 Well, thanks everyone for coming in today. So my name is Emily Hansen, and I recently graduated from Illinois State University with my master's in biological sciences, and while I was there, my research focused on how cover crops are impacting soil microbial communities. Okay, so the global population is projected to reach 9.7 billion people by 2050. And with this, we're going to see food demand increasing by 50%. So with already more than 12% of the world's population malnourished and our agricultural systems continuing to be strained by the effects of climate change and decreases in soil fertility, we need to start to adapt our agricultural practices to increased yields while also feeding this growing population. So when we're thinking about the future of farming, we need to keep sustainable intensification in mind. So this is where we're increasing yields on our existing farmland without added negative environmental impacts. So cover crops could be one way to start ourselves on this more sustainable journey with conventional farming. So plants can impact soil microbial communities through their production of sugars and lipids. So these sugars that plants produce help feed microbes in the soil. And then in turn, our microbial communities will make available different nutrients that plants need and also extra water. So we have this sort of reciprocal relationship between plants and microbes in the soil. So plants can cultivate their own unique microbial communities by producing these carbon-rich root exodus. And these help attract mycorrhizal fungi and nitrogen-fixing bacteria. And plants also can influence their microbial communities by the quantity and the quality of the litter that they're producing. So when plants are dropping their leaves or dying in the case of cover crops at the end of the season or being terminated, the makeup of this plant litter is going to have an impact on our microbial communities. So litter that's high in carbon can increase the microbial biomass. And then also litter that's high in nitrogen can help add some of that back into our systems. And then also plants can increase soil moisture. And this is particularly beneficial for microbes that occupy shallower soil depths by the surface. So having sufficient soil moisture is really important to sustaining this microbial community. And then microbes in turn can influence plant growth through their interactions with plant tissues in the rhizosphere. So the rhizosphere is this area right around plant roots where we have microbes that are living within or in very close association with the plant roots. And also those free living in the soil. So as you can see from this image here, the rhizosphere is this area really close to the living plant roots. And then we get into the tritosphere where there's more decaying plant matter and then the bulk soil where there aren't these roots in decaying matter present in these high quantities. So these processes can make available or increase the supply of plant essential nutrients. So these can be things like nitrogen, phosphorus, and potassium that are really common agricultural inputs. And these microbes can also perform biological nitrogen fixation. So they're making more nitrogen available to plants. They can also produce antibiotics that can help fight some of these soil pathogens that we see. And they also help build soil aggregates. So in agriculture, it's important to have good aggregation in the soil to help with water flow and reduce the effects of runoff. So these reciprocal relationships that we see with plants and soil microbes are called plant soil feedbacks or PSFs. So in agriculture, the most common microbes that we're going to see in the soil are mycorrhizofungi, nitrogen fixers, and different nitrogen processing bacteria. And the land management decisions that we make can influence how these plant microbe interactions play out. So typical agricultural inputs that we'll see in conventional systems like fertilizer, herbicides, pesticides, can degrade soils over time and fertilizer in particular can discourage plants from forming these beneficial associations with soil microbes. So if the plants are getting all the nutrition that they need from our inputs, there's no advantage for them to essentially give up some of their nutritional resources to microbes. So we won't see these relationships happening as much when we have a lot of agricultural inputs. And then other management decisions like tillage intensity and the actual identity of our crops can also influence these interactions. So this could be something I think we're all familiar with, soybeans and how they form these nodules. They have the nitrogen fixing bacteria. So that's very different from what we see with corn, where it doesn't have the same types of associations like that. And then in turn requires way more inputs from ours. So most of the time when we talk about plant soil feedbacks, we're focusing on the positive aspects of them. So what are plants and then microbes gaining from forming these relationships? But we can also see negative plant soil feedbacks arising over time, especially in monocultures from the accumulation of soil borne pathogens. And this is sometimes termed soil sickness. So anything that we can do to help break up this monoculture is going to have positive effects on our plant soil feedbacks. So this could be as simple as rotating crops. So even without a cover crop in the system, alternating between corn and soy is helping to break up some of those negative plant soil feedbacks. But intercropping can also be one way to do this. And then cover crops can help break up these negative feedbacks and then help establish some positive feedbacks. So cover crops have a ton of benefits to farmlands. I think everyone here is probably more familiar than most with all of these benefits. So these are things like preventing soil erosion, helping to build organic matter in the soil. So as the carbon in our plants is decomposing, this is going to help add to the soil organic matter and make our soils richer and healthier. And they also can help reduce the amount of nitrogen lost to groundwater. So in Illinois, we have the nutrient loss reduction strategy with goals of reducing how much nitrogen and phosphorus we're losing to groundwater. So cover crops can actually reduce the amount of nitrogen that we're losing and capture some of that nitrogen to be put back into the soil. And then also certain cover crops like oil seed radish that have these really big tap roots can help alleviate some subsoil compaction, which can be useful in a no-till system. And then Brassica cover crops can help control weeds and disease by production of compounds called glucosinolates. So currently in Illinois, there are about 1.4 million acres of cover crops that have been planted, which sounds great on paper, but that's actually only about 3 percent of our farmland in this state. So there's definitely room for improvement. So the addition of cover crops to our existing agricultural systems can benefit our productivity. So growers can choose cover crops from diverse plant functional groups like grasses, legumes, and Brassicas to help manipulate the soil microbial community. And additionally, plants like cover crops can provide nutrients to microbes during the winter and the early spring when we usually don't have anything on the field. So when this land is fallow, there's not that food there for the microbes. So adding a cover crop in can help sustain them, and this can result in increased productivity in the spring. So overall with cover crops, we can see an increase in microbial diversity, better nutrient cycling, an increase in our soil organic matter, and better maintenance of our topsoil. So a lot of studies have looked into cover crops and have really shown all of these different benefits. So this one in particular that I pulled out really demonstrates how each cover crop can uniquely manipulate their microbial communities. So in this study, they planted a wide variety of cover crops and different mixes. And the ones highlighted here are ones that overlap with my own study. And what they saw was these species specific interactions between cover crops and their microbial communities, where with each of these cover crops, we're seeing a different ratio of fungi to bacteria in the soil. So these cover crops are not only adding to the taxonomic diversity in our microbial community, but also to the functional diversity. So what the microbes are actually doing in the soil. So the goals of my study were to investigate how the sustainable practice of planting cover crops influences the health of our soils, and also to contribute to a broader understanding of plant soil feedbacks in agricultural systems. So with this, I hypothesized that because of these strong effects of plant root growth on the rhizosphere and these interactions with microbes in the rhizosphere, the type of cover crop we plant and the soil depth that we sample at will be strong determinants of the functional diversity of our microbial community. So with this study, we planted two different single cover crops and then a mix of cover crops. So the first we planted was a cereal rye. This is a great cover crop because it can be planted a lot later in the fall than some other cover crops and it's relatively easy to grow. It does have the disadvantage of getting very, very large and sometimes being difficult to terminate. And it has a very extensive root system. So cereal rye can capture 60% of the residual nitrogen left after corn. And obviously, it grows a bunch of dry matter and when we're thinking about terminating this and how we're going to do that, you need to be mindful of how much of this dry biomass that we want to leave on the soil. So there can be kind of some pros and cons to leaving various amounts on the soil. This plant has a really high carbon and nitrogen ratio, so 80 to 1. So it's going to decompose really slowly, but it can put a lot of carbon back into the soil over time. The next cover crop that we used was pennycress. So the one that we use in this study was the wild type of pennycress. I don't know if anyone here is familiar, but at Illinois State and some other universities they're developing pennycress into a cover cash crop with the company covercress. So with this, they're developing it to be used as a biodiesel source and can provide extra income to farmers. So the latest I heard was that last fall was their first commercial planting of pennycress in some limited areas. And the figures that they were touting were that this could net farmers $150 per acre. So this would obviously be very appealing to a lot of people. This has a carbon and nitrogen ratio that's pretty much in the middle, so 26 to 1. It's not really adding anything or taking anything away from the soil. But pennycress is one of those cover crops that can help reduce the amount of nitrogen when we're lost to groundwater. So some of my colleagues at Illinois State are looking at this, and they're seeing major reductions in the amount of nitrogen lost to groundwater when pennycress is on the field. And with the wild type of pennycress, it has that unique property where it can suppress weed and fungal pathogens via these glucose scintillates. And then we had a mix of pea clover or radish and oat. So the pea and clover are legumes, and they'll provide nitrogen to the soil. And then the oats are added into this mix to help enhance the growth of the legumes. And then the radishes are ones with those deep tap roots that can help break up some of that subsoil compaction. And this has our lowest carbon and nitrogen ratio of 12 to 1. So this is adding nitrogen into the soil. And then our last treatment group are fallow plots. This is how most farmland is left after harvest, especially in Illinois, driving down the highway. This is mostly what you see in the winter. There can be some weeds or crop residue present, depending on how this land's managed. In our case, what you'll see is that we have a lot more weeds than you would typically see around here, because we don't use herbicides on these experimental plots. So it adds a little layer of complexity to this. So before getting into a little bit more, I wanted to orient you to the root systems of these plants. So I have corn and soy, and then our cereal, rye and penny crust, which are our single cover crops. And the top line here is the soil surface. And then this is 15 centimeters, and then 45 centimeters, which was our deepest sampling depth. So corn has a pretty extensive root system. And so does soy. So we wanted to make sure when we were sampling that we were getting samples that were both within the rhizosphere and being heavily influenced by these plant root properties, and also those that are more outside of the rhizosphere or where the plant roots are starting to thin. So with our cereal rye, the roots are starting to thin a bit at our deepest sampling point, but the penny crust were essentially completely outside of the root zone. And then here is the pea clover, radish, and oat in relation to the soy. So with most of our cover crops that we are sampling, we're getting a representation of what's going on within the rhizosphere and then both outside of the rhizosphere. So the first thing I wanted to look at was how the functional diversity or what these microbes are able to do is being influenced by our different cover crops. And I predicted that based on the carbon and nitrogen ratios and different properties that are unique to each of these plants, we'll see different levels of functional diversity with our microbial community. And then my second aim was to look at how this functional diversity is changing across depths. So what we would expect to see is that at shallower depths, we have the highest diversity and this will decline as we move through the soil profile. So our experimental site was at the ISU farm in Lexington, Illinois. We had four blocks established. So this study was part of an ongoing experiment that's being conducted by researchers in the ag department. And they're looking at more of how these cover crops are building organic matter over time. So I wanted to come in and then see, you know, as we're building this organic matter, how is this impacting our microbial community and how is that changing with these different crops and then across depths? So we had four blocks and then within each of our blocks, there were our four different treatment groups. So our three cover crops and then the fallow plot. And this land was managed pretty conventionally. So we did a rotational planning of corn and soy and there was not herbicide used on these plots, but there was fertilizer applied. And there was also no till. So it was kind of a mixed bag of techniques used here. The reason why we didn't use any tilling in this case is because we wanted to see how that organic matter is being built. So we didn't want to disturb the soil at all. Okay. So I sampled the soils in the fall of 2021 and then again in the spring of 2022. So with our fall sampling, we're mostly going to see the effect of our cash crop, which in this case was soy. And then in the spring, we're expecting to see the effect of our different cover crops. So once again, I sampled in these two centimeter depths both within and outside of the rhizosphere. So to look at how the functional diversity of our microbial community is changing, I use these things called eco plates. So they're a 96 wall micro plate. They're about this big and they're preloaded with 31 different carbon sources. So these are things like carbohydrates, amino acids, polymers, carboxylic acids. These are all things that microbes can use as a food source essentially. And it's showing us what these microbes are actually doing in our soils. So we're not getting information about what species are there, but we are seeing what they're functionally doing in the soils. So when I take my soil samples, I dilute them and then I plate them out into these plates. And then we incubate them over a five day period. And then each day, I measure the optical density of the plate. And from that, we get a measure of how active this community is and how well they're able to utilize these different carbon sources. So as we can see from this picture here, if the community is able to use a particular carbon source really well, we'll get this deep purple color development. But if they're not able to use that carbon source as well, it might just be a lighter purple or it could be completely clear if they're not able to use that source at all. So the results that we get from these eco plates is called the community level physiological profile or the CLPP. And this involves three main components. The first is the rate of color development. So how quickly are these microbes using these different carbon sources? Next, we get the richness and the evenness of the response among the wells. So richness in our case, how we calculate this is that so in each of the three sets of our carbon sources, we'll have a control well. And once we correct out for any sort of particulate that might be in the control well, anything above this minimum threshold value is considered positive for use of that carbon source. So we're sort of getting a yes or no. So yes, this micro can use this polymer. No, this community cannot use that polymer. And then evenness is the variation in that color development. So are we seeing that all of the carbon sources are utilized about the same amount? So we're getting about the same level of purple in our sample. Or are we seeing that some are used more than others? And then we can also look at the overall pattern of utilization among the wells. So are there more carbohydrates used or are there more polymers used and use that to kind of tease out these sort of differences that we're seeing between plots and then across depths? So as far as my results go, I'll kind of go through this kind of quickly and get hit on the main things. So I had four main categories of results. So we looked at the amount of soil moisture between the fall and the spring and the amount of coverage on these plots. And then we looked at richness, evenness, and our diversity measure, which is called Shannon's H. And those are our three measures of functional diversity. So richness and evenness are sort of combined together with the Shannon's to give us a picture of how diverse that community is. And then we don't need to talk about what principle components analysis is. That's a little boring, but I'll give you the brief version of it when we get there. And then I looked at each of these different functional groups. So on the left here, what we're seeing is the fall sampling in the orange and the spring in the blue. And this is looking at across depth. So what we saw overall was that in the fall, we had much higher moisture in the soil than we did in the spring. And this sort of affected the results that we saw. And what we see is that at the soil surface, that's where most of our soil moisture is, and that sort of declines with depth. And then on the right here is our results for the different cover crops. So our fall is in the orange. So we had all soybeans planted at this time. So there was no significant difference between the soil moisture and any of these plots, which is what we would expect to see. And then in the spring, what we saw was that the fowl plots actually had greater soil moisture than our cover crop plots, which does make sense because they have lower coverage overall. So these plants aren't there kind of using that moisture. So in the spring, we had a lot of problems with establishment, which I think goes to show how finicky working with cover crops can be. So the year before I sampled, there was fantastic establishment of all of the cover crops. Everything looked great. And it really made me hopeful for when I would come in a year later and actually take my samples. But then we did not see that. That did not happen. So all the way on the left is our fallow control plot. And as we can see, there were a lot of weeds there. And it had actually greater plant diversity than our other cover crop plots. So because we're not using herbicide here and we weren't doing any sort of other methods of weed control, that sort of complicated things. Yeah. So then next we had our cereal rye plots. These had the best coverage overall. So this sort of shows the ease of the cereal rye. These were planted pretty late, which wasn't up to me. But you know how things go, whether schedules on the farm and whatnot. So these were seeded pretty late. And with the cereal rye, that's totally fine. And it was a pretty great establishment, grew really well. Next to that is our pennycrest, which also had pretty good establishment. Not as good as the year before, but not terrible. And then the real big disappointment was our mix plot, which had absolutely terrible establishment. So none of the clover germinated. The peas were sparse, few and far in between. The radishes did something kind of funky, where they were supposed to germinate in the fall and then decompose and essentially not be present in the spring. Instead, what happened is they did not germinate in the fall because it was too cold. And they instead germinated in the spring. So essentially what we're seeing in this plot is a bunch of little baby radish seedlings. And that was really all that was there. This is a weed, so terrible, really disappointing. But we move on. So when we were looking at the richness, so how many carbon sources these soil communities were able to use, we saw a really consistent trend with depth. So at our shallower depths in both the fall and the spring, more carbon sources are able to be metabolized by the community, then deeper in the soil profile. So this really goes to show that most of the activity that we're seeing with our microbes is happening in that plant root zone. So right at the surface there is going to be where we are having the most activity. So on average in the fall, 80% of these 31 carbon sources were able to be metabolized at the soil surface and that declined to about half at 43 centimeters. And then in the spring, this was a little bit lower. So 74% of those 31 carbon sources were able to be metabolized at the surface and then that declined to about 30% at our deepest sampling depth. And then when we look at the evenness of these samples, so high evenness means that we had low variability in our metabolism. So overall, that community is metabolizing all these 31 carbon sources about the same amount. And then if we had low evenness, that would be high variability. So a similar trend to what we saw with richness where at the soil surface, we're seeing more even utilization and less variation in that metabolism. And then that's going to decline as we move deeper through the soil profile. And then same sort of trend with the functional diversity. So this measure of diversity kind of combines the richness and evenness together. And we're seeing the same thing where at the soil surface we have a community that's able to use a more diverse amount of carbon sources and that's declining as we move deeper through the soil profile. So unfortunately with how things pan down in the spring, we weren't able to see any impact of our cover crops on these three diversity measures. But we were able to see, so this is the principal components analysis, kind of complicated, but essentially it's separating out these 31 carbon sources and it tells us which ones are actually important. So factor two here is correlated with carbohydrates and polymers. So if a cover crop like our fellow, or not a cover crop, but if our fellow plots, you know, if they're high in factor two, that means that community is able to metabolize carbohydrates and polymers really well. And then factor three was correlated with carboxylic acids. So as we can see from the fall here cereal, rye and our mix are sort of clustering together in the middle there and then our fellow plots are separating out to either side here. And this is interesting because in the fall when we sampled this, this was all soybeans. So we shouldn't expect to see really any sort of differences between these plots, but we actually did see some differences. So this goes to show that these cover crops that we're planning, the previous spring are actually having an influence even into the next fall when we've had a cash crop there in between. So these cover crops, you know, they can have a lasting impact. And when we compare that then to what we saw in the spring, that utilization pattern really changed. So instead now in the spring, we're seeing our cereal rye separating off and then our other three treatments kind of grouping together. And in the spring, we had different functional groups that were weighing heavily on each of these factors. So for factor two this time, it was only carbohydrates that were really important to it. With factor three, there was representation across the board from a lot of the functional groups, but amino acids were not represented at all. So we're seeing that different things are weighing more heavily on the microbial community once we have these cover crops out there. And that even when we have sort of terrible establishment, there is some things going on. So I think with the cereal rye having really good establishment, I think that's why we're seeing it separating out from these other three. And then to further analyze this, I broke down each of these functional groups by themselves and looked across depth. So there are six different functional groups here. This is how we're grouping these carbon sources together. So as we move across depths, we're seeing that there are different carbon sources able to be metabolized by the community. So at the soil surface, polymers and carbohydrates were very important to this community and were able to be metabolized really well. But as we get deeper in the soil profile, we're not seeing that anymore. And so maybe a carboxylic acids and amino acids are becoming more important. And then when we look at the spring sampling, we're seeing that shifting again. We're now at our shallower depths, carbohydrates, carboxylics and amino acids are more important. So this goes to show again that these cover crops are causing shifts in the metabolism and the usage of these carbon sources. So to summarize my results, what I saw was that microbial communities have greater functional diversity at the soil surface than deeper in our soil profile. And as depth increases, so as we're getting deeper into the soil, the metabolism of these different carbon sources by our microbial community is becoming more variable and there's less carbon sources able to be utilized. We also saw that each cover crop has a different pattern of carbon source metabolism. So while we didn't see as many differences in the functional diversity components, we are seeing that overall with the pattern of utilization of these carbon sources, there is something different going on with these cover crops and they are uniquely impacting their microbial community. So cover crops can really only be one component of sustainable intensification. They're not the one answer and the one solution to everything and I think some of the problems that we have go to show how challenging implementing this can be. Can you speak on that last point a little bit more? Yeah. Cover crops, the most influential component or? I think, so coming from looking at this from a conventional agriculture standpoint, with organic farming, this is gonna be kind of different because you have a lot more going on than the conventional people do. So when we're thinking about conventional agriculture and sustainable intensification, so not adding any more land into our usage. So keeping the same amount of farmland, but then not having these negative environmental impacts, cover crops are an easy or sell to farmers. So something like changing how they're applying their nitrogen fertilizer that could be kind of palatable, but it might be foreign to people, thinking about okay, the way that I've been doing it for 50 years might not be appropriate anymore. So we need to change how we're doing this nitrogen. We need to apply it at a different time or a different rate. We can also have things like buffer strips. So having land set off near waterways, so we're getting less nutrient runoff. So there's a lot of different things that we can do to make how we're farming land more intensive and more sustainable. I think GMO crops from a conventional standpoint are really useful for that too, because you're able to get higher yields from the same amount of land. So I think cover crops are a good area to focus on for conventional farmers. And it's something that they could more easily integrate into their existing practices. Okay, so I only had one more slide. I just wanted to show some pictures. So I was funded by SARA for this project. And as part of this, I got to do outreach with farmers and I got to speak at a lot of field days and go to different events. And I just wanted to hit on that. I really loved doing that and it was fantastic. Part of this project that I wouldn't have gotten to do otherwise. So I just wanted to thank again, the people at Illinois State that helped me. I had some really great undergraduate students that worked with me over the course of this project. And once again, my funding. So I can take any other questions now.