Belowground Arthropod Communities & Soil Health with Dane Elmquist


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Episode Transcription:

Drew Lyon: Hello. Welcome to the WSU Wheat Beat podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. In each episode, I speak with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat podcast, do us a favor and subscribe on iTunes or your favorite podcast app and leave us a review so others can find the show too.

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Drew Lyon: We regularly have guests from WSU and the USDA-ARS on the show. But today is one of a three episode series I have with colleagues from the University of Idaho for an extended discussion on the role of crop diversity and soil health. My guest today is Dane Elmquist. Dane is a Ph.D. candidate in the Department of Entomology, plant pathology and nematology at the University of Idaho. Dane received his B.S. and ecology from the University of Minnesota, his M.S. and entomology from Washington State University, and previously worked as a biological technician for the USDA-ARS at the Tree Fruit Research Lab in Yakima, Washington. Dane’s current research focuses on understanding how different crop diversification strategies influenced the biodiversity, structure, and function of soil arthropod communities. He also aims to increase producer and public awareness about the incredible world of soil arthropods and how these often overlooked organisms contribute to soil health and agroecosystem sustainability. Hello, Dane.

Dane Elmquist: Hey, Drew. Thanks for having me.

Drew Lyon: You’re welcome to be my guest here today. Tell us about some of the alternative crop rotations and the focus of your research.

Dane Elmquist: Yeah. So for a long time, agriculture in the inland Pacific Northwest has really been characterized by high inputs and intensive wheat production with near monocultures of wheat and frequently the use of fallow and the drier parts of our region. So given the increasing concerns about environmental variation, soil health and long term sustainability, we know that many producers in our region are really interested in crop diversification. These diversification strategies can really vary, but many producers are interested in incorporating cover crops and new varieties of winter pea into cereal based rotations. However, really little research has been conducted on these crops in our region. So researchers from the Landscapes in Transition Project, which is a USDA funded CAP project that involves University of Idaho, WSU and Oregon State. We’re working on generating information to help us better understand how to diversify our agroecosystems with research focused on optimum seeding dates, you know, planting depths as well as understanding weed and insect pressure. So in addition to this, this agronomic focus, we’re also looking to understand how diversification with these alternative crops like winter pea impacts soil health and the soil biology that really fuels and regulates these soil processes that impact agricultural production. So I’m part of the entomology team on the Landscapes in Transition Project. Our entomology team is led by Sanford Eigenbrode at the University of Idaho. And the focus of our research is really understanding how these crops and alternative rotations affect soil insects and other arthropods. So many of your listeners are probably familiar with earthworms and the soil microbiome biome, but there’s this whole other group of really important organisms in the soil, the arthropods. You know, this includes things like insects, centipedes, spiders and mites. And we really don’t know a lot about this group. So all of the agronomy research in the region that’s addressed cereal systems has really ignored the role of soil arthropods. So we’re really seeking to change that.

Drew Lyon: Okay. When I when I think of those underground soil pests are… I shouldn’t… I’ve already told you what I think of them. A lot of them are pests or that’s at least what a lot of us think. How how do subsurface arthropods work to improve soil health?

Dane Elmquist: Yeah, that’s a really great question. So as you mentioned, we’re familiar with a lot of these soil pests like wireworms or the pea leaf weevil larvae that are present in our region. So many people, you know, think that all organisms under the ground, all arthropods under the ground are pests. However, the situation is kind of similar to insects and arthropods aboveground. So above ground we know that very few insects are actually pests, whereas many more are beneficial, like pollinators or natural enemies, and even more of them don’t really affect humans or crops at all. So it’s really kind of the same thing below ground. There aren’t necessarily bees flying around, but we do have other beneficial organisms like predatory mites and beetles that act as natural enemies, they feed on arthropods and potentially pathogenic nematodes in the soil. There are these really charismatic organisms called spring tails. They’re some of my favorite arthropods, and they’re really important in the decomposition process and nutrient cycling in the soil. So these arthropod communities are really vital component of a healthy soil. Some of our experiments that we’ve been conducting in, say, a greenhouse setting have shown that if you actually remove the arthropods from the soil, you plant some some winter wheat, you actually really see a dramatic reduction in the plant available nitrogen in the soil, reduction in the root length of our wheat crop, and even some impacts on aboveground biomass. So you can maybe imagine that some pest management techniques that are employed, like the use of seed treatments, these might negatively affect our soil arthropod communities. So we might be actually, you know, some somewhat detriment or to these benefits that these communities provide to our crops. Data from other labs suggests that seed treatments actually affect the function of these communities and can actually reduce their contributions to decomposition and nitrogen cycling. So it’s very important that these critters are in our soils. They have the potential to affect agricultural production by regulating soil processes. And we know that what farmers do actually influences these communities.

Drew Lyon: Okay. As a weed scientist, I think I’ve seen papers where they actually affect seed longevity in the soil. So predation of of seeds, is that another role that you’re you’re aware of or maybe looking at?

Dane Elmquist: Yeah. Absolutely. Actually, one of my one of my colleagues, Jessica Kalan, who’s a recently graduated master’s student at the University of Idaho. She investigated the impacts of, say, crabbed ground beetles on weed seed predation and found that they are really important in our systems and they’re one of those really charismatic soil insects as well.

Drew Lyon: Okay. So weed scientists can be pretty interested in these critters, too, then?

Dane Elmquist: Absolutely.

Drew Lyon: So how do alternative crops and rotations influence belowground arthropods?

Dane Elmquist: Yeah, that’s a that’s a great question. So some of these alternative crops that we’re researching kind of provide us some new opportunities to consider and manage these these new important players in the game. And this is especially true with winter pea. So planning winter pea into our traditional cereal-based rotations actually increases the abundance and the biodiversity of the beneficial soil arthropods like we’ve been talking about. So these predatory mites, these spring tail decomposers, and they improve the abundance and biodiversity more than the spring planted crops that winter could replace in a rotation like spring pea or spring wheat. And so seeing this increase in biodiversity was really promising. And I think a good way to think about the benefits of biodiversity is it’s kind of like an insurance policy, right? So if a group of arthropods that are providing a specific function in the soil, like nutrient cycling or biological control, if this type of group is negatively affected by management practices or some type of environmental change, another group of soil arthropods can step up and fill in that functional role, therefore providing, you know, some sustainability and resiliency in the agroecosystem.

Drew Lyon: Any speculation on why the winter crop, just like winter pea, helps biodiversity more than a spring pea? Or is it just the fact is growing over a longer period of time or is there some other thing going on there?

Dane Elmquist: Yeah, so that’s a great question. And this is this is some speculation. I do I do imagine that the longer time that the winter is actually in the ground compared to the spring crop does boost our soil biology. And also the litter quality of winter is is really pretty high compared to some of these other spring crops. And that also is beneficial for the soil arthropod communities.

Drew Lyon: Okay. Interesting. So can these communities be used to assess soil health in response to alternative rotations?

Dane Elmquist: Yeah, that’s a that’s a great question. So as another part of our study and this is somewhat unique, I think we wanted to see if we could actually use these arthropods as bioindicators to measure soil health. And I think a good way to think about this is it’s somewhat analogous to the use of aquatic insects and aquatic invertebrates that are used to measure the health of freshwater streams. So how to measure soil health is is a contentious topic, but it’s definitely a frontline in agroecosystem management. And implicit in this concept of soil health, I think, is that the soil is is a living ecosystem. And despite what we know about the influence of soil arthropods on soil processes, they’re really not included in the soil biological community assessments. So common frameworks for measuring soil health, you know, incorporate physicochemical parameters like pH, they measure microorganisms like bacteria and fungi, as well as earthworms. But again, we’re overlooking this this critical soil arthropod community. So as part of our study, we use this soil biological quality index as a measure of soil health. And this index focuses on using arthropods as biological indicators. It was developed over in Italy around 2005. It’s enjoyed some use around Europe. But as far as I know, we’re kind of the first people here in North America to take this idea and run with it. So we wanted to measure soil health across the entire kind of three year annual rotations that incorporated winter pea. And we found that soils under the rotations that did incorporate winter had increased soil health, you know, measured using these arthropods as bioindicators compared to conventional rotations. And this happened in multiple climatic zones across the region. So we saw some consistency with this incorporation of winter pea. Importantly, we’ve also shown that using these arthropods and especially this soil biological quality index, it actually correlates pretty well with other soil health measurements, especially those related to the microbial communities in the soil and even the Haney Soil Health Test. So it’s nice to see that consistency there. I think so. Again, this kind of tells us that there’s a lot of potential to actually incorporate these soil arthropods into the soil health framework. But we we definitely still have a lot more to learn about these belowground communities. Our research is is pretty fresh here. And talking with my my boss is kind of reminds us of of Dr. James Cook, who’s a famous plant pathologist at WSU and USDA-ARS, and he discovered that there were lots of soil microbes that we wouldn’t necessarily call pathogens in the soil, but they were affecting our ecosystem performance in some way. And so he was really important and raising the understanding of the soil microbe dimension to crop performance, to kind of transcend this concept of a pathogen. And at this stage, our research suggests that soil arthropods are kind of the same. You know, they’re affecting crop performance and ecosystem functioning in ways that we really haven’t appreciated before outside of them functioning as pests. And so I think this work, you know, merits continued investigation so that we can really, you know, learn some new strategies to keep our soils productive.

Drew Lyon: And the whole topic of soil health is really at the cutting edge and lots to be learned, but lots of interesting work being done there. And and this sounds like it’s part of that mix there. So outside of the benefits to soil biology, why would dryland farmers want to incorporate a winter pea in as an alternative rotation crop?

Dane Elmquist: Yeah, that’s another great question. So wheat growers here really have a very few economically viable alternative crops that they can use in rotation with winter wheat and winter wheat — winter pea, excuse me — is attractive for its potential to diversify and intensify our wheat based cropping systems here and the Palouse. And as you mentioned, there are other potential benefits to winter outside of our soil biology. Yield is a really big one. So winter pea typically out yields spring pea. I was at a field day yesterday they were presenting some data that, you know, winter peas out yielding spring pea in some cases by more than 200%. So winter peas are also less susceptible to heat and drought stress during their flowering time, which is what frequently limits the yield of spring planted peas. Heat and drought stress can also lead to highly variable crop yields in spring planted crops, so yield is more consistent in winter pea compared to, say, a spring planted legume. Winter peas are also reduce spring planting risk significantly. So as we saw last year, 2021 was a historically hot and dry spring and a lot of spring crops just weren’t planted due to the conditions. This year, we saw the opposite, right? Spring was really wet, which caused a lot of delaying of the planting of spring crops. So again, winter kind of reduces that spring planting risk. We talked about the improved soil biology, but there are also other soil health benefits. You know, winter peas have the ability to fix nitrogen, which is super important now kind of considering the price of fertilizer. And this nitrogen fixation can also benefit the subsequent wheat crops. And finally, there’s this emerging market for food grade winter peas. So there should be some economic benefit as well to planting these peas, especially in the future as we move forward with with breeding for these food grade winter peas. So I think crops like winter pea are going to be very important in the future where we’re expected to have even further yield advantages over spring planted crops with the warmer summers that are predicted for this region under future climate change scenarios. So incorporating recipe into rotation seems to really boost our soil biology, soil health, and improve sustainability. So I think winter pea has great agronomic potential and is really poised to be an important crop in the region in the future.

Drew Lyon: And I might add to that, being a wheat scientist to help us manage some of our annual grassy weeds that tend to be a problem in our wheat systems.

Dane Elmquist: Absolutely.

Drew Lyon: So some real advantages there as well, working research to go to learn more about your work.

Dane Elmquist: Yeah. So they can go to, which is kind of the main website for the Landscapes and Transition Project. I’m also involved in a Western SARE Project that’s evaluating the effects of cover crops on soil, arthropods, and so that work can be viewed on the Western SARE website as well.

Drew Lyon: Okay, we’ll make sure we get both those into our show notes for our listeners.

Dane Elmquist: All right. Great.

Drew Lyon: Thank you, Dane.

Dane Elmquist: Thank you, Drew. It’s been a pleasure.

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Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat podcast. If you like what you hear don’t forget to subscribe and leave a review on iTunes or your favorite podcast app. If you have questions or topics, you’d like to hear on future episodes please email me at drew.lyon — that’s — ( You can find us online at and on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat podcast is a production of CAHNRS Communications and the College of Agricultural, Human and Natural Resource Sciences at Washington State University. I’m Drew Lyon, we’ll see you next time.

The views, thoughts, and opinions expressed by guests of this podcast are their own and does not imply Washington State University’s endorsement.