S4E1: Ag Innovations: How cover crops change the soil biology and the way corn smells!

Recorded: 8/20/25

Not only do cover crops influence soil microbiology, but they can also change the odor molecules that the following crop emits! In this first episode of season 4, Justin and Ryan chat with Dr. Jared Ali, an entomology professor at Penn State, who shared how cover crops can influence the way that pest insects perceive and feed on corn. They also sit down with PHD student Jennifer Harris to discuss how cover crop mixtures can modify the soil microbiome.  

Hosts: Ryan Spelman and Justin Brackenrich, Penn State Extension

Guest(s): Dr. Jared Ali and Jennifer Harris, Penn State

Links:
Northeast Cover Crop Decision Support Tool
MULTI-TROPHIC INTERACTIONS & CHEMICAL ECOLOGY

Photo credit: Ryan Spelman, Penn State Extension

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Transcript

Season Four Introduction

Ryan 0:17

Welcome to another episode of the Agronomy Highlights podcast . As always , I'm your host , Ryan Spellman . I'm joined here with my lovely co-host , Justin Brackenrich . Justin , it's the beginning of season four .

Justin 0:30

How are ?

Ryan 0:30

you doing .

Justin 0:31

Yeah , I'm excited . We've had a lot of growth . We've had a lot of good conversations in three . But , just like with everything you know rebirth , new beginning , ready to start over for the year how about you ?

Ryan 0:45

That's right . I'm really excited that we had a little bit of a break . So sorry to leave our listeners hanging for a little bit , but we've been brainstorming all kinds of things In the meantime . We have a lot of exciting episodes coming and we have a lot of ideas for growth of the podcast over the next year .

Justin 0:59

So you know not to miss an important one , but we , you know you might hear another friendlier voice from the past coming in on some of these episodes , Right ? So Dwayne Miller is back and going to be joining . You would maybe remember him from season one and parts of season two , but Dwayne's going to be back , and so we're going to be able to split this up and have another host joining us from time to time .

Ryan 1:25

Yeah , that's right . We're really happy to have duane back . Like you said , if you've been listening , you've you've heard him before . He was recording back when when joey was co-host as well . Um , so it's awesome to have duane back and I think the way we're going to do this is we're just kind of kind of wrote do a rotating co-host thing . So rather than you guys having to listen to me and Justin every week , it might be Justin or Dwayne , or me and Dwayne , or you know whatever combination of the three of us we pick . So I think that'll allow for us to get some different perspectives on the show from the hosting end and get some new topics tossed around . So that's one big development , and I'll leave some of the others for when they occur .

Justin 2:06

But we can't let all our secrets out , right ? I know , I know .

Ryan 2:10

Yeah , yeah . So I'll leave it there . We have some other big things and we'll let you guys know as those roll out

Cover Crop Cocktail Field Plot Overview

Ryan 2:17

. So today for our first episode of the season , we have another exciting one . So this is going to be in our Ag Innovations , emerging Technologies series and we're going to focus on work that's being done in the Cover Crops Cocktail Field Plot . It's a mouthful at Penn State and I'll give you guys a little bit of a background here on the cover crop cocktails field plot .

Ryan 2:45

So the cover crop cocktail , you know what I'm going to call it , the CCC . The CCC plot was started in 2012 , and it's meant to highlight kind of a long-term rotation of a bunch of different cover crops . So it's a corn , soybean , wheat cover crop , a cover crop . Following that that wheat crop and the cover crops that they test in this field plot are crimson , clover , winter pea , forage , radish , canola , triticale and oats . So what they have is they basically have monocultures of all of these different cover crops and they have replications of all of these across this whole big plot and they also have mixtures of these crops , different mixtures , three species mixtures , two species mixtures of these crops . So it's a really kind of complicated design but it enables a lot of researchers at Penn State to study all different kinds of things in these cover crop fields . So it enables them to focus on maybe little interactions that they're seeing between a cover crop and the fallen corn crop . Maybe it allows them to track differences in the soil type .

Ryan 3:55

And I'll say , if there's a plot that gets you know , let's say it gets radish as a cover crop , it gets radish in its cover crop every time it reaches the cover crop in the rotation . So we call these legacies . So that's kind of the gist of the cover crop cocktail field plot . Again , it's been . It was initiated in 2012 . So it's had 13 years in rotation . So we're going to have a bunch of guests on who work in this plot that are going to talk about the little piece of the puzzle that they're studying in this field plot . So , justin , does that sound good to you ? You want to introduce the first guest then ?

Justin 4:30

or have anything else to say . No , I think you've done a good job setting the scene . We've got a lot of really interesting guests today . So Jared and Jennifer are going to be joining us today to talk about their work and I don't want to take too much from it . But what we're going to get now we have someone that's looking at some of the insect kind of applications within this and then Jennifer is working on the microbes , the nitrogen fixing bacteria kind of more specifically and how that interaction changes within these cover crop mixes . So we'll let them get into a little bit more , but we're looking forward to hearing what they have to tell us over the next hour . That's right .

Ryan 5:09

Let's get started . So next we have Dr Jared Ali ,

Dr. Jared Ali: Plant-Insect Interactions

Ryan 5:14

and Jared is a entomology professor at Penn State and his work is surrounding insect plant interactions , and a lot of the work he's doing is looking at how different cover crop communities drive some of the the insect pest interactions that we see in our crops , like corn and I think mostly corn and and maybe soybeans . He can tell us himself , but um , so with that , I'll let Jared introduce himself and some of the work his lab does .

Jared 5:43

Um , right now introduce himself and some of the work his lab does right now . Yeah well , nice to be here . Thanks for having me to chat about our cover crops research that's going on here at Penn State . My background is my kind of focus study . Although I'm in entomology , I also serve as a chair for the ecology program , which is an inter-college program , and I'm also the director for Huck's Center for Chemical Ecology . So with that you can kind of guess , I kind of do research that has , in the agricultural settings , agroecological perspective , and I use this discipline called chemical ecology or this field of study called chemical ecology to make ecological connections using chemicals .

Jared 6:27

And so a lot of my research is trying to understand how molecules that are in the air like volatiles , odors , metabolites in the plants like toxins or other chemicals that the plants produce , how those link all of the organisms in agro-ecosystems .

Jared 6:43

And so I initially came to this kind of cover crop plot when another research lab , jason Kay , was doing research out there and they had all these cool projects going on with cover crops and I asked them have you ever noticed if the plants respond differently based off of the cover crops that were there first ? And they're like no , we don't have anyone doing that and I was like , well , maybe I should write a proposal to do that . So in 2018 , 2017 , I submitted a project to USDA . It got funded and then , since I've had follow-up studies by the foundation for food and agricultural reset research , which is FAR and then I just got another funded project through USDA although it's trapped in that the current funding system that we have right now to go further with our research , because they've seen a lot of the cool work that we've been producing , yeah , out of that field site .

Ryan 7:41

Yeah , so I'll say you know you mentioned chemical ecology and that's kind of when I was doing my research , kind of looking at some of the similar relationships with fungi . Jared's lab was super helpful in helping to understand . You know how to look at these little molecules that are signaling , and it was mind blowing to me how many different molecules plants are putting out to communicate with the world around them , and that includes with insect interactions . So when you overlay cover crops and then a crop after it , you're totally making different smells . You know different pheromones that are attracting different insect populations . So I guess , with that , what have you noticed ? Have you noticed exactly that ? Are there huge difference in some of these cover crops and what they you noticed ? Have you noticed exactly that ? Are there huge difference in some of these cover crops and what they're promoting , what smells they're releasing , and have you seen them drive any large interactions ?

Jared 8:34

Yeah , well , one fundamental part of our research and chemical ecology has been identifying the way a plant just smells Like . We can all recognize plant odor , especially if you're growing , if you work on a farm . You can smell the difference between each plot , each type of crop you're growing . You can appreciate that they also smell different when they're damaged . You know , you can recognize this just by going outside . You can tell when the grass is mowed before you even see it . Right , because you can smell it . And that's because when you affect or change a plant , whether by damaging it or infecting it with something , often its metabolism shifts in a way that it just starts smelling differently . And so when we first started doing our cover crop research , one of our first projects were if you had maize grown after something like a triticale , or after pea or after radish , did it smell different than if it was in fallow soil ? And would each kind of maze smell different ? And this is because there's this idea of soil legacy . So when a plant occupies a space , it changes that soil environment for its own benefit . It just interacts with microbes differently . Different plants pull different resources and you know that something like a radish supports a really different community than something like a wheat . And one thing you could directly know is , like you know , radish just is non-mycorrhizal , so that's going to reduce a lot of the fungal populations , whereas a wheat is mycorrhizal , so you'll expect to see higher AMF . That means when you put that maize seed , that corn seed in there , it's going to be in a different history , right ? I always say , like when I was just giving a talk in Michigan about this and I was like if you moved into an apartment , your lifestyle and your experience is going to really change based off who lived there first . If a slob was there , it's going to change your experience for the next few years . If you had someone that kept that pristine and great , it's going to change your experience , maybe for better or worse . And the same thing happens to corn . When you change that environment , that that seed's growing in by a cover crop , it's going to change a lot of the trajectories for that plant .

Jared 10:39

And so what we first found is when we took soil from things like radish and triticale and pea and we grew maize seedlings up in there and put herbivores on them , my graduate student , elizabeth Davidson Lowe , she first discovered that you know she couldn't even recover tissue from maize plants that were grown in radish soil . It was crazy . She came back to the lab and was like I can't get any tissue back , like the , the , the fall armyworm , completely decimate the plants when we have them growing in the soil . From radish versus triticale the larvae were growing really small and the plants look pretty healthy . So we immediately realized like wow , the soil legacy can lead some plants to be more susceptible to to pests like fall armyworm and other soils can lead some plants to be more susceptible to pests like fall armyworm and other soils can lead the plants to be more resistant . And so we went on to do more research with that soil line . We're like well , if an herbivore or pest is walking up to a plant that's going to do really bad on , maybe they're not as attracted to that plant because the chemicals in it might be more indicative of a challenging situation . And so when we did behavioral assays with the larvae , we found that they did not prefer even going to the plants that were growing in triticale compared to plants that were growing in radish or pea , and that they would avoid those plants . And when they had the option , when they could had differences in choices , they would not choose a triticale plant because they did really bad on , they just wouldn't walk to it .

Jared 12:12

So we sampled the odors for this , which is something we do a lot in the lab , and we found that the plants smelled differently based off of the soil that was there , and so this kind of blew open the whole top for us realizing like , wow , I didn't know what we would see going into this , but I was really amazed to realize you can really make a monoculture super diverse by using these soil legacies and that the story for each of these plants dramatically changes by this ability to change kind of their , their phenotype . Like you , this , the same mate , the same cultivar , that same uh hype that same corn seed is not the same based off of what soil you put it in . And we all know that from like soil health , from what you feed your plants but cover crops directly kind of , can have dramatic impacts that I don't think we were really appreciating in terms of how they were changing the way the plant smelled , how they changed the way they were affecting resistance , how they were affecting things like the defensive chemicals the maize would produce . And so it started off with that study and then we realized maybe there are trade-offs .

Jared 13:21

Maybe that corn plant conditioned by radish , although it's really bad against herbivores , might now be more tolerant against things like pathogens , because often when an organism is primed to fight in one direction , it usually comes at the cost of something else . And so this plant seemed now it was really bad at fighting against fall armyworm . Maybe it meant it was in a resistance syndrome that would be better against pathogens . And so we did some inoculations with fusarium and we saw that the the seedling blight was much lower , so we had better germination in radish than we did in things like triticale . And then we also saw that when we were inoculating directly on the husk or right on the cob , that the spread of infection was smaller when the maize was growing in radish soils .

Jared 14:17

And so we just kept going further and asked funding agencies for more money because they thought this was exciting research as we were starting to publish it and we wanted to test what other pests respond differently , what other factors change . How do the ? What defensive chemicals are there ? That shift in this and it it's bringing really cool . Now we're at the point where we want to start bringing it on farm more and start to really push the system a bit more . I can blabber on it , but I have an idea about how we want to push it , so I keep going unless you guys have more questions .

Justin 14:54

I'd like to ask a little bit about the smell , right , and so this is not my field . So I'm trying to simplify this to something I understand and we can think about roses having a smell , or I thought your grass analogy was great . I don't know that I've ever really paid much attention to the smell of a corn plant and , like you know , this , um , in my head I pictured you like a wine sommelier , like walking around with , like you know , subtle notes of leather and tobacco , and you know and like taking off these tassels . But are you using equipment to do this or is this something ? Talk to me a little bit about that .

Jared 15:31

That's great . No , we don't sniff them with our nose . That's a great question . I always say smell

Soil Legacy and Pest Resistance

Jared 15:35

so , but I do . You know a lot of chemical ecologists this is , I know a bunch of them have been , over the years , been able to start recognizing their systems . So I have a student in the lab that is now at the point that he can walk in and he can tell whether a plant has been chewed on by a specific caterpillar or not , To the point that the other students ask him to sniff their plants to see if they're likely to find data . That'll be interesting and he's been amazing . So we call him the human GCMS .

Jared 16:07

So we use a lot of cool tools that can trap these small molecules in the air .

Jared 16:14

The same way , your car filter often has a charcoal layer in it that'll filter out all the funkiness when you have air passing over that .

Jared 16:24

It actually absorbs because it's more attracted to those small molecules than the outside air . And so we basically take these filters and we can bag plants or put them in glass jars , pull air over them , trap them onto a filter and then we can dump solvent onto that filter and extract all the chemicals that were there , and we can do this for all types of contexts . So we could , like we could , take a little probe , put it in the room you're in and sample that airspace in that room and be like , oh , this is the profile for Justin , and then we could do a profile for Ryan's house and Ryan might be cooking spicy foods there . He could have pets or use his favorite Axe deodorant spray and it would smell much different from you , a respectable person that doesn't use Axe deodorant as much . So we can use these little traps to trap odor profiles for different things . Ryan , I won't let you respond to whether or not you're using that .

Ryan 17:19

Hey , you know , once you find something that works in middle school , you keep with it . Hey , you know , once you find something , that works in middle school .

Jared 17:26

You keep with it , so that's how we smell stuff .

Justin 17:28

Yeah , my follow-up to that , and maybe this is off topic again , but one of the bigger challenges we deal with in agriculture are slugs and you know is this is seemingly like a perfect opportunity to think about . Is there research or have you thought about how this could be applicable to slugs and cover crops through smells you ?

Jared 17:49

just gave me my next grand idea like . So ryan brought me out to a farm and I remember someone talking about the slugs and at that point I was like , oh yeah , we should do slug differences too . Um , so we , what we're doing is we're realizing , you , the hardest thing about chemical ecology and a lot of the fundamental researchers people research , people do in in ag at universities is sometimes they get so far removed from what's really going on . Right , like I can make these fun ecological stories , but maybe the biggest problem for farmers isn't fall army worm or for fusarium , it's slugs . And then also realizing , like farmers are using so many different rotations of cultivars and doing so many things it's hard for us to like capture what's really going on in the farm . And so , yeah , when I went out to a farm recently with Ryan , I realized like man , there's so many other questions I should be asking , like slugs , and it's likely , you know , if you just think of soil content , changing a lot of the attributes of a plant . If you have high silica content in your soil , that's probably going to be a bigger pain in the butt for a slug , which is basically an animal that walks around with its mouth on its stomach and it just eats everything that walks around with its mouth on its stomach and it just eats everything . And so if you could have soil that could actually facilitate the plant with certain types of resources that could be more tolerant to a slug , or even adjacently make soil that can make it more susceptible to make a trap for that slug , you could have a way to push or pull slugs in certain directions and make traps better . And so you just made me think of that . I was like you know , there's probably certain traits that would make that plant we could just look at the leaf pressure and the leaf , the leaf area thickness that changed based off soil properties and maybe some other chemicals that we know change . Like I know now that certain soils , like pea , corn grown in pea , has way more of these defensive compounds called benzoxazinoids that are really hard for organisms to deal with and feed on . Maybe the slugs don't like those so much . So I could put pea and radish rows near each other and you could predict which one the slugs are going to be feeding more . You might focus a spray in that area or put more traps there in that spot so you could , you could focus and you'd know where most of your slug damage is going to be . Reduce your sprays and wipe them out earlier in the season , because you know you can predict where they might go , because they use things like odor and chemicals to to decide where they're going to be at .

Jared 20:25

And the thing about the corn odors that's really important to add is that we don't detect all the differences these insects and pests detect . So I know that , although you probably don't think about the smell of corn , I could give you a cob of corn and a tomato , blindfold you and you could smell them the differences . Now you might be able to smell the difference between corn that's fully developed and tasseled and hasn't even started to sprout yet , right Like . But those things we don't think about a lot . But these herbivores and pests that have been evolved to feed on these things are sensitive to the smallest changes , you know , because they they can't always develop on corn , depending on the stage or if it's infected with the pathogen and one little molecule that shifts in its profile , their little antenna are tuned to . Even though we can't smell the difference Although my one student's really good at that Sometimes our machines will pick that up and then we realize that explains why the insects were changing their behavior . That makes sense .

Ryan 21:33

Interesting . So you know , going back to and I think you brought up a really good point , is , as we know more about these relationships , right , they're really nuanced . So , like , maybe we find out in your case that some defoliators you know like plants after radish or , but then fungi don't . So it depends what you're managing , for Maybe you have an area that , for whatever reason , you have a lot of ear rots so you use a radish , but then maybe you have an area that you have a lot of problems with defoliators so you opt for triticale , and that can be part of your management strategy . But until you understand those relationships , you can't add that to your management practices .

Ryan 22:18

Especially in an organic system , like what you all are working at , you have limited spray options . So how do you leverage things the best you can ? And so , going back to that , that you know that relationship between your , your fall army worm and maybe some other , um , caterpillar feeders , um , did you notice that that , like , were all defoliators attracted to the same thing or were ? Was it different , right ? Like , maybe you didn't test all of them , but you know , maybe you know grasshoppers have a different taste . Is that the case ? Or does it seem like if , if one type of insect pest feeds in a certain way , it's attracted to the same thing .

Jared 22:58

What we're doing now . We're getting more on-farm data . So initially what we often do in the lab is we kind of take the system and we bring it into the greenhouse so we can control and try to find predictable traits and then we see if we can see that out in the field . And so this summer my students were out in the field all summer taking surveys of insect populations , predators that were there , performance of the plants . They were taking soil samples to get soil microbiome data . They were taking plant samples to get information on how the microbial community , even on the surface of the plant , changes based off of the soil type . And so we're going to start getting all those findings this summer . And anecdotally , like the students notice it like they go out there and it's not always who you think changed , like you , you go out there and they they noticed like one plot has way more pressures in it , um has way more predators in it . And our data in the lab had showed us already that when you take a cover crop choice and you feed a fall armyworm on three different types of cover crops , the ladybugs or other predators can recognize that and they prefer to feed on the herbivores that were feeding on the different plants . It was crazy . You put this little dish with a predator and you have four caterpillars in there and we know the identity of each caterpillar and it would just pick almost 50 percent more . One of them that were feeding on like a pea cover crop , and I think it has to do with the nitrogen . Like nitrogen was higher , it was getting into insects and they could . But they could smell that and taste it . They would touch each one and preferentially pick . But in the field now we're seeing like oh , that plays out in the field . Certain cover crops are more attracted to predators and that might be through the odor of the plants that changes and because the prey feeding on those plants taste in a way that provide more nutrients to them or don't have as much toxins in the insect blood or in their bodies . And then for the chewers each species seems to be a species . That's what we're starting to notice .

Jared 25:12

Like fall armyworm . We took beet armyworm and fall armyworm and put them armyworm and farm worm , put them on these , these different plants and cover crops , and fall armyworm is really good at feeding on maize and they seem like they don't care as much about certain defensive chemicals as other caterpillars like . They're really good at grasses and they can even take the specialized metabolite that maize uses to defend off all the other insects that don't feed on it like it . If you just think about it , the world is green . Insects should be mowing down every plant , right , but they can't . Each plant has a specific defensive profile that only some insects can feed on it and , and a pest-like fall armyworm has mastered things like the grasses . And because it's mastered the grasses , those specialized defenses in the grasses , it can not only detoxify

Breeding Plants with Natural Defenses

Jared 26:05

them , it has a specific enzyme that reconjugates it so it's not toxic anymore . But then some herbivores , they're super hurt by that . But then some herbivores , they're super hurt by that so they can't deal with it .

Justin 26:16

If you can put it in a soil that elevates it like P , that really escalates the amount of these defensive , the benzoxyazinoids in the maze , it's just such a like we often think about , like bean leaf beetles not a problem in grass , right , but no one ever digs deeper to think like why is that not a problem ? Well , I mean , I'm sure other people have you do , but as like just a general agronomist , we just like yep , I know that's not a problem here and I , I know this one's more of a problem for this one , and it's just such an interesting way to to think about why that's happening .

Jared 26:52

Yeah , yeah , like if another mind blower for me today that's .

Jared 26:56

That's where that's why I'm more mind blown when I get to talk to actual practitioners , because they have the stories , they have the anecdotes and they're even using chemical ecology in ways like trap crops , pushing and pulling insects around , knowing where they're going to predict them , but they're not thinking like , oh , the reason they're going there is because that odor is attracting them over there , like what's an insect really interacting with ? It's interacting with vision , it's interacting with chemicals that it can smell , and so you're really playing on their chemical ecology without realizing it . Um , so when you want to attract or push things , you're using chemical ecology .

Jared 27:31

I go into the field and I see farmers doing this stuff and I'm like , let me sample those plants . Like I'm walking around the farm the other week with Ryan and I just saw like certain spots had way more predators and way more damage and I went to immediately grab some of that tissue and see what was going on with that plant , even though we knew that was the same corn cultivar across that or crop across that landscape . The different areas were making the plants do different things to the insects , and so , yeah , I think about that immediately . If you tell me about a pest that won't feed on something . I immediately want to sample what's going on with it and what chemicals are upregulated .

Justin 28:08

So my last question is exactly following up to what you said is if you go out and you're starting to sample areas that maybe have no predation or areas that have extreme high predation , is there a way to look at that profile and potentially start breeding plants with a different profile , knowing for whatever reason these plants in this area are deterring this ? Is that like a direction of this , or is that so crazy ?

Jared 28:36

that's not even in the ballpark yeah , I'll take that way zoomed out . The way I think about it is like this you know , maize comes from this ancestral teosinte line that's been around forever . We started domesticating it like 10 000 years ago or something . Change in maize when corn was grown by itself it looked really different . It was allocating its carbon because it evolved in this manner where it could use its carbon in ways to release volatiles that were attractive , repellent . It probably had a lot more defensive chemicals in it to protect it because it lived by itself . It didn't have humans protecting it right . Like I think about this , I have a French bulldog , one of those most overbred dog you could have no way . But you know its ancestor came from a wolf . We basically take a wolf like a wild corn and we take away its fangs and you get a French bulldog or you get domesticated maize varieties . Now we have so many different hybrids and cultivars . What I think we can start finding is which cultivars still have fangs and we don't notice that .

Jared 29:44

But when I took I started to get more field relevant . I started looking at different hybrid lines . Often in my field people use inbred lines to do their research and I started realizing that's never gonna float for a farmer . They're using these crazy hybrids that have way more genetic diversity and that have more variability . And so we started just only using hybrids now , which I think is a breakthrough , because nobody's doing that in my field and they always caution you like , you'll get too much variation there . You can't predict what's going to happen . I was like , well , that's what the farmers are growing . But then I realized you , you know , talking to people like ryan , he's like , but they're wrote , they're changing their , their cultivars , they're getting different varieties every season .

Jared 30:24

And I just took started doing comparisons with different cultivars , just smell , just sampling the odor of them and the defense of chemistry . And sometimes you'll find a plant that we've been using in the lab , one hybrid . We've found that when we switched to another type of variety it had exponentially lower defenses , just without doing anything , than some other varieties of maize . And I was just like , do people even sample that ? Nobody even knows that this thing it was off the charts , even knows that this thing , it was off the charts . My student , she came back with the data and she's like this thing has so much defensive metabolites in it that it's like it made our other air bars or other things look like they were . They weren't even defended , and so that should suggest to me , especially in organic lines that are getting selected for , without the management they might be selecting for more fangs coming back than conventional ag .

Jared 31:19

Right , because if you're going to keep giving farmers organic lines that don't have any treatment on them for neonics and whatnot or fungicides , directly , they're gonna what their farmers are going to come back and say this didn't work , this one did work and you're going to keep giving them lines that are good without all the defenses put in there , right ? Like the same way I have to keep giving my French bulldog shots . I had to protect it . I had to make sure nobody's going to hurt it . Put a fence around it . If I let that thing get more wolfy , like a German shepherd , I could let it run further , and so what we're starting to screen for is like are there varieties that not only have more fangs but also respond to some of these context shifts , like soil , in a way that you can predict how they'll respond to different pests and pathogens ? So I lied and I have one more .

Justin 32:11

Now we might just have to stop this conversation . No-transcript in a direction , this becomes an analytical kind of definitive . This is here that doesn't like it . Boom , if that's your problem , here's resistance if you that that's the dream , right .

Jared 32:53

Like that's amazing . Like if you talk to breeders , they kind of brute force select for what has highest yield and lowest disease resistance . But when I talk to those huge breeding programs and they look at their field , sometimes I've asked them like do you ever notice sometimes you have more pests in some plots than others ? They're like , yeah , but we didn't think about that , either one because they know they can dump pesticides to deal with that , or two because it's just something they're not thinking about . Why ? And I'll often ask them like could you give me the one that had the most damage here and the least damage by the same pest or pathogen ? And we find crazy profiles . It's just like this is a resistant line you have because , xyz , but we just don't screen for that right , right now .

Jared 33:41

And I think it's mostly because some of this fundamental work that we do as chemical ecologists we're not talking to the farmers enough , we're not seeing , we're not making it relevant . You know , I love working with penn state extension more and more because I'm , I'm , I want to go on farm , I want to hear what the farmers are doing and I want to make sure that what I'm doing is relevant in a way that can be used , and the cover crop was my first step in that , because it's a practice that people are already doing . I don't have to be like , hey , I want to convince you to dump this chemical out in your field you know this funky , weird thing or twist your plants around like this . It's like oh , you use different cover crops , why don't you try this for this issue ? So it's something that's already used . We just didn't recognize what we were manipulating and that's what my lab's trying to figure out now .

Ryan 34:31

Yeah , thanks , jared . I mean it's cool to see you take that route . You know where , you're seeing what's actually going on in the field , and I mean this idea of understanding the profile of an individual corn plant and how it's protecting itself , and it's amazing to me how variable that can be . So it's really cool . You know we can say corn the French bulldog of the plant world now . So you know I'll let you get out of here because I know you got to get somewhere , but I just want to give you a second here because you do have a lot of extension educators that do listen to this . So is there anything right now that you would like more samples of , or some some direction you would like to go with this where you are working more on farm , if you want to , if you have a second here to to advertise that one of the projects we got funded from the foundation of food and agricultural research , ffar , um , that funded this research .

Jared 35:29

they invited me to go for a second round of funding to move further , because they want to see us apply this work and so , as a part of that , one thing we want to do is start doing more cultivars and looking at more locations , working with different growers , because the soil property of where we've been at our cover crop site might not be the same depending on where we are in PA . You know you can look at the soil profiles across the state . It's completely different , probably different microbes . But I wonder , if radish , say radish , and triticale , five different farms , do we see the same outcomes ? Do the same chemicals change and we did that with three or four varieties Does each variety respond differently to the different soils ? Or can we make a clear cut , conserved response and finally make a recommendation like this cover crop at least changes this , no matter what , regardless of your cultivar , based on the insect community , the predators , the damage and the yield . And we want to expand this network not only just to pa but also see how it works for other farmers across the the country . So we're looking for farmers , extension agents that are interested or have different cover crops they've been using . We also want to see if we can leverage mixtures of cover crops more than anything else , because we're finding that if you increase diversity in your crop , which everyone can appreciate , you really can reap benefits in terms of pest management .

Jared 36:59

And now that we know each cover crop makes these plants so different , where you have a monoculture , if you use a mixture , you're actually diversifying that a lot , right , like each maize crop . We can show this with the chemistry and the odor grown up where pea was right next to one , near radish , right near triticale . Those plants have completely different defensive chemical profiles . So you've taken that monoculture , that big target of French bulldogs with no fangs , and you prime them differentially and you make them have different types of defenses , different diversity of responses . It's going to be hard for herbivores to just hit that Because it adds complexity , and predators like that and other organisms like that because they've evolved to depend on our monocultures with no variability and soil legacy . There's really cool promise to kind of understand these chemical ecology ways and have them benefit for yields and reduce kind of applications .

Ryan 38:02

Cool . Well , thank you . This has been a really awesome discussion and I think it's a great discussion for folks on the agronomy side to be listening in on as well . So for that , you know , for our extension educators that are out there and listening , and farmers , if you have a farm that they're already playing around with a lot of different cover crops , we'll make sure that we put your information in the description so that they can reach out directly and hopefully get you on some more farms . So we appreciate that . So , justin , you have anything else ?

Justin 38:33

No , no , that was fascinating , wonderful conversation . Thank you so much .

Jared 38:38

Look forward to chatting with you both more . I love it .

Ryan 38:50

Thanks , jared . So next up we have Jennifer Harris , and Jennifer is a PhD student in

Jennifer Harris: Microbial Relationships

Ryan 38:53

Leanna Burkhart's lab . Dr Leanna Burkhart , now she'll probably do a better job of describing their work , but you know a lot of their work has to do with microbial populations in the soil talking , and a lot of rhizobia work as well , kind of nitrogen fixers and and kind of microbes that have a nutritional benefit to the plant and , you know , maybe help with mineralization or nitrification . So I don't know how I did with that , but I'll let Jennifer describe her work and her lab's work for herself .

Jennifer 39:22

Absolutely . Thanks so much , ryan . So I think really kind of the premise of a lot of my work is if , when we consider in cover crop mixtures a lot of the benefits that cover crops are doing things like increasing the amount of nitrogen or helping to store carbon in the soil a lot of those processes are mediated by microbes . So my work is all about understanding how different cover crops are promoting those helpful microbes and how we can continue to foster that mutualistic relationship . Yeah , I have a couple of different projects to this effect , but one of them that's kind of recently finishing up is determining when in some cover crop combinations there is increased microbial activity , a different microbial community , and then in addition those two microbial factors also are showing the same patterns as increased plant biomass in those combinations as well . So trying to kind of connect the dots of when microbes are forming a different community , when they're doing something helpful , and then that's affecting the plants as well .

Ryan 40:39

Very cool . So I guess let's start just one of the like nitty gritty details of how you're doing this work . How are you understanding , like sampling , what microbes are there , which ones are beneficial , like how does this process work ? And then maybe from there we can then talk about some of the results ?

Jennifer 40:59

Totally . Yeah , that's a good question . The problem with working microbes is you can't see them , so you can't just like go look , like is this helpful or not ? So what we do a lot of is we collect the soil from the plant roots , so that rhizosphere soil , because that often has really high microbial populations and then we sequence the DNA from that rhizosphere soil , we amplify a specific region . That's kind of like a marker gene called 16S rRNA , and with that marker gene we can get kind of a fingerprint of what that microbial community is like , um , so we can determine who is there Um . In addition , I also use a technique , um called BONCAT , or bio-orthogonal non-canonical amino acid tagging , which is like such a mouthful but essentially it's a way to be able to determine which microbes are actually , um , functionally active and awake and doing a function ?

Jennifer 42:00

um , because you can , in the soil a lot of microbes are dormant , so they're just kind of you can imagine like they're like a bear sleeping through the winter . They're not doing anything , and so when we are thinking about microbes that are actually helpful to plants , we really want to zero in on not just who's there , but what microbes are there that are actually functionally active , because those are the ones that are able to do benefits to the plant , like fighting off pathogens or fixing nitrogen or helping mineralize nitrogen as well . So I think those are kind of the combination of techniques I use , so both sequencing but also using BondCat , to be able to zero in on the microbes that are actually functionally active .

Justin 42:46

So this may be an easy question for you to answer . It may be completely ridiculous , but if you're looking at a bunch of different microbes in the soil and you're finding that this one is functionally active and doing something for the plant , what about the others ? Are we missing a lot of opportunity to benefit our plants from the ones that are hibernating quote unquote hibernating . And then how can we wake them up ? What does that look like ?

Jennifer 43:14

yeah , that's a good question . Thanks for asking that , justin . This is fascinating .

Jennifer 43:19

So the general um knowledge is typically that just having a plant root there can wake up microbes , because plant roots are able to excrete um different compounds , um but they're going to be rich in carbon . So you think about it's almost like they're making candy for microbes , they're making food that could be helpful and beneficial . However , I actually have a paper that was recently published this month , that shows that like , that's not always true . It kind of depends on the conditions or exactly when you're looking . So this kind of intuition that just putting a plant there is going to suddenly make a bunch of microbes wake up and be helpful is it's maybe just a little bit more nuanced than that . Like there are typically more microbes next to the plant and more active microbes . However , it's not necessarily always like this huge , huge impact , and a recent study that's not yet published is kind of focusing on the plant that's there actually really matters . So you're going to get a different response depending on what cover crop or what cash crop really that you're planting .

Justin 44:31

So I have no knowledge of this at all , but I believe exactly what you said . If you would have said , like , how do you think this works , I would have thought it would have been as complicated as what you're saying . Right , certain microbes are going to respond to certain plant roots , at certain depths and certain things and the conditions that there's just no silver bullet that we can wake up a 100% of the microbes with one thing and get everybody marching in the right direction . Right , it feels like soil and bugs and microbes is always such a complicated process . So you validated all of my suspicions .

Jennifer 45:04

Yeah , I mean , I think part of my work is working on untangling that . Like it'd be so nice and so easy just to be able to have a silver bullet and say , like you plant this and now you're going to get all the nitrogen you need . But seems like it's a little bit more complicated . But maybe through kind of tailoring these mixtures of cover crops we can get closer to promoting the functions we need at the level we need . So working on pushing that forward . But but you're right , it is a complicated system and we're just learning more about it all the time .

Ryan 45:37

So this is probably a pretty good and natural segue to okay . So what do you have a good idea of , like what different cover crops are driving more beneficial functions or , you know , are there specific functions that you see a bigger signal from from different cover crops ?

Jennifer 45:54

Totally Thanks for asking that , ryan . So take a little bit of this gram salt , because not everything is published yet , but some really seems to be . Clear impacts when you're growing a cover crop mixture . Is that the presence of having a in my case I've only looked at clover , but the presence of having clover or another legume in these mixtures seems to really have an impact on what the microbiome , like the microbiome community , is forming into and , in addition , connecting to functions . I think most of us are familiar with that .

Jennifer 46:29

Legumes form association with nitrogen fixing microbes . So they form these little below ground structures called nodules and it seems in mixtures when legume is there they're going to be fixing nitrogen , but actually they're going to fix more nitrogen when they're in a mixture . So if you're thinking about the amount of benefit you could get , a mixture that has some legumes in it is going to be able to fix more nitrogen than if you're just growing a legume by itself , in terms of the per , the amount of biomass , I guess , to kind of put that in context . So yeah , but I think the kind of too long didn't read . Is that having legumes there really matters for the shape of the microbiome , the amount of microbial activity , so what microbes are doing in the soil , but then also in terms of the nitrogen fixation , so having more nitrogen that came from the atmosphere in your plant tissue .

Ryan 47:30

So that's interesting . So when you have the leg legume in a mixture , it's though it's the

Nitrogen Fixation in Cover Crop Mixtures

Ryan 47:37

nitrogen fixtures are the fixers are functionally more active , which I guess you know . Part of that makes sense , because all of a sudden they're not . They want to be lazy if they can , right , so is there . Do you know of like , is there a threshold there ? I know you guys do some biomass sampling . Have you seen that this is pronounced like once you have you know 40% legume . That doesn't work anymore . Do you know anything about that ?

Jennifer 48:06

Yeah , that's a good question . I don't know if I can answer that super directly , super directly , Like , I think that . But I think they're pretty spot on in terms of like the . The microbes would like to be lazy and so , but when they're putting this mixture and they're kind of like have to kind of go and overdrive because they have to make more nitrogen because it's not just a legume there , they're , you know , working with and competing with the other plants there . But related to the community composition , I have found that in I still see this pattern when we're going from a legume monoculture to legume plus one other species , to like 33% legumes , so legume in equal parts to two other species . So seems like it's working at that .

Jennifer 49:00

You know , one-third legume factor but I don't know if I could say like where it drops off or where that effect happens .

Ryan 49:11

Like as in . You see the like as in . You see the the additional nitrogen fixation happening when you have three species and not when you have two or like . There's this linear difference ?

Jennifer 49:22

well , like a linear pattern , yeah , clarifying that . Yeah , so when you have a monoculture , you're getting some nitrogen fixation , um , and then , when you've got , um , this two species mixture , you're getting a little bit more . And then , when you've got this two species mixture , you're getting a little bit more , and then with three species mixture you're getting a little bit more , yeah , so kind of stepwise getting a little bit more nitrogen from fixation when you're increasing the amount of diversity maybe I'm asking this question late and I should have been thinking faster .

Justin 49:50

But this is including like inoculated rhizobia bacteria that you would put on these legumes , or are you only looking at maybe like natural um colonizing bacteria that are in the soil prior to like an outside inoculum ?

Jennifer 50:06

yeah , okay , thanks for asking that , justin . That's a yeah , I feel like the rhizobia inoculum question is always very curious . So in a field that has had repeated plantings of cover crops , typically the local population of rhizobia that lives in the soil .

Jennifer 50:30

They are typically also present in the natural , so I think there's lots of yeah , I mean , I know that putting inoculum on your plants I think totally is helpful when you don't have a history of planting of that specific legume . But yeah , and I'll just quote , like for for the experiment that I'm talking about , um , we were just working with the microbial population that's like local to the soil , um , in fields that had experienced cover crops for the last 10 years . So , because our plants , like , had this history of management of cover crops , um , we decided that we didn't need to inoculate them because we expected that there would already be rhizobium in the soil and we had data to back that up . But yeah , I think it kind of depends on the field history . But I think I would say that this pattern is not necessarily . Didn't test it on just the inoculate , the first of your inoculum , so I can't say necessarily if it's different , but in the sample we tested and we've been using this like local community this is what we were finding .

Ryan 51:43

Yeah , and I think the interesting part with the mixture of having three species is , you know if you can have a similar amount of fixation or nitrogen fixation , maybe those microbes are working . Over time you can add those other species in there to get some other ecosystem benefits and not really sacrifice . So my and maybe that is true , maybe it's not , but I guess . My other question did you guys find that there was , or are you seeing signals that there are , any other functions that different cover crops or cover crop mixtures are driving , or is it mostly what you can tell is related to the nitrogen fixation ?

Jennifer 52:21

I think I'd maybe just speak about like biomass a little bit , and activity .

Jennifer 52:26

So I think what kind of a curious pattern we're seeing in the data is that you know , I think I like have this expectation just like more diversity is better .

Jennifer 52:35

You know , like just put more species in there you're going to get more benefits .

Jennifer 52:40

But I think in this experiment we didn't always see that .

Jennifer 52:44

So what we saw in this experiment is , like when we grew a legume , brassica in grass together , so a clover , canola and triticale all together thought maybe this would be like the best , and they did have the highest amount of nitrogen from fixation , but their amount of biomass produced , compared to what we'd expect when they're grown by themselves , was actually a little bit lower , and so therefore , it was just kind of a scenario where , if you're thinking about the if like a important value is you want to like increase the amount of biomass on your soil or you're trying to like sequester carbon or something like that , like it kind of depends like the mixture that you select would probably depend on what function you're starting you're focusing on enriching , um I think is kind of the main takeaway we're starting to see like if you maybe if nitrofixation is super important .

Jennifer 53:39

Then you pick one mixture , but if you're trying to promote a certain amount of biomass , you might pick a slightly different mixture , um . So , for example , we saw um like a higher biomass than expected compared to performance in monocultures when we grew crimson , clover and triticale together and that combination also had very high microbial activity in the soil as well interesting .

Ryan 54:06

Yeah , so it's . I mean , I think we could probably talk about this for a long time . But , um , when you start digging into the little nuances , you do hear that a lot of times is like the more species , the better , right , you get more services all the time At least . That's like something that's not informed , that sometimes people say , but what you're saying is actually it's about the specific species you have and it's about testing that specific mixture and seeing what benefits . Do you ? Are you looking for a biomass benefit , where you get , like , the right release of nitrogen later on , or are you and more organic matter ? Is that your goal ? Then it might be a different mixture and maybe it's a monoculture , a biculture , you know , and or are you looking for the nitrogen fixation plus that ?

Jennifer 54:54

like there's these different functions that you really have to be thoughtful of , rather than just like , yeah , the more the better yeah , like it kind of depends what you're tailoring for that might affect how much diversity you want and who do you want there um yeah , but I do think there is an overall pattern , um and there's , I feel , like some papers that have been published about this that like when you're growing multiple species together , like you are like there's an increase in multifunctionality .

Jennifer 55:20

So that would be kind of just like if you want a little bit of everything , then growing a bunch of species together , I think , is like that's the way to go . But if you're kind of have something specific you're aiming for , then kind of tailoring that mixture to what you need is probably more effective .

Justin 55:40

And I think so . This is one of those places like the Northeast Cover Crop Council has their cover crop tool selector and there's all of these other groups and proprietary things that you can follow up with this and they allow you to say what's my first priority , biomass ? What's my set , you know ? And so this , this is an opportunity for people to go out and do exactly what you're saying is try some of these tools , try some of these selectors , and make this fit their needs and their goals within their operation , not just this one size fits all that everyone's looking for .

Jennifer 56:10

Yeah , exactly yeah , and I think it's so good that you pointed out some of those tools because , yeah , exactly Like , I think there's groups yeah , like the Northeast Cover Crop Council have been helpful at kind of pointing people towards like posting on what you want and like selecting something for that specific need . Yeah , and I think you know research is growing to better inform those tools as well , to be able to have more effective , tailored options .

Ryan 56:39

Cool , and including the research that you guys are all doing over there , so we really appreciate it . Jennifer , thank you for coming on again . That was really interesting .

Jennifer 56:48

Thank you so much , ryan , and thanks Nice to meet you , justin . Thank you so much .

Ryan 56:51

Yeah , thanks , this has been fun . Much , ryan , and thanks , nice to meet you , justin . Thank you so much . Yeah , thanks , this has been fun . All right , and to our listeners uh , thank you for sticking with us through those two interviews and we'll catch you on the next episode of the agronomy highlights podcast . Thank you ,