Dr. Laura Van Eerd: So that's the early, early results, however-  

Hannah Bokor: Okay.  

Dr. Laura Van Eerd: So, yeah, we didn't talk about that previously, Hannah. So yeah, if you [00:12:00] only plant it one time, the cover crop can capture enough nitrogen, right? And store it in its above-ground biomass or in its plant tissues, but it just doesn't release enough when the corn crop needs it to lower fertilizer needs. However- 

Hannah Bokor: Okay.  

Dr. Laura Van Eerd: What we talked about and what we're finding most recently, so after about 15 years of cover cropping, we have found that we've improved soil health and we've improved soil organic matter. 

Now it's not statistically different except for if we collect a lot of samples and with a lot of samples and by comparing multiple sites, then we can see statistical differences in soil organic matter. I think what we're seeing in our trials in [00:13:00] 2020 to 2023 is the cycling of nitrogen and the availability of nitrogen has changed. 

And now we're less reliant on nitrogen fertilizer because we've improved soil organic matter.  

Hannah Bokor: Oh, that's really interesting. Okay. So we're kind of getting into better corn yields there. So can you discuss some of the benefits of cover cropping?  

Dr. Laura Van Eerd: Yeah. So those benefits. I guess they occur at different scales, right? 

Or they occur at different time points. So, in our early work when we first established the trial, we were looking at weeds. So if you cover the soil, then weeds have to compete with the cover crops. And we saw a decrease in winter annual weeds and that carried on with less weed pressure into the corn [00:14:00] growing season. 

So sometimes benefits can happen after one time growing a cover crop. You know, what I'm really excited about sharing with you and the listeners are those long-term impacts, right? That the benefits to soil health and all of the good things that come with improving soil health. 

And one of those things that we've quantified in terms of corn is increase in corn yields with the long-term cover cropping. And it's because of nitrogen availability to the corn crop.  

Hannah Bokor: Oh, something I think I forgot to ask earlier is, you have this long-term crop experiment and that's how you're obviously getting these long-term results. How long has this been going on for?  

Dr. Laura Van Eerd: Yeah, so we're about 16 years. We're coming up to 16 years, and for most of [00:15:00] those years, probably three times, we haven't been able, or we didn't have a cover crop planted.  

Hannah Bokor: With this long-term research, does it have an end date, or are you just going to be continuing it until you can get as much data as you think you can? 

Dr. Laura Van Eerd: Yeah, no, it doesn't have an end date, and I think that's probably a pretty powerful thing is that, you know, the questions we asked when it first started have changed. And so when I first started, I didn't think we would be measuring soil carbon, and now, going forward, I'm curious about drought and drought tolerance because we know soils with greater soil organic matter tend to hold water and be less prone to drought. So that's kind of the questions I've been thinking about.  

Hannah Bokor: Yeah, that's super interesting, [00:16:00] especially with the impacts of climate change, and I think it's really good that you're already starting to think about looking at drought resistance. 

Dr. Laura Van Eerd: Yeah, exactly. And then, you know, one of the other things is kind of yield stability, right? It’s the ability that you can produce good crop yields regardless of the weather. To me, that's a resilient cropping system. It's one where, okay we've built up our soil. We're protecting the soil. 

We're caring for the soil. And now, it's caring for the crop. We'll just ignore the weather. And that's, I guess, one of my favorite quotes that I tend to show or tell to growers.  

Hannah Bokor: So then, what you were saying about the healthy soil retaining more moisture. I know when we met before, we talked [00:17:00] about how that can impact other fields like algal blooms and how you had researched with, I believe it was Dr. Merrin Macrae?  

Dr. Laura Van Eerd: Basically, we found that there was, in our climate, cover crops can help minimize dissolved reactive phosphorus from leaving the field and that would have a positive influence in terms of algal blooms in fresh water. 

Hannah Bokor: Okay. Perfect. I just wanted to ask if there's anything else that you wanted to add that you thought the audience should know.  

Dr. Laura Van Eerd: Absolutely. I really want the audience to know that agriculture is a great place to study. It's a great place to learn and there's lots of exciting big picture questions that agriculture can be part of the solution to. We talked about some of those today. The, the last thing I'd like [00:18:00] to add is that it takes a big team to do this research and I really want to acknowledge and thank my team. So we have research technician, Sean Vink, who makes sure the field work is done to what we would expect farmers to do. So I have a postdoctoral fellow, Dr. Inderjot Chahal, who enjoys finding those linkages in soil health, and then numerous graduate students who ask great questions of the science, right? And we are always aiming to understand what are the mechanisms that explain what we're observing in our research plots but also what farmers are seeing in their fields. 

 And so it's a really exciting and rewarding career to be in agriculture.  

Hannah Bokor: I agree. Thank you so much for joining me.  

Dr. Laura Van Eerd: You're welcome, Hannah. 

[00:19:00]  

Hannah Bokor: [Music] Thank you for listening to the Sustainable Solutions from Guelph to Gainesville series on the Streaming Science Podcast to learn about cover cropping with Dr. Laura Van Eerd. Make sure to check out our website and social media for more of our work. If you enjoyed this episode, we encourage you to tune in to other episodes in our series and to visit the University of Guelph OAC webpages and social media for more information. 

Once again, I'm your host, Hannah Bokor, and thank you so much for listening. For more information about this episode, visit the links in our show notes.