Addressing topsoil deficits

Video transcript

Good morning all, and welcome to this morning's seminar on creating alternate growth media presented by the office of the Queensland Mine Rehabilitation Commissioner in partnership with Verterra Ecological. My name is Sam Wildie and it's a pleasure to have you all online today. We've had plenty of registration so it's great to see such an awesome uptake. Before I begin, I would like to acknowledge the traditional owners across the land on which we're meeting today and pay my respect to the elders past and present. Also, just a couple of housekeeping items to get to before I hand today's MC. First of all, we are recording today's session, so it will be made available on our website after the session's completion. Please feel free to share that amongst your network or anyone who couldn't make it today's session. We also hope to field as many questions as possible throughout the session. To lodge questions, there is a Q&A bubble at the top of your Teams screen. If you click on that, you can pose questions to our team or the presenters. They will disappear for a period of time, however, our team will receive all of them and then we'll get through as many as we can or as many time permits. So, with that all squared away, it's now my pleasure to hand over today's MC, our lead technical officer, Louisa Nicholson. Over you to Louisa. Thanks Sam and good morning, everyone. It's a pleasure to have you online and join us today. Most of you may be aware of the role of our office, but for those who aren't, one of our key functions is to produce technical reports regarding leading practice rehabilitation. And one such topic which we're speaking of today is addressing topsoil deficits. So, the purpose of our seminars is to discuss recent publications and in today it will be on creating alternate growth media to achieve successful revegetation Queensland mines. These seminars give us the opportunity to highlight the work that our technical experts produce but also allows you to hear from the authors and ask questions as we have discussions throughout this morning. So, please get your fingers ready to type some questions into the Q&A section. In a moment, I'm going to present our presenters for today. But before I do that, it's important for us to reflect on the fact that takes a lot of time and input from authors to develop these technical products. But we also rely on the assistance of many others. For example, key stakeholders help us to develop the scope of projects to ensure that we focus on the most relevant technical matters, but also during the development of these papers, we receive a lot of valuable input from other content experts who do peer reviews for us. And so, the authors and I today wanted to publicly acknowledge the contributions of Brad Radloff, Andrew Bauer, Thomas Baumgartl, and other Verterra colleagues. So, thank you very much to all who contributed to this work. So, moving along I think we'll introduce our presenters for today and firstly we have Dr. Bernhard Wehr with us online. Bernhard is a certified professional soil scientist. He is the principal soil scientist and sector lead for mining and energy at Verterra Ecological Engineering. Bernhard has over 20 years’ experience in soil science, land rehab and environmental management. And with a PhD in soil science and a background in biochemistry and horticulture, Bernhard brought a deep expertise in managing soil constraints across mine sites and degraded landscapes to help us deliver the resilient environmental outcomes that we need for industry. Dr. Glenn Dale is the main presenter for today and Glenn is the managing director and chief technical officer at Verterra Ecological Engineering. Glenn holds a Bachelor of Science in forestry and biochemistry, a PhD in molecular and quantitative genetics and an MBA. Glenn also has appointments as adjunct associate professor with the University of Southern Queensland. Glenn brings 40 years of practical experience to this work and works across a variety of sectors both domestically and internationally. So welcome Bernhard and Glenn. So, I might just hand over to Glenn and look forward to the presentation this morning Glenn. Thanks.

Thanks Louis and thanks for everyone attending. Great to have such interest in this topic. And thanks for the office of mine rehab commissioner for promoting this work because we you know we're very well aware that it's a major issue in industry. So originally both Bernard and I were presenting this but Bernard is in a remote area the moment so unfortunately, you've got me for most of the seminar and Bernard will be available for questions. We'll move through I'll start off with a bit of a context and we'll talk about why we need to create growth media, characteristics of growth media. Topsoil and subsoil you know does it matter? And then look at how we go about may go about ameliorating medium that we have available to create a soil and identifying constraints and then the importance of trials. So, we'll have a couple of stop points during the presentation where we can catch up on questions for each section. So, with that I'll get started. So, this might seem a funny slide to start talking about creating growth media for mine rehab. But this a photo of the dust bowl in the US in the 1930s and you know it was a major impact on US agriculture. But it really came about because farming practitioners didn't understand soil ecology. And that's a really key theme throughout all of the discussion today. What we're really trying to do is recreate a self- sustaining soil ecology and understanding the factors that lead to that. A positive out of the dust bowl in the US was it was the impetus for development of the RUSLE which I'm sure most people would be familiar with. And the RUSLE is actually portrayed as possibly one of the biggest science experiments in history. It was an enormous amount of data collected over a very long period of time. But and we tend to think of the RUSLE in terms of estimating erosion, estimating soil loss, but it's also a fantastic guide for rehabilitating soils as well. And I and I guess you ignoring the parameters that go into it the structure of the of the RUSLE is very important in terms of erosion is a function of energy input the R factor which is what we have to deal with we can't change that but also a function of soul for physical and to some degree chemical properties slope length practice control factors and crop management. Some of the, a lot of the work we're presenting today comes out of a few long-term ACARP projects that we ran from over about eight years from 2014 to 2022. And at the very start of that ACARP work, we looked at successful and unsuccessful rehab on a whole range of mine sites in Queensland. And what we found was a very strong focus on landform on slope lengths on slope length. We've actually added a factor in here slope shape not so much concentration that. Reasonable concentration practice control factors in terms of creating waterways contours but very minimal emphasis on dealing with soil physical constraints and creating a soil that could support healthy crop growth. And I guess if there's a there's a couple of key takeaway messages from today, but one really key message is if we're not focusing on all of the factors here and not thinking about those or all factors in rehab, rehab design, soil amelioration, then we might get away with a successful site where the soil is very benign. But where we're dealing with difficult soils or no soil then can almost certainly guarantee failure. So, a lot of the discussion today will be around how do we ameliorate and manage and design topsoils to address issues with the K factor and particularly the C factor in the RUSLE. Again, probably a slide here that is a bit unusual for a mine rehab site. This not a mine rehab. This an alluvial gully on grazing land that we've worked on in the in the Burdekin. Some of you may know the Burdekin or three small sub catchments of the Burdekin contribute 25% of the total fine sediment that is lost to the reef every year and has a major impact on reef health. So, there’s quite a lot of focus on rehabilitating those the bow and broken bogey catchments. But a lot of similar issues, highly sodic soils in this case. Topsoil is long gone. A lot of this topsoil went 80 years ago and, in some cases, we can find it. A bit of it left a kilometre downstream. But dealing with no topsoil and after rehabilitation there's a reference hill in the background here. This now a stable self- sustaining site. It's been monitored every year since the rehabilitation in 2018 and the resilience of this site is actually improving every year since that site. So, I guess just a demonstration that when you're dealing with highly hostile soils, no topsoil to start with, it is possible to achieve rehab. And similarly, just to put this into a mining context, this a trial site that was established as part of the ACARP projects we talked about earlier. As many of you will know dealing with sodic soils in the Bowen Basin rock mulches is often or has in in the past been specified in closure criteria. This this trial actually compares rock mulch which is this treatment and this treatment to a range of soil amelioration treatments and not just soil and spoil underlying spoil treatment. And this trial passed what I call the intraocular trauma test. We didn't need statistics to tell us that soil loss was much greater on the rock mulch sites than it was on the you know the well ameliorated sites and the sites that were designed with the you to minimise erosion and again the principles behind this were we're addressing all the factors in in the RUSLE.

So, to get on to the onto the core of the presentation, why are we creating growth media in the first place? And growth media is, you know, quite specifically used because we are dealing in situations where there is no topsoil available. We're dealing with hostile soils or it might be old topsoils that have been poorly looked after and have lost their health. Stripping hasn't been able to remove sufficient material in the first place. And in this case and dealing with hostile subs soils as well where putting a good quality a thin veneer of good quality topsoil over a hostile subs soil is not likely to give good long-term results. And the challenge in mining is dealing with the scale of the problem. If we're dealing with rehabilitation of the road verge, for instance, on a freeway, relatively small areas, you can create bring in materials and create very high performing soils, but it’s difficult to do that at scale in mining rehab where you're lacking good topsoil in the first place. So, it really requires the ability to work with what you have available, ameliorate that and get it to the point that you can put it on a trajectory to becoming a soil over time. I guess since the green revolution in agriculture, there's been a huge amount of work in dealing with the chemical limitations of soil and particularly nutrients, nitrogen and phosphorus. But soil is there's a major distinction between soil and dirt and soil is really a living organism in a way. We need to really consider not just the chemical properties but the physical and the biological properties. The soil has the soil needs to function to be able to support plant growth. It has a number of really key important functions more than simply just providing nutrients, but being able to store water, being able to allow oxygen to penetrate to maintain rig growth. Not being so dense due to compaction that you have physical restrictions on root penetration. So, all of these factors need to be considered and there is growing realisation that soil biology is just as important as soil chemistry. I guess on you know and coming back to the experience with working across a lot of mine sites you know very very commonly and I guess and relating it back to the RUSLE commonly we'll see a recipe-based approach to dealing with topsoil amelioration and if I had a dollar for every time I've heard someone say we're going to put on 200 kgs of DAP a hectare okay. It's we really need to understand the characteristics of the soil that we're dealing with and design and amelioration and simply adding nutrients is ignoring other key physical and biological properties. So, I guess the point we can't emphasise enough the biological function of topsoil in particular is what distinguishes it from simply dirt or any other media that plants can potentially grow in. That biological function of saw microbes, microflora, fungi, bacteria, microlayer is fragile and that's the reason for how I guess guidelines around the management of topsoil stockpiles. A topsoil stockpile made too high stored for too long allowed to grow a high density of weeds, can lose its you know biological function over time and convert from being soil back into dirt to lose that biological function which is important for aggregation of soil particles that provide soil structure. It's important for mineralisation of nutrients both from the mineral properties of the soil but also from the organic matter in the soil. So, maintaining that biological function is key when you have topsoil and re-establishing the biological function is critical to think of when you're trying to create a new soil media. Chemical properties as I mentioned I guess was where a lot of focus has been since the green revolution with the development of mineral fertilisers particularly nitrogen and phosphorous fertilisers, they can be easily manipulated you we you can and but even still I guess and again from experience having a good soil analysis and spatially representative soil analysis really key to ameliorating and chemical properties. So, I guess and again from experience we've seen a lot of sites particularly in the Bowen Basin where the micronutrients are just as important or a deficiency in micronutrients is just as important as the macronutrients like nitrogen and phosphorus. And if you're not working based on what the soil is telling you, if you're working on a recipe rather than what the soil is telling you, then it's difficult to achieve successful rehabilitation.

Physical properties of the soil again more difficult to measure. I guess requires a bit more experience and some of the physical properties can't be changed. So, we have to work with generally with the texture that we have. As most people will know texture is defined by the combination of sand, silt and clay. At scale very very difficult to change and again it could be changed in a main road setting on the side of a road. But you know difficult to change at scale and once you start mixing different materials it can have unexpected results. The while it's very difficult to change texture of soil other pro other physical properties can be managed and in particular we'll talk about it in a bit dispersive soils are I guess a special case in point where you know the energy that leads to erosion is actually not coming through rainfall it's coming through the ionic repulsion between parts particles. And so, it is possible with sodic soils to change the physical properties by manipulating by you know by adding calcium to offset the effects of sodium and restore soil structure and soil permeability. The other way that physical properties can be affected is through aggregate formation and again it comes back to this very complex interaction between chemical physical biological properties. Organic matter and soil micro the microflora responsible for improving the aggregation of soil particles and improving soil structure. So, encouraging and re-establishing that biological function is a key part of managing soil physical properties. So, I guess I talked a little bit about this already. So, functionality and you know it's really important that we think of soil in terms of how it functions how soil vegetation and water interact with each other in designing a strategy to create a growth meter medium. And I guess what you know what this means is that we can convert spoil into soil if we understand the characteristics of what we’re starting with and the end point of where we want to get to. And of course, you where we are in a situation where our only option is to try to create a growing media from spoil. We can recreate that relatively quickly when it's very difficult to create from a you when we're just lacking soil in the first place. And understanding you know the mineral fraction the mineralogy of the soil that we're dealing with and the organic and organic matter is really critical in an often-overlooked part of moving soil along that trajectory. So just to I guess to you know conceptualise that that change. Spoil is generally a fairly inert mineral material and by adding ameliorant like nitrogen, phosphorus, organic matter, we're incorporating those into the soil as an additive. And over time the phosphorus will bind to the clay fraction. Nitrogen will be incorporated into organic matter in the soil. And the aim is really to kickstart restart soil ecology in a way that it can build its own organic matter over time. Initially the mulch that we add on will mineralise will break down release nutrients and effectively feed if you like or fertilise the soil microflora it's providing the carbon that the soil microbiology needs to function and I guess there's a lot of products on the market that purport to you know re-establish soil microbiology. But in in all cases in the absence of a carbon source there's effectively no food for soil microbiology to function. So, it's you know it's very important to think of how to really kickstart that process in a way that gets organic matter mineralisation going allows microbiology to re-establish which then allows plants to grow and as plants grow and roots continually cycle roots die litters redeposited into the soil. Well, the organic matter builds up over time. And really what we're trying to do in mine rehab, is move this, along this trajectory sufficiently to allow the system to become self- sustaining. In if we had a thousand-year view of things, this this trajectory would happen naturally. But you know allowing a thousand years for these processes to re-establish is not an option. So, we'll just pause at this point and open the floor to questions.

Thanks Glenn. So, we're off to a good start. We have one question here which if Bernhard if you're willing to answer otherwise Glenn can pick it up but just reflecting back one of your earlier slides about the biological activity of you know making topsoil and soil and amended spoiled not dirt. Are there some important things we can do to maintain that biological activity of stockpiled material? We often hear about stockpiling topsoil, which you know sometimes has to happen and the problems that are associated with doing that for long periods of time. So just wondering if there's some important things we can do to maintain the biological activity of that material as it sits in a stockpile. Want to go first? Yeah, why you go then? Well firstly I have seen stockpiles that are 20 m tall that is more mountain and not a soil. So clearly the importance would be to keep your stockpiles relatively low. I know that has got certain limitations in terms of space available, but essentially even if you're trying to maintain aeration inside the stock pile, it's still not going to be nearly as small as having a shallow stock pile where you've got roots growing into the soil and actually maintaining that organic matter in that would impact once the organic metals have been used the biological activity goes off the pharmacy.

Thanks Bernhard. I think we had a little bit of sound issues there but I feel you were saying keep your stockpiles low and height and keep your organic matter in them in those stockpiles to help keep the microbiological activity happening. I'm assuming Glenn, pull me up if I've got that wrong. No, correct, Louisa. And really, you know, you can think of it in terms of availability of water and oxygen in the stockpile and in organic matter. So, stockpiles that are created too high will become a toxic at depth and the biological activity is lost and I guess in a you know ideal situation you want to be preserving that you know that biological function in topsoil stockpiles. Once it's lost then efforts got to be put in to recreate that biological function and it can lead to a range of other issues as well. But you know I guess as everyone knows in a perfect scenario the ideal is to pick the topsoil up from here and replace it directly over here. But often you know mind design and I and I guess you know that's an issue a bigger issue that we need to think of in terms of how you know rehabilitation specialists interact with mine planners and you know there are certainly examples where in Australia and in coal mining where that is achieved where The design of mining allows immediate replacement of or you know very very short periods of stockpiling at worse but early replacement of topsoil soil and preservation of its of its biological function. But where that's not possible managing stockpiles to maintain the permeability the ability of oxygen and water to infiltrate and to maintain the biological function is important and the higher you make stockpiles the less likely that's achieved at the base of the stockpile. That's great advice. We have a follow-up question just to wrap this little question and discussion section up and that is from Lisa and it's what kind of time frame are we looking at for mulch or fertiliser to develop biological activity? So, assuming there's a bit of a lag before that materials incorporated and active. So, do we have any sort of time frames that that have generalised or realistic I suppose? Yeah. It's a really good question and it’s difficult to put a number on it. But I guess in both those examples that I showed you with the alluvial gully and the spoil dump rehabilitation. That process effectively started within you know very very quickly within 6 months. Both sites were and on lots of other sites I guess and even shorter have got to the point their vegetation is re-established. It's healthy and that that succession of vegetation as well has started. So, it's not just a succession of soil type. I guess it's a succession of vegetation often of course you know starting with cover crops that establish very quickly but die but, in the process, put start to put organic matter back into the soil and then slower. Establishing pasture species and native species establish slower. And as they establish then they build more biomass which then puts more organic matter back into the soil. So, I guess probably the best numbers we actually have is from some of the gully rehabilitation. It's been harder to get good numbers from mine rehab work, but we've seen you know galleys within and been monitored over quite a period of time go from around 88% effectiveness at the first assessment which is a couple of months after rehabilitation to getting up to 97% effectiveness on that particular one that I showed you which is actually the oldest one at about what's it about 8 years after rehabilitation. So, you know get it right and I guess the important thing is getting onto that trajectory and getting the system function re-established and the soil ecology functioning again quickly. That's great. Thank you. Just goes to show that natural processes don't really go to the plan sometimes and we need to give them time and the right conditions I suppose to get going. We might continue moving on Glenn if you've had a little bit of a break there before we charge back into the next section. Righty keep going. Okay. Topsoil or subs soil doesn't matter. In this diagram on the right here, we're looking at a gradational soil and the boundary between where topsoil stops and subs soil starts is not clear and topsoil is, you know, in lots of ways it's a really interesting thing. If you try and Google a definition of topsoil, it's really hard to get a really clear definition of what it is. But ultimately, it's the part of the soil profile that does have biological activity in it that has high higher organic matter content as a result of that biological activity. It's where there is a there is a seedbank. So, try I guess in rehab trying to define the depth of that of that topsoil is quite important in terms of specifying stripping depth and it really is you know a valuable resource and if where it can be preserved then it’s really important to try to preserve it as much as possible. On the other hand, subs soil the you know the BC horizons are generally fairly low in organic carbon they will have organic carbon because roots should be penetrating into the subs soil and you can see you low down in the image there roots at quite a depth. So, it is contributing some organic matter into the in the profile. Generally, there's no there's no seed bank and I'm sure everyone's seen the case on just even on native soils where the topsoil is stripped for whatever reason there's a slip a bit of erosion. Sub soil is very even where it's not hostile very slow to re-establish. Conversely, Queensland is blessed with the fact that, probably some of the worst soils that got ever created. And there is a very high, frequency of, soil dispersive and hostile subs soils. And that that's a that's a function of the old geology of Australia. So very small amounts of salt coming in on rainfall even in inland areas over millennia builds up sodium in the soil and salt in the soil. So large, massive areas of Queensland in particular of sodic soils and across Australia of saline soils if they're not managed well. However, subs soil I guess you know the last point is quite relevant here. Soil isn't actually a requirement to grow plants per se. And the whole the whole idea of hydroponics is providing oxygen, providing nutrients to plants and not obstructing root growth through the physical properties of a liquid media have no restrictions no physical restriction root growth. And you could grow very healthy plants very comfortably so subsoil in its own right can be ameliorated. And but again and I guess the other key message of today in addition to addressing all the elements of the RUSLE I is characterising what you're working with. Once you've characterised what you have available, then it's possible to design an amelioration strategy that that addresses that physical, biological, chemical properties to create a media that can support plant growth. And that becomes more important when you do have you know hostile conditions like salinity and dispersion. So, creating a got ahead of myself again a bit here. creating a growth medium. A couple of approaches look at reference analogue sites but also you know look at the depth the physical properties of the soil but also, we need to consider what the post mining land use is. So, it's around in designing an amelioration strategy it should be a strategy that is fit for purpose. I guessing for those of you who aren't familiar and I don't know if people can see this but the what we call the brown book from CSIRO interpreting soil test results what do all the numbers mean is an incredibly valuable reference that you'll continue to use in interpreting what the analysis of so physical, chemical, biological properties you have and how you design an amelioration strategy in terms of that strategy being designed as fit for purpose. If you're looking at a postmining land use, say you know grazing or agriculture production systems they will need greater inputs than you know a native forest system. As some of you might remember Chris Moran from who headed up sustainable minerals institute for a while and Chris stood up in front of a sore science society meeting many years ago and he and he said in in the way that he does the only difference between mining and agriculture is that agriculture is slow mining. and you he's dead right. Any production system is removing nutrients. It's removing organic matter out of the system. And some of that may be replaced by mineralisation of nutrients in the soil. But where it's not replaced through that process then those inputs need to be replaced through fertilisers and even or you know I guess there's growing recognition and in agriculture even of the need to replace or manage to replace organic matter losses. If we look at and again, I guess the analogy is instructive. If we look at agricultural soils worldwide the average soil or guard organic carbon content has declined from about 2% to 1%. Which doesn’t sound a lot but effectively it's a 50% loss in in carbon. And so, from a production point of view that's winding down the capital value of the soil. So, managing to either rebuild that carbon or to maintain that carbon is important in any production system and equally important if the production system post mining is grazing is pasture is cropping or any other land use. And of course, it's important that if it's producing food crops, producing animals for human consumption that there are no toxic materials. So, I guess you know and these can be materials at low concentrations such as you know selenium is critically important for animal growth up to a certain concentration and beyond that it becomes toxic. And so again characterising what you're working with understanding and designing for purpose is really important. on the other hand, if post mining land use is a native woodland, it becomes you know, a self-supporting system over time. We’re not there's no removals from the system. So, nutrients that are put in are going into biomass being lost as debris coming back and being recycled in in the soil. And so in in this case the design for amelioration is around kickstarting the system getting enough nutrients enough organic matter enough biological function back in the soil to allow it to you know to get started and then get onto its own trajectory. The so I guess a really important point here is that native systems the analogue system or using native systems as analogue often so are low in phosphorus they're low in nitrogen and it's probably a case where it is important to be careful of using analogue sites because it you know some of those applied nutrients will be lost out of the system in any case. So, the initial amelioration needs to be sufficient to get vegetation established quickly. The quicker you can establish vegetation and particularly ground cover, the quicker the resilience of the site will improve. That fine sediment loss will be reduced and any inputs are maintained on the site and get into a into a cycling phase. End with where you're looking at it at something like a post mining land use. It is it is a dynamic system. I guess everything we're talking about here really is ecological engineering where we're providing the conditions to allow the system to organise itself and so we I guess we're guiding where it's going. We're not directing where it's going per se in terms of that trajectory from bear rehab toto a native woodland if that's the final land use. Okay, we'll have another quick break for questions and Sure. We have a number of questions and thank you to everyone who's contributing. I've held off a few of those because they really are going to be relevant for the slides coming up that Glenn will be speaking to. In the meanwhile, we have another question talking earlier about the subs soil sort of layers particularly in you know these formed landforms that we're creating in mine rehabilitation. Just wondering how deep down we should assess whether subsoil material is suitable that is not hostile for plant growth. really good question and it will come up in the next set of slides. So, I guess just to answer that and again coming back to think of it in terms of the RUSLE in terms of both the K and the C factor you know the soil physical properties and the ability to grow a crop. and I guess an early comment about putting a thin layer of topsoil over a subs soil. a soil profile you know, is itself you know quite a complex functional unit. While plants might pick up a lot of the nutrients out of the topsoil, they need to be able to penetrate their roots to depth in the subs soil both and you obviously for trees for physical stability but to tap the volume of water. So, this will we'll come into some of the slides in a second in terms of u plant available water holding but you know water holding might vary between anywhere between you know 660 mm you know providing water can get into the soil you know 60 mm per meter depth of soil to 220-240 mm per depth of soil. So, two saw profiles of the same depth, let's say they're both a meter, one that's holding 60 mls of water and one that's holding 220 mls of water are going to perform very differently. So that combination of depth and water holding you know the greater the depth and the greater the water holding the greater the biomass that that site can support. So, look, I guess as a number, a minimum depth of 80 cm to so you even probably really minimum 60 is pretty marginal, but ideally at least a meter and ideally a meter and a half to 2 meters of profile in which plant roots can grow is ideal. And we'll talk about some of the strategies for managing that in a second. Thanks Bernhard. I don't know if you had anything to add there but that seems to be related very much to the rooting depth of the vegetation that you're going to be growing. Yes, certainly that is one consideration and the other one is really the answer here is how long is a piece of string. So, it is really difficult to give a hard and fast rule how deep the wood medium should be. But the deeper you can do it the better it probably will be. So, if you have got a choice between 60 cm and 100 cm go for the 100 cm. Lovely. Thank you. Okay. We might keep rolling on just to keep because we have got some other questions on the sidelines ready to go after the next section. Thanks, Glenn. Yeah, just a one minor additional thought would try to avoid getting involved in environmental court cases, but I got sucked in years ago to one it was a quarry that was rehabilitating benches, hard rock benches, and they were they had planned to put 10 cm of topsoil and grow trees on and you know the you can that that amount of topsoil if even if you had 100 mls of water per meter would store about 10 mls of water which is about a day water supply for the trees. The chance of you know I guess it's an extreme example but the chance of growing trees on 10 cm of soil is two or two chances. Buckley's and none. And so, it is around that mixture of depth and fertility.

Okay, I guess get getting on to the nitty-gritty end of the paper in terms of identifying and ameliorating so constraints and we've just had that discussion. I guess another outcome of that you know the AAP you know the review we did at the start of the ACARP work years ago a lot of focus on topsoil and very little focus on soil and what we're you know I guess we need to not think of it as topsoil and spoil but recreating trying to recreate a soil profile a functional soil profile. So, managing both of those is very important and it does require characterising the whole raft of chemical, physical, physicochemical and biological properties. And we'll just run through a few key ones here. PH through to organic matter. So, I guess understanding what your characterising is important as well. So again for anyone who hasn't isn't aware and I don't know if people can see that but one of the other bibles of soil science so chemical methods by Raymond and Lions which is again what we call the green book a CSR another CSIRO publication it’s really important to understand what the chemical tests that you're getting done mean so pH measured in calcium in chloride or water will give very different results. And if you're making a decision one and think you're making a decision if you're getting analyst analysis for one and making a decision using the other as a reference scale, then you may have some issues. And as I'm sure many people may know PH is a log scale. At low pH you can have issues like aluminium toxicity, low availability of P. At high pH we can have trace element deficiency and again deficiency of P. At high pH you can have in alkaline soils you can have a what appears to be a contradictory scenario where there might actually be a lot of calcium but not much of that calcium is available because it is you know precipitates out and moves into insoluble form. So, pH is I guess it’s often measured but not often really explicitly considered in design of amelioration but it is it is very important and in that you know goldilocks range so to speaking pH water between that 5 and a half to 7 8 and a half. Plant nutrients are available and diff different nutrients will become available in or toxic as you move into more acid soils or more alkaline soils. So obviously low pH soils can be ameliorated by addition of calcium lime bringing up the calcium concentration high pH soils can be ameliorated by using sulphur materials like sulphur bentonite which stimulates all microbial activity to increase the acidity and reduce the ph. And reducing pH is not something that we've seen is very common in practice on mine sites, but it is import an important consideration if you're dealing with extreme pH values and no matter how much nutrient you put on, you're still going to be having an induced deficiencies if you're outside the Goldilocks range. Dispersion. There’s an estimate that roughly half the soils in the Bowen basin and are dispersive. And from an industry point of view, you know really rough estimate is that actually represents about a $2 billion liability in rehabilitation in additional cost of rehabilitation. So, it really is a significant problem and it's one of the major constraints to achieving successful rehabilitation. You can and it's one of the easiest things toto determine in the field and simply popping a couple of soil aggregates into ideally into distilled water. you'll see almost immediately if it's dispersive it will form a cloud. If the soil is stable, it will remain clear. So, you know and I guess again coming back to the RUSLE, US the energy you know dispersive soils will actually erode in still water. They don't need heavy rainfall. they don't need high flow velocities. The energy is actually coming from the fact that a high proportion of sodium ions which have got a large electron shell and they when the when the soil is moistened it loses strength. The particles actually push each other apart and you know that's how you know tunnel erosion forms as an example. So really easy to test in the field in and really instructive and particularly when you get some soils will actually explode when you put them into water. Sodic dispersion in terms of a lab test dispersions often measured in terms of ESP, exchangeable sodium percentage. It’s it can be an indict and I guess you know the tech most textbooks will say less than about an ESP of 6% a non-sodic six to around 15% areas sodic and above that they're highly sodic and highly dispersive. It is an indication but it's not the entire indication and we'll get onto a slide in a second just to explain that in a bit more detail. And salt in the soil salinity is bad in terms of plant growth, but it can actually counteract the physical effects of dispersion and getting the balance right. Again, you know, solidity is a is a continuum. there's no hard and fast cut off. Plants will have a threshold at which salt will start to affect them and then they will decline in growth above that up to a certain point beyond which they won't grow. But I guess we've seen examples where people have applied very hard cut offs for salinity and not used topsoil resources that could have been ameliorated and well managed. The salt can be leeched out of those soils and they can actually be quite useful. The treatment for dispersion is to increase calcium through gypsum application. Because you generally dispersive soils are high pH. So, you don't want to increase the pH with lime. You want to increase the calcium content without increasing the pH. And gypsum in fact gypsum there is some recent research that indicates gypsum will actually reduce the pH a little bit as well which is beneficial. But you need rainfall to activate the gypsum for that calcium to exchange with sodium on the clay exchange of the clay fraction of the soil. I’ve seen sites where people have said to me gypsum doesn't work in mining. Is chemistry is chemistry whether it's agriculture or mining. And what they were really describing is they applied gypsum, had really heavy rainfall the next day or the next week before the gypsum had done its thing by exchanging on this the cation exchange complex and got erosion. It's it wasn't because the gypsum hadn't worked. It was that it hadn't had time there hadn't been moisture in the soil to allow it to exchange. And the rate of the required rate of gypsum can easily be calculated from soil chemistry. We’ve talked a little bit about salinity already. Really easy to measure as well. Can be done in the field. equally easy in the lab. Normally it's measured as a 1 to 5 suspension in water. And then converted to what's called an EC of which is the electrical conductivity of a saturated extract. That just brings it to a number that can be used to look at across different soil types of the potential effect of salinity on plants of differing salt tolerance. So, it provides aa universal number in that sense or a universal reference. The thing about salt in the soil is it's highly mobile and you know Australia has around about 17 million hectares of agricultural land that's affected by salinity. It wasn't always sine a lot of that land we've changed the hydrology. removed native vegetation which allows you know as a really generic average. under native vegetation you might get 5mls of deep drainage a year. Under crops you might get 50 mls of deep drainage a year. So, if we have a really simple number if you've got 50 mls of deep drainage and a porosity of 30%. Then you're actually going to increase the water table by 150 mls each year. So, keep doing that for 50 100 years and the water table rises and once the water table rises it brings salt back up dissolves salt and brings it back up to the surface. So again, understanding not just the properties of soil but the properties of the landscape that you're working in as well. And designing in a way that you're able to promote flushing down the profile of salt. Salt deepen the profile below the root zone is it’s not an issue. And again coming back to the trials I showed right at the start on the rehabilitated spoil dump were actually some of the one of the best examples I've actually seen in in mine rehab where we actually achieved extremely significant flushing of salt down the profile within one to two years of rehabilitation there because we re-established permeability of the soil throughout the whole profile and allowed salt to move down. So, the salinity sodicity story is a really important one and particularly again for Queensland soils. These curves represent what's called the threshold electrolyte concentration and it's the point so this for a generic relationship for soils of different clay content but it's the point at which due to dispersion a soil loses 80% of its permeability. So, if we're in this part of the curve here, I'm not sure if people can see my mouse, but the top left corner of the curve, we've got very low electrical conductivity, but, a high sodium absorption ratio or you can read that as exchangeable sodium percentage and soils will disperse to the point that they've lost greater than 80% of their permeability. down in the bottom right of the corner soil is maintaining its permeability. So, there is this this interaction between the two. We don't want to get too high on the salinity curve or salt will become toxic to plants and equally you don't want to get too high on the exchangeable sodium percentage or s or soil structure will be destroyed and plants won't grow for a whole range of reasons. But this graph is really important in terms of designing amelioration of subs soils in particular. it's equally important for topsoils but I guess in practice it it's we found it really important for subs soils from the point of view that if you use the simple 5% 5 6% ESP number you've got to put so much gypsum on to make the soil non sodic that it becomes impractical and it might be perfectly and you know I guess we've seen a lot of cases it might be perfectly tolerable to have a subs soil ESP of 15% just as an example well you're only sitting at around two decisiemens and most native vegetation will easily tolerate two decisiemens of salinity but in that range if you're on a you a 25 to 30, you know, using this particular graph, 25 to 30% clay soil, it will be stable. The plants will tolerate the level of salinity and you won't have erosion and the amount of gypsum that needs to be applied to bring it to that level is a practical amount. So, amelioration of spoil prior to application of topsoil to create a permeable non-hostile subs soil. You know that this this disc graph is a really critical element in in doing that that improving the structure of both the topsoil and the subs soil improves the ability of soil to hold water for two reasons and I'll probably get ahead of myself on the next slide. first is if water doesn't get into the soil in the first place, then it can't hold water. But once it does get in beyond the top centimetre, it has to be able to permeate to depth to be able to be stored. So again, we can't change the clay mineralogy easily but by increasing in increasing organic matter itself doesn’t t directly affect the plant water holding capacity but by changing the structure it improves the ability of water to infiltrate and store water. And coming back to the earlier question, for a given soil water holding capacity, increasing depth, will increase available soil water. So if your plant available water holding capacity is let's say it's 100 mls per meter depth if you can create 2 m of growing media then automatically you're holding 200 m of depth but if you've only got 50 cm then you're only storing 50 mm of water and you know the ability to sustain some a native vegetation system, a native woodland on 50 cm of soil or 50 mls of water if it's at 100 mls per meter is going to be very marginal. It you will have drought deaths.

And sorry just to interrupt you. I'm very apologetic about this. We've only got like about no more than 10 minutes left before we have to throw out to final questions. I just thought I'd remind you of that. Thank you. No, very good. I think we're pretty close now. So, yep. Talking too much here. Okay. And so, yeah, again minimising comp compaction, limiting runoff and storing soil in the water in the soil is important. I saw a paper years ago of a mine rehab paper where someone had the realisation that a store and release cover was similar to a soil profile. And that's exactly what we're trying to achieve. The functions of storing water and then re-releasing it through transpiration.

Identifying or characterising the nutrients that are in the with I guess the most people will be familiar with this. Most agronomic soil analyses will limit them generally limit themselves to this part and identify what the limitations are what any toxicities are. But again, you know, coming back to the book on interpreting soil analysis, what all the numbers mean is a really invaluable guide to determining what your nutrient amelioration strategy needs to be. And again, it's not just the macronutrients NPK and S, but micronutrients can be equally important in in achieving a functional soil or a healthy soil that will support plant growth. And I guess we've touched on infiltration rate. We can have the best plant unavailable water capacity in the soil possible but if the surface soil is such that it seals and doesn't allow rainfall to infiltrate then that water doesn't get into the soil. So, maintaining good structure at the surface deep rooted plants will create channels root channels and promote infiltration and again it's that concept of I guess you know environmental engineering design of water shedding it might be mechanically stable but doesn't allow water to infiltrate and be re-released through transpiration, which is really what we're trying to achieve. And organic matter. I guess the third takeaway from today is we can’t underestimate the importance of organic matter. And when we're dealing with trying to create a topsoil and there is no organic matter, we haven't got topsoil stockpiles, then putting organic matter back in to start that transition process to kick it off to provide the energy to get initial colonies of soil microbes or microflora functioning is really important. I guess an important consideration here is understanding not all so not all organic matter is the same. And I guess you know were looking at some analyses recently for two different organic matter sources. I forget the exact numbers but one had let's say it was 50% organic carbon the other had 25% organic carbon. So effectively, you could pay twice as much for the one with 50% organic carbon that you pay for the one with 25% because you’re getting it's the organic carbon component of organic matter that is important and that you know that that depends on the source of material that you're working with. And of course, by reestablishing the function by of soil through plants and root leaf debris turnover you're effectively converting sunlight into organic matter and building that up over time. I’ve talked about considering the type of organic matter material and that you're putting on. But you should we should be aiming for somewhere between about 24 to 30 a ratio of carbon to nitrogen of 24 to 30 to 1 above that ratio then the soil microbes are actually going to use up all the available nitrogen trying to break down the carbon. Below that ratio you have an excess of nitrogen which can be lost to leeching. So again, there is a goldilocks zone that you need to be aiming for there both in terms of what's in the soil but also in terms of the quality of the organic matter that you're applying. A couple of sources of organic matter biosolids composted manure composted green waste. Wood chips might be good for improving soil structure by creating large particles, but they've got a very high carbon to nitrogen ratio and they can actually induce a nutrient deficiency because the soil microbes will out compete plants for available nitrogen.

Okay so just in terms of an approach and this this in the paper there's a process to work I won't go through this in detail but I guess a process to work through in terms of analysing the soil physical properties the chemical properties the biological properties the physicochemical properties those chemical properties that have an effect on the physical structure and physical properties that have an effect on the chemical structure of soil and working through those designing an amelioration strategy that is fit for purpose in terms of what you're starting with, what you're trying to get to, and what the post mining land use is. And I guess that’s the other take-home message from this paper. And I guess finally just to wrap up you know there's a there's a saying that so science is not rocket science it's harder and there are just multiple interactions between physical chemical biological properties. So, it's invaluable even with the you know the best designed amelioration strategy it's still valuable to implement trials and both from a proof point of view but also from a learning point of view in terms of how far you can push the system either side of what is theoretical optimum. So, trials I guess are the acid tests that you have designed your amelioration strategy well and will give confidence in in future amelioration strategies and trials like any scientific experiment should be designed to be statistically robust. You should have replicates that are meaningful in size that don t have too much environmental variation so you can they're not confounded in terms of the results that you're getting. But you know really valuable in I guess confirming successful mine strategy and particularly if they can be done early, they can be used as a lead indicator in mine rehab. And yeah, I guess yeah, I think I've pretty much covered off on the importance and the sorts of things that might be assessed in terms of biomass. And overall ecosystem health. So, at that we'll get back to the final session for questions and discussion.

Thank you, Glenn. That's great. I we've got a few questions that have coming up and we'd like to answer them all. So, I think we might take a bit of a different strategy today where I will wrap up the presentation formally in a couple of minutes and then we'll just hang around and answer a few of the other questions afterwards if that's okay. Perfect. Yeah. Sounds quick, Louisa. Well, would you mind popping on the next slide and then I'll just do that formal wrap up now so that folks if you need to leave at 11:30 because you have other commitments. Thank you very much for your time. We do want to respect that and appreciate people are busy. One of the slides here I've generated because everything that Glenn has presented today and Bernhard has included in the paper as well is really discussing the approach that we've presented in the paper. And the idea of having an approach is that it allows you to take each of those steps and consider your very specific site circumstances as you develop your growth medium. So that was what was quite important to us to have that come out through the paper. And then there's just one other slide Glenn where we've got a QR code and that's for some feedback on today's presentation. we really do appreciate everyone s feedback from previous workshops. It does help us to make sure that we improve these. There's three questions. One of them is multiple choice, so it's not hard to fill out. So, we'll probably pop that slide back up later towards the end, but we'll just now we can go back off to some questions. This we've got a few questions here around dis the dispersity issues that we have and so the first question from Rebecca I think I can sort of answer that essentially at the moment because it her question was we have highly dispersed soils at our minds how would you approach adding calcium to offset the sodium a step-by-step guide and then I'll answer that in saying Rebecca we put quite a detailed discussion about this in paper including an example of one of the equations that are available to help you calculate your gypsum application rates. There's quite a bit of conversation and discussion in the paper about that. The second part of Rebecca and sorry that's in a later section of the paper you’ll find towards the end of the document. Rebecca's second part to her question also sort of marries in with another question. So, Rebecca asks also is calcium the best offset for sodium or is there some other chemical suit chemical element best suited? And then we have another question magnesium levels often neglected in dispersive soils. Can you comment on the importance of including magnesium as part of the cat's balance to reduce dispersity? So, I’ll throw that back to you Glenn. Sure Louisa. Yeah. Obviously, calcium and magnesium both develop cations ions. Sodium and potassium are monovalent. ESP is not normally concentrated calculated simply as the ratio of calcium to magnesium. There is a different metric that's used called cross on ratio of source stability I think it is which I actually doesn't give you significantly different answers but it's more instructive. It recognises that sodium is more dispersive than potassium which is more dispersive again than magnesium and calcium. So, there is a there is aa gradient there between their dispersity and their effect on stability. If you know there are if we could ameliorate soil with tri trivalent cations ions and there’s a whole raft of options there that they're actually more effective again in stabilising dispersive soils. But one of the great benefits of calcium is really important and often undervalued nutrient. And you know some of the trivalent cations ions or you know aluminium will create toxic problems high aluminium soils are often very stable. They're just toxic. So, in terms of magnesium didn't talk about it in the discussion but obviously getting the calcium magnesium ratio right as well. So, it's one of those other interactions that shouldn't be ignored in in your humiliation design. And I remember learning many years ago that, you know, you've got to have those things in the right balance, haven't you? Because too much magnesium can make memory a very blocky soil, which is hard to wasn't really very appropriate in its structure. we have another question, but before that, I just wanted to let everyone know, if you haven't noticed, Glenn had talked about a few key texts throughout his, presentation this morning, and we've put, links to those. They're basically part of a CSIRO series of textbooks that are quite recognised in Australia around soil. And so, we've put links to the two that you mentioned, Glenn, and I threw a third one in just for free money, which is the yellow survey handbook, which I've used a bit over the years. Yeah, the yellow book, the red book. That's right. So, there's links to those in the Q&A chat as well. So just for those who have not noticed, another question, how do we best translate to mining engineers and accountants that poor soil management or restoration presents a risk? Presents as a risk cost or liability. What examples have you seen? Yeah, it's a really good question as well and the liability and I guess it's you should in theory be partly addressed by the requirement for progressive rehab but you know the liability of getting 20 years and the I'm sure everyone's familiar. There are plenty of sites like this that are 20 years down the track and you can drop a couple of buses into just individual parts of erosion and a couple of skyscrapers into erosion some sites which really create a very massive liability for rehab. So fit for future rehab. I guess one of the things we probably haven't really progressed to is distinguishing between rehabilitation and relinquishment and it's you know I guess we've and again this part actually part of the ACARP work that we did was create aa model that looks at the you know the relatively small additional cost up front of ameliorating correctly versus the liability that it creates a longer term. minutes there. So, it's very easy to do a discounted cash flow on that to and the longer it takes to get to that point of relinquishment, potential for relinquishment, the cost of holding that land in in mine tenure you know just keeps compounding. It’s like compound interest. So, every side is going to be different, but a discounted cash flow approach is really the way to be able to demonstrate that a small additional investment at the front pays financial dividends of rehabilitating a failed site in the future. I have a little thing to add there as well, which is that we recently were speaking with some people at a metalliferous mind who had trouble with a trial that they were running. And then when they did the trial again a second time, they made it really front and centre to all the different operational teams in parts of the mining business about the trial and the importance of it and how it was going. and they got a lot of success out of that because they would go and present to different team meetings for those parts of the business. They had a chart in a common area that was you know following tracking the progress of the trial and the things that they were learning in the benefits. And so, they really brought those parts of the business along as well because it seems to me that sometimes these things that we do as environmental folks happen a little bit in a silo. So, if that helps as well maybe to just really work hard at engaging with those other parts of the mining operation. Yeah. Then that's certainly where trials can be valuable as well. And I guess probably just to add to that point the designing based on the characteristics can actually be cheaper. The probably you know the most you know the highest return is doing good. soil, good spatially representative soil analysis. It's the most important investment. So again, you know, coming back to those trials I showed right at the start, it not only did we achieve actually much lower erosion the rehabilitated sites relative to rock mulching, substantially cheaper to implement that am that rehabilitation strategy. I guess you know I've seen examples where people have applied recipe approach where they've effectively taken the worst soil sample and applied gypsum over the entire are at that rate and there has been potential to save an enormous cost in in gypsum u by applying it at the rate that's required. So, you know moving away from blanket recipe applications to and you know the same is true in precision agriculture. It’s a similar principle. Okay we have a couple more just to wrap up the morning. So, thank you for those who are able to stay on with us. If mines are meeting all slope, a million and vegetative milestones that are required to meet stable landform, how can we combat settling and swelling of soils that lead to erosion?

Happy to read that again. Yeah, if I if I got the question right. So, assuming that the mine is meeting all the slope, a million and vegetative milestones necessary to you know achieve a stable landform, how can we combat settling and swelling of soils that lead to erosion? I guess I if you're achieving your amelioration strategy correctly then then we should be avoiding those problems in in the first place. Obviously, you know settling is and I guess you know this probably it's an important part of mine rehab design and I guess what we haven't talked about in here is what we're really discussing in this paper is what do you do with the last one and a half 2 meters of material that goes on top of the rehabilitated landform. So, you know landform evolution modelling is really important in terms of design of the landform in the first place and construction of that you know that that's the underlying foundation that may or may not affect particularly settling over time. So, it in maybe to answer it another way in any large area rehabilitation project whether it's mining its alluvial gullies or anything. An important part is ongoing monitoring as well. So you'll never get 100% of the area 100% right and because we have you know the tools are available now to you know get away from you the old approach of doing a couple of transects that give you about this much visibility on how your site's performing and you it's possible to run LAR over the entire are and monitor quite regularly. And so early intervention again comes back to that financial question early intervention or early identification monitoring early identification early remediation of those bits of a site that don t you may have issues through settling through swelling through haven t quite been implemented properly in the design. Weren't quite representative of the amelioration strategy whatever it might be is pretty important and I guess our experience is it's you might get 90% right in the first year and you fix up the little bit that you don't get right and then in the next year there's a much smaller bit that hasn't. So pretty quickly you've addressed the whole area. Thank you. That's a tough one to answer because there's so many different aspects to that, isn't there? So, thank you for that question, but we'll keep moving on. We've got three more to answer and then we'll be able to wrap up for the day. Does sheeting a sand layer before topsoil placement help in plant growth? I've never heard of that before. Sheeting a what? Sorry. A sand layer. Yeah. Interesting idea. I guess you yeah, common a common practice had been putting topsoil on to spoil and then ripping everything to try to notionally keep the topsoil in. And you definitely I guess don't want to create a beautifully graded and smoothed soil landform and put topsoil on that which increases the risk of slippage. So, yeah, I think I think the answer to that is really what you're aiming for is, you know, what and while a beautifully graded spoil layer might look really good, and look very engineered. You know to in addition to being smooth and increasing the risk of topsoil slippage in the process it's also likely to be more heavily compacted. So, you creating a layer where you may have restricted water infiltration that just further exaggerates that risk of loss of topsoil. So, it’s probably a case of ugly is beautiful. Yeah, creating a rough topsoil and I guess it's something we didn't talk about which is you know once the topsoil is gone on it's both very difficult to ameliorate the sub soil and any incorporation into the spoil is likely to bring up rocks and bring up more sodic material. So yeah, I guess our recommended strategy is when the spoil has been placed to rip the ameliorants into that to you know at least 50 cm create that rough layer, reduce compaction and bulk density and then apply topsoil to that to that rough layer. Which effectively if you're putting you know if you're putting on topsoil then you're getting you know another 10 or 20 cm. So effectively you've got a treated depth of 60 or 70 cm. So, trying to maximise that treated depth is important in the process. Thank you. The last two questions are about organic amendments and we did touch on these in the paper as well. So, Johan has a question the use of biochar as part of soil amelioration with a question. So should we can we should we and then we can move on to the other question after that. Yeah. You biochar has some useful properties and I assume it's Johannes Bano no okay useful properties but it is biologically inactive form of carbon. So, it will improve soil structure, it will improve water holding. And there's some interesting work to show that by sequestering root exudates that mineralise organic labile forms of organic carbon, it can actually help build organic carbon over time, per se. It's not an available energy source for plant microbes. So, it doesn't contribute to kickstarting the microbial system in the soil. So, it has a place. And you know some work being done on using biochar as a carrier for nutrients because it can help u with slow release of nutrients into the soil, reduce losses. But again, you know, it’s understanding what function you're trying to achieve. And I guess yeah, we haven t seen large scale application of biochar in in either agriculture or mine rehab. It definitely has a function in high performance soil. So, things like street trees in Brisbane that effectively live in a pot. Yes. Yeah. You need a really high performance a high functioning soil in those situations and u you know it's a great application. Okay. Well, that's lovely. That's a good conversation because biochar is obviously something people are quite interested in and emerging. last question. Wood chips. This was interesting and not what I was expecting. When the wood chips break down and steals the soil nitrogen, I suppose the question is when the process is complete, is the nitrogen released back into the soil? Does the nitrogen become available at a later date essentially? Yeah. Yeah. it will do. and I guess that's the plus side and it's a reflection of the composting process. I guess if anyone's familiar with composting you take organic matter it goes from effectively and that you know the standard talks about this going from mulch to immature compost to mature compost and that's the point where you know that carbon nitrogen ratio is back in the in the Goldilocks zone. But it can also and I guess you know again it's this where it’s more complex than rocket science. Under stress conditions or you know under you can have different outcomes under drought conditions and in high rainfall conditions. So, under high rainfall conditions, microbes in the soil are trying to do all they can. So, they really will be mopping up all the nitrogen they can to break down u woody matter under drought conditions. They’re not as active and it's not necessarily such a problem. Yes, there is there's actually quite a good paper on that by Natasha Banning from a couple of years ago in WA. I can't remember the exact date of that, but if it’s worth having a look at that paper which explains that really well. Thank you. Okay. Well, thanks everybody. Went 15 minutes over, but we had a lovely conversation there. Thank you for all those questions that were very thought provoking. I really just want to take the opportunity to say thank you to Glenn and thank you to Bernhard for preparing the paper and for spending the time to present today. Sam, I see has put a link to the QMRC feedback code that we put up earlier. So, we really do appreciate your feedback. However, you want to reach out to us, that's fine. but I'll close off and say thanks to everyone and we'll see you at the next QMRC event sometime in the future. through we'll advertise that through the normal channels. Okay, lovely. Thank you very much. Bye. Thanks Louis and thanks everyone.