What Cover Crops Do for Your Soil: On-Farm Research Results from Nebraska

0:00 I'm Dylan, one of the sales reps here for Green Cover. I live with my family here in Western Kansas. And happy to introduce our guest here today, Andrea. She's an associate professor at the department of agronomy and horticulture at the University of Nebraska Lincoln. Her and her team studied different aspects of diversified cropping systems that include nutrient cycling, water and weed dynamics and also the policy and the human decision-making that go on behind that as well. She teaches undergraduate classes in crop management. She's nationally recognized leader in cover crops, soil health and climate impacts. And since 2018 has delivered over 90 invited presentations and media interviews. So today her topic is explaining what cover crops can do for Nebraska soils.

1:02 She's going to share some of her on-farm research conducted across Nebraska focusing on nutrient cycling, weed impacts and specifically soil test biologies and cover crop decay and then above and below ground pigweed effects following multiple years of cover crop use. So Andrea with that I'll let you take it away.

1:28 Well, thank you so much, Dylan, and thank you everybody for joining this afternoon. I really appreciate the invitation. As Dylan said, my team and I study a lot of different aspects of diversified cropping systems, and I do get invited to talk a lot. I might just be bad at saying no, but I think that the information that we are learning about is really valuable to share. So I love to talk when invited and I really appreciate Keith and Green Cover hosting this series. I had a chance to look a little bit at what Jenny Burhill and Aaron Silva had presented and I really appreciated the messages they gave about Erin in particular about cover cropping being really like the lynch pin of how we can pivot into low input systems and improve soil health. And Jenny I thought had such a great intro and deep dive into on-farm research testing, giving yourself data to have confidence in what you're doing and I'm going to underscore more of that today.

2:25 So I do think that what I have to share is not just specific to my results at least not just specific to Nebraska. I think they really could be transferable to many different environments. So my focus today is what we've learned in Nebraska. Nearly everything that I'm going to show you is from a collaboration that we had with the NRCS that went from about 2016 to 2022. So actually started before I came. I started at Nebraska December 1st of 2017. So this is my ninth year there. And this project had actually gotten started before I came.

3:03 So I'm going to talk a little bit about the project in my introduction. And then I've got two experiments, two projects to talk about that have to do with soil in particular, also about some of the strategies that we use to find differences and to really look at how different soil health management systems were impacting soil health. And that I think could be really valuable as you think about how do you have confidence in what you look at on your own farms. And then the last study that I will include from all of these farms as well is about weeds. We found some interesting and surprising things. And then I'll try to tie all of this work up together.

3:47 So that is where I'm headed this afternoon. And just a little bit more images to illustrate some of the work that I do in Nebraska. So as Dylan mentioned in my introduction, I've had a research team of graduate students, research technician, postdocs, who study again a lot of different elements of diversified cropping systems. I was telling Dylan and Jonathan before we got on the webinar that I have done a lot of different kinds of research in my career, including studying my students and talking to farmers and doing more social science research and I have just learned so much from listening and trying to ask good questions.

4:16 So a lot of the aspects that we study have to do with how can we get more continuous living cover cropping systems on our landscapes. And as Jonathan mentioned, it's a very windy day here in eastern Nebraska. I think a lot about the fact that these are the times that we get dust storms that can be very problematic and so how can we have landscape cover this time of the year preventing dust storms being one of them. So I have done a lot of annual cover crop research in my career. We also have done a little bit of research with intermediate wheat grass or kernza. Some of you might be familiar with that.

4:48 Familiar with it. I think it's an interesting and future solution. Still needs a lot of work, but really I think the perennial grain concept has a lot of potential to improve profitability, can really work well with livestock system and address issues that we have in agriculture right now.

5:08 So I also teach a few different courses in crop management, including a senior capstone course. And I just want to highlight that one of the ways I've connected with farmers is not just through on-farm research, but is also through my teaching. And I've been so grateful for many of the connections that I've built in Nebraska and bringing my students to use. So I see Jeff Stefen on our call. I'm grateful to Jeff and Jolene Stefen and Crofton who host my students in this senior class. You can see Jeff and I here in the right of the screen doing a soil health assessment with my senior students in the last trip that we do and really showing them what his management has done for the soil. And it's a clear difference from other spots that we've sampled on that trip. And Scott Ravencamp from Green Cover Seed here in the photo too. And I'm just really grateful for how generous many of you are with your time. The lessons that you can teach my students mean a lot more coming from you than probably from me.

6:06 And I welcome your thoughts. I welcome you to use the chat if you have Gen Z folks in your orbit, maybe that you work with on your farm or who are your nieces or nephews or children. How do we best connect with them? Because I'm kind of endlessly curious about how I can help reach them and get them into a path into the regenerative future that we all hope to stimulate.

6:31 So I was going to just share a motivating question here in the introduction of my work which is what might our soils look like in 2050. And as an agronomist when we go to our conferences and I'm sure you hear and read similar things too where folks talk about how much food we need to produce by 2050 and the productivity needs and gains, I would ask what is our soil going to look like in 50 years.

7:00 So if anyone's been to this rest stop in southwest Iowa, you can only access it if you're driving east. It is a tribute to Henry Wallace. And what you see here on the pillars, the black middle parts are meant to depict the depth of the topsoil in Iowa from 1850 until 2000. And I don't probably have to remind anybody, it's 2026. We're closer to 2050 than we were the last year or two from 2000. So essentially the depth of topsoil being depicted here as being cut in half in that time and I know that many of you are trying to learn and do everything that you can to try to reverse these trends and I appreciate that but this is really a motivating question for me.

7:44 And just a little bit more before I dive into some of our research studies that I wanted to highlight some of the differences related to on-farm and experiment station research. So the research that we might do with a university on small plots and my colleague Katia Kler Cole who's a soil health extension educator in Nebraska, we've been working together for years and has done a lot of great work in cover cropping and organic systems. We had the idea to look at our on-farm research network book, which is publications of all the on-farm research that has been done in Nebraska and in the extent of its program, and we compared how that looked to research that had been published in science journals that had been done on experiment station work. And what we found I think was simple but interesting. And I just wanted to make a plug for, I know that all the research that we do is imperfect, but I do think that there is rigorous and has its value and on-farm research has great value and farmers are often very nimble and able to experiment in a very fast way in a way that we can't always do at a university.

8:55 So I will include and all of my slides, all the references, I put QR codes and actually when we get into the chat portion, I've organized all my links here. So I'll drop those in the chat for you as well if you want to look at anything further. So in this publication, we looked at again what had been done on farm, what had been done on experiment station, and we found which is probably not a surprise that there was more topographic conditions on farms, more diverse soil conditions on farms, and we had typically lower slopes and.

9:29 More optimal soil texture on experiment stations. We also found, I thought this was really interesting, that farmers were more likely to test things that were, I thought almost a little bit simpler in scope, cover, no cover. That wasn't something that we found in the publications from Nebraska on experiment station, but we were looking at things that might be really difficult to test on a farm. Cover crop termination method, if you were doing tillage with a cover crop or if you had irrigation or not, would be harder from a practicality in a farm operation to test some of these things.

10:07 Consistently we found that either on experiment station or on a farm there were no significant yield changes with and without cover crops. And that actually more biomass was grown on experiment station research from the studies that we had. Of course, that's not comprehensive of everything, but I just thought that some of these things were valuable to point out in the context of what you are doing on this webinar series.

10:32 My take on it is that there are pros and cons to both types of research. And there's a lot of benefit to working on experiment station, but you know, we try on farm and also experimentation to really look at things that are more process-based, underlying principles. But of course the practicality and the testing on your farm is invaluable and I will move into what we have done here in Nebraska. With that said, so again pivoting to tell you about the project that comprises a main portion of what I'd like to share with you today.

11:03 So even prior to my coming to the university, there was work underway in 2016 and earlier in 2017 where the NRCS and colleagues of mine with the on-farm research network and others in research at the university came together and had worked out with collaborating farmers, those who wanted to test soil health management systems on their farms. So the farmers had contracts with NRCS to do this and to collaborate with us and everyone got to design what they wanted to do. So they got to pick if they wanted to test different cover crop species, if they wanted to graze or not graze a cover crop, if they wanted to look at different crop rotations, all elements of the principles of soil health that farmers got to design.

11:55 Not only did we have this great swath of different experiments that were done, I do think that this was really designed by farmers with a more systems approach than the more reductionist type of way that we will look at one treatment in what we call a factorial design. But that gives us some confidence in just attributing an effect to one treatment, right? But this was more systems. So we had to be more creative in the way that we analyze our information. And I think that although some of our analysis is I think even for myself a little complicated, but I also think it led us to some interesting understanding of these systems.

12:33 So we had 17 farmers you can see across the state and they all had different experimental designs in this project. And I want to just quickly show like what this would look like on a farm. So this is just a snapshot of the strip trials. I know Jenny talked a good bit about this and I imagine it's pretty familiar to many of you, where the farmers for their contracts were asked to have a common practice and then also something that was new. So they had to have at least two treatments and they were randomized and replicated.

13:03 These strips go across the whole field in a random order in order for us to capture the variability that exists in a field and also so we can calculate statistics on that, but really we do that because we want to have confidence in our results that we're not looking at just one half of the field and the other half of the field with different treatments, that we are able to really have confidence that the effect that we're seeing is not just due to something that's happening on that part of the field, site history or soil topography, etc. So we want to have confidence in that and that's why we work with farmers, design these based on their equipment and constraints, and the plot sizes in our experiment range from 30 feet wide to a few hundred feet wide and up to almost half a mile long. So these were farm scale.

13:58 The information in general that we collected, what we used for the on-farm research reports are yield information as well as management information. So our on-farm research reports are pretty straightforward.

14:09 Describe what the experiment and treatments were. They show yields. They show partial budgets usually. But what we also did was to collect more information from soils and weeds for a few years over the course of the experiments. So we not only had the breadth of different experiments at the farm scale, but we also really tried to dig into like what might be happening and why on a few different elements. So I'm going to try to go through this and stick to our time. And again if you want to see anything you'll see the QR codes here.

14:44 The first project I wanted to share was a focus on 10 on-farm study sites from soils that were sampled in 2019. So that would have been just a few years after some of these projects or these experiments were initiated. And the goal here was to try to understand what was the effect of the soil health management systems on different elements of soil physical, chemical and biological properties. And we did not in any of these experiments really or any of these projects really get to work with the full swath of those 17 farms. We tried our best to work with as many as possible. And this project working with 10 of the farms I think was really great and comprehensive. So I do want to point out too that we always try in our science to write CropWatch articles about our projects because that is a way that we can kind of synthesize results to a shorter way and make it more accessible, easier to share. So that's what the second link here is that you see and the top link is the journal article. We try always to make our publications freely available or open access. So again, I'll drop those links in so you'll be able to find them if you are interested.

15:52 There was a range of different soil health management systems that were tested in these projects where people were comparing different cover crop species, grazing or no grazing, some of the things I've already mentioned. Some folks had different crop rotations. But the really creative thing that we did and this was led by the outstanding graduate student Fernando, who's now at Ohio State University. What she did was talk to all the farmers and understand their site history because we obviously know that just imposing those strips on a field does not negate the many decades of what has happened prior on that soil. Right? So she also captured what was the history of cover crop use, no-till, livestock, etc. And what she did was to create indices where this was based on what other people had done in research to essentially take the maximum that had been done in all of these categories. So for crop diversity if there had been up to the least number of species was two, the most was 18. So 18 became the maximum and then the numerator was based on the treatment and the site history at all of these strip trials at the farms. And years of cover crop use, the maximum was 12 years. Without soil disturbance, the maximum was 30. So we basically tried to standardize what was the history, which I think is a really interesting approach because I know of other projects out there where there's different farmers and people want to try to compare what they found and where and why. And it can be really messy. I'm going to be honest, this could have not worked out, that we found a lot of conclusive trends, but we did find some things I think that were really interesting by trying to group these sites in a common way based on their history and what the new experiments that were started a few years prior to this.

17:51 So we used this classification approach and then we applied the findings to 21 different indicators of soil physical, chemical and biological health. This was actually only sampled 0 to 15 cm. So not really getting into deeper depths of the soil but still giving us a snapshot of where we're often thinking about nutrient cycling and action and happening in the soil. So we used a soil assessment that was done with our NRCS partners and with our team as well as capturing the soils for the Haney test. So there were a lot of different properties that were considered in this and we tried to link those again to what we know about how can we relate these different properties to these different management practices.

18:44 So what we did, I will talk you through this graph to try to understand which of those management practices might be having the greatest effect on these different soil properties. We basically did a ranking. So this kind of analysis is called a relative.

19:04 Importance analysis and you could think of it like a ranking. So if we do our math, our multiple regression analysis, the statistics, we're really trying again to compare which practices have the greatest effect on which properties. And so you see the ranking at the bottom here that cover crops across all these farms and these different experiments had the greatest contribution to all of the properties overall. So it was cover crop use then years without disturbance and you can see the percentage ranking essentially.

19:39 And then when we look a little bit more closely at some of the specific properties. So those in the Haney test related to carbon and nitrogen cycling we found that cover crops in this tan color were responsible for a really significant portion more than what they were in the overall of that ranking.

19:58 And then when we looked at some of the soil health assessment that was done by the NRCS, we could see actually that crop diversity had a strong relationship to some of the properties related to water. So this is y'all are very smart. I don't think this is too complicated to show, but the reason I think that it's the trend is not just a yes no. It's again trying to look at a ranking of how some of these different properties compare to or are affected by some of these different management systems. So cover crops being the highest overall and having strong relationship to carbon and nitrogen cycling which might be no surprise but the fact that we could actually see that with this different swath of studies was really encouraging to us.

20:48 And then the other result that I want to show from the first project was this relationship between the soil test biological activity and the predicted nitrogen release and the potential nitrogen savings. So if you have familiarity with the Haney test, I'm sure many of you do you're probably familiar with some of these additional tests. The Haney test is interesting because it is meant to capture more of the biological and chemical function and activity in the soil to account beyond what a standard chemical test would.

21:24 And so because the cover crop use we found to be the most important management affecting these properties that are closely related to carbon and nitrogen, we wanted to further explore this. And so, this organic nitrogen release, a soil test biological activity, the 24-hour incubation of soil that is dry that you then rewet and you measure the CO2 coming off of it, has actually proven over a lot of research over time, if anyone's interested to hear more about that, I could share more of that with you too, that there's this really strong relationship between not just the biological test activity but also a lot of other important soil health indicators including total SOC.

22:06 Right? So, so this relationship between biological test activity and organic nitrogen release is used in the Haney test to show what might be a potential nitrogen savings that is not accounted for in a standard chemical test. So what we found and here the cover crop use index is showing the longer the farms had used cover crops in darker green and bigger circles that those and then so that's the biological test activity relationship to nitrogen release on the left and then on the right the potential nitrogen savings. So we see this clear differentiation between once those farms had started to use cover crops over eight years where you could detect this difference.

22:53 And do I think that that eight is a magic number? I don't. I just think it's the way that we had this data set available to us with the farmers and the site history. But we were really encouraged to see that there was evidence as I'm sure many of you know and are already working with around how much nitrogen might be additionally available with a longer history of cover crop use.

23:19 I'm showing you the QR codes here again to the Cropwatch article journal article. Again, just to summarize this, we found cover crops have the greatest effect across all these properties especially related to carbon and nitrogen. The longer that cover crops were available, we saw that relationship between greater biological test activity, greater nitrogen release, potential nitrogen savings. And again, I don't think that eight is a magic number. I just think that it was the way that our data was related. But this longer-term use and pattern we thought

23:56 Was really a valuable trend to highlight from all of these farms and different soil health management systems.

24:06 That was the first project I wanted to mention. I wanted to talk about these two others related to soil and also related to weeds. So I think that this project has a nice potential to help think about what are great ways to sample to really be able to show and understand what's happening on your field. So for this project we just focused on four of the farms that had the same experimental design that for us scientists who like to think about standardization, we liked that where there was just a cover crop and no cover crop control. So we had these no cover crop control areas on four of the farms.

24:50 And we wanted to see how there were differences there, but also compare the cover, no cover to a reference state, which might be something that's familiar to you, and I will say more about that. But also we wanted to look at the intensity of sampling, the number of samples that we were taking, and how that affected some properties, including water infiltration. So we honed in on these four farms again because they had the same experimental design. They were mostly located in central and eastern Nebraska as you can see here the four counties of the farms where they were located. These soil samples were taken in July of 2019, so in the reproductive growth stage of soybean when they were sampled. So we have some information here from soybean as well. And then there were a number of other different soil properties that were investigated as well.

25:47 And so I want to explain what we mean when we say a reference state. Right? So this concept of the reference state has been around in ecology. It's the idea that a reference state reflects soils or areas that have been less disturbed, minimum human modification and kind of minimal management. And so my colleague Bes Maharjan who's based out in Scottsbluff and his team have piloted this idea that if we're looking at a similar soil type, similar environment where we have less degraded soil that really can tell us the potential. So what is the potential of our agricultural soil with different management? So what might be we striving to in terms of properties, processes, functions, and this is something that we have colleagues that do with crop yields, what's the crop yield potential, but I think that this is such a great overarching concept for us to think about what is the potential of our soils if you can think about reference states, I would encourage you to be thinking about this way.

26:52 So what we did in this analysis was to calculate a relative soil health score and that essentially is a ratio of what is a soil property value in our cover crop or no cover crop strips divided by the reference state. So if our reference state is one and our soil properties are 0.5 or 0.8, then we're at 50% or 80% to that ratio. So that's the idea of the reference state. And then the idea of sampling intensity. We wanted to really be sure that we could detect differences because often what happens is we go out, we sample with the best intent but we may not have done that in a way that's really going to have enough power to show a difference.

27:39 So I think about an example of a friend in graduate school at Iowa State who had great soils in Iowa, really high percent organic matter. He was looking at an experiment that had cover crops for following rye, cover crop following corn silage, so kind of an optimal amount of biomass for over 15 years, and he took in a small area over a hundred samples to be able to detect a 0.5% change in organic matter. Right? So that has always stuck with me in my mental model of like sometimes we really do have to sample with a high intensity to detect differences. So sometimes there are differences but we just are not able to capture them because it's actually really hard. We're limited by time, money, etc. But what we did with this, we designed our sampling and for the prior project really intentionally where we looked at a soil map. We looked at the design of these experiments and we captured within a 6 meter by 24 meter area several different points where we would take our samples from. For infiltration, we're not doing composites, for putting a ring in the ground, putting water into the ring and hitting start on a timer, right? But where we were taking other properties that we would.

28:48 Samples where we would do a composite sample, we would take from several different areas within that area which was defined as you can see. We tried to capture within every strip, but really designed those areas based on topography, soil type, etc. And so we did calculations of what the differences were in infiltration if we had only taken two measurements, three measurements, four measurements, or five measurements. And I'm going to show you what the results of that were.

29:16 So the first thing I want to show is how did the four different farms compare with respect to this relative soil health score. So I'm showing you six of the properties here which if they increased would be what we want to see. So if we think about our reference state having a score of one then a score of six for these six different properties that I'm showing you here in the graph would be 100%. So that would mean either the cover crop or the no cover crop were we're already at the reference state. So what we can see so the so these are the four different counties that we looked at for this study. And on the left of each of those, the bar for those sites has represents the cover cropping. So here's the cover cropping bars and then here's the no cover cropping bars. So a few things that we found. So again, a six would be a perfect score.

30:14 There were significant differences overall at two of the sites for the overall score meaning to us that these two sites were able to with the use of cover cropping which was new on that field and new on those strips in just a few years get closer to the reference state which is really encouraging. So two of the four overall were closer to the reference state from a significant standpoint. Infiltration and nitrate levels increased at three of the sites and then aggregate stability, cation exchange capacity and organic matter increased respectively at one of the sites. So where you're seeing these stars, you're seeing where there was a difference between the cover and the no cover.

30:58 This was really encouraging and it was really encouraging to me because the reference state gave us another baseline to compare. So we weren't just looking at the treatment effects of one property to another, but when we aggregated them and looked at that reference date, it did show us that two of those four sites in just a few years were able to improve. And I really was encouraged by this because I often hear people say, 'Oh, it takes a lot of time to see change.' And I'm not always convinced that's true. I do think that is true. You can all attest to that, I'm sure, on your farms. But I also think that it can be the way that we sample that it doesn't give us the best opportunity to detect a difference. So I think that we did some things very well here in this project to try to really understand what was happening. The other thing that I'll show is a little bit of a messy scatter plot, but you know this is the real world and farms are messy.

31:56 When we looked at the soybean yield on those strips from and we compared that to measurements that were taken both in 2019 for infiltration. We went back in 2021 and we took infiltration measurements as well. The relative soil health score is essentially if your infiltration value was closer to the reference state. So the higher score means that the infiltration in the cover no cover strip was higher. So not altogether but just that one on its own. And this is for each of the locations in the years that we took measurements. So it wasn't for all of them but we were just looking at where we saw soybean. But you can see this increasing pattern where soybean yields were higher on some of the fields on some of those strips in those areas of the fields where the relative soil health score for infiltration was higher. So I think that this is interesting and it is a little messy. This is part of that publication. But what it does give us is I think a trend and some confidence linking the practices, the soil change and the crop productivity, which is really the win-win-win. We don't always get to that last stage of linking productivity because it's complicated as you can see here.

33:16 And then the last that I want to show from this project is the value of the sampling intensity. So I've already alluded to that with infiltration, we had those circles in different areas of our representative spots of the fields where we identified to sample. And what I want you to be looking at, as I've shown here, is that

38:22 Up to over 300% of pigweed seed in the soil where there were cover crops. And these were sites at two farms and one of the experiment stations that we found this, that had a history of cover cropping between four and seven years. So kind of like medium-term amount of cover cropping. So the interesting part of that, we have some ideas of why that might be happening. I'd love to hear folks' thoughts if they've observed that or if that makes sense to you or have thoughts about it.

38:58 But what we found in the season when she went back to take the measurements was that there were reductions at some of the sites or no changes, no differences between the cover and no cover treatments in total weed density. In fact the cover crop treatments here's one at one of the experiment stations and at one of the farms were reduced at different sampling points.

39:22 So there were not increases in total weeds where we had cover crops. We had reductions. We did note that we had greater weed density at our experiment station. So maybe kudos to the farmers who we participated with who really did a great job with managing their weeds overall. I think a testament to the fact that cover crops really are a part of an integrated weed plan. So we didn't see increases in total weeds. We saw decreases at some sites, but we did not see pigweeds increase at the sites above ground. So even though we saw them at some of the sites more, we did not find them to be in the soil. We did not find them emerging during that crop season.

40:11 And then the last thing that I want to share that I think is probably interesting and maybe explains some of what we're seeing at a few of those sites where there's actually more pigweed seed in the soil seed bank under cover cropping is that we found that at several of the sites including two of the farms that there were distinct and different seedbank compositions. So when we look at all those different species of weeds that Elizabeth categorized, there was a distinct and different composition of these weeds. And so this is actually interesting in ecological theory that having more diverse weeds can be a benefit because it keeps all of the weeds less competitive. I think this is a group who can handle that information. There could actually be an increase in the seedbank and that thinking about your weed seed bank and weed communities as more diverse can actually have some benefit and there's a good amount of information out there and a lot in the ecological realm that would suggest that this has a benefit. And we did find small but non-significant increases in weed diversity in the cover crop treatments at all of the sites. But it was not significant, it was kind of just a slight trend.

41:30 So really interesting results I think from the weeds here and did show that above ground the cover crops were having a positive effect. But some interesting things to consider when we think about the soil seed bank, that perhaps one of the ideas that we had is that perhaps the cover crops are limiting what emerges. They're potentially deposits that are remaining or staying in the soil seed bank. And so we would really advocate for researchers who have the capacity to do this to study the soil seed bank a bit more to understand what is happening here. So that's what I have to say about weeds and I will conclude now so we can have some time before the hour for questions.

42:17 I did see and actually we have a nice end of project summary here in this publication that I'm pointing to that cover crops are accruing soil benefit, bringing soils closer to a reference state, having the potential to reduce fertilizer use and costs. They are suppressing weeds, shifting weed communities. And we do in the publication that I'm pointing to here show kind of some overall trends from some of the different projects about slight yield differences, but mainly being neutral to positive. And then the last thing I did want to share too is that from this project, NRCS has conservation programs you can use including the 216 soil testing practice that allows you to include costs for reference state and SEMA 204 actually includes on-farm.

43:15 Experimentation. So you can visit with NRCS and look for ways to support doing on-farm research and experimentation on your own farms.

43:24 And then just a few more things about our group here on my last slide. We've done variety testing of cover crops in my team. If anyone is in Nebraska and interested, we do have a YouTube channel where we try to archive talks like this and other presentations. We have some nice videos there as well. So encourage you to check that out. And I really want to thank Green Cover, Dylan, Jonathan, Keith, everyone for inviting me and just for everything that you do to conserve and regenerate the soil and even more importantly perhaps to build community and share knowledge. I can't underscore how valuable that is. So thank you with that and I will be happy to answer questions. I see many comments in the chat that I'm going to look at now.

44:04 Yeah, thank you Andrea. We do have several questions in the Q&A, so I'll get started with those and then I'll follow up with some here in the chat as they've come in. So Doug here asked, could you provide a statement about cover crop termination using chemical termination versus roller crimping and the below ground process of both methods?

44:28 Yeah. So I admittedly don't have a lot of experience roller crimping. It's not something I've done in my research program. I think that is probably a gold standard that people will want to get to and that there's probably some evidence about chemical use and soil communities, but I still think that the benefit of the cover crop and the roots that you have with chemical termination is a positive. So I don't know that I have too much more to say than that, that the benefit of roller crimping and having that much biomass and much more residue potential to recycle if you're growing it longer is great and good for below ground and maybe less chemical disturbance. But chemical termination is the approach that people are getting started with and finding success.

45:28 Yeah. I think it's, you know, they're both tools to use and really have to work with what's in your context. I think those.

45:36 Um Jack here asks, it's in the, so I'm not sure where he's referring, but the first 15 centimeters, how does that correlate with the deeper sole characteristics of perennial plants, some going to 15 feet?

45:52 So how does it correlate? I think it really depends on the soil that you are in and how uniform it would be. I don't expect that most soils would be extremely uniform and I know that this is a limitation of what we did in terms of really measuring just the first 6 to 8 inches of soil versus deeper. But that is a reality and practicality. So when anytime we've sampled to three feet, it is a huge effort, but I think those efforts are very worthwhile. And if you want to follow up with me, I'm thinking about a publication a student recently wrote from Nebraska where they did some deep soil sampling and carbon analysis. So I could get that to you if you're really interested in it. I don't know if you're in Nebraska, but that might be another more deep response to your question.

46:52 Very good. Let's see. Um another anonymous attendee here. Really interesting work. Says, 'Thank you for sharing. For study one, was it the 0 to 15 cm or inches for soil sampling? At what depths did you measure temperature?'

47:08 Yeah, so it was 0 to 15 cm. So it would be about 6 to 8 in.

47:21 Um I'm not sure. Nelia here would like to know more info on cover crops and grass burr reduction. Any help or things we could consider dry this spring or summer?

47:34 I don't know that I have anything specific to grass burrs other than and I would actually love if anyone does have any observations. It's not something that at least in our experiments, I mean I see it around but not necessarily at our experiments. Um, if anyone has thoughts on it, please I encourage you to share that information. But I think that there is a lot of evidence that would suggest cover cropping in the short and longer term has benefit above and below ground for weed communities and there's a lot.

48:07 Of processes that are happening. So I have just kind of a general positive on the weed reduction potential in the shorter and longer term using cover crops as a tool.

48:20 Yeah. Do you are you very familiar with the wind weeds talk? A little bit. Yeah, I know the grassy sandber is in there and there's several things that, you know, several reasons why it grows. So, you know, there's something to look at there. And you can get that book on Amazon. It offers alternative things to try to maybe eradicate some of those species.

48:51 Kind of go I think I'll go to the Q&A here or the chat here. I think Chris is going back to your weed study and just I think he's asking the question here about you know are the exodates from the weeds helping the soil biology and does the pig weed itself help pull up calcium and make it more available anything to that that you guys?

49:17 I don't know that we looked at it but I appreciate that thought and in other work I've done we have seen where it is possible that cover crops could be increasing? This was one of the not exactly the calcium question, but just like is there something in the cover crop cover cropped areas that could be creating a better soil environment for some weeds not to weed seeds not to die. And I think it's a great theory, but we didn't look more carefully. That's a great like process into this question. I my instinct is that some of those like that I want to say like meoscale kind of process would be probably pretty variable in different places. And I've only found a few studies that have reported kind of this finding like we have but I actually found an experiment in Kansas that found something similar. But so I think there's really something to the idea that below ground it could be that the environment that the cover crop is creating is allowing the seeds to persist.

50:28 Okay. So if it's good for soil and water movement, might be good for weed seeds, too.

50:35 Sure. Brent here is asking I think he's referring to your the winter rye. He's asking as a single cover, what was the rate? What point did you terminate it? Did you did you collect how much biomass it produced? And then what was the method of termination on that?

50:58 So for I'm near certain for all of these experiments it was chemical termination and the farmers I can't say with certainty. In our publication, we have the at least for the weeds, the numbers for the biomass. It ranged from I want to say about a thousand to 2,000 pounds. I don't know if we have what the seating rates were. I want to say they would have been within recommended rates. And recommended rates would be between, you know, 60 maybe to 120 cereal rye, 20 being on the high end for broadcast seating and I know people who are planting at much lower rates to be more economical and still getting good biomass. So that's not a great response but our biomass growth was I mean you can see it here in the photos. This is from one of our on-farm experiments. I mean it was not huge but pretty good for what I've seen in Nebraska and Iowa.

52:03 Okay. Going back to the Q&A here a little bit. Jeff asked, 'Was there any attempt was there an attempt to follow profitability on the four farms that you guys studied?'

52:15 We do have partial budgets in the on-farm research reports. The issue with those partial budgets is that if you just include the cost of the cover crop, the termination of the cover crop, and you don't have a big yield increase, then you will have a negative partial budget. So, we did not on those four farms make a huge effort or really in our publications talk too much about this, but it would be in the on-farm research reports. I think the partial budget is going to have to require a bigger swath. Like you're seeing some of these results come out now. The soil health institute has published it. Our soil health coalition in Nebraska has published some of these budgets. You really need to account for what is the input use savings to show the bigger potential of what these systems can do. So the partial budgets are I feel sometimes a little underwhelming. Say it that way. Okay. Derek here is I think he's going back to the the weed

53:21 Study and he just asked how much of that 355% of amaranth seed was viable. How long does amaranth seed stay viable in the soil?

53:34 It was viable enough that when we put it into the greenhouse it germinated. So what Elizabeth did it was briefly on one of the slides we watered it we watched what came up and after she did that for about a month and then after there were no more weeds coming up she reived the soil and did that all over again she did that three times basically to try to deplete what was remaining. I don't actually know the question that but if you want to email me I could look it up but I bet you could look it up too in terms of how long I don't want to tell you the wrong thing. I do know that many weed seeds can persist for decades in the soil. I mean, weeds are ecologically fascinating because of how potent they can be. I'm not sure about pigeed, but I will just say that they were viable enough that under optimal conditions with sunlight, warmth, and water, they emerged. Now, would that be optimal in the field? Of course, what we saw was that they were not emerging in the field.

54:34 Yeah, I think it goes back to the context of the soil and the operation on some of that. Let's see. Roger here asks just to describe the sites where the reference data was collected and he has you know prairie or cemetery as like I guess maybe describe what the sites were like.

54:58 Not cemeteries to my knowledge. So, we worked with NRCS and the land owners to identify reference states uh reference soils and they would have been in in more I think prairie or a perennial land use less disturbed over recent years. That's probably the most detail that I can give you. But not cemetery.

55:22 Yeah, just I think we have a few questions here, comments, Christie here. She says don't understand how if weed seeds in the soil are increasing how this aligns with lower germ rates. Do we know where the additional seeds are coming from?

55:41 I think that it probably relates to that last question of it could be the persistence that maybe there's something in the soil that allows them to persist longer. And I think that the lower germination, the idea that there are these other processes happening above ground, that the cover crop is out competing the weed for soil or for water and sunlight and that it's not allowing it to emerge. If there's especially if you're thinking about the residue cover of a decomposing cover crop that that is you know preventing sunlight from reaching the soil surface. So the process is happening above ground preventing that germination from occurring.

56:36 Okay, thank you. Doug here is asking, he says, 'Would getting the cover crop on the ground earlier in the fall assist in getting the plant to anthesis for crimping and having living root versus the chemical termination?'

56:58 The anthesis question is going to depend on your spring growing degree days as well. But the fall earlier planting is fantastic. So, we have a publication that we worked on. We did a simulation based on a planting timing study that was done at Clay Center. And we calculate, you know, the heat units in fall are actually more important than spring for biomass. So, like even a one or two week additional increase in the fall would make a really big difference on your spring biomass. Maybe not anthesis. But so I think earlier planning if you can manage it is always going to be better.

57:43 Yeah, your earlier planning is going to help that tiller more too. So that's going to help with your biomass and yeah the anthesis thing that's just going to depend on how what your spring when you come out of winter dormancy and how your yeah how your spring what your spring's like. So I think with that Andrea we'll wrap it up here. All right. I thank you for your presentation and just the you know the ability for you to go and work with these producers and just you know share your knowledge and yeah just being able to do these studies with them. So appreciate your time today Andrea. Appreciate everybody else hopping on and joining and asking great questions. Next week, we will have, Anthony Bellye, talk about cover crop nutrient cycling, other soil health benefits, on South Dakota crop land. So, next week, April 15th, we'll have another one here at noon. So, thank you all again and thank you, Andrea. Yeah, everybody have a great day.

58:45 Thank you. Thanks, everybody.