Episode 146: Logan Labs, Soil Testing, & Nitrogen Management with Bryant Mason

Welcome to the Cannabis Cultivation and Science Podcast. I'm your host Tad Hussey of KISS Organics. This is the podcast where we discuss the cutting edge of growing from a science based perspective and draw on top experts from around the industry to share their wisdom and knowledge. My guest this week is Bryant Mason. I've had Bryant on the podcast a few times in the past and he's one of my favorite guests. Bryant is a certified Crop advisor who specializes in organic cannabis nutrition. He has spent the last eight years working to combine precision laboratory techniques with data science in an effort to unravel the complexities of cannabis soil and crop nutrition. Along with his work on soilless media, he also helps outdoor cultivators around the United States with nutrient management and cover cropping. If you would like to do soil testing, help interpreting a soil test, or are interested in an online course on these subjects. His website is www.soildoctorconsulting.com and if you want to save $100 on his course, you can use the discount code Kisorganics all one word. I've taken this course and was recently going back to review some of the content. It's excellent and I highly recommend it for anyone wanting to do a deep dive on cannabis fertility and reusing your soil. Now, after recording the podcast with Bryant, he had a couple of points he wanted to clarify, so there is a short addendum that I added in at the very beginning of the podcast. Now onto the show, hey Bryant, I know you wanted to, after recording the podcast, come back on and talk a little bit more about some of these topics that we covered in the podcast. Let's just dive right into the first part, which was where we discussed Logan Labs and one of the questions I'm seeing from my most recent post on social media is do we need to retest? Are these tests that we got during this period, which we'll get into a little more detail with here. As you listen to the podcast, are these tests erroneous or can we still utilize that data?

It's a great question. The majority of the data on those tests is totally accurate. For one thing, the soil report, what I call the standard test, is, is accurate and most of the paste information is is accurate or fairly accurate. What I've been telling growers, at least in the period of time where sulfur chloride and a few of the cations were elevated, is really if your plants look good and you're not seeing any problems related to salt stress, then there really isn't any need to retest. You can just retest at your normal interval and you'll see the updated, more accurate data. So just take those numbers with a grain of salt. And in terms of the interpretation, if you're seeing really, really high numbers, I would suggest not leeching and just sort of ignoring them for the time being. If your plants look good, and this.

Is something we just talked about off air, but essentially this is a good rule of thumb anyway. So typically if we see high ec, high soluble salts from, I know you listed sulfur, I'm thinking more of like chloride, sodium nitrates, then you'll typically recommend leaching the beds to reduce those numbers down to a better level to reduce osmotic pressure on the root system. It's just easier for the plants to take up nutrients. However, if your plants look great and you're not seeing that reflected what's showing on the test reflected on in your plants, what's your recommendation then?

Yeah, this is a good nuance to cover because I have thresholds at which I recommend leaching and the idea is we're trying to optimize even if the plants are relatively healthy, if we can reduce the osmotic stress to the roots, you can have better, healthier plants that are higher yielding. But there's a, there's a line between what's operationally feasible and the marginal improvement in, in plant health. That really has to be an on site decision. So if your plants look healthy and you're very satisfied with the production, then then you may not need to leech even when there's a leaching recommendation. And that's just really sort of a, of a, a grower decision. Now I, I'd say that if you, if you see any poor plant health or negative symptoms then I would absolutely recommend leaching when levels are high. And this is just in general, so.

There isn't a magic number. I mean we have thresholds where, you know, if you were at 300 chlorides, we would recommend leaching at 300 ppm. However, if your plants look great and you're not seeing any visual symptoms and leaching is, you know, obviously a lot of work, it's a lot of water, it's labor intensive, it's material intensive in terms of the amount of water you have to use, you don't necessarily have to do that. There is no magic number that above that number your plants are going to look like crap and suffer or below that number your plants are going to be amazing. It's really just what we've seen based on looking at hundreds, if not thousands of these soil tests and sort of where we think that this, this level sort of exists, but it is a very arbitrary number.

Well, yeah, and, and the reason that there's not a hard and fast number is because the, the osmotic problem gets worse when evaporation rates are higher. So high temperature, high airflow, high radiation is when the plant needs to be uptaking more water. And so oftentimes that higher EC is preventing it from doing so. And that's when you start to see issues. So the environmental conditions are going to in many ways determine when the plants are actually suffering from osmotic stress. And so that's a number. Another reason these numbers are a little loose. Now if you're in the winter and it's temperatures are depressed or the radiation, you know, your PPFD is a little lower, your evaporation, your total evaporation is just on the lower side, then you might be able to get away with quite a bit higher levels of salts. So again it's, it's, you sort of have to determine how your plants are doing.

That's a great point. And I want to also add that there is the possibility of sampling error here where if a small amount of fishbone meal or alfalfa meal or whatever organic amendment, gypsum ends up in your tiny sample, that could dramatically skew your results and, and show numbers that might be higher than what's actually in your soil or reflected in your soil. Because one of the things that you mentioned in this podcast is later on is that soil is not homogeneous. We, we think of it as homogeneous, but really it's, it's not homogeneous at all. Even with these potting soils. So through no fault of the lab, potentially the results could be skewed just from, from sampling.

Yes, that. So I, I sometimes have that concern with nitrogen because it's on the soil report and the scoop size is quite small. But when it comes to most the soluble salts, I'm looking at them on the paste report and the sample size is a cup. So it, that does help eliminate, you know, a small chunk of one thing or the other because the sample is quite large when we're looking at the past phase test. But it's a, it's a, it's a valid point to consider. And yeah, I mean when we were talking about ph reactions, that's really where there's these very small, there's, there's a non homogeneous soil. So there's small pockets of low ph, high ph. The rhizosphere is different. There's not the bulk. Soil ph is a bit of a misnomer in the sense that there's just many different pockets of. Of different chemistry in a soil.

I think that's a good transition into the conversation that we had on the podcast about nitrogen. And there was a couple of things that you wanted to go back and clarify around that, that topic. Do you want to share that?

Yeah, thanks. I. We hung up after the initial podcast and I thought, you know, my, my answer to your question on how nitrogen amendments affects ph wasn't totally precise when I thought about it more so I just want to clarify. So we talked about the nitrogen conversion process. When nitrogen mineralizes from organic nitrogen to ammonium, there's a slight increase in ph because the ammonia combines with a hydrogen ion to create ammonium. So and that consumes a hydrogen ion, and that will therefore increase the ph. Then in that second part of the nitrogen conversion process, when ammonium goes to nitrate, there's actually a decrease in ph, and that's because it goes to nitrite and then to nitrate. And in both of those steps, hydrogen ions are released. So that's going to acidify the soil. And so the, the. There is a slightly acidifying effect when organic nitrogen converts to nitrate. I said that there's a net zero effect in the PH change. And so technically the nitrogen conversion process acidifying. But the reason that I generally don't see a ph change in living soils is because there's also the influence of. Of the. The characteristics of the amendment that you're using. So, for example, when alfalfa meal mineralizes, there's a number of base cations that are contributing that are contributed to the soil that more than offset the acidity contributed by the nitrification. Now, other amendments, and I use this example to you, is cottonseed meal. Not that many people use cottonseed meal. It contributes a lot of sulfur and not many base cations. So it can have a strong acidic acidifying effect. But both of these are sort of independent from the nitrogen conversion process. So there's the ph effect from nitrogen conversion, and then there's the ph effect from the actual characteristics and the chemistry of the amendment. And both of those are different. And that's ultimately what's going to determine the net ph change when you apply a nitrogen amendment. And what I see generally is not much change in a living soil. The other reason is living soils have more buffering capacity. So if there is slight downward pressure or upward pressure from the amendment being applied, the soil is often buffering. That and there's not a huge change, but, you know, there's always exceptions. And I think a lot of it depends on the rate of mineralization and the quantity of amendment being used. And then, like I said, the. Which amendment you're applying, so. So there's a lot of variables.

So you're saying essentially something like alfalfa meal or fishbone meal is giving you more than just nitrogen conversion. It's also giving you calcium or magnesium or these other cations that are going to put upward pressure on ph, therefore sort of neutralizing the effects of this nitrogen cycling that's occurring from a ph perspective.

That's exactly right.

So I guess my. The reason I asked this question, what I was thinking in my head and I didn't fully explain this, was if I already have a freshly mixed soil where that nitrogen is in the form of ammonium. And in my head I'm thinking, okay, that's going to be, if anything, raising ph slightly because it's showing as ammonium, and my ph is 626 1. When that ammonium converts by ph is certainly not going up. If anything, it may drop a point or slightly, depending on how these other factors come into play. And like you mentioned, the buffering capacity. But my expectation is that ph is going to maintain or drop, and it's already low. So I like to wait to take the soil test after, you know, wait for that nitrogen to cycle. And I do sometimes see the ph drop a little bit, because on the flip side, when I have a very high ph, you know, if I were to test the soil right away and I'm 7:3, I might see a drop down just slightly. Does that make any sense?

Yeah, it does. And we have to keep in mind that these can. This conversion process is actually happening simultaneously. And there's. You're at different steps in the process, you know, depending on the different particles of nitrogen. So when ammonium is elevating, yeah, you're seeing the ph go up, but at the same time, there's also ammonium going to nitrate, that's putting pressure down. So you can never really pinpoint what's going to happen next. And I think what you're saying is accurate is just wait, just wait till it cooks or mineralizes, whatever you want to say, and sort of levels out wherever it's going to end up. And that's when you want to test it and make decisions.

Great. And one other thing you mentioned later in the podcast, just for folks that you didn't mention just now, is that there is this organic Pool of nitrogen. And you'll explain more about that later in the podcast. But for people who are just listening, I don't want you to think we're ignoring a major source of nitrogen here in this conversation. We're just hyper focused on this one aspect of something. We elaborate on podcast cool. And then there was one other topic that you wanted to just offer some clarification around. I'll be honest, it's not. I'm not as informed around environmental controls and some of that. So I'm going to let you just kind of explain. Explain that.

Yeah, I was just sort of explaining a scenario in which it's possible to cool your greenhouse by venting, even if the outside air is warmer than the inside of your greenhouse, which sounds. It's completely counterintuitive, it sounds impossible, but you can bring in warmer air and it can actually cool your greenhouse. And the reason is that's possible is because temperature changes when there's a change in total energy. So in other words, the temperature of your greenhouse will only change if the enthalpy increases or decreases. And enthalpy is a, is a combination of temperature and relative humidity. So let's say it's super hot outside. It's like 97 degrees Fahrenheit and very dry, 20% relative humidity, and you're in. And your greenhouse is slightly cooler, maybe 95 degrees Fahrenheit, Fahrenheit and 40% relative humidity. If you vent, the temperature in your greenhouse will actually drop because there's a reduction in enthalpy. So this is just one very niche example of what I was explaining has been kind of blowing my mind as I, as I go deeper into the. The science of energy balance and, and ventilation optimization for greenhouses.

Very cool. Well, thanks for clarifying those points and coming back on, and I hope folks continue to listen as we start the rest of the podcast here. Hey, Bryant, you're a popular guest. Thanks for coming back on the show today.

Thanks for having me again. I'm excited to be here.

Yeah. Well, for people who are unfamiliar, please do go back and check out the previous podcasts that I've done with Bryant if you want to get an idea of some of the things we've already talked about. But we have some new topics for today. And let's just start off talking about Logan Labs a little bit and lab testing in general, because just to throw it out there, I know you found some inconsistencies in the test results starting around in August, and I'd seen some things too, on my End that were often. We'd both reached out to Logan, we'd reached out, we talked to each other about this, and some other people had reached out to us. Can you just give us a little more context of what was going on and, and where to go from here?

Yeah, sure. Like you said, In August of 2024, I saw a number of tests that were all very elevated in sulfur on the saturated paste test. So soluble sulfur and abnormally high levels. And I pretty much within a day or two, I told the lab, and this type of thing happens occasionally, and the lab is very responsive to this type of feedback because I'm looking at so many tests and I'm one of their partner agronomists, they jumped on it and they brought in what's called an ICP technician. And ICP is the advanced piece of equipment that actually looks and determines nutrient concentrations. The technician serviced the instrument, calibrated it. They went through multiple sort of steps in qc. But unfortunately, the issue seemed to persist for, for a while. And I've just been thinking about it and working with them slowly throughout the months, and it took a while to figure it out. But ultimately I can just tell you we can jump into what was going on.

Before you do, can you just talk about what the issue was that we were, that we were all seeing on our test results?

Mostly elevated levels of sulfur, but also slightly elevated levels of chloride. And a few of the cations, calcium, magnesium, potassium, although those were less so than, than sulfur. Now, with that higher sulfur and chloride number, the, the soluble salts number was therefore a little bit higher because that's one of the components of soluble salts. So what that led to was not necessarily an over application of anything, but rather an under application in certain instances, because as, as someone writing recommendations, I would see high levels of sulfur. And so I started, for example, suggesting potassium silicate instead of potassium sulfate in some instances. I also use what I call a governor in the soil doctor Tool algorithm. Like a car has a governor that prevents you from going too fast. I essentially stop the use of gypsum and potassium sulfate above very, very elevated levels of sulfur. So in really high EC situations, some of the recommendations didn't include gypsum or potassium sulfate. And then the final thing which we've discussed is in some instances, I was telling growers to leach their soil. So essentially to flush the excess levels of chloride, sulfur, and I guess sodium as a, as a fourth cation I didn't mention out of their soil to reduce the EC to reduce those levels. So those Are the substantial things that were happening in the recommendations due to these elevated levels. Now, to be clear, that wasn't happening in all or even most of the recommendations, but definitely in some instances that was happening.

That's great. And I also want to add a couple, just a little thing, more context here. So, and you already know this, but for folks who are unfamiliar, sulfur in general is a pretty safe mineral in the sense that high levels of sulfur are not really having negative impacts on your plants. You're not going to see a sulfur toxicity per se. The issue there is it's going to raise the EC or the soluble salt level of your soil and potentially lead to a little bit more osmotic pressure on the roots, making it harder for your roots have to work harder to pull nutrients up versus a slightly lower ec. So that's the issue with sulfur. Now with the chlorides. I just want to emphasize that for folks that may have had the, may have been given a flushing recommendation, that that doesn't mean they were, you know, you were at 0 chlorides or 100 chlorides and all of a sudden it's reporting 400 plus chlorides and you're, you're having to flush. These are probably test results where you were borderline or on your way to needing to flush anyway. So it's not the worst thing, but obviously not ideal either. We want to be as targeted and accurate with these tests as possible.

I think that's really well said, especially on the sulfur front. I'll also add that for years I've been trying to figure out how to organically push calcium and potassium levels high without spiking the EC in the soluble salts, which is a very difficult challenge because we're using large quantities of just gypsum and potassium sulfate, in some instances Lang Benite, a lot of sulfur containing amendments. So to your point, sometimes leaching is a really great thing because you're just sort of pushing levels down. And also when I saw this, I changed my recommendations a bit, my thresholds, adjusting certain leaching thresholds. And so there was, you know, some self correction along the way because this has been going on for several months. But anyway, that's, that's a little background.

So let's, let's talk about what the actual issue was and how that relates to Logan and if it's even specific to Logan.

Yeah, so, and this is where I've spent a lot of time is not only figuring out the solution, but just sort of putting the solution in a larger framework of is this Logan specific? Is it Lab specific, et cetera. So what happened is Logan actually has really vigorous quality control. They recalibrate their ICP every 20 samples, which is far more than most labs. Some labs do it twice a day, some labs do it every hundred samples, but every 20 samples is very rigorous. And, and when they do that, they use what's called a standard, which is a calibration solution that's provided by the ICP company or technician. And unfortunately they were sold a standard solution, the high end. They have a low end standard solution and a high end solution to tell the machine what's low, what's high, and those are known values. And the high end solution, they were sold a bad solution that was overly concentrated. So they were calibrating that ICP machine to the wrong standard because they were sold the wrong liquid solution. And that's a really tough thing to figure out because they're continually recalibrating, they're cleaning everything, they're troubleshooting everything. But the known standard that's supposed to be ground truth was off. And so unfortunately it was just calibrating to the high side. I'll mention that any soils that were low, so usually traditionally topsoils, anything that's low in soluble salts really didn't have this issue because that lower standard was accurate. One of the reasons I love Logan and working with Logan is they participate in something called the NAPT North American Proficiency Testing Program. I believe there's 150 participating labs and it's a quality control level between labs. So they do a quarterly blind or double blind statistical evaluation of soil, plant and water samples. And there's essentially, you know, they're given a sample, they run it, and then this NAP program tells them how close they are, how precise they are to the known levels, and they compare it across 150 labs. And Logan always has an extremely precise score. So to me, that's always given me confidence with Logan. The problem is those samples are topsoil, they're low in nutrient concentrations. We're working with peat based medias that often were really pushing nutrition and EC quite a bit higher. So they were, they kept passing N A P T. But that's because it was on that, it was, it was a low concentration sample and we were seeing these issues in high concentration, high EC soils.

Yeah, that's a great point. And for those unfamiliar as well with ICP machines, we're talking parts per million here. Parts per billion in some cases. So they're extremely, I guess, accurate in that regard. Now when we're talking about Such small amounts, there's just greater opportunity for sampling error and for other things too, to keep in mind. So one of the things that I always try to emphasize with the growers we work with is if we have a test result that is just really far off the standard that we expect it to be, then we can always, you know, we can, we can always ask Logan to retest it, or we can assume that maybe something got into that sample to contaminate it. Maybe there was a piece of, like fishbone meal, for example, that was undissolved, ended up in there and suddenly our phosphorus levels are just through the roof and our ph has dropped dramatically or, or, you know, something like that. So it's always good to take these tests, I think, with a small grain of salt. I think they're the most useful tool that we have agronomically for making data driven decisions about our garden and about our soil. But it's still not perfect. And it's, it's never going to be perfect. And then on that note, I think, okay, well, so Logan had this issue. It wasn't really their fault, but unfortunately it happened. Um, what about switching to another lab? Well, this could have happened in any lab. So it's not necessarily unique to them in that sense. And if you were to switch labs, like, I know that's something, you know, you and I talked about, like, what, what does that really look like for a grower? The one thing it does mean is you're really, you're starting over in a sense. You can't take your old Logan tests and then correlate them with your new tests at the, the other, the next lab you go to, you know, and there's so many labs out there, so whatever lab you go with, you kind of need to stay with because these test results don't. It. It's like apples to oranges, I guess. So I just wanted to share a little bit more around this idea also.

Yeah, I want to add one thing which is that this act, these issues actually happen at all labs, unfortunately, and you just don't know. And so the reason I've personally committed deeply to Logan A is because of what you're saying. So I can really calibrate to one lab and have a very extensive database that I'm comfortable with. But also I can see these issues. I'm so familiar with the data, their process, the people in the lab, everything that when these issues do arise, I can see them and identify them very quickly. And this is part of the. Even though it took a long time to solve the problem. I was able to help them solve that problem. And so it's sort of, it's been sort of a mutual and collaborative process. And if you go to another lab and you're just doing, let's say one to even up to 100 tests per year, you're not going to see that. And so you're not going to know when issues arise. So for me and the growers I work with, I think there's actually a major benefit to being deeply committed and involved with One Labs data set because at least I know what's happening.

Yeah, I would guess we see probably about a thousand tests a year. I'm guessing you're significantly higher than that with the number of growers you work with. So you do have this database that builds up over time. And so yeah, if you suddenly see a 20 increase in, in your soluble salts across all your tests starting on this date, that's a really good clue. And I know you're working with Logan for instituting, you know, even more additional controls to hopefully match these sorts of things in the future.

Yeah, let me mention that so that the, you can recalibrate the machine over and over again. But if it's still giving high levels, what does that mean? And so I actually went back into our database. So internally we anonymously put all the tests into a database and then we essentially ran statistics looking at the average levels before and after August of 2024. And the, the trend was clear, specifically with sulfur. We also looked at the variation between months, et cetera. It was statistics. And so we're, I'm working with them to actually institute another step of, of QC where they, they look at their own internal database, see how close it is month to month or quarter to quarter. Especially when these, when these issues arise, they can just look straight to the database instead of continuing to try to figure out the equipment malfunction.

Yeah, and if folks have questions about this, I'd say feel free to reach out to me. I assume you can reach out to you Bryant definitely, or even Logan directly. But this issue has been corrected as of what date? Bryant?

Mid March. I don't, I'd have to go back and look at the exact date. But yeah, if you see, you know, if you have a test and you're thinking why is chloride 450ppm? It's so that doesn't make any sense to me. It's always been quite a bit lower. And your test result was before mid March. I would assume you're fine. You could probably, if they still have your sample, they could rerun it for you. But ultimately, anything after mid March will be accurate. And I think I've gotten some questions around. Well, is it. How can I still use these tests? Absolutely. I mean, I would just look at specifically sulfur and chloride with a grain of salt. And you can assume, you know, on average, looking at a few thousand samples before August of 2024 and about a thousand after. The other cations are. There's a lot of variability, but let's just say 25% elevated. So it's not going to change your management decisions very dramatically. And you can still use the data, and most of the data is still very good. So that's sort of what I would say. We wrote a lot of really good recommendations with very small things I mentioned that may have been different, but the data is still good. Just take it with a grain of salt.

And the good news in this is, if anything, you might have underapplied nutrients, which is always vastly preferred over. Over applying nutrients.

Absolutely, I would have. And if I saw the trend go in the other direction, where I was seeing things weight artificially low, leading to excessive high application rates, I would have taken much more aggressive action because that's such a higher risk. But instead, we kind of took the slow route, didn't, didn't sort of overreact and figured it out over time. I also just want to say that I think you and I both are huge believers in transparency, and that's why we're actually talking about it. We want people to know this because ultimately I feel like that is what builds trust and credibility as opposed to covering things up, which, again, is kind of what happens in other labs. They see internal issues and they fix them, but they don't really say anything about it. So I think we were both eager to actually talk about it. Yeah.

And I want to be clear because there was. There were a couple growers who reached out to me directly, and I was not aware of the full solution until very recently, within the last couple weeks. So what I. What I knew prior to that date was I had reached out to Susan. We had. We'd scheduled a meeting. We went. We went through tests. We went through sort of their protocols and how they do these tests, which was. Which, you know, was. Was really interesting. And I learned some things in that process which was great. But, you know, they hadn't changed any of their staffing, they hadn't changed any of their procedures. And so if you had talked to me prior to, you know, our Conversation Bryant, you know, a week ago, whenever that was, I would have told you that, like, as far as I know, I'm not aware of any issues. And this is, this is where we're at with it. But we, we have seen some inconsistencies with higher numbers. So I just want to throw that out there because I, I, there's some people that have been pretty vocal about this on, online and yeah, it's a little bit of vindication for them. But also I want to make sure that we're approaching it in a way that's solution driven, I guess, so we can all continue on. Definitely. Great. So moving on, you brought up, you mentioned nitrogen and I just want to talk a little bit about nitrogen. I'm going to, I know we have a list here we're working off. I want to jump around a little bit. First off, before we dive into your, your topic on nitrogen, I wanted to say can we talk a little bit about how nitrogen cycles and how we see it on, on these soil tests and its impact on ph. Because what we know that that night, that the cannabis wants nitrogen in the form of nitrates for the most part. And when we first add compost, when we first mix our soils, we're going to see a lower nitrate number and a, you know, high, what we would consider a high ammonium number, not high relative to the nitrate number, ammonium, you know, maybe like a three or a six or something like that. But how does that, how does that cycling process really work and what is the impact and implications for a grower?

Great. So for the most part, growers, in living soil, organic growers are only applying organic forms of nitrogen. So nitrogen in the form of proteins and amino acids. But let's just say soybean meal, alfalfa meal, blood meal, all these are actually full proteins. The biology in the soil mineralizes those organic forms of nitrogen into smaller and smaller organic compounds. So they take a protein, they turn into amino acid, for example, and the plant actually can uptake those organic forms of nitrogen. And it's not the primary form of nitrogen that's uptaken even in organic soils where you're just feeding amino acids and organic compounds. But it is a plant available form of nitrogen that's very, very beneficial when the plant does uptake it. And that's typically skipped in the scientific literature because Most, I'd say 99% of studies use the inorganic forms, which are ammonium and nitrate. So in our systems, the plants, we can assume the plants are uptaking a certain amount of organic Nitrogen. So once it's turned into organic nitrogen, a different set of biology transforms it into ammonium very, very quickly. In a warm, moist soil, this, these, this transition happens very, very quickly. And then a different set of, of bacteria convert the ammonium into nitrate. So nitrate is, is the final form. All of the organic nitrogen we apply to the soil eventually ends up as nitrate. And it's a pretty quick transition from ammonium to nitrate as well. And in again with the conditions we're talking about. So you can sort of see where your soil is in that mineralization process based on that level of ammonia, that middle step. The weakness of soil testing is it doesn't show us the entire quantity of organic nitrogen in the soil. We're only seeing those final two pools of nitrogen, ammonium and nitrate. So you can sort of gauge how much nitrogen is in the soil just based on ammonium and nitrate. And you can see how mineralized it is based on how low ammonium is and how high nitrate is. So I hope that makes sense. I mean, essentially what we're doing is we're just throwing nitrogen into the organic bucket, and the biology is transforming it pretty quickly into the nitrate bucket. So when I see ammonium, let's say over 2 or 3 ppm, I can assume that there was some sort of nitrogen previously applied fairly recently, and it's still moving into nitrate. It is true that you definitely. So let's say we were in a hydro system and you fed 100% ammonium ammonium sulfate or something versus 100% nitrate. So I don't know. Let's just say calcium nitrate. The cannabis plant absolutely will perform better in the nitrate scenario. But the soils we're working in, again, they have a lot of access to amino acids and small organic compounds. The ammonium tends to be pretty low. The nitrogen or the nitrate tends to be pretty high. Just because that conversion process is happening so quickly. So, you know, in organic systems, you're not actually, you don't really have much control over whether the, the nitrogen is in the ammonium or nitrate form, other than time. You can wait longer and it'll all convert to nitrate.

Yeah. A couple other things around that that I'd like to add is. So we. So we have this organic pool of nitrogen that's. It's essentially tied up within the microorganisms, within the organic matter, within these fertilizers that we're adding, and it's being converted or cover crops that are breaking down. All those things are going to have nitrogen that's going to slowly be releasing it. Then this is the organic pool of nitrogen that we can't really measure as effectively. And that's what you're referring to there. And then it, you know, converts to ammonium like you said. Now ammonium. And this is where I want to get some, some clarification. You ammonium would put upward pressure on our ph, whereas nitrate, being an anion, would put negative downward pressure on ph. And where I see ammonium levels on soil tests is typically when people mix a soil and then send it in for a test right away or when they add compost or organic matter that's not fully composted. And the implications of that is our nitrate, nitrates and our nitrogen recommendation is just going to be a little bit harder to dial in. So ideally what we like to do with our soil tests is we, we mix the soil, we wait two to three weeks in and let me emphasize in warm conditions, if I did this in the winter in a pile outside, that nitrogen is not converting at a very quick, very fast rate and it's not going to, it's not going to switch to nitrates. But if we wait, you know, two to three weeks and then send in our soil test, the result we get back is going to be more accurate in terms of our nitrate levels, which will allow us to make a better decision about where we're at for nitrogen. And I would assume, and this is where I want your clarification, I would assume our ph would be a little more accurate too. I know you and I talked about this and you didn't feel like it change ph as much, but I have, I feel like I've seen that a little bit on tests. I don't know. What are your thoughts?

Yeah, so in a, in a living soil there's a, well first off there's way more buffering capacity and also these transitions happen quickly and sort of non homogeneously in the soil to a certain extent. So yes, in theory if you put down a large application of a fast releasing nitrogen source, that first conversion will drop the ph. So if you tested in the middle of like you amended the soil immediately took a test, you might see a dip in ph, especially in a soil that sort of doesn't have a lot of buffering capacity. But typically if you wait a few.

Weeks, a drop or a raise, wouldn't you see a raise from the ammonium?

Well, so you would see an increase at first and then a drop. So, so, but again, I don't actually see that in, in most peat based soils, I just don't I. I can't even think of an instance when I've seen that. And I believe that's because I'm telling people to. To wait and to let the full conversion process happen. And I also just think that I'm not even sure in most soils that that is that visual. Maybe a couple tenths of a PH drop. Are you seeing significant PH drops? Like the soil's at a 6, 8, and it drops to a 5, 5, that type of thing?

It's hard for me to say because I don't see enough tests, like in a row, you know, two weeks apart or three weeks apart, right to where I can really say. But I do see a tr. I do worry that if I see a high ammonium number, and I know that's going for in nitrates, and I'm already at a low pH, you know, six, three or something, I'm worried that that ph, as those nitrates mineralize, could potentially drop further. I know you're less concerned about that, but I just. Something I was thinking of. One thing I do want to highlight, though, that you said is that we're. We're. These soils are not homogenous. We're acting like soil is homogeneous. It's not. There's all these different pockets.

Exactly.

Phs and mineralization and nutrient availability, microbes. And I just think that's important for people to try and keep in mind. It's really like. It's like visualizing space. I don't feel like we can fully understand it. But also the other thing with this nitrogen conversion, especially when we add nutrients to the soil, if we add a large amount of fertility, we really have to treat it like a. Like a thermophilic compost in the sense that that soil potentially is going to heat up because the bacteria is reproducing so rapidly as they get this food source. And the concern with that is that it's going to make it inhospitable to plant roots or less hospitable plant roots. So that's another reason when I see a higher ammonium number, I say, okay, let's not plant yet. We need to let the soil cycle a little further to allow this nitrogen to convert, make sure the soil temperature is good, not too hot, so that nitrogen is available.

Yeah, I think when. When a soil heats up, it's. It's just tons of cellular respiration happening with the bacteria primarily, and they're actually consuming a lot of oxygen. So my. My fear is you're just. You're planting into a low oxygen environment because the microbes are using so much oxygen. And as you mentioned previously, definitely a really young plant isn't going to want a high ammonium nitrogen environment. So waiting is preferable. But I just want to emphasize when you put it in organic nitrogen that the net change in ph should be zero. So yes, you're going to get, you're going to get a fluctuation, boop boop. But that conversion process is quick, it super dynamic and so to try to manage the ph during that blip of time doesn't make sense to me because it should start at 7 and end at 7, for example. Now if you are using, and if you use a non organic form of nitrogen, it's different. So. But we're primarily talking about organic amendments here.

Yeah, I guess the context for me is more like I see a soil test on freshly mixed soil that is a low ph, high ammonium. I worry that it may drop a little further because we don't know where we're starting with that mix. Whereas like you said with re amendment with nitrogen, that makes a lot of sense. That's really useful. Now one thing that you also wanted to talk about was why nitrogen targets in living soil that's being used multiple rounds might be different than other cultivation methods.

Yeah, this is, this is something that I think is an important point that I've thought about a lot, honestly for years. The a soil fresh out of the bag, you know, my target level of nitrogen which is should, should totally be based on the soil volume per plant, the length of time the plant is in the soil, how much supplemental feeding is done, et cetera. But generally speaking, 100 to 150 ppm of nitrate, nitrogen, low ammonium shows that the soil is fully mineralized. That's a really good target number. Every time I test a fresh kiss soil it's somewhere, you know, approximately in that range. Also let me just add actually one nuance here. Testing a fresh soil out of the bag is going to be less accurate than testing a soil after it's been through a round. It's just always less homogeneous even if you mix it super super well. But point being, if you're somewhere in that, let's say 100 ppm, 125 ppm range, that's a lot of nitrogen. What happens though if you use the soil, let's say 10 rounds in a row is every round you're applying more organic nitrogen, more alfalfa meal, more compost, more granular poultry, manure, whatever, and the majority of that nitrogen in that, in those amendments. And that compost does get broken down within a round, but a lot of it remains because of two things, the carbon and nitrogen ratio and the particle size. So if you put in a big wood, if you put, drop a wood chip into the soil, that's going to take a fairly long time to mineralize and to, to decompose in your soil compared to a tiny little particle of blood meal which is really, really high in nitrogen, low in carbon, and has a small particle size. So as you put in all this organic nitrogen over time, not all of it's releasing and you start to build this reservoir of organic nitrogen that's releasing slowly. And so over many rounds, you actually have this, this large reservoir of nitrogen that is releasing slowly that we're not seeing on a soil test. And so in general, I think growers who are, who are on multiple rounds in the same soil can start to lower their nitrogen target well below 125 ppm. And I've gotten feedback from growers who are in, you know, around 25 that that my nitrogen target feels a little too high in their soils and that they're actually getting really good results with. And their plants are finishing at a coloration they like, a greenness level they like with much, much lower levels. And I just think that's because they have 25 rounds of alfalfa meal application that's still slowly mineralizing. So for example, in agronomy, you assume that 50% of a compost would become available in year one, 25 the next year, 25% the third year. So we can sort of think of it as that there's sort of a staggering release rate across some of these amendments.

Yeah, I would expect release rates to be faster in soilless media because we have, you know, more biology, warmer temperatures and controlled environment agriculture, you know, indoors. But I think the principle of it still makes a lot.

Absolutely. Just think of that 50, 25, 25 as a principle and not as, as a, as a rule to follow in, in the soils we're talking about.

Yeah, I don't have a lot to add to that. I think that's really interesting and I think that's a very good point. And we do, you know, we see the same thing. And the nice thing about nitrogen is it's pretty easy to add and it's pretty easy to visually see symptoms of. It's, it's the easiest deficiency. Well, and maybe even toxicity to really see in your plants. And too much nitrogen, you're gonna, you're gonna have Issues, you're gonna see the clawing, you're gonna see, you know, lower yields, potentially greater pest pressure. So really, having proper levels of nitrogen is, Is important. And then if you need to add nitrogen, I mean, fish hydrolysate is probably my favorite quick liquid feed that's affordable and not, you know, you're not buying a marketing branded product, I guess, per se.

Yeah, absolutely. That's one of two options I love. I. I'd also say that to me, the, the best bet, the best way to create your own internal nitrogen targets, internal meaning in your own operation, is to, is to just judge your plants at harvest. Did they fade too too fast and too early, or are they too green and too vegetative, too leafy at harvest, and, and look at where your nitrogen is and kind of adjust from there. I tell people this all the time where it's like, I'm going to recommend a certain amount of nitrogen to hit the nitrogen target. But ultimately you should be reading your plants like you said. And I think just where your last round ended is the best metric for that.

Yeah, my last round, which I shared on Instagram if people want to see, but I felt like I finished a little high in nitrogen. So I'll, I'll go through, get the test, get the recommendation, and then I, I'll probably take my nitrogen target and adjust it down by 15.

Exactly. That's exactly right.

But I'll still work off the same target and then I'll just lower it and then I'll see how that round goes. And if it's, if it's still high, you know, if it's high, then I can adjust it down further or if it starts to get low and I find I have to apply something. The other thing, you know, you could look at is, is blood meal would be another pretty fast nitrogen source that you mentioned. So, yeah, you could just make adjustments like that. I think that's a really good point. Something that's not on your list of topics, but something I wanted to talk about because I've been thinking a lot about it lately is, is rock dusts in living soils. I know certain mixes, like the coot mix, for example, recommends pretty high levels of rock dust, and people are always worried about getting their trace minerals. Now, my. Lately, the way I've been approaching it is one, you know, particle size is king here. The smaller the particle size, the sooner these, know, these rock dust will become available. But the amount of time it would take for the microbes to break it down for, you know, any sort of weathering and mineralization is not a timeline that I want for like production cannabis just because it's such an unknown variable. And then I worry that all of these rock dust are bringing in some level of heavy metals. And I'm just so hypervigilant about heavy metals these days with, you know, working with law facilities that are regulated for it, that I'm more inclined to lean towards sulfates or you know, just a tiny amount of rock dust, a tiny amount of kelp meal. I don't know. What are your thoughts on this? I know I'm throwing you a curveball. Not at all.

I never recommend rock dust or kelp meal in cannabis production primarily for a concern around heavy metals, but also I do not see them as a replacement for micronutrient sulfates. And when I say micronutrients, I'm talking about the five essential micronutrients, iron, manganese, zinc, copper and boron. There are dozens of non essential trace minerals that are brought in with rock dust and kelp meal that the plant doesn't need, but in theory would make it stronger. Could be a bio stimulant, could feed biology, could make some kind of expression happen. But personally I've, I've used rock dust and kelp meal for over a decade in my own growing and I've never seen amazing crop responses or any, I've actually never seen anything from rock dust. I've seen stuff from kelp meal but kelp meal also has a little bit of nitrogen in it and quite a bit of potassium. So it's tough to know exactly where that response is coming from. But in general you apply, you apply these products for the non essential trace minerals. You're never going to get a high enough quantity of the five essential micronutrients from those products. So they may help, they may be bio stimulating, they generally don't hurt, except when they're used in high quantities. You can run into issues with heavy metals, so I'm not adamantly against them, but I think that growers often want to skip the, the micronutrient sulfates, the iron sulfate, manganese sulfate soluble, that type of stuff, and use rock dust instead. And it's just not a one to one replacement. And I'll also mention that growers don't like the micronutrient sulfates, which I sort of understand why intuitively if you use them and you look at them, they, they just don't feel that natural. So to put them in a living soil feels weird. Especially copper sulfate. It's got that weird blue color. And, but generally they express the concern around sulfur. You're applying orders of magnitude more sulfur with the use of gypsum, which is not villainized in cannabis production to the same extent the micronutrient sulfates are. So if you're trying to minimize sulfur, you really have to sort of eliminate gypsum and potassium sulfate and langbenite and Epsom salt way before you eliminate manganese sulfate, which I'm recommending at two teaspoons, just very tiny quantities, just a couple grams in an entire cubic yard of soil volume. So, yeah, I don't, that's why I don't recommend rock dust.

And when you are getting trace minerals from your compost fraction in your soil too, that's probably a lot more available.

And all the other amendments from bone meals and anything from the ocean has a huge amount of these trace minerals. You know, alfalfa meal all, it's got it all in really small quantities. And generally the trace minerals that aren't essential if they're going to work, if they're going to do anything, they're needed in extremely small quantities anyway. So you should be in these soils that were amending heavily and that have tons of compost. There should be plenty of these trace minerals. Now, that said, I may be a little bit of a hypocrite because before I planted a thousand trees on my farm, I definitely threw in a little bit of, of just small, small quantity of rock dust. But, you know, that's mostly because I just had it lying around and I wanted to use it. I would not bet a dollar that it's actually doing anything to my trees. People can disagree with me and that's totally fine. It's just, I'm just speaking to my own experience here.

Yeah, I did some trials when we were re amending or creating our nutrient pack and I with long conversations with Coot back in the day, we did some trials at the local horticulture college and one of them on his recommendation was high levels of rock dust. The re amendment with the idea of getting these trace minerals and basically there just was inadequate fertility because there, there, there was no available nutrients in it. And so we've kind of, we've kind of, I've kind of moved away from rock dust philosophically for the same reasons you're listing. And I just thought it was, I thought it was an interesting topic because a lot of people have been asking me about azomite and rock dust in general. I mean, yeah, I think kelp meal has other benefits.

Kelp meal definitely does. Oatmeal has all kinds of biosteam stimulating effects and hormonal effects. And like I said, it has nitrogen and a lot of potassium. So kelp meal is a more complicated topic. It's also much more available. Yeah, but it, but to me, the, the, the rate, you know, the dose makes the poison and the rate, for whatever reason, kelp meal rates in cannabis production are just generally too high. You're also bringing in a ton of sodium and chloride if you apply it in really high quantities. So less is more. With kelp meal, I'm not as clearly, I'm not anti kelp meal. I just think you want to watch the quantity also. Just, you know, there's a lot of arsenic, so if you're getting tested, you don't want to use it in high quantities. And any bio stimulant should be acting in a very low dose.

One note to add to all this is if you do want to play around with these micronutrient sulfates, I would highly suggest you don't add anything without a soil test to go off of. And if you do add anything, we are talking minute amounts because you can absolutely screw up your soil with toxicities by adding too much. So, and you really have to know what you're doing because like soluble, for example, is significantly stronger than borax. So if, if you screw up for some reason and grab Solubort on a borax recommendation, you can way overdo your boron. So just be careful playing mad scientists with micronutrients.

Yeah, and there's also a spectrum within them. You know, you can apply quite a bit of ferrous, you know, iron sulfate, but not so much copper or boron. So, and what my, just to kind of run through it, when I use micronutrient sulfates, I dissolve them in water at a carbon source of some kind. So typically that's a humic substance, like a dissolvable humic acid or molasses. And maybe to go back to this conversation, a kelp is a source of carbon. So just a touch of kelp and then I, and then I always apply it in water because it's distributed more evenly than you never apply them dry. So I, I injected into my irrigation system. So anyway, the, the, the theory there is you're, you may be chelating a little bit with a carbon source. You're also buffering it biologically a little bit. So you're giving the microbes something to eat with it. So you're, you know, when the the microbes consume the carbon or the sugar source. They may be incorporating those, those micronutrients into their bodies. And that's a, that's a, that remains that keeps those micronutrients in a more plant available form longer because they, you're essentially taking an inorganic salt and turning it into an organic form. And that the issue with some of these, like iron sulfate specifically, but a little bit manganese sulfate too, is, is redox matters a lot. So most if you just drench iron sulfate straight into a soil with a pH over 6 or 6, 5, it'll immediately oxidize and just rust turns to rust. And it's not plant available. So trying to chelate specifically iron or put it into a more organic form will keep it available longer.

That's a really great point around iron. Yeah, thank you for reminding folks of that. Yeah, I just, I just take like for. I recently did a manganese sulfate application. I, I just mixed it with water and then applied it over the top of my beds with a, just a sprinkler can even. But I, I haven't, I hadn't thought about adding a little bit of molasses or some other carbon source in there. So I might have to experiment with that. That's a good idea. Okay, moving on then. Let's talk a little bit about transpiration in plants and what role that plays in sort of the nutrient uptake that we're talking about.

Yeah, fun. So it's, you know, I think my nutrition a lot and I look at a lot of tissue tests. We've been talking about soil and I really look at a lot of tissue tests next to soil tests. And it's always bothered me a little bit that they're not perfectly correlated. And so I spend a lot of time trying to understand why if you have great sufficiency and balance in the soil, it doesn't always translate into the right sufficiency and plant leaves. And I've always known that the biggest reason is, is transpiration. Although there's other factors too. And so I've gone into sort of the, the science of what causes transpiration and it, there's a lot of misconception in horticulture around what drives transpiration. So for example, you know, I've always thought like VPD drives transpiration rate, but that's actually not that, not quite accurate. The. If you really dive into the physics of plants and energy, energy to the leaves drives evaporation from the leaves. And so that's radiation energy and convection. So air movement, warm Air and, and then sunlight. And that is ultimately what's going to drive the rate of evaporation out of leaves. And then the final thing to note is the stomata have to be open. So relative humidity does play a role in that, temperature plays a role in that. But ultimately it's the. It's the differential in vapor pressure inside the leaf versus outside the leaf. But ultimately you're changing your evaporation rate based on the total energy hitting the leaf. During the day, when the lights are on or when the sun is out, the majority of that energy is radiation. It's from light. And so in a sense, the VPD doesn't actually matter nearly as much during the day. It matters more at night because convection is the only source of energy driving transpiration. But during the day, light intensity and whether or not the stomata are open are the key variables to the rate of transpiration. So, anyway, I'm kind of going too far into the weeds here, but if you think about how plants uptake nutrients, sufficiency and balance in the soil absolutely matters. But the rate of evaporation out of the leaves is. Is the second thing that we don't quantify, we often don't really think about, but is ultimately going to determine how many nutrients are moving into the plant. So, for example, I just see really poor correlation between calcium and boron immobile nutrients in the plant tissue and how much is in the soil. And that's totally because of transpiration rates.

Because they move within the xylem, which essentially where water moves to the plant now.

Exactly. So as soon as evaporation stops, you're not getting calcium uptake, and maybe not in indoor environments as much as definitely in greenhouse environments. Growers don't think about nighttime evaporation. But as soon as there's tons of heat emission coming off of the plant leaves. And so plant leaves cool down, especially when they're exposed to the open sky at night. And so the leaf temperature can drop, you're not getting any radiation. And evaporation can essentially stop at night, which is a major problem for creating weak cells at the top of the plant, increases disease susceptibility, but also just stops nutrient transport. And you want nutrient transport happening 24 hours a day. So there's a number of issues around evaporation that I think about.

So I've always thought of it a little bit differently in the sense that evapotranspiration is being pushed by VPD as well as airflow across the leaf surface, because that higher levels of airflow. If you have a plant near a fan and then you start to get that leaf tip burn, essentially, is a lack of calcium that's developing is because the plant can't evapotranspirate fast enough to accommodate the amount of nutrients that are going up through the le. And so it's not pulling up calcium fast enough to allow for that. Is. Is how Nadia, Dr. Greenhouse explained it to me, and I thought that was really interesting. And I do see plants and people, you know, people could do this experiment. But essentially, if you put a plant near a fan, it's going to dramatically impact the level the water needs and the amount of evapotranspiration that's occurring in that plant versus a plant that's further away from a fan that's not getting the same airflow across the leaf surface.

So, yeah, so airflow will. Will increase that. That. So there's radiation energy and convection energy. And so if you increase airflow, you're increasing the convection energy to the leaf, which will increase the evaporation rate. Absolutely. The problem with what you're seeing is the leaf probably can't keep up with the rate of evaporation, so it closes its stomata, because when it experiences water stress, it'll close its stomata. And the. Then the only way for it to maintain energy balance is to radiate heat. So the leaf temperature will go up and you can start to see, you know, burning issues, essentially. And so the issue there to me with, is, with excessive airflow is the stomata are closing.

Yeah, I wasn't aware of that. It's really interesting. So the way I've always, you know, here.

Oh, yeah, go ahead.

I was going to say, like, when I see issues on plants, the first thing I look at too is, is watering and vpd, because those are. Which is another way of approaching this transpiration thing that you're talking about. Is this idea that is there sufficient water in the media in the soil for plant roots to take up and transpire? And then, you know, what. What is the humidity in the room that allows for these sorts of. This transpiration to occur?

Yeah, so. Sorry, the. So relative humidity matters a lot in terms of the opening and the closing of the stomata. But what I always. I always thought, and this was a misconception, that low relative humidity would increase transpiration. So if you dry out the air, it'll increase transpiration. In other words, if you increase the bpd, like the plant's trying to compensate.

For the dry air and transpire more.

Right, right, It's. And so it transpires more. I mean, this is what people say if you increase, increase vpd, you increase transpiration. But I, but for what? I, I wouldn't see that in the tissue data with calcium. And it turns out that this isn't necessarily true. In fact, in certain instances, a high relative humidity creates more evaporation because a high relative humidity can open the stomata, allowing the plant to actually evaporate water out. So it's not a humidity matters, but it matters because in part because it's opening and closing the stomata, which allows for evaporation. So when someone says vpd, growers usually think of temperature and relative humidity on the chart, and it's not necessarily the right metric to determine stomatal opening. Again, temperature and relative humidity matter, but the air vapor pressure deficit in itself doesn't. So if you know growers, what really matters is leaf temperature. And so I think a lot of people have heard that they should use a leaf temperature adjustment, and that is the key to keeping stomata open and closed. And anyone who's transitioned from an HPS to an LED light knows that you get wildly different results if you keep the VPD the same. And it's because there's a change in leaf temperature. So the key here to really understand evaporation rate, to really understand if the stomata are open and closed, is to, is to understand leaf temperature and to use leaf temperature to do the VPD calculation.

Hmm, that's really interesting. I never really thought of it that way.

Yeah, yeah, it's, it's kind of been difficult for me to, to, to learn because I'm having to relearn and it's, it's like there's these certain principles that I've always held as this is how it works. And it's taken me a long time to try to understand these new concepts around evaporation because it doesn't really work with my existing sort of, my previous learning around how it worked. But now that I'm sort of understanding the opening and closing of stomata and evaporation rate, it's helping me immensely in sort of understanding how these high tech greenhouses are managing their environmental conditions.

Yeah, I'm gonna have to reach out to Nadia for more of an explanation or more discussion around this topic because I think it's really interesting and I don't want to say that I fully understand everything you're saying here in regards to it. I'm still processing It, But I think that's interesting and that's what I love about plants and you know, agronomy and all of this is I feel like I never stop learning or being challenged by, by new concepts or new ways of thinking around things with, with growing plants. And I love that.

Yeah, yeah, definitely. I mean, there's a, it's, it, it's sort of a whole world of plants are like these incredibly complex systems. And so, and what I think the hardest part for me in understanding is when you change one variable, multiple other variables change simultaneously. So that's sort of what makes it complex.

Yeah. Okay. So on the topic of tissue testing, just to stay on that topic, you mentioned some stuff around sampling. Did you want to touch on that any further?

Yeah, you know, tissue testing, that there, there's a few things I just want to communicate to growers who are already tissue testing or thinking about it, which is the, the need to test. There's a couple things you, it's important to test at the right time in a cycle. There's, because as you know, tad that the plant will translocate nutrients late in the cycle. So usually there's, you know, after sort of the plants stop stretching, the flowers are stacking, the majority of the assimilates are going toward the flowers and there's less leaf growth. And so certain immobile nutrients are going to accumulate more and more and more in the large fan leaves and other nutrients that are mobile are going to be moved out of the fan leaves and moved into the flower flowers where they're needed. So after about week two of flower and more so after week four. But I like week two as the target time to tissue test. But after week two, three, four, the, the nutrients get really odd on a tissue test. And there's not an easy way to analyze the results of a tissue test. So I, I'm, I've received so many tissue tests on cannabis from like plants at harvest and it's just, I, I can't even make a recommendation on it because the calcium levels are sky high and the nitrogen is low and there's not really a target level that we're looking at. So I think it's really important for growers to tissue test before week two of flower. You can tissue test in veg really anytime before then. You know, week one, week two, you could go to week three, probably. But after that it's really unhelpful data. So that's the first thing. The other thing is the size of the leaf really matters because like I said, calcium will accumulate in the larger leaves, the older leaves, I should say. So if you're taking fan leaves three or four nodes down, you're going to get a much different number than if you're taking the new small leaves at the top of the plant. And so you can think you have low calcium because the leaves that you're pulling are too small, too young. So it's really important to stay consistent and to make sure that the leaves that you're pulling are, are fully expanded large leaves. I like a couple nodes down, just the first leaf on a branch that you think is, you know, mature. And then whatever you choose, you stay consistent with that sampling protocol. And those are the two big mistakes that people make. And I, I always feel bad because, you know, this is a lot of time and money that people are spending sampling. So week two of flower, fully expanded new growth.

So I, I think those are good points. I like the idea of tissue testing for the data that it gives us. I think it's expensive relative to soil testing for managing fertility. And I've actually used tissue testing a little differently in the sense that later in flower. So if you want to use tissue testing as a agronomic tool for data driven decisions, then I think week two makes a lot of sense. But where I've used it is I have a plant, let's say week five, week six, and something's going on and I can't figure out what it is. I'll do a tissue test and then that'll tell me, oh, this reflects, you know, what I thought I was seeing visually and then I have a better idea of what a visual symptom for that nutrient is and then I make sure to address it on the next round. I'm not, I can't, I don't feel I can use that tissue test to make definitive decisions about my fertility applications the next cycle. But it's like a one more piece of information that supports what I'm seeing visually and allows me to, you know, make that decision. I don't know.

And so just to clarify, are you SAP testing or are you tissue?

Tissue? I haven't gotten into SAP testing for a few reasons. I think it's really interesting. But my concerns around it are the cost, the fact that the databases are not really publicly available. They're all sort of internal to these labs, which I struggle with, is a, you know, wanting more transparency there and then. Yeah, the fact that it's a number that's going to be changing so much. I would just need to be really, I Feel like dialed in with consistency on testing. That being said, I do think it's really interesting and I think it has value. I just, I haven't personally gotten to where that's one of the tools that I'm really relying on for things. What are your thoughts?

Yeah, similar. I, I, I like, I like to just say start with tissue testing. It's $40 a test compared to, you know, I think 75 to 100 for SAP testing. You also have to get the sample of the lab sooner. It's gotta be on ice so that the cost ends up being more than double when you're SAP testing. It also in my experience, doesn't help to see a single SAP test at any random point in the cycle. It should be done like every two weeks. So then you, you're looking at a much larger expense. I also see, I also totally agree with, I struggle with the lack of, yeah, transparency. I mean new age has, has, has become my go to lab. But I've been working with SAP testing before they were around and I've just continued to have issues. Also you're getting recommendations from the lab and I tend to disagree with a lot of these lab recommendations, especially around high chloride. So yeah, I have a bunch of small issues with SAP testing but at the end of the day I just think the low hanging fruit, if you want to test your tissue, is to get a 40 tissue test at week two of flower. Just start with one. There's research established target levels, multiple different researched levels that are all pretty similar. And so that's just like an easy interpretation. It's 40 bucks you do it once self testing. I do use in, in large production systems where let's say a 3% increase in yield makes a huge difference economically. Yeah, layering and SAP testing on top of tissue testing makes sense, but it, but honestly how I've used it is to do tissue testing, do SAP testing. And the idea is you're just trying to validate one, you're trying to validate the test to really pinpoint, to be extra super confident when you're targeting nutrients just because it just gives you more confidence in that that application is gonna be the right one. So for example, I use it in orchard crops a lot because we're talking about just huge swaths, huge applications. You know, if you're gonna, if you apply, let's say you apply potassium, that could be, you know, a $10,000 application. So you just want to have as much data as possible to back it up. Um, but yeah, I mean I would be concerned about tissue testing that late because I don't really know what the numbers are supposed to say. Um, you're always gonna see deficient nitrogen at week eight, for example.

Yeah, I don't, I don't use it so much for nitrogen that late but, but more just to see if there's a trace mineral issue or if what I'm seeing visually matches with like what deficiency I think it is is reflected on that test. And again it's, I don't use it very often as a tool. I, I'm more focused on soil testing at this point in time. But I, I absolutely understand and especially in things like hydro, I think it makes a lot, a lot of sense and I will just say as a shout out to New Age and Scott, I've met him a couple years now at the soil summit and he's a great guy. I always enjoy hearing his talks. I think it's really interesting. It's just not a technology that I've really explored too deeply for the reasons we just discussed.

But yeah, yeah, I mean I, I, I have sent SAP samples to the Netherlands for years. I've se, sent them to, to New Age and actually I did some split tests last year for people who, who do want to SAP test and actually the results in, in Stone Fruit between New Age and Nova Crop Control in the Netherlands were, were very similar. So no need to send them across the ocean if you're going to SAP test. I think New Age is the way to go.

Great. Well, we're running out of time, but I wanted to talk to you just briefly or not so briefly. We'll see how it goes about sort of your new philosophies that you've been exploring around cultivation. Now for those that aren't familiar, you have a course through your Soul Doctor website that you've had for years now. I've audited the course. It's, it's wonderful for people who want to deep dive in soil testing and want the ability to really understand those results and read their own tests and make their own recommendation. This is the best publicly available tool for folks. You can check it out on the Soul Doctor website. But you're, you're working on something new. What, what do you want us to share with that?

Yeah, yeah, thanks. The. So I've spent almost eight months, the last eight months deeply studying greenhouse optimization. So I've been learning the principles used in some of the world's largest, most high tech greenhouses, the Dutch glass houses, where they're just achieving unbelievable yields and Plant health, like sweet pepper plants that are 10ft tall, just loaded with peppers, and just really amazing results. And so with all this, I'm sort of creating this, this program that will teach professional growers principles of what creates general plant balance in a greenhouse or indoor grow room and the techniques and tools to achieve, you know, this kind of performance depending on what level of technology people have. So this involves the use of various different technology as well as sensors and automation to improve facilities. And so I'm developing it for commercial growers who have some degree of control of their environment. So unfortunately, outdoor production, you don't necessarily have much control over the different conditions. But I'm trying to take these principles that are used in the highest tech autonomous greenhouses and apply them all the way down to like low tech high tunnels. So from sort of CEA all the way to low tunnel or low tech high tunnels and greenhouses. And the content has traditionally just been for these really advanced greenhouses. But I don't see why some of these principles can't be applied to every level of grower. And so I'm trying to, that's kind of my inspiration behind it. It's kind of a Robinhood scheme to, to take this amazing information from these big companies and universities and change it a bit and apply it to multiple different contexts and, and present it as succinctly as possible. So that's what I've been working on doing. It's been, it's taken a long time. It's a lot of learning for me. It's also just a lot of content and research to go through. But most of this is content from Wahanigen University in the Netherlands. There's some professors there that have really innovated how to think about greenhouse production. So that's what I've been working on. I mean, it goes through like a lot of the scientific balance of plants and then it goes into sort of the goal of the grower and different checklists and how to measure things, what to measure, different tools for creating balance. So if you're in a greenhouse, what kind of materials to be using in your greenhouse? Diffusion, plastics, high pressure, fogging, ac. And then I go through most of the courses actually going through scenarios. So I'm trying to connect the principles to a ton of real world grower situations.

So can you give me some examples of these principles that you mentioned that are in the course just so we can have a better idea of, can flesh out what you're, what you're describing?

Sure. So one of the scenarios That I discuss is around disease and how to reduce the susceptibility of disease. And so traditionally you know, we're thinking a lot about humidity and airflow and air movement. I really talk a lot in this program about how to prevent free water on the leaves, which is often one of the root causes of disease, either plant cell damage or condensation. So while relative humidity does increase risk of condensation, condensation can also happen at relatively low humidity levels. And the final thing that can cause disease is a weak plant, which is almost always from an assimilant or a photosynthetic, photosynthetic imbalance in the plant. So soil borne diseases, but also above ground diseases always happen when the plant's natural immune system isn't powerful enough to fight back, which is often due to an assimilate imbalance or an assimilant deficit really. So a steady production and consumption of assimilates leads to steady root growth and steady root exudation. And this is what feeds a healthy microbial population. So if your microbes lose their primary food source, they won't be able to defend the roots nearly as well. So that's sort of where I'm kind of coming from, from an assimilate balance standpoint. And there's a number of different techniques that you can use to balance assimilate consumption and production in the plant. Production being photosynthesis. And one is looking at your average daily temperature compared to the dli. That is like a really, really powerful steering technique. And just, it's a, it's a really great way to keep the production and consumption of assimilants stable on a 24 hour basis. So that's an example. And then going back to disease, I talk a lot about how to prevent condensation and depending on the facility, for example, in greenhouses I mentioned you get a lot of heat emission at night. So I talk about ways to, to make sure your plant temperature doesn't reach dew point using climate screens and other other means, increasing air movement, how to increase air movement. So I, I've mentioned this too. I love your convection tubing in the canopy. I'm also doing a lot of experiments with vertical air fans. So like V flow fans and trying to create airflow into the canopy and then finally temperature swings. And that can happen through, you know, all kinds of different things. So I've talked a lot about ventilation optimization and how to sort of manage your, your vents and how to ventilate your greenhouse to avoid temperature swings. And like I said, condensation can happen at relatively low relative humidity. So I talk about how to. How to determine your ventilation. And for example, growers should be using absolute humidity, not necessarily relative humidity, to determine ventilation. There's this really sort of wild example that always confused me. You can have a, let's say an outdoor temperature of like 68 degrees Fahrenheit, 20 Celsius, and 85 relative humidity. And if it's. If it's warmer outside with a lower relative humidity and you vent, you can actually cool your greenhouse because the enthalpy or the energy outside is lower than inside. So there's all these fascinating examples of where ventilation should be toggled with absolute humidity instead. So things like that. Just tons of scenarios on how to manage the environment inside a greenhouse.

Yeah. I so wish you were able to. I mean, first of all, this is fascinating, and I know it's a. It's a little bit of a different direction for you here, but I'm really excited for this and to learn more about this course. Do you know when it's. Do you have an approximate date for release or is it still.

You know, I'm trying to finish something this year, but I have, you know, I'm still working extensively with growers on nutrient management. I have, you know, a large farm I'm managing, especially in the spring. There's a lot of work, and I just have a lot more to dive into. So it probably won't be done for several months, but late, late 2025 is my goal.

Awesome. I. I was going to say, I so wish you were able to make it to. To the Cannabis Cultivation and Science Conference in Bozeman this year, because Collective Elevation, where we're hosting it, has all of these things. They have under a hampi airflow. They have the vertical airflow fans and all of these different things working. And Adam, the owner, is so excited to have Nadia, Dr. Greenhouse, come out and walk as part of the workshop. Walk through the facility and point out everything and talk about how they may be doing things right or wrong or optimized because airflow and humidity and DBD is such a complicated topic, and it's so misunderstood. And it's one thing that I know. It's one of the things I'm least confident in myself when it comes to cultivation practices. So, yeah, I really. I know you're one of the first people I reached out to, and I know you're busy, but I was really hoping you'd be able to make it if things change.

Yeah, I'm sorry. If things Change. I'll absolutely let you know. I would love to see that. That facility. Is it, is it fully indoor with supplemental lighting or are they, is it a greenhouse?

Open next gen greenhouses in Bozeman Montgomery with. Yeah, that's, we do have light depth capability, but you know, they're growing in what, like negative 20. I'm probably under exaggerating at negative 20. And then you know, in the winter and then all the way in the summer when it's, you know, it can be in the 90s or higher. So they deal with all types of climates there and they're able to grow year round, which is, and grow healthy plants. It's pretty awesome. They're the largest living soil producer in Montana. They may be one of the larger ones, greenhouse ones that I'm aware of in the country. And they're just phenomenally good people and good growers and it's, it's cool to see.

You know, I, I am fascinated with these mixed environments, greenhouses with supplemental lights because there's so much more potential. But also they're, they're also much more difficult. You really have to be good because the, the, the sun and the variability, you're still working with the variability of nature. So you're not just setting your, your lights. You're like having to, to sort of adjust and move on the fly to varying radiation levels and also even cloud coverage. So you know, for example, at night you're going to lose a lot more heat with an open sky versus cloudy sky and you have to adjust. So it's a very technical and fascinating form of cultivation.

Yeah, I'm sure they'd love to have you out even if you can't make the conference.

So what, what day is the, is the, the Greenhouse tour?

The 5th. September 5th. There's going to be the tour as well as the workshop with Nadia going concurrently at the same time as a workshop with Suzanne Wainwright Evans, the bug lady.

She's gonna be doing workshop. Well, maybe I can try to do some kind of strike mission. I'm in the. It'll. I'll be right in the middle of a massive peach harvest that's like high intensity and high consequence. So that's why I'm not really able to make it. But I'll keep it in mind. Tad and I appreciate the invite and we'll see if anything shifts.

Awesome. Well, I really appreciate your time today. I always learn a ton when we get to talk and it's always a lot of fun to have these conversations and people ask actually quite a bit like, when am I going to have you back on the show? So I really appreciate you coming back.

Yeah, thank you. And I've loved watching you grow this podcast and grow your business over the years. It's, it's, it's been really inspirational and I really appreciate what you've done. I really appreciate you having me on and our relationship. So just thanks goes to you.

That was Bryant Mason and you are listening to the Cannabis Cultivation and Science Podcast. Don't forget to check out the podcast page at www.kisorganics.com. just click on the Learn tab and then podcast. And just a friendly reminder that we have a Patreon channel with a free 7 day trial and tiers as low as $5 a month. We do book club, special cultivation tips and tricks, monthly video hangouts, and that allows you to connect or share your grow. And we even give out seed packs and other gifts as well. Certain tier levels. Your support of Patreon or sourcing your products through Kiss Organics is what supports the podcast and I really appreciate it. We also have the upcoming Cannabis Cultivation and Science Conference in Bozeman, Montana this year with many of our favorite guest speakers who have come on the podcast in the past. It's happening in September at Collective Elevation and there's a lot more information available as well as tickets on our website. Thanks for listening.