GROUNDED Live - 2026: Susan Orgill - Soil Carbon: the Misunderstood Opportunity

Welcome to a new season of GROUNDED Live. This season features presentations recorded at GROUNDED Festival 2026, held over two memorable days on Yan Yan Gurt West Farm in Victoria, Australia. Each episode captures the ideas, stories and practical knowledge shared by the farmers, researchers, chefs, practitioners and thinkers who came together to explore healthier landscapes, healthier food systems and healthier communities.

In this session, soil scientist Susan Orgill takes a closer look at one of agriculture's most talked-about topics: carbon. Moving beyond carbon credits alone, she explores the many benefits of building carbon in agricultural soils, from improved soil function and resilience to healthier landscapes and more productive farming systems.

GROUNDED Festival is a cross between a farming conference and a food festival, held on a different farm each year. Every festival is unique, celebrating the people, landscapes and food of its host region through an inspiring line-up of speakers, local producers and hands-on learning.

With multiple stages running concurrently, GROUNDED brings together science and technology, ancient wisdom and fresh thinking. It provides a respectful place for lively discussion, an audience as interesting as the speakers, and an excellent menu of local food, drinks and music, all on a beautiful, regeneratively managed farm.

Each year, we record many of the presentations and make them freely available as the GROUNDED Live podcast. We hope you enjoy the conversations.

Thanks for listening, and if you enjoy this episode, we'd love to welcome you to a future GROUNDED Festival.

Transcript

SPEAKER_00 0:05

G'day there. I'm Matthew Evans, and I'm the founder and curator of the Grounded Festival. And what follows is the Grounded Podcast. Now, this is the audio that we capture from the speakers in the tent, live on the day. It's unedited. And I hope you enjoy it. There's a lot of talk about carbon in the farming space, and you could look at it as you know getting carbon credits, maybe being paid to store carbon in soil or in trees on your farm. But I wanted to dig deeper into this idea of what carbon is and what it does. And I managed to get Suze Orgill, who is like the one of the pre-eminent soil scientists and soil communicators in Australia. And her topic is soil carbon, the misunderstood opportunity, and looking at what we can get from carbon, which is not just carbon credits. But I want to include that too.

SPEAKER_03 0:57

Here we go. We have the pleasure of hearing from a speaker for the second time at this event, Susan Orgill. You may have seen Susan yesterday speaking about why soil matters. So, an applied soil scientist with over 20 years' experience. She works with farmers to understand soils as living dynamic systems and to enhance soil function and natural capital uplift that supports profitable farm businesses. Today, Susan is going to take a more focused lens to soil and unpack why soil carbon is often misunderstood and what the real opportunity is when we get it right. It's a topic that sits right at the intersection of productivity, resilience, and climate. And one that's highly relevant to the future of farming everywhere, but in Australia, obviously. I know that I definitely have a huge landing curve to climb with this with regard to this topic. So I can't wait to dive in. Now we're going to do it slightly differently. If you do have questions during Madeline and I are going to be wandering around with the microphone. I'll just ask you to raise your hand and Susan will pause and take your question so that it's a little bit more of an interactive session. So just make sure that you wait for the microphone, please, so that we can get your question on the recording of this session. So can we please welcome Susan?

SPEAKER_02 2:22

Well, good morning, everyone. Like it's always interesting being introduced to Susan, because that's my mum calls me Susan. Everyone else says Suze. No, it's nice just to pause and think about my mum, because I actually don't come from a farming background, but my mum has totally embraced kind of farming since I've been working in soil science and sends me things all the time related to this, including that the Grounded Festival was on, not seeing that Dr. Suze Orgel was presenting at it. So it was like a double excitement for mum. It's like you should go to this. I'm like, I am gonna go. And she's like, there's some great speakers. And I'm like, I'm thanks, there are. Obviously, she was not talking about me. Um, so I have worked in soil science for over 20 years now, and um and very passionate about soil science and soil communication. And I started my career in soil science as a junior geoscientist, which was a thing, right? Which makes me sound like I was 14 years old. And now when I think about it, I probably acted like it, and I almost was. I was definitely closer to 14 than I am now. Um, and then I worked as a soils extension officer. And what I used to do is we'd roam around the landscape for New South Wales DPI, running workshops with farmers on soil health. And we'd run these series of four workshops where we'd dig soil pits, we'd like to look at horizons and soil description, we'd talk about um soil testing. The farmers would collect soil samples, we'd do run them through the kind of recipe of how you use a conventional soil test and look at your nitrogen, phosphorus, potassium, sulfur to calculate fertilizer requirements. But oh shit, it's the millennium drought. So don't need to do that because you need water if you're gonna grow plants as well as nutrients, and we'll get to that in a minute. But the last workshop that we would run with these farmers was around, so we ran over, I think it was over three or four thousand farmers through these workshops. And there's this recurrent question because the last workshop was around farm planning and soil carbon, so soil organic matter, and really around the role of organic matter in driving biological functions in soil. And farmers would ask me these questions, going, right, so we've spoken about the phosphorus cycle, and you know, we tip it out of a bag and 10% is available this year, 90% goes bloody, who knows where, and then something else happens so that we can access that 90%, but through this kind of black box of soil biology. Tell me more about that. Tell me more about the role of earthworms, tell me more about the role of increasing soil carbon. And at that point, I realized that while we've got decades worth of soil science literature around strategies to increase soil carbon and stabilize it, we actually hadn't scaled it to the point of thinking about the practice change for that development. So the scalability. So while working for DPI, I did my PhD on farm management strategies to increase soil carbon. And and through that, realized that you know, we're sitting on this amazing opportunity as people, as oh my goodness, meat microbes, no, microbe meat, sorry, which is what the speaker before me referred to a human as. And I'm like, wow, that is like that is a different use of the word meat. Um, so um, we've got this amazing ability to influence the process to increase soil carbon. Uh, and so that's what we're going to be talking about today. It's a different scale to what the previous speakers have had around uh soil nutrients and the micronutrients. It's definitely related, though, and it's definitely related to human health. But I want to think about what you could go home and do tomorrow to make sure that you're optimizing that carbon accumulation and why we want to do it. So let's think about why we want to do it. So when I was running those workshops, we were in the middle of the millennium drought and we were focused on water capture and retention. So, how do we be more rainfall ready so that we've got soils that can be a sponge, so that when it rains, it can infiltrate water and hold on to that water. And it will hold on to water in a biologically structured system so that water is available to plants, so that it's responsive. So that's really important. And we're talking about the function of soil organic matter. And I like to think I was kind of just I'm definitely not the OG in this space, the original gangster, but I was just before the soil carbon sexy scene came along. And then politicians, actually, I don't know that politicians make it any sexier, to be honest. But anyway, politicians started talking about this kind of soil solution of pouring more carbon in the soil means less in the atmosphere. But it's really around that and the additional benefits that we get through our farm management strategies. Now, when we think about carbon, there's government grants and systems out there that talk about low carbon landscapes, right? And for a soil carbon scientist, which is focused on practices which increase soil carbon, feel like we've almost pivoted around. So I'm around high carbon landscapes, so lots of carbon in trees and vegetation, so that we can support productive and profitable farming systems. And that's what we're going to focus on today. Um, so the way that we get carbon into the soil is through the process of photosynthesis. So as plants grow, they photosynthesize and they use carbon dioxide from the atmosphere, which is in that gaseous form, energy from the sunlight and moisture to turn that carbon dioxide into a liquid and then a solid form. So that carbon goes from that gas into leaves and stems and roots and root exudates. So those sticky carbohydrate-rich substances which leak out through the plant roots. And that's a really important process. And Christine Jones, who is an amazing um communicator and coins the term the liquid carbon pathway, and that's essentially what she was talking about. Now, the benefit of being with New South Wales DPI in this space and being young and female, there was like maybe a few, only a few really good benefits in ag at that stage in DPI. One of the things was I had this theory that if you stay weird enough for long enough, you're eventually going to become cool, or you just get so old that you don't give a shit. Anyway, and then I don't know which came first because they're definitely not cool, and I'm definitely pushing the older now. Um, but it was around I got access to all of these courses. So the early innovators, so around Elaine, um Elaine's kind of Soul Food Web workshops and Christine Jones workshops, because like I was pretty much the only person that put my hand up to go. So I was at them all because I've always been interested in the outliers, you know. So as a scientist and as a reductionist trained scientist, we're taught to control everything, right? And in our studies, it's really great when you can use a controlled environment room, you've got a greenhouse or a glass house where you can control everything. But the reality is what you farm every day, there's so many variables that are happening all of the time. And so being armed with this information about the mechanisms and the process, it becomes a tool. You don't become the tool, it becomes the tool. You think, what am I going to do back on my farm to influence that process? So coming back to that influence on photosynthesis, if we want to fast track and amplify that process, it's about how do we have more photosynthetic material on our farms for longer periods of time so that we're capturing more carbon dioxide. So that's as if you're one of if you're at like a seminar snoozer, which some people are, and that's totally cool. Now's the time when you've got that's the takeaway, right? So if I'm amplifying and having more photosynthetic panels, solar panels on my farm to capture more carbon dioxide, influencing that through healthy plant growth, that uh plant capture and pumping of carbon from the atmosphere into the soil, then that's like a key takeaway. And we've got very good at overcomplicating things. I'm going to try and not do that, and actually probably couldn't do it if I tried anyway, um, today. Now, more than 60% of that carbon dioxide that gets captured by plants actually goes below ground. So the plant will put that below ground in the form of roots to explore for nutrients and for water. And over half of that will actually leave the plant roots and those root exudates into the rhizosphere. And the reason it does that is to encourage those microbial partnerships because it knows that to survive our fluctuating soil temperature, soil moisture, to access nutrients, it needs to have those partnerships with microbes. And there's been some fantastic talks at this event around the value of that. What I'm talking about is that carbon economy. The plant does that and makes those partnerships so that it can regulate its growing environment. So the rhizosphere, which is that thin film of soil around the plant root, about a millimeter in diameter, is more microbially active and diverse than the bulk soil. And root exudation and the science of that has shown that plants can change the chemical signal of root exudates to attract certain organisms to live within the rhizosphere. So if it needs phosphorus, it can attract like mycorrhizal fungi. If it needs sulfur, it can attract, you know, your cyobacillus. And so it can alter that, it can alter the pH buffer. And research has shown that it can alter it in a matter of minutes. So they've shown plant responses once they are getting that plants start to get grayed. And these microbial communities can exist within the rhizosphere, but also are connected between plants as well. So plants can share this carbon. Now, the carbon that leaks out of plant roots, it's kind of a fast and rapid turnover carbon. The way we build more stable carbon, though, is through that biological pathway. So more biological activity and biological products in the soil, the more stable that carbon becomes. So if we stay below ground on the soil surface, we've got our plant leader, we don't define that as soil organic matter. Soil organic matter, in terms of like the ACTUSCEM soil carbon method, or the labs, when you send your soil sample to a lab, it needs to be everything that is less than two millimeters in diameter. So you send off a soil sample, they crush it up, we sieve it so that it's less than two millimeters, and then that's the part that's analyzed. And the nationally and internationally recognized tests for total organic carbon is the dry combustion method. So it's not lost on ignition, but they measure the carbon which is lost from that soil when you heat it up. And there's a calculation that occurs there. So it's a direct measurement though. Now, what I have just described though, isn't the role of organic matter in soil. So the role doesn't matter if it's bloody less than two millimeters or if it's two meters long, right? So organic matter in soil, when you take a handful of soil, its function is related to not just length, right? So there's other roles of it there. But the reason that we have that less than two millimeter rule is to standardize things across labs. So we're comparing like with life. The other reason is in soil science, there's a lot of correlations between the less than two mil fraction with uh nutrient storage, cation exchange capacity, and water holding capacity. So that's where the scientific literature sits with those with those correlations. And that's why we like to standardize it. Now, once carbon is in the soil, it can be stabilized in different ways. So it can be wrapped up nice and tightly within a soil aggregate or a soil crumb, and that protects it from further decomposition. So the process that I've just described there, where I've taken the soil sample, brought it back to the lab, dried it, crushed it up, and measured it and said that this soil carbon might have been lost within years or decades, doesn't really hold up. And some of our research in western New South Wales around Narrabri has shown that particulate organic matter, so organic matter which would have been lost quite rapidly if it wasn't protected within the soil structure with goods good ground cover, would have been lost within kind of those months to years. But the role of land management in building soil structure and having perennial plants where uh organic matter can be deposited deeper in the soil profile influences organic matter's residence time. So organic matter can be protected. And when we talk about being protected, it's being protected from further decomposition. Now you've got to remember here, right? So it's a carbon economy down there. So we actually like organic matter turning over. That can be agronomically desirable because that's where plants get their nutrients from. So most of the nutrients that your plants take up need to first pass through a microorganism. So it's really important that that engine is firing. Now, organic carbon can also be stabilized by attaching itself to clay plates in the soil. So in our soil, we've got our sand-sized particle, silt-sized particle, and our clay. Now, our clays are chemically transformed minerals that are very, very complex. And I described it yesterday like a rim of A4 paper. So they've got this rim of A4 paper. If you laid out those individual sheets of paper and that have an enormous surface area, they're very good at holding on to small molecules of water as well as our cations. And we're going to get to that uh later on in the talk. But by influencing carbon accumulation deeper in our soil profile, we can stabilize organic carbon within that high surface area matrix. So the amount of clay that you have in soil also influences your kind of your easy upper limit, I call it now, not your point of saturation, but your easy upper limit of carbon accumulation. And that's why when we look at soil carbon stocks, so the weight of carbon in soil, it's typically in the same environment, higher in a clay-rich soil than a sandy soil, because clays can just hold onto it more. So the other part that we talk about, and that can be mineral-associated organic carbon. The other part of stable carbon in our soils is the humic soil fraction. So in soil circles these days, which is where I, my kind of natural habitat, it's referred to as mineral associated organic carbon, but it's humus. So it's microbial necromats or microbial products, microbial detritus. So the more activity that you have in your soil, microbiologically, the more humus that you can have. When we think about our veggie patches back home, if we think about our A1 horizon, I wanted to say topsoil and film mold is over there, and he said no to topsoil. But the topsoil, which is A1 and it's dark and it's humic in colour, uh, that is our humus, so our microbial detritus. And there's been a lot of work done globally, but also by Clive Kirkby looking at the relationship between nutrients in that fraction of soil. So fraction of soil carbon can influence its residence time, as can land management. So when we take that test which I mentioned earlier around that dry combustion test, which is total organic carbon, and that tells us the total organic carbon pool. Now that is made up of different fractions, and when we talk about carbon fractions, really we're talking about how vulnerable they are to decomposition. So our particulate organic matter or our particulate organic carbon, it is that rapidly turning over pool of carbon. It really drives the system. It's a good energy source. Our mineral-associated organic carbon or our humus fraction, which is typically most of the carbon that we have in our soil, it's the most important for those biological glues as a nutrient reservoir, as a source of buffering against pH, and as a cation exchange store. So it's really important. And then in our Australian soils, we also sometimes have a very large amount of char. So very microfine bits of charcoal, which are in our soils from uh tens and or thousands of years of landscape burning. And in some of our Australian soils, this can be as high as 35% of that total organic carbon pulled. It's not easily influenced by management. So, what is easily influenced by management? So we've already said structure, so protecting and storing that organic matter in our soil. Plants which can store carbon or organic matter deeper down in the soil profile, where it's less vulnerable to those climate fluctuations, so changes in our soil temperature, soil moisture, and land management. So deep-rooted perennial pastures are really important, deep-rooted crops are really important. Um, and also that mineral-associated organic carbon. So, like in South Australian soils, some people do clay delving, but I typically say you can't really influence the amount of clay in your soil, but we know that there's more clay typically deeper down in the soil profile because clay, the really fine particles, eluviate down through the soil profile and accumulate deeper down. So we've got this enormous capacity in our Australian soils to store carbon in our subsoil. The bucket is bigger because there's more clay down there, and the bucket is emptier because we haven't had plants that are always putting carbon down there in our kind of more recent agricultural history, if we kind of think about the last hundred years. So there's a few things that we can influence. So I've said, right, so more photosynthetic material, more carbon capture for grazing management. We're thinking about um periods of rest and recovery, biodiverse pastures. So we've got um a wider array of materials going back into our soil, different root morphology, different organic matter substances, practices which promote ground cover. Ground cover is clean no matter where you are in whatever system you are farming, be it horticulture, broadacre farming, or pastures. So the more ground cover, the better, to the extent that you possibly can. Making sure that our plants have everything they need to grow big, healthy, extensive root systems, because that is the carbon pump, but putting carbon below ground, deep-rooted perennial pastures in our cropping systems around that rotation management. So listing things that we're hearing about, such as at grounded field days over the last couple of days. Now, the thing is that we have had decades worth of uh peer-reviewed scientific literature in this space. So in the 60s, 70s, and 80s, there was a huge amount of literature published in New South Wales alone around uh perennial pastures, around crop rotations, pasture phases in rotation, the importance of legumes, uh, the importance of the rest phase. So we actually have enough evidence. In fact, we had so much evidence, that is why Australia had the first soil carbon method registered under the ACU scheme and why it's seen as one of the most defensibly high integrity carbon methods in the world. Because it's backed, it's based on literature. So we know the practices, and there's 13 practices in that method. We know a lot about the sampling, which is attributed to. Pioneers like Phil Mulby's work in this space as well. But what we also understand as Australian farmers and being really innovative in this space, that not everything works everywhere all the time, right? So context matters. So picking the right practice for your farming system for the right soil type, thinking of the climate and soil envelope. So many years ago, this amazing publication by Yenny came out and it was looking at the role of parent material and soil type influencing soil functions and organic matter accumulation. And it makes a lot of sense. So the climate and soil type will influence that kind of easy upper limit of accumulating soil organic matter because it influences plant growth, what you can grow where, it influences soil fertility. So climate and soil type matter. Then once we look at our practices that we can use within that climate and soil type window, that's when we start to think about how we integrate it into our farm management system. So the literature is there to show that it works. So the way when we're assessing kind of what to do where, it's thinking about first of all, like how big is your bucket. So when we're thinking about that, it's important to know the texture of the soil. So that's something, as I said before, it's not easy to influence. So we're gonna do like a little activity now. And we're gonna talk about that. And we did a bit of a texture and structure activity yesterday. It's gonna be a bit like that, but a bit different. First of all, I need to know who has the letter C in their first name, middle name, or surname? Can you put your hand up? That's a lot. Can all this can all the C's come out the front? Okay. These are now our carbon atoms in the soil. So for the rest of you, I just don't want to get, I don't want to lose our carbon ever in the soil. So this is now our soil environment. So for the rest of you, now I want you to stand up because you're our soil particles. So when we talk about soil texture, our soil texture is the amount of clay, silt, and sand, different size particles within the soil. So have a look around. There was no judgment. We just look every little bit bigger than they were to say because the food's so amazing. So look around as different particles, different shapes and sizes, right? I can't readily or easily influence this unless I kind of offend people and then they start to leave. Well, they get awkward because I'm making eye contact, and they're like, thank God my name doesn't have a little C in it. See, people stay there. Okay, now what I want you to do, soil texture particles, I want you to get together in groups of six, right? So quickly six. This lets me see who can count and who can self-organize. That's all right. Like if you're like twice the value, you need half the people. There you go. All right, so um while there's a lot of work on ecoacoustics, this soil can't talk, which is like a saying, right? So this soil can't talk. Okay, so I have not changed the soil texture, the amount of sand, silt, and clay. I've changed the soil structure, the arrangement of the particles, right? So now if I'm a microbe and I'm zooming around, looking for a root, uh, folks, as maybe like there's no judgment, right? I now can move through this soil really easily, right? We've got space for air, we've got space for um we've got space for air, we've got space for water movement, we've got space for microbes to zoom around and look for a root because there is no judgment here. And the more roots, the better, right? Yes, that's it. Um, so that's what we're about when we're talking about increasing soil carbon. So now let's think about our carbon molecules here, right? So what we've got here is we've got carbon that we want to stabilize in the soil. Now, there's a couple of ways that we can do that. So, as a microbe, as I move around, I'm creating an electrostatic charge, which is creating this um force for clay plates to stick together. I'm exuding substances which will stick particles together. So, now what I want these carbon molecules to do, some of you are gonna be on the outside, and some of you are gonna be inside the aggregate. So go. And I want you to put your hands up so I know who the carbons are. You're either inside or outside.

SPEAKER_09 26:27

Give an aggregate a hug. Right? That's what we want to do. We see it's not evenly distributed. All right. Okay, so what do we see here?

SPEAKER_02 26:51

We see a few things. Carbon molecules still moving around in solution over here. Okay, so first of all, we learn that soil aggregates people, right? Yes, that's the R moment. We can say that carbon can be occluded, so inside an aggregate, or on the outside of an aggregate. Right? We know that carbon can move through the soil. The more structure that you have in your soil, the more protection that you can have for your soil carbon. And texture is one of the things that we influence with our land management. Clay will hold on to those organic carbon molecules. And there was a lot of literature, there is a lot of literature around the point of saturation. So where the clays can't hold on to any more carbon and become saturated. And someone who's just always interested in the outlier, I was starting to look at the data. And while I've published in this space, what I have now seen, this amazing, way better literature than papers that I've published, come out to say that perhaps there is no point of saturation. So clays can actually hold on to those organic carbon molecules. That's the easily attainable upper limit, right? But then what they've seen with some research coming out of Europe is that they'll make these almost organic carbon molecules skyscrapers when you look at it under a really powerful microscope, where carbon can hold on to other bits of carbon. You know the dribble castles at the beach? It look like it actually looks very much like a dribble castle, and that's why I'm a bucket saw scientist and someone has a very clever name for it, which I can't remember. So from today, it's going to be the dribble castle of soil carbon. Um, so we actually know that we can go beyond that point of saturation. So science helps us guide and understand processes and mechanisms and practices. But just because, like evident, when we don't have evidence that something works, that isn't the same as evidence that it doesn't work, right? Like, so what you're seeing on your farm matters. And sometimes science needs to catch up because we've got some other rules to play by as well when we're trying to get some of those publications. Science is the guardrail, your farm is your farm. Think about how you influence that. Now we're going to talk about the soil samples that are here. So, to the extent when you can see the um the table here, just come around and you can disaggregate, act like sodium was in there and we didn't have good organic glues and disperse. Not all, yes, all magnesium. If you've got too much magnesium, that makes you spewy too spewy too, but not in the Epsom salt bath way that Graham was talking about, like or maybe this morning's for some people. All right, so come around. So now we're going to talk about the role of soil type, the role of structure and plant material as well. So what we have here is we've got different soils from locally and a little bit further afield, collected in a very biosecure way. If we're thinking about sand to begin with, sand is the biggest particle, it is a primary weathering particle, so it kind of comes from that physical breakdown of materials. Um, and sand kind of it's really hard to store that's a rot. It's really hard to store water in sand if you don't have soil structure. So practices which enhance soil structure with the same sand content can store more water, and we know that. So our practices are going to influence that. Colour tells us a lot about soil samples as well. So if we have a look at these two soil samples here, we've got a dark sand which is high in soil organic carbon. So the soil organic carbon concentration of the top 10 centimeters of this soil measured using that dry combustion test, that's about um it was 1.2%. Whereas this sand here from a different environment, lower rainfall environment, different management practices, had 0.4%. Same soil texture, environment and management made it different. And you can visually see that through the organic um, the humus, right? And I've got a really good sense of humus. And Alison's a fun guy to be around or girl, so stay on for her talk after because it's going to be better than mine. Um, so because like dad jokes are also like my specialty, right?

SPEAKER_03 31:08

Um would it be it's just Jen over here behind you, this way. Um just wondering if we can ask people in a moment to just, once they've had a bit of a look, to just shift around and allow some other people to come forward. Yes, excellent. We're adults, we can organize ourselves.

SPEAKER_02 31:23

Absolutely, yeah, great, thank you. Um and then yeah, all right, and maybe, yep, you'll be able to see as we go along. Um, so soil texture makes the difference. Uh, when we think about the role of the organic glues, and so you can actually see soil structure. And so if we look at where we've got these soil organic matter pumps being our plants and how we've worked out that we're what the right nutrition is, what our right grazing management strategy is, grazing management strategy. There is so much debate in the scientific literature around labels for grazing management, right? Um, and so, and a lot of you would have experienced that. And it's really hard. I've published in this space as well, because I can give the same recipe to three people in this audience, and the cake will be completely different, right? Like you guys know that. So, some like and same recipe. And I think that is the challenge when we're talking about grazing management, whether it's cell grazing, rotational grazing, it's adaptive management, it's like all these different practices. Really, that part I'm less concerned about. And but we've spent a lot of time in the literature looking at that. Um, really, it's around the function. So thinking about grazing management is not a recipe, it needs to be adaptive all the time, and it needs your patterns of observation and tools to support that. And there's great kind of grazing management tools that support that and grazing educators as well. Um, so what we're trying to do is optimize this photosynthetic potential. We're trying to optimize the biodiversity above ground, so biodiverse pastures, or if you're in a cropping system, the types of rotation, so the disruptions. Because what happens in soil when it starts to accumulate organic matter under a singular practice, it starts to reach this point called equilibrium. So you get the biggest change in soil organic carbon for the first kind of five to 10 years, and then it starts to plateau off. So then you need to think about what is the next system disruption? So, what are you going to do now? And so regular soil monitoring can help you point, uh, point out that kind of tipping point where you need to have that next stepwise change. It's a living system. We know that there's more microbes in the soil or more diversity in the soil than on the soil, right? So, and if we're feeding them the same thing all the time and treating them the same all the time, they're very good at self-regulating, right? So that's the type of thing that we're trying to trying to influence. We know that roots of different shapes and sizes. So the loosened root, which is really good for kind of this deep root penetration, but it's not great at those fibrous roots. It's very good at fixing nitrogen for itself because it's a lazy bastard, right? So this is good for stock feed, but if you want nitrogen in your soil, don't think that this alone is going to help you, right? You need to companion plant with another another legume, which is like a little bit more generous with its nitrogen sharing. We know that by looking at root nodules, so those kind of cities of bacteria, rhizobia, on legume roots, um, we are fixing nitrogen. Bust them open. Are they pink inside? Are they actively fixing nitrogen or are they using nitrogen from the soil? These are all visual techniques you can use. Another visual technique that you can use is looking at the shape and size of the um of the soil crumbs or chunks, as my son calls them, which doesn't sound nice. Um, but soil crumbs, really important. You can look at how they behave when you immerse them in water. So Emerson was a soil scientist from Adelaide back a very long time ago, like 60s, 50s. There you go, in the 50s. And what he did is he came up with this amazing skate. So did a lot of work on sodic soils and soil structure and did this work around what we call the Emerson dispersion test. So, how does soil behave when you put it in water? Um, and it is genuinely life-changing what you're about to see, because you will see how soil behaves and the importance of soil organic matter. It also tells you about sodium in the soil as well, if the soil disperses. Um, but why I like to do this is it tells you a little bit more. First of all, we get three aggregates of soil which are similar sizes. Do you reckon you can, would you mind helping? Yeah, grab three crumbs of soil out of there that aren't rock. Rock is cheating. You want crumbs crumbs or chunks of soil. If chunk is the word Xavier Orgle coined coined the word many things, but chunk of soil, it's not very good. Yep. So we get three aggregates of soil that are about one centimeter in diameter. And you guys have done this, it's hard, right? There you go. No, they're all right. That's it. Yeah, use them. Yep. You've seen my style of science already. Yep, it's how's your mother with my mother? Mom, I'm at a head grounded. Saw a good presentation. Um, okay, so, and then so we can do this test. We, this is a little trick that I learned in Darling Harbor in Sydney last year. If anyone's at the Grain Growers Association event, if you do this with sparkling water on the table in the middle of a city, it has a very different effect. We use nice still rain water. Um, we don't want to have water that has uh uh salts in it because salts cause soils to flocculate. And so when soil flocculates, it holds together. And that's why salty dams always look nice and clear, right? Because of that flocculation. Do not put flocculation into a text message because it says something else. Um, that is like yeah, like you know you have these little things that you stick in your belt. You're like, right, always look for the word orgasm in your soil microorganism presentation so that you're not like here it is again. Right, that's there we go. It's like tiny bits of excitement in Susan Orgel's presentation. It's like the microorganism orgasms. And then I talk about looking for a root. So people are like, What are you talking about? Okay, um, back to this. The other reason I like to do this is we can look for whether or not the soil is hydrophobic. So when you've got your three crumbs or chunks of soil, which are about one centimeter in diameter and you're ready to go, you've got your still water, not um not sparkling water, that you're going to immerse these chunks in. The first thing you're actually going to look for is whether or not that prime of soil floats around on the soil surface. Like, is the soil hydrophobic? Now, in Australia, we have hydrophobic soils because of the waxes that's come off our eucalypts. We've got these little buggers in the soil, which bacteria, and their predator is a nematode. And the way the nematode cruises around the soil is in these thin films of water. So this very, very clever bacteria has gone, do you know what? If I don't want to get eaten, I'm going to create a wax so you cannot get to me and I'm protected there. So we have this hydrophobicity in our soils as well. You also get it where you get lignum breaking down, cellulose breaking down from crop stubble if there's a bit of an imbalance as well. So hydrophobic soils is a thing, means it's even more important to have good ground cover, slow water down, give it a better chance to infiltrate. The way that you can fix it is through uh other bacterial activity and fungal activity as well. So they actually eat the waxes. You can stimulate it through applying molasses to your soil. Um, there's also some like fancy other products that you can put on as well, but we've just used sugar and water and molasses to break it down. Um, it's most important at the soil surface, right? Because that's where we want water to infiltrate. When we have that activity, which we and that soil structural activity and promotion that we spoke about earlier, we've got channels for that infiltration. So we're increasing the sponge or the bucket size for water to infiltrate, which is really important. Now, the biological glues, so the C's in the room before that were hiding in the aggregates, but also gluing the aggregates together, are what we're going to also observe in this test. So we're saying when the water the soil gets wet, first of all, we want to see air bubbles come out, right? Because air bubbles means we've got those poor spaces that Phil Mulvey was speaking about yesterday. So we've got good aggregation, we've got space for air and that oxygenation, root exploration, and for microbes zooming around. The next thing we're gonna look at, if it's a clay, it will get a bit bigger because that sh that ream of A4 paper, water floods in there, right? So water's gonna go in, the molecule, the um the aggregates get bigger, and we want it to get so big, but we want it to hold together because it's got those biological glues. So it's gonna get bigger but hold together. If it slakes, which is looks like an avalanche, that means that the biological glues are low. And if that is our topsoil, that is an issue because that's when you get hard-setting soils and it's hard to get seeds coming out, water going in. That's an issue. Um, practices which promote ground cover, perennial um pastures, diversity, uh, carbon inputs through organic amendments, all scientifically proven to create those biological glues. But you want the system to be fixing itself. Work with your soil, not against it. So it's not about kind of bringing everything in to fix it. It's thinking, you know, I'm gonna get some stepwise change with what I bring in, but how do I actually make that system fix itself and grow soil, growing soil down? Um, everyone's thinking she's never gonna put these crumbs of soil in here. I'm gonna do it, all right, but I can't do it by myself. Can you guys come in? So grab three crumbs of soil, someone can sprinkle some sand on the top just to make a point. Come on in, because I want you to have a look at those things. Do we see floating kind of hydrophobic nature of soil, the meniscus, or does the soil um sink to the bottom? Do we see air bubbles coming out? Well, our well-structured soil as we carefully place it in there, right? When it gets when the air bubbles come out, does the soil hold together? Now there's another thing that we can use this test for. The reason we do three is because we're trying to replicate something. It's like it's a bit bucket science-y. There we go, put it in. So you can see those. Ah, that's the sign of like hydrophobic nature. Deeper down in the soil, if you've got good ground cover, it doesn't matter. If that was exposed at the soil surface, the water pearls and runs off. So we're looking for that. We're also looking for the soil and whether or not it disperses. So after about 10 minutes, if you did this at home, you might be looking to see if there is a milky cloudy ring which forms around the soil crumb. And that indicates that the soil is dispersive in nature. So going back to the A4 ream of paper, not only do those thin sheets store water, but they also have negatively charged and they can hold on to cations, so positively charged ions in the soil. Our calcium, magnesium, potassium, sodium, aluminium, for example. Now, what happens when the sodium ion gets wet? So the water floods into that ream of A4 paper, it starts to get big. The sodium ion also gets a bit excited and gets bigger as well. And if there is more than 6% of those exchange plates charged with sodium, those clay plates can push apart. Magnesium can do the same thing. So if your magnesium is higher than 25% on those exchange plates, it can cause that dispersion as well. Now, in the field, what that looks like is your topsoils looking like this, right? There you go. Like dozen, like I so no. So in soils like this, you can fix them, but it takes a little bit more work. So now let's end by thinking about how do we actually build soil organic carbon and why do we do it? So coming back to the point that what we are trying to do is influence how much photosynthesis is happening above ground. Because not only does that directly take carbon dioxide from the atmosphere, but it also promotes the biological stabilization of carbon in our soils. So it's not just as simple as going net primary productivity, means that how much green and capture happen here, it happens here, adds it to the soil. We lose some with respiration as organisms break down organic matter, and the net is the carbon accumulation. It's more complicated than that, right? Because that pump that I've just described is actually supporting carbon accumulation and flows through fungal hyphae, for example, which are accumulating more carbon and stabilizing more carbon as well. So practices which promote structure, uh surface soil promotion and protection, um, and structural deep soil carbon accumulation can increase soil carbon. So we know that those practices work. If you have a soil which is low in carbon to begin with, and you have a practice change, it's easier to detect that change in soil carbon when we're using our traditional tests. So, for example, um, if we had these two buckets, they're the same size. Um, one is empty and one is full of soil, and then I add just a teaspoon of soil to the empty bucket, you would Be able to see it. We can detect it. If I add exactly the same amount of carbon to the already full bucket, like the amount I'm adding in there doesn't change, but it's already full. You can't see it, right? Like it looks the same as a bloody did before. So when we're thinking about these high background levels of carbon, sometimes it's hard to detect small incremental changes. That does not mean that they're not happening. So the value of carbon to end on this in our soils is around its ability to create soil structure so that the soil can hold on to moisture, infiltrate moisture, exchange air, and allow for that root exploration. So we know that a 1% increase in soil organic matter can influence the water holding capacity of a sandy soil by up to 30 times. Right? That's really important. In clay soils, it's typically around that 10%. But it's very, very important when we think about kind of our soils wanting to be rainfall ready and having that moisture available. The way we make money from farming is by growing crops and pastures and livestock. The way we do that is by making sure that we are feeding our soil and growing our soil so that our soil can store more water and more nutrients. That same 1% increase in soil organic matter in terms of nutrients adds a 1% increase in soil organic matter in a loamy soil, adds a ton of nitrogen and up to 250 kilos of phosphorus being stored in that soil, 168 kilos of sulfur. So I've used two words interchangeably in this presentation. I've been speaking about soil organic matter and soil organic carbon. So soil organic matter is what we see and is what matters, right? So and soil organic matter is 58% carbon by weight and 42% other stuff. And that's why when I just gave that example about that 1% increase in soil organic matter having an increase in stocks of nitrogen and phosphorus and sulfur and other micronutrients, it's because soil organic matter is more than just carbon. So it's like the carbon with benefits. And that's why I speak about that. If we have practices which are enhancing soil organic matter, we can infiltrate and store moisture more readily and effectively. Peer-reviewed literature, up to 40 to 60% in Australian soils correlated with higher amounts of soil organic carbon, where making phosphorus more available. So phosphorus is more available if you have more soil organic matter, up to 30% more available. And this is tested and tried under very kind of reductionist guardrail science. So it's probably even bigger than that in some situations. So the literature gives us the confidence and the guidance that it works. But to actually achieve that change on your farms, it's around knowing your soil type, understanding the constraints, and really understanding the opportunity. So have you got practices in place which are optimizing plant growth, root development, and supporting biological activity? And if you're doing that, then you've got a practice which is starting to rebuild, grow soil, and store more carbon.

SPEAKER_09 48:09

Thanks so much, Zoom.

SPEAKER_03 48:15

All right, we've got uh probably about 10 minutes so that um we have a little break before the next session at 1245. Um have you got questions?

SPEAKER_08 48:33

Um we're often told that you can't grow soil. You've just obviously told us we can increase soil carbon and organic matter. Do you think we can actually grow soil to increase the actual volume and depth?

SPEAKER_02 48:49

Yeah, we absolutely can and we must. Um so if we think about when I'm talking about growing soil, what I'm talking about is the living component of soil and facilitating that source, what we define as soil development. So when we talk about topsoil or the A1 horizon, what we're actually farming, so the depth of which plants are supporting microbial communities, they're acquiring nutrients and they're getting the energy to dive deep into the soil to get nutrients and water. So we can grow soil through aggregation. That would be the definition. We know that if we wait for climate to break down parent material in the absence of life, so just with moisture, temperature, and acids in the soil, and the acids come from microbes anyway. So there's a bit of life, a sprinkle of life in there, but without active inputs of organic matter, we're talking about like one millimeter for 600 years, right? Some of so I was looking at some research the other day, and it was talking about rapid soil loss where some sites were losing topsoil at a rate of 50 tons per hectare per year. 50 tons soil loss. Like so, absolutely. So I think there's two things. We want to protect, conserve, and grow. And it's the growing part, growing soil down, is the part that's gonna underpin our profitable and productive systems. Um, because people talk about, you know, farmers these days either need to grow out or get out. And I'm like, I don't I get I get that conversation, but it's also all grow down, right? If you're not gonna buy the next farm, how do you make your farm more productive and more resilient?

SPEAKER_05 50:46

In terms of monitoring the progress, um, I guess you can monitor the progress of organic uh of organic matter by observation. Um is that enough, or do you need to be doing um organic carbon testing in the lab? And is that the only way to evaluate progress in that direction?

SPEAKER_02 51:06

Yeah. Um, I guess it depends on the why, you know, like what if you want to know. We know that the dry combustion total organic carbon test is reliable and repeatable if you've got a good sampling strategy. So it's really useful for monitoring over time. And that's not the same as saying that it needs to be monitored annually, um, but collecting that information. And then I kind of think the why part is just to inform the practices that you're doing in the right place at the right time. So I'm a big believer and promoter in monitoring soil organic carbon, um, but recognizing that it is one of many metrics, right? And I've had lots of really innovative farmers pushing the envelope on lots of things and then not seeing an increase in soil organic carbon. But you're like, but you've got more function, you've got more infiltration, like your engine's running really smoothly. So you're putting more organic matter in there and you're getting value out of things rather than just carbon buildup, you're actually seeing that as well. And we did have done a lot of work at West, and I think there's some classic examples of that where we've measured more increases in soil or in soil organic matter inputs, but no increases in soil carbon. But there was better nutrient availability, better infiltration, all the things that we were trying to promote first.

SPEAKER_05 52:26

So if you're on a strict budget, then just observing organic matter is a good surrogate for potentially a good surrogate for carbon.

SPEAKER_02 52:35

Yeah, absolutely. I think just I think just getting like, you know, you kind of I think someone said it yesterday around kind of your eyes, your boots, and a shovel, just kind of being really familiar with what's happening where and being comfortable with that. Um, and then like and then the opposite end of the spectrum to that is a very sophisticated carbon market that we have here in Australia, which is, you know, it's absolutely wild. We've got there's a lot of confidence in the monitoring and the technology around carbon accumulation for the ACU scheme, also.

SPEAKER_07 53:14

Hi, I'm I'm Josh from New South Wales. Uh, I love the fact that we've got all this wisdom and learning and experience in the ACU market for sequestration. And I love the leadership. Um my question's about how the other markets are going and that our removals translate to something that would be understood and appreciated and acknowledged in other markets. Because the real scale to me is where an acu from Australia is something that could be traded like our gas molecules. And what I hear from Europe is they're not as accepting of soil carbon. And hopefully that's just a a pathway to acceptance. But could you comment on that? About about the internationalization of soil carbon as a thing and potential linkages.

SPEAKER_02 54:08

Yeah. So, like so, if you generate so an accu is an Australian carbon credit unit, and it can only be used and retired within Australia because we've got a compliance-based market, and we've got sophisticated methods to do that. But you can't take your ACU, which is equivalent to one tonne of carbon dioxide, and retire it internationally. So it has to be used and retired here in Australia. Um, and because of our compliance market, like we're able to do that and we've got confidence with the literature to do that. Think globally, um, where we have um kind of different issues with boundaries and confidence in methods where there's multiple methods, people are more and focus on insetting in particular rather than offsetting, which is kind of one of the key drivers of our Australian carbon credit unit market here, the ACU scheme here. I think people are more confident in above-ground carbon avoided emissions and carbon dioxide removals. Um, in Australia, though, I think like what we have is not only the demand side from the compliance market, the burning, terrible words, burning need from a soil growth and kind of productivity point of view. So I think we've been able to fast track some of those conversations because we don't have the benefit or the luxury of this kind of soil from this farm here down to like 60 centimeters. So I think we're just more progressive in that space as well. But yeah, it absolutely soil carbon is one tool, it's not the only tool in that like low decarbonisation of the environment. There's the whole biogenic cycle as well to be considered and understanding that and agriculture's role in that. But agriculture is the only, I said yesterday, the only sector with the scale and agency to be both a food producer and a tool to help mitigate and adapt to climate change. Um, and I think we've got a a really important role, but I hope to see internationally that it will kind of mature um at the same rate.

SPEAKER_04 56:14

I know there's lots of questions, but Nalan, we've got two gentlemen at the back. First one closest to you. Oh no, sorry. Yeah, just there. And then we'll go to you and we'll see what time we've got if we've got any more for after these two. Thanks.

SPEAKER_06 56:28

Um, you alluded to um disturbance succession cycles in you know, uh establishing your perennial communities. Um I have been thinking a lot about annuals versus perennials um today and yesterday. Um I was just wondering if you have any specific examples of disturbances you're suggesting, and like also like practical how it would look like in in a grazing or cropping system to you know say a perennial pasture to try and kick start uh next level of succession, you know, like introducing species by species, or yeah, yeah. What does that look like in a practical sense?

SPEAKER_02 57:15

Um that's a really big question. So I'm gonna cover up on a couple of things quickly. So there's been like a people pe not you, like, but people love a number, right? So for ages it's got to be eight species, or it has to be a multi-species. And I think it's more coming back to kind of what is the process and function that we're trying to build back into the system. And that's the key. So I've seen some quite degraded soils because they are just multi-species pastures, like cropping all the time. So multi-species pastures, sorry, um, crops, for example, as a cover crop, is an important tool to get the soil ready and busted up and active enough so that when you sow your perennial pasture, it is ready to kind of take that perennial pasture and giving it the best chance it possibly can. So I kind of think about these little windows of opportunity where we can have disturbance. So always the more the better in terms of species, but also recognizing the way we do that is we either do it intentionally, multi-species cover crop, and then a multi-species pasture that's planted, making sure that those species are suited to that context, really important. If you've already got a perennial pasture and you want to oversow or bring new species in, there's great technologies to do that. And also thinking about the history of that site, because with our great what plants need, um, as well as everything that's in the soil being nutrients and water, they need access to sunlight. So sometimes they need space. And so that's where I kind of think tactical grazing management as well. So there are a few of the things that I think about when I walk into a perennial pasture that says flaris and sub clover, um, that's because we've got something wrong in that balance of our grazing management. And there's a lot of research that's come out going, doesn't matter what you sow, it's just going to end up as flaris and sub anyway. So bloody, forget the bird mix and just put that in. I just do not agree because the reason it's come back to flaris and sub is because we missed that biodiversity opportunity, biodiverse pasture opportunity in our grazing management. So chicory should last for a bit longer, for example. Our cocks would should be able to last longer. We should have the other naturalized species coming back in there. And then you're more resilient as well. And like you guys, like preaching to convert, you guys know that, you know, plant for every situation because we can't plan the environment necessarily in terms of the climate, but we can help with having that diversity. It's better for our animals as well. It's better for the bugs and insects.

SPEAKER_09 59:38

So yep. I think we've got just one more.

SPEAKER_03 59:44

We've got one minute, so it needs to be fairly speedy.

SPEAKER_01 59:46

Uh I'll try and make it succinct. Hi, Chris. Uh hi, Susan. I won't be talking geology. Um, I just want to read a very quick uh quote, which I don't think too many people would disagree with, and then I'll tell you who said it. Success of agriculture depends on cheapening of production, tick. Cheapest food for stock is grass, tick. Cheapest manure for soil is turf. It's an interesting term. Cheapest, deepest, and best tillers of the soil are roots. Finishes with a quote: give me a good turf, and I don't care what the soil underneath it is. That's coming chap called Robert Elliott in 1898, as part of what was then probably a seven-course rotation. So building plant roots, what Susan's talking about, is part of their rotation. They still use fertilizers, but as part of building fertility and that part of the rotation. So really emphasizes, I think, what you're talking about. Thank you. Thank you.

SPEAKER_02 1:00:38

And I think on that, like root growth, we have like really cool data now around hard-seeded legumes, like we've published in that space. So, around the role of a crop to provide that nitrogen, like your bicyrulas and some of those other species. Like we can be very innovative in our crop rotations. And I think our cropping soils need it. We speak a lot about livestock, absolutely, and integrating livestock back into cropping. That's important. If you can't do that though, like our croppers are doing a great job in some of that rotation work now as well. So we're seeing lots of innovations coming back. And I think some of those hard-seeded legumes, you know, within a couple of months, they're punching down roots to 1.8 meters in a clay soil. We're not talking sandy soils. So they're kind of fixing nitrogen, they're creating macro, meso, micropores, they're feeding microbes, and then we're starting to see soil growing in the subsoil. You know, you see, like in the subsoil, and it kind of looks like topsoil, A1, but it's down there. Anyway, thank you very much.