Why Nutrient Availability is Not Determined Only by pH

So the topic for our webinar today is a discussion about why nutrient availability is not determined only by ph. And I think this is becoming fairly well known and particularly in the domain of regenerative agronomy and agriculture. Today, people are beginning to understand that nutrient availability is in fact significantly determined by microbial activity and the degree of bacterial populations, fungal populations that are able to extract nutrients from the soil mineral matrix and make them available to plants. But yet we still, when we look at soil analysis, we get a soil analysis back. Our soil analysis does not report at least most mainstream soil analysis today do not report nutrient availability according to biology. They still report nutrient availability according to chemistry and according to physical. So we get a soil report back, we look at the ph number, and that ph number automatically indicates to us in our mind what the relative availability of different nutrients could be. And this is a very inaccurate, or I should say an incomplete perspective. So we are all familiar with this Nutrient Availability according to ph chart. How Soil Ph affects availability of Plant Nutrients is the title for this particular chart. If you do a quick Google search for nutrient availability according to ph, you will find dozens, actually probably hundreds of diagrams and charts similar to this one. For this presentation. Until we get to the end, I'm going to not focus on the biology piece. We know that biological delivery is important, but we still tend to approach soil mineral availability from a chemistry perspective. I'm going to focus just on the chemistry perspective for the sake of this conversation and describe why looking at ph only from a chemistry perspective is incomplete. So we're familiar with this diagram and with this chart. The problem is that it looks at nutrient ph only from a single dimension. Ph. It's one dimensional, left versus right, high versus low phone. And in over the last year or two, I've hosted Olivier Husson on the podcast and we've conducted a very long webinar with him which is available in the Academy, where we talk about redox and the impact of reducing versus oxidizing environments on nutrient availability, on plant health, disease resistance, insect resistance and so forth. But it has become clear that this is a very nuanced topic, or shouldn't say nuanced. There's a lot of detail, it's an unfamiliar concept. And so I wanted to I've been thinking about a way how can we describe this unfamiliar concept of redox and nutrient availability in a more simple and easy to understand manner. So that's the intent of this webinar, is to change our thinking from this single dimension ph of nutrient availability. Ph is Determining nutrient availability to multi dimensional and in this case, two dimensional, including both ph and redox. So I'd like to introduce you to what is known as a poor bay diagram or a redox diagram. So this is a diagram that is two dimensional instead of one dimensional. So across the bottom of the graph we have pH from 0 to 14. On the right we have this redox axis where that is measured in electron volts or pe. So now instead of looking at nutrient availability in terms of just left or right on the chart, we should be looking at it diagonally. So it's upper right versus lower left. So nutrient availability is different forms of nutrients are available or show up at different places on this chart. So this is just an example that we pull up pretty quickly from iron. So we can see that we have different oxidation states of iron at different locations on this graph, all the way from the upper right to the lower left and at different locations. So we're going to go through a conversation or a slide deck that we have put together where we look at different poor bay diagrams that we have put together for different nutrients in agricultural soils. But before we go there, I want to offer a bit of context. So if you do a Google search for poor bay diagram and for a specific nutrient, let's say manganese or whatever, in this specific one selected sulfur, and you look at an image search, you will find dozens of images, hundreds of images, and they may be somewhat similar or they may look completely different from each other. So why the differences and why all the variability? Well, there are several reasons for the variability. Some of the reasons are that these diagrams change based on temperature. They change based on nutrient concentrations. They change based on the nutrient ratios when different nutrients are contained within the same solution. And they change based on the presence or absence of organic acids and humic acids, as well as a number of other variables. But these are just four significant ones that I wanted to point out because of their relevance in the agricultural context. Now, another challenge also is that these diagrams, and I'll speak to this more a bit later, but another challenge is that these diagrams are all based on interactions in pure solutions in a laboratory beaker, which isn't how real world agriculture actually works when we look at these various factors that can produce variability. The first one is temperature. So we know that higher soil temperatures, because soils are exposed or not covered, they're exposed to sunlight, that increases oxidation and it expands the zone on the upper right of the diagram. So the upper right of the diagram is where you have your oxidized and alkali zone. And on that end of the diagram, where often you'll have limited nutrient availability. So when you have higher soil temperatures, that expands that oxidized zone and shrinks the reduced zone. So there can be very significant changes between 25 and 50 degrees Celsius, which is 77 to 122 degrees Fahrenheit, when you change the temperature settings in producing these diagrams. And so when you consider 77 to 122 degrees Fahrenheit, this is the typical shift or within a common range of soils that are covered with crop residue or cover crops or shaded by a crop canopy versus soils that are exposed to direct sunlight. So when you have soils that are exposed to direct sunlight at higher temperatures, that's going to have a very strong oxidizing effect and increase expand the zone on the upper right of the diagram. A second important factor that produces variability is the nutrient concentration, particularly of all the oxidized nutrients. So when we apply nitrate, nitrogen, or when we apply any form of nitrogen that gets converted to nitrate, nitrate is the oxidized form of nitrogen. So that also expands the oxidized zone on the upper right of the diagram. When we look at nutrient ratios, some of the nutrient interactions will influence how the diagram gets shaped. So if you have, for example, if you have the presence of levels of calcium, that influences phosphorus availability, which is something that we've already known from a chemistry perspective, but we often don't discuss the fact that this is a redox reaction that is causing this to occur. And then, of course, organic and humic acids. So we know that organic acids increase the reduced zone. In other words, they increase on the lower left side of the chart, they increase the zone of nutrient availability and increase because they have obviously a reducing effect, being organic acids. And this has the effect of increasing nutrient availability, which is why plants send out a lot of organic acids as root exudates to increase nutrient supply. And then we have the humic acids, humic substances, which greatly increase the poising or the buffering of the soil system so that there is less variability. So all of these factors influence the diagrams. And this is why you can do a Google search and find dozens of different diagrams. So what we have tried to do in preparing for this webinar and putting together this slide deck is to put together a set of diagrams that somewhat reasonably reflects soil conditions. And obviously this is really impossible to do because there is no such thing as average soil nutrient concentrations and average soil temperatures. We did try to depict some of the extremes as well. But this is also the software to develop these diagrams is available. It's clunky and user vicious, but certainly anyone, it's open source software and anyone has access to, can have access to developing their own diagrams as well. So the diagrams that we have put together are based on a standard temperature that is used in the modeling software of 25 degrees Celsius, 77 Fahrenheit and nutrient concentrations based on average soil levels. So for the software's benefit, we converted all of these standard part per million metrics to moles and molar weights. And all of the data that we use, all parameters that we used is on the slide decks themselves that you can reference if you want to dig into that a little bit more deeply. So let's look at some of these common elements. We're going to look at some of the macronutrients, some of the trace minerals. First one is calcium. So we have on the lower side of the chart we have ph range from 3 to 11 and millivolts reduction along the side. And if you look at the parameters on the upper left, temperature is set at 25 degrees Celsius and calcium concentrations are set at 10 millimoles, which is the equivalent, I think of about 2,000 parts per million if I recall correctly. So you look at this diagram and you see that well, calcium is very highly available across a broad range. The CA2 +ION, which is the form of calcium that plants actually absorb the most readily, is widely available at a broad range of different pH and EH factors. So it's available at a broad range across this chart. And so this is one of the reasons why we often don't think about calcium availability in terms of ph. Similarly with magnesium, Magnesium is also very available across a very wide range. What is based on what is present in soil profile, we don't spend a lot of time thinking about magnesium availability in terms of ph. Most of the nutrients that we spend time thinking about, their availability would be phosphorus for example, or the trace minerals. So the conversation will get to be quite interesting when we start looking at trace minerals. Here is what sulfur looks like. A typical concentrations in the soil. I think this represents about 35 parts per million of sulfur. You can see we have sulfate and then the hydrogen sulfide forms that show up on the lower left side of the chart in extremely reduced environments. Like if you have anaerobic fermentation, let's say in a liquid manure pit and you produce hydrogen sulfide, that rotten egg smell. So that shows up on the lower left side of the Chart Zinc is interesting. Zinc availability, or the zinc 2 plus double positive form oxidation state that plants absorb, also has a very broad swath of availability. And I find this to be really interesting that zinc is the one trace mineral that is widely used, most widely used by the mainstream agricultural industry. And I believe the reason for this is because it is easy to apply and get a crop response with other trace minerals like manganese and iron and so forth. They have a much smaller zone. And when we have challenged soil environments that are excessively oxidized, in particular, we can put on applications of those nutrients to the soil and not get a crop response or not even get a soil response. And I suspect this is one of the reasons why zinc use has become so popular and other trace minerals have not, is because they have not been applied properly and it hasn't been understood how to get plant performance from them. So if we look at cobalt, the zone of availability for cobalt is significantly smaller than it is with zinc that we just looked at or with calcium. So we have this optimal zone, eh range and pH range, in which we have good cobalt availability in a form that plants can actually absorb. When we look at copper, similarly, we have a fairly small zone of copper availability. When we look at iron, we have. If you look at this from ph perspective, you can see that you have most of the chart here being in the red zone. Our experience and our observation has been that plants can actually absorb these various oxidized forms of iron, but that they are not physiologically active inside the plant. We look at manganese. Manganese has a surprisingly large zone, but again, remember that this is based on, on a certain temperature range. And the concentration here, 1.6 micromoles, is, I believe, in the neighborhood of 80 to 90 parts per million. It's a fairly small concentration. Now we come to a fun one. Let's look at nitrogen. So with nitrogen, you have the oxidized form of nitrogen versus the reduced form of nitrogen, which is nitrate versus ammonium. I think for this particular diagram, it was set at 200 parts per million, if I recall correctly, but I could easily be mistaken about that. But the important point is that if you look at where we are, so we have oxidized nitrogen, which is nitrate showing up on the upper right hand of the chart, and ammonium showing up on the lower left. And then we have ammonia as a gas, NH3 showing up on the far right. And then of course, nitrite in here as well. Now, I mentioned at the beginning that these concentrations are the positions on this two Dimensional diagram can shift depending on nutrient concentrations. So imagine that you have soil that has been historically covered with crop residue and has been managed in a biological manner. So this soil will be cooler, 25 degrees Celsius, let's say, for the sake of conversation. And it has some substantial nitrogen reserves in the form of amino sugars and amino acids, and some free nitrogen in the form of ammonium. So the majority of nitrogen in that type of a soil profile will be in an ammonium form. So now if we. Let's just say we go through and we till that soil, we aerate it, cultivate it, introduce oxygen into the soil, we remove the crop residue and now it's exposed to the sun. Then we go through and add, for the sake of discussion, say that we add 150 pounds of nitrogen per acre in the form of liquid 32 or liquid 28. When that happens, we have now just added three different very strong oxidizing influences. We added nitrogen that will convert to nitrate. That's oxidizer number one. Tillage is oxidizer number two. And exposure to sunlight and increased temperatures is oxidizer number three. The effect of those combined three different oxidative measures or oxidative influences means that this diagram would shift and change. And what is currently the upper right of the chart represented as Nitrate no. 3 with a negative charge. That zone on the upper right will expand and move down towards the lower left and it might expand to the point where it consumes a larger space than the ammonium zone because you have now had all these oxidizing influences and these oxidizing effects on the soil system. Of course, as Olivier has very clearly described in the course that he has put together that is available on the Academy, is that the lower left zone is the zone where you have disease suppression and optimal health, and the upper right zone is where you have limited nutrient availability and disease enhancing effects and you end up with crop quality challenges and so forth. So I wanted to describe these poor bay diagrams to have them serve as an illustration that nutrient availability is not just one dimensional. If we only consider chemistry, then nutrient availability is at least two dimensional. We need to take into consideration both ph and redox values. However, even when we look at these diagrams, they all have one significant problem. I called it a minor problem, rather tongue in cheek. But they all have a very significant problem or actually have several significant problems. And these problems are that they are all incorrect in biologically active soils because biology actually determines nutrient availability. And these diagrams are all based on chemistry models of chemistry Interactions that occur in pure liquid solutions, in a beaker, in the laboratory. And we all know that that is not how real world agriculture actually works. So we can use these models as approximations for what might be happening and what might be going on. And they're certainly useful to have a conversation around. But at the end of the day, we need to remember that it is the biology in the soil that determines the chemistry. It is biology that will actively shift and move oxidized iron to reduced iron. It is biology that will shift oxidized manganese to reduced manganese. This is how biological ecosystems in soil actually function. They are not based on, only on chemistry interactions. In fact, the healthier a soil becomes, the less chemistry interactions are actually relevant to in field application. And so ultimately, that means that at the end of the day, if you want to assess a soil's capacity to deliver nutrients to a crop, the only valid indicator of what is truly planned, available, looking at what the crop actually absorbs, and looking at SAP analysis. This whole conversation around redox is a giant blind spot in our current approach to measuring soil and soil analysis. Soil analysis can give you a report on iron content, but it gives you no indication of whether that iron is in the oxidized or the reduced form. Same is true of manganese and the same is true of copper and cobalt. It doesn't show you where on the chart these nutrients show up. And there's a good reason why they don't. It's because the nutrients can shift from the oxidized to the reduced form and back and forth fairly rapidly, based on our cultural management practices and based on biology. So I talked about having three very strong oxidizing factors, such as combination of tillage and removing mulch, exposure to sunlight and nitrate application. Those are three strong oxidizing factors. But if you look, if you consider an equivalent of three strong reducing factors, let's say you have constant steady rainfall and the soil is wet for an extended period of a couple of weeks, and you get a shading effect by a growing cover crop that completely covers the soil. This cover crop also transmits a lot of organic acids into the soil profile. Let's say buckwheat, for example. The combination of all those things can have a very strong reducing effect. And so it can quickly change the state, the oxidation state of the iron and the manganese and so forth that is available in your soil profile. So I hope this provides a little bit more clarity on the discussion of nutrient availability. Ultimately, what we have to remember is that nutrient availability is ultimately determined by biological activity. As long as we approach nutrient availability from a chemistry perspective, then we'll be able to produce crops at a certain level of health and vitality. But we will always hit the ceiling. There's a certain threshold that we can't get past which is ultimately the change from level 2 to level 3 in the plant health pyramid. We can't really get to level three on the plant health pyramid until we have really active soil biology. That's the conclusion of the slide deck in the presentation. I'm going to open it up for Q and a question from Roger on the slide deck that I provided. Is the red not available and the green available? And the answer to that is yes, that is the color coding that we had used. And you can also many plant nutrition handbooks. The kind of the classical reference is Petra Marschner has now edited the third edition of Mineral Nutrition of Higher Plants. And usually when you look at these textbooks in the first couple of paragraphs they will describe the oxidation state of a given nutrient that plants absorb. So the information is readily available out there for you to identify exactly what the correct oxidation state is for optimum plant absorption. What exactly is a SAP analysis? It's where we're measuring the nutrient content in the plant SAP itself. Check out Crop Health Labs for more information on that question from John Heywood. What is the best way of measuring the biological availability and activity of the soil? John, I would love to have an easy great answer for that question. And I don't. Let me say that there isn't a laboratory assay or a laboratory report that I am aware of right now that gives us the type of information that we need to make good management decisions from. Because what we are really looking for is we're looking for a laboratory report that does two things. One, it identifies the type, the different types of species that are present and two, it identifies the quantity of each species that is present. And I'm not familiar with any laboratory assay that does that, that provides that type of information at this moment in time. So what our approach has been has been to look at this from a really practical field performance perspective. And ultimately the best measurement of healthy soil biological activity is twofold. Question number one is what proportion of your crops total nitrogen requirement and total nutritional requirement is this soil capable of delivering really healthy soil with active biology can deliver 100% of a crop's nitrogen requirement with no additional nitrogen inputs. And question number two is does this soil have the capacity to suppress all the soil borne pathogens? So PYTOPHTHORA and Verticillium and Pythium and Rhizoctonia and Pisareum and so forth. Really healthy soil will suppress all of these pathogens and prevent them from ever forming an infection in the first place. So if, when we look at it from an experiential perspective, if you have soils that suppress the development of all these diseases, then you can be confident that you have good biological activity. And that's the best answer that I have for that question at this moment. Question from Jerry Snyder. Hi Jerry. Does AEA have biological soil reducing products? The answer is that all of the microbial inoculants that we have used for years include microbial strains that are facultative aerobes and facultative anaerobes that have a reducing effect on the soil. Question what about the redox reaction and ph within the plant and how it impacts nutrient availability after plant uptake? If you want to dig a bit more deeply into that, Olivier actually describes redox reactions inside plants and how the different forms of nutrients impact the redox environment in the plant vascular tissue. In the webinar that we put together, I think it's in the fourth or fifth section that is talks about nutrient interactions and plant health. So that's, that's the place where I would go to get more of that information. It certainly does influence it, but describing how it influences it is beyond my capacity at the moment. Question from Magnus. Hi Magnus. I'm not a farmer but a golf course manager working with sandy soils. All through last year I use nitrogen fixing bacteria and some organic fertilizer. I've increased Brix levels from 1 to 14 in a single year. Does this mean I have managed to achieve a bit more reduced soil? The answer is. Well, I don't know for certain. There's a good probability that the answer is yes, because in order to achieve a brix of 14 on grass, you need to have good manganese availability and you need to have good iron availability, which only occurs in a reduced soil environment. So I would guess that the answer is probably yes. Follow up question from Ed. Hi Ed, what do you think about the PLFA analysis? I think my perspective on the PLFA analysis is that it can give us a useful benchmark of where we are right now, but it doesn't give us manageable data, at least in the way that I understand it. And perhaps I don't fully understand it, but I don't understand how having a PLFA report gives us data to make decisions that we should guide our soil in a more oxidizing direction or a more reducing direction, or how we should manage soil biology. So I think in order for data to be useful other than just to serve as a benchmark of overall health and performance, we need to know how to make management decisions from the data. And it's not clear to me how the PLFA delivers that. Question from John do you determine that certain plants such cover crop species are reducing or oxidizing, for example wheat and oats? Based on experience or through testing, we tend to let weeds grow in our tree crops and manage them with mowing. But I wonder if those species are helping or herding. Is there a resource to identify their activity? For various grass species, the species for which I know the answers, I have learned from direct conversations with people who studied them, usually 40 or 50 years ago. Don Huber has been an invaluable resource in connecting some of the dots. I found that this information is not readily available, or should say it's not available at all. I haven't been able to discover it in the English literature. Olivier Husson identified a book that is written in French. He spoke about it on the podcast interview. We linked it in the podcast Show Notes, where they actually have determined the redox influencing characteristics of hundreds of different plant species. So that information is out there in France and I would be delighted if someone were to translate that because I think it's very valuable information that we need. And I suppose if no one else tackles it, then I will at some point when I was going to say when my to do list goes shorter, but it'll be before that because my to do list will never grow shorter, I'm sure. So that is the. Those are the best resources. The only. That's kind of the only resource that I know of at the moment. Question from Darren Petzer. Hi Darren, could you please expand upon why plants cannot utilize iron, for example, in an oxidized form for their physiological processes, but they take it up anyways. If the plant was in a high energy state, could it reduce the iron within itself? Darren, you asked the same question that I have asked many times and I don't know the answer. I know from lots of data and observation that I think we can kind of see what is happening. My hypothesis is that plants sense they have a strong iron need and they absorb iron in the oxidized form from the soil and once it is absorbed, they recognize that it's not physiologically active and it rapidly gets stored in cell vacuoles. It gets kind of locked up in Storage rooms inside the cell and somewhat ignored, because that's my hypothesis and I would be happy to be mistaken about that. But my reason for that hypothesis is because what we have observed is when we conduct side by side dry matter based tissue analysis and SAP analysis, the dry matter based tissue analysis will report that plants have a surplus of iron because they're measuring the total iron that is present, including the oxidized iron, where the SAP analysis will report an iron deficiency. When we begin foliar feeding reduced iron, the iron levels on the SAP analysis goes up and the iron levels on the tissue analysis go down. It's as if, though the plant recognizes that it now has enough iron that is in a physiologically active form and it no longer continues to absorb and pull up more iron in the oxidized form from the soil profile. So that's what we have observed. Exactly why that is happening and how it is happening. I don't know the answers to that. But now I'll allow you to surmise from those observations what you think might be happening. See, lots of questions are coming, coming through here and I'm trying to. Some of them are repeats that I have already answered. So I'm skinning, skimming through them fairly quickly. What is the relationship between leaf and plant biosphere and nutrient absorption after the ph and redox of the plant? This question doesn't quite make sense. This is a question from Angelo, if you would like to clarify that question. It seems like a very good question, but I'm not quite following the train of thought and connecting the dots on that one question from Alan. What forms of fertility are best used to ensure that they are plant available? For example, manganese sulfate would be an oxidized version. So what form should we use? You will want to use minerals that are speaking specifically about these trace minerals that can be present in the oxidized or reduced state. Take manganese or iron or cobalt or copper for example. You will want these trace minerals if you are purchasing them, to apply them, which in many soils and many crop environments is necessary until soil biology recovers. You will want to purchase them in the form of amino acid or organic acid chelates, because they in the process, if they are properly manufactured and properly produced, then manganese sulfate might be the raw material. But through the manufacturing process, as they are chelated, they will convert to the reduced form and then they're also stabilized in the reduced form through the chelation process. What are the best reducing actions we could easily put in place on a tomato based farm? Well, for any farm. The reducing actions that you can take is to keep the soil covered, keep it cool, don't expose it to sunlight, aerate it, do not aerate it excessively. Don't till it excessively. Use as minimum tillage as possible. Don't apply unnecessary limestone or any oxidizing materials. Salt fertilizers are almost all oxidizers and avoid the application of nitrate. So it's really, it's those big things. It is excess of temperatures, excess of aeration, excess of salt fertilizers, and excess of limestone. Those are the biggest oxidizing influences that we should try to limit. And then on the other side of the coin, reducing actions is plant cover crops that are known to have a strong reducing effect, such as buckwheat and alfalfa and oats and so forth. And some of the COVID crop species that I've mentioned in my previous webinars. Question Is it possible to grow blueberries in peat with a Ph of 2.5 and 2.8 with strong microbiology, feeding foliars, and in a highly reduced environment with natural chelated micronutrients and amino acids as a source of nitrogen? I don't know the answer to that question. Obviously, blueberries are natively adapted to growing in peat bogs in very reduced environments, which is why they have. If you think about the plants that are adapted to living in highly reduced environments, like rice and blueberries, blueberries even more so than rice, they are dependent on their nitrogen in the reduced form, which is the ammonium form, and they have very high requirements for manganese and iron and phosphorus, which are very bioavailable in very reduced environments. So they're certainly adapted to that type of environment. The only question that I have, which is an unknown for me, is how acidic can blueberries really thrive in 2.5 to 2.8? Seems to me that it's probably on well below the lowest threshold, which I would guess would be in the 3.5 to 4 range. But I don't actually know for certain. I haven't experienced it and I don't know for certain. That's kind of my best guess. I suspect that it's perhaps too acidic, but I don't know. Question from Alberto we have very alkaline soils with greater than 8.4 ph and too much calcium. Is it possible to get a better reducing condition of the soil by adding leonardite and cover crops? The answer is yes, if you emphasize cover crops that have a reducing associated microbiome in the rhizosphere and using leonardite to increase the poising effect, you can have a very strong reducing effect. Repeats of the question on soil biology Question how can soil ph affect plant SAP ph? Have you found any correlations? And the answer is there is zero correlation between soil ph and plant SAP ph. There's no correlation whatsoever. The two do not connect in any fashion. Question from Greg pennyroyall hi Greg, this is an invaluable perspective and the course by Olivier was a paradigm shift. If biology rules and plants are in charge, what are the top observable indicators that can give us an idea of where on the EH ph scale we are in the system so we can hack the system to get the system into a biologically driven homeostatic homeostatic state. Greg, perhaps you and I should collaborate on translating the French book into something that we can understand. Because I think the answer to your question is that if we understood each niche that these different plants occupied, because I'm sure every plant is an indicator of a given ph EH zone in the environment and if we understood what that would be, then we no longer need laboratory assays to measure what's happening and what's going on. Follow up Questions on Applications how is a nutrient spray absorbed by the plant? I would suggest if you have questions about foliar sprays and nutrient absorptions, look at the webinar recording that we have that is titled how to Design Foliar Sprays. It's available on the Advancing Eco Agriculture YouTube channel. Question from Michael Grove can managing water and biological inoculants replace the need to apply foliar or dry fertilizers over time in a healthy ecosystem? Yes. And even in the short term it has a very significant impact. But can you? The answer is it depends. It depends on your geological context. Do your soils have the capacity do your soils even contain enough manganese or enough copper to be released when you have good biological activity? Most soils do, a few do not. So depending on the context, yes, managing water and biological inoculants can have a significant, significant impact. Lots of questions that are coming through, a number of them off topic. So I'm going through and screening and focusing on the ones that are specifically on the topic that we've been speaking about. Question from Jason Cook what influences irrigation water have on the oxidation or reduction of soil? Well, Jason, in general, soils that are saturated are, soils that are kept wet have are tended to be more reduced. So you can actually have a strong reducing effect on soil by keeping it moist all the time. But that isn't really the answer to your question, the direct effect of irrigation water depends on the carbonate and bicarbonate load of the irrigation water. So carbonates and bicarbonates are very oxidizing because they carry oxygen with them in the carbonate fraction, CO3, and as a result they can be very oxidizing. So it's really a question of what is the mineral load. If you have clean water that doesn't contain carbonates and bicarbonates, then that will have the effect of actually having a reducing effect on the. On the soil profile. Overall, what is my thoughts on the iron and manganese interaction in the plant affecting iron availability? Considering that iron is a reducer and manganese is an oxidizer, My understanding is that both iron and manganese can be present in either the oxidized or the reduced state liquid. Gypsum is an oxidizer. And yeah, a couple of questions on gypsum. Excuse me, Excuse me, I misspoke just a moment ago. I was processing too many things at once. Gypsum is not an oxidizer. Gypsum tends to have, even though it carries oxygen in a sulfate form. My understanding is that it is fairly neutral or even slightly on the reducing side of the spectrum. And again, it is context dependent, as I described in the diagrams. It depends a little bit what soil context you put it into, but my understanding is that gypsum tends to have a reducing rather than oxidizing effect. I misspoke when I first answered that question. Question from Roger. Can you give examples of fertilizer salts to be avoided to improve reduce conditions? Yes, Roger, it's very easy. Any, any fertilizer that can be termed soluble, in other words, anything that can be dissolved into separate ions in a water solution. So phosphorus, like DAP MAP applications, basically anything that can be considered a salt fertilizer, it's called a salt fertilizer not because it contains sodium chloride, but because the ions within it disassociate. So if you have sodium chloride, you add it to water, the sodium becomes one ion, the chloride becomes a separate ion, they disassociate. So that is. And the same can be true of potassium chloride. Potassium chloride is a salt fertilizer. So any fertilizer that has a high electrical conductivity that disassociates into ions, that is termed a salt fertilizer, is going to have a strong oxidizing effect. If you get some fertilizer into a cut on your finger and it burns, that burning is oxidation of the cells. It's the same thing that happens when you add these fertilizers to soil and they become come in contact with living biology. Question on our AEA rebound line yes, our rebound line of trace minerals is in the reduced form and they are chelated. And by the way, chelation and being in the reduced form are two different things. It's possible to be in it's possible to be chelated and be oxidized. It's important that they be both Question Will facultative anaerobic bacteria increase reduction potential of soil? I answer I talked about this in a previous webinar, but in brief, it is the facultative aerobes and the facultative anaerobes that have a reducing effect on the soil. Question from Niels Korfeld hi Niels, can the reference text of When Weeds Talk by Jay McCammon be cross referenced with Redox? If so, how to translate these tables? Niels My guess is that the answer is yes. We could possibly cross reference that with the work that has been done in France and begin connecting those dots and put those pieces together. So I would anticipate there are many leaps that we can make. For example, if we have a particular plant species that is known to significantly increase the availability of manganese and iron and phosphorus, there is a very good probability that that plant likely has a strong reducing effect, because that's a common characteristic that is shared by all the plants that we know that have a reducing effect. If there is a plant that enhances Another way of thinking about reduction versus Oxidation from a biological perspective is thinking about nitrification versus denitrification. So are there plant species that encourage nitrification? Are there plant species that encourage denitrification? Those are simply different words to describe having an oxidizing effect or having a reducing effect. This is a great question or comment from Thomas Robinson. Follow up to Greg Pennyroy's question. A comment the longer we go down the regenerative agriculture path and reduce synthetic fertilizers, keeping the ground covered and with zero till, we have more and more wild oats growing in our crops. Is this telling me that I need to grow oats to reduce my soil further, or is my soil becoming reducing? That's a fast. That's a great observation, Thomas, and a great question. It's very common to observe weed patterns changing as soil health and soil microbial population shift. So what are the oats telling us about your soil profile? Well, first of all, I do know that modern domesticated oats have a very strong reducing effect, but that's not necessarily true of wild oats I've heard the story of Don Huber may have discussed it on our podcast, but we've certainly talked about stories that he has shared about how oats were bred to become resistant to a specific disease. And when that disease resistance was produced, it also shifted oats from being an oxidizing, having an oxidizing effect to having a reducing effect. So my guess would almost be that there's a good probability that wild oats are probably oxidizers. But I don't know that for sure. And however you raise another part of your question, one of the ways to think about the plants that show up in a certain ecosystem is that they are there to help bring that ecosystem into a more optimal balance. And what I have observed and experienced hundreds of times is that the fastest way to rebuild and regenerate soils is to use as cover crops those plants which desire to grow there. In fact, we have I've had, I don't know, dozens of experiences over the years where, for whatever reason, climactic reasons or whatever the reasons might have been, farmers were unable to get a cover crop planted in time. And they grew a luxurious crop of weeds. When they incorporated those weeds or terminated them, whatever happened when they grew the weeds as a cover crop and they just let them grow, then turn them back into the soil, that changed the soil faster than almost any cover crop that I have observed. And it's because those soils are there to correct and fix the precise problem that that soil, excuse me, those weeds are there. Those plant species are there to fix the precise problem that the soil has. So why don't we take advantage of that? Why don't we use that to our advantage? Question from Beth Goodwin could you give us the name of the work done in France which needs translation? I don't recall it off the top of my head, but it is linked in the show notes on the Olivier Houston podcast. And it might also be linked on the blog post where I introduced Olivier's work on the blog. I know for sure it's on the podcast. Show Notes Question from Stephanie Parker if soluble fertilizers have an oxidizing effect the soil microbes, would they also inhibit the pathogenic ones? No, the exact opposite. They enhance the pathogenic ones because the pathogenic ones are oxidizers, which is something that Olivier describes in some detail in his course Question from Anthony Granatelli. Hi Anthony, when some apply elemental sulfur to reduce soil ph, how can this affect the composition of soil biology? I've not seen lab tests to actually know for certain how it changes the soil biology. I'm quite certain that it does. I mean, you can imagine particularly higher application rates. That's quite a PH shock to the system when ph drops by two full points in a matter of 14 days, which I've observed. So there is a definite shock to the biological system. I'm confident of that. I have not often observed that to have a negative effect on crop health though, which is interesting when I stop to think about it because I've never thought about it quite in those terms. I know Elaine Ingham, I shouldn't actually say that. I know I have heard that Elaine Ingham and other microbiologists have indicated that high application rates of elemental sulfur are very detrimental to soil biology. And I can imagine that that would be the case. But when we think about it from a plant health perspective and a long term soil ecosystem health perspective, I've actually tended to see more positive responses in the long term. And I can't recall that I've seen any negative responses in the long term, although there might be short term negative responses. Question from Joe Volk. Will adding sugar to the soil lower oxidation? The answer is it depends on the type of sugar and it depends on the type of biology that you are feeding. And so I actually have a blog post that I wrote just before this webinar that is going out tomorrow morning where I talk about this in some detail. In the blog post a couple of days ago, Robert Kramer described how genetically modified plants have a pathogen enhancing effect, the disease enhancing effect, because of the types of sugars that they sent out through their root system. And whereas other crops have a disease suppressive effect because of the types of sugars they send out through their root system, it's really about sugar quality and the microbial community that is already present. Question from Darren Petzer Is all organic matter not created equal regarding it being an electron reservoir? Darren, I love the question. My understanding is that it is not. It depends on. Depends on a lot of things, but it depends principally in my understanding on the biophysics of the environment in which that organic matter was created. So if you want to dig into that a bit more deeply. Olivier Houson is the co author on a paper describing how to produce and the effects of paramagnetic biochar. So we know that biochar is a very strong electron sink and electron channel, but biochar can have radically different effects depending on whether it is paramagnetic or diamagnetic. And the majority of what is commercially available and used is diamagnetic. So it depends on the soil's paramagnetism. It depends on the soil's electrical conductivity. There's a lot of factors of the biophysics of the environment, when that organic matter was created, that determine its capacity to hold, absorb, and store and release electrons. Question from rod. Are oats reducing at all growth stages, specifically early growth for northern climates? Would it have reducing enough effects to show results with a couple weeks of growth? Would it be worth our time? The answer is yes, they are reducing at all growth stages, and the degree of their reducing effect is going to correspond to the quantity of carbohydrates that they send out through their root system as root exudates, because it is really the root exudates that drive the reducing effect in the soil microbial community. And so for oats, or for any crop for that matter, the majority of the root exudates occur during the vegetative stages, because the moment you start approaching reproduction, then the majority of the carbohydrates go, of course, into the grain. So the answer is that even when you only have a couple of weeks of growth, they will have a reducing effect. And I think it'll be something worth considering for sure. Question from Malcolm. Can you elaborate on the way silicon levels rise in SAP analysis when biology is good, and its relationship to redox? That's a great question, Malcolm, and I haven't thought about it quite in the redox context up to this point. The form of silicon that plants can absorb from a chemistry perspective. And again, I don't believe this is a chemistry process, but it is described from a chemistry perspective as being monosilicic acid, which is, as you can tell from the name, an acid, and would be in the reduced state. So we have observed on SAP analysis that there is. We can actually almost. We can use silicon levels on a SAP analysis as an analog indicator for biological activity in the soil profile, because the better silicon absorption we have, the better biological activity we have in the soil profile. And you raise an interesting point, and it's worth digging into a bit more deeply. But there's a good probability that that is actually an indicator of better reducing activity. Can diluted apple cider vinegar help reduce oxidized soil? The answer is yes, it can, because apple cider vinegar is a very strong reducing material, and you may have to apply reasonably large quantities of it. But there's actually, this brings to mind these are the types of materials, these natural fermentation materials that we should try to use, if possible, and try to find uses for natural ecosystems. There is a small group of growers that are experimenting with applying waste sauerkraut juice to help remediate pesticide accumulation in the soil. They have to be concerned, of course, with sodium and chloride levels because there's a lot of salt added to the sauerkraut during the fermenting process. But this has been the first year they're trying it. We're still waiting for end of year results, but the crop response has been very interesting. Crops have responded very well. This is specifically on corn and soybeans. They have responded very well to the application of about 10 gallons per acre of fermented sauerkraut juice. So I think those types of fermented materials, remember these are all these are highly reduced materials. Apple cider vinegar is extremely reduced sauerkraut. So forth Question from Luke Are you familiar with any data regarding the application of lime and soil carbon content over time? How is ph affecting the mineralization of carbon and the ability of microbial communities to grow? This is part of my college research project, yet I have not found significant literature on the topic. Luke, this is a fascinating question. There is some literature on the topic. It is going to be related to the influence of basalt on producing rapid weathering reactions and carbon sequestration. The literature might not all be there, but if you follow the logic dots, then these reactions that are occurring to rapidly sequester carbon from rapid weathering are reducing reactions and limestone is going to contribute an oxidizing reaction because of the presence of oxygen.