Back to Basics: Soil’s Crucial Role in Cannabis Cultivation

For cannabis cultivators, it can be overwhelming, daunting, and a consistent learning experience figuring out what works and what doesn’t. With growing, there are so many components to take into consideration. Such as, what type of grow facility you would like to use, will you cultivate indoors or outdoors, what type of lighting you will use, and so much more. Something very important that can be overlooked is the soil composition, which perhaps is the most important piece to any kind of grower’s journey. In this interview, Adam Jacques, a world-renowned expert with more than 20 years’ experience cultivating various unique strains of cannabis, where he has developed more than 300 high-cannabidiol (CBD) strains of cannabis, and Chief Geneticist at AgSense LLC, andZacariah L. Hildenbrand, a research Professor at the University of Texas at El Paso, the principal founder of Inform Environmental, a partner of Medusa Analytical, and is a director of the Curtis Mathes Corporation, bring us back to the basics of cannabis cultivation and explain the crucial role soil plays in your grow.

Can you tell us a little bit about yourselves and how you became interested in the cannabis industry?

Adam Jacques, Chief Geneticist at AgSense LLC | Image Credit: © Adam Jacques

Adam Jacques: My interest in cannabis started when I was about 14 years old. I was in sports, and I had an injury and it hurt and my brain has never been quite right. I was hanging out with these kids that like things like Dungeons and Dragons and things like that, and High Times magazine, and things of that nature. I tried cannabis for the first time, and I felt more normal than I had in my entire life. Now I'm not saying people should smoke cannabis at 14, but it was awesome. So, you know, I didn't really use it that much into adulthood, had to be a kid and figure my life out. But yeah, I started using cannabis because it helped me deal with my brain. Turned out cannabis is really expensive, like really expensive, especially back then. So, then I started growing it for myself, because that was a lot less expensive. And that's how I started. Very shortly after that, I got involved with the Compassion Center in Eugene, Oregon, offering, like low, no-cost medicine to people and things. But it all started off with like, like a centerfold love of the plant, right, like High Times magazine, you know. Stoner culture, the whole thing was my entry point to it.

Zacariah Hildenbrand: Yeah, mine is a little different. I got into this space in about 2015. I've been fortunate I was able to meet Adam. We became fast friends, shortly after I entered this space, but I saw it as kind of the new frontier of medicine. My first venture was opening up an analytical testing lab in Arizona and then from there, I just started working with Adam and his team in Oregon on genetics projects and helping patients and so I've done a little bit of everything. But yeah, it's been a wild ride the last nine years, I suppose.

On a scale of 1 to 10, how does the role of soil health rank in importance of cannabis cultivation?

Zacariah Hildenbrand, PhD, research Professor at the University of Texas at El Paso, the principal founder of Inform Environmental, a partner of Medusa Analytical, and a director of the Curtis Mathes Corporation | Image Credit: © Zacariah Hildenbrand

Hildenbrand: Yeah, so I'll just hop in there first. Obviously when anyone's trying to grow the best plants they possibly can, you want to get the best genetics, you want to get the most efficacious lighting, you want to use the best water, and you want to get the healthiest soil. With the plant being so effective, at a process called bioremediation, it can uptake a lot of metals and minerals out of the soil. That if you start with a soil laden with arsenic or lead or any kind of additives that you don't want in there, there's a chance that that could migrate into your plant tissue and then you have a negative impact. So even if you're using the world's best genetics from Adam Jacques and you have the world's best LED lighting, if you have bad soil that doesn't have the right nutrients, or the right structure, or the right microbes, or is laden with heavy metals, you're kind of setting yourself up for failure.

Jacques: Yeah, I mean, when you're growing with soil, you're entering you know how important is your soil? 10. But there's levels, right? There's multiple different levels to what somebody would consider soil health. Is healthy soil for you, bagged soil from the hardware stores? Healthy soil to you, like no-till living soil completely amended out? It's like completely different levels of how important and how important is soil in comparison to like hydroponics and aeroponics? Is that what we're thinking? Because then you know, you're looking at the difference between anything grown in soil. It's like as a sit down, fancy dinner and you know, aeroponics/hydroponics is like, McDonald's. There’s levels, but if your soil health isn't right, it’s ruined. Other than having, let's say no light, it's like the most detrimental thing that can happen to your grow.

Hildenbrand: The last thing I'd say on that is, it also depends on what sort of cultivation facility you're running here. Are you doing organic? In which case your soil quality is really, really important, more so than ever because you got to have all the nutrients in there as well. Or are you running salt-based nutrients, where you can kind of get away with a little bit more of a run of the mill. I mean, obviously, we advocate for a more holistic, organic approach. So, that's again, you want to be using the best soil you possibly can.

Jacques: Zac's right. A lot of people do use soil is a carrier device, just something to keep moisture around the root ball of the plant, and they just force feed with salt-based nutrients and chelated metals.

Do you need to measure the natural composition in soil when growing cannabis?

Jacques: When we’re looking at compostion during flower is difficult. We'll do runoff tests. So, we'll run water through and then we'll test the water coming out. I do not have the ability currently to soil sample on-site. So, everything is sent out. The data I would get back would be two weeks, too late kind of thing. For us at this point, it's more of a nose, eye, and field test for soil with runoff, checking the runoff, and making sure that there's nothing in there. That's about the best you can do. I believe, if you really want to check, actively check that with high-performance liquid chromatography (HPLC) or something. You could definitely test the composition that's happening in there and what it was releasing. And that's very, very important with a fresh soil batch or when you're building soil. You definitely want to look at those things and see where your soil's at, you don't want to use hot soil. But as far as like once the car's in drive and everything's moving, you better hope that the inputs are correct at that point.

Hildenbrand: When you when you go out and buy soil for your indoor grow, though, I mean, there's already available data that the manufacturer would provide, right? I mean, okay, here's your matrix. If you wanted to have that information, you could, I think where soil testing is really, really important as you're kind of in an outdoor setting, you kind of want to know what the nitrogen, carbon content is, you want to look at calcium, magnesium, the hardness of the soil, per se. Looking at the structure of the soil, is it loamy? Is it sandy? Maybe less important, but to me, you want to look the major constituents in there for sure, and then know what you have to amend in. I mean, on the large scale.

How different is growing cannabis from your typical backyard garden?

Jacques: Growing tomatoes is a lot like growing cannabis. You can be really good at it, or you can be really bad at it. As far as like, what do plants need to live? And then what does a flowering cycle look like? What does fruiting look like? There's not a ton of difference between a vegetable garden and like an herb garden and the cannabis plant. Difference being is like a cannabis plant, we can't postprocess it with a good handwashing to get the bugs and dust off of it. Generally, if you're using it for edibles less, but you know, if you're smoking it, it's a bit harder to keep clean. It’s not like fruit in that way. But, as far as like what it takes to grow it, if you were to build a bed for tomatoes and put tomatoes in there, and plant a cannabis seed in the middle, you would get something at the end of the year.

Hildenbrand: Yeah, I would say in my experience, I love gardening, I've kind of learned to love gardening through my friend Adam here and he grows a whole bunch of exotic plants beyond cannabis. So, my first year playing trying to play Joe gardener, you know, you just don't really know what you're doing. And so you start with whatever native soil you've gotten, that probably isn't very good. I live in El Paso, Texas, so it's going to be kind of a sandy soil. So, it's not going to be very good for much of anything other than desert plants. The next logical step is, 'I guess I'm going to buy this bag soil because that's what it looks like I'm supposed to do’, and it turns out, that's not very good either.

What I've really come to find out is, if I can have a compost that I'm amending with native soil, and maybe some manure, and things like that. My goodness, I mean, the plants do so amazingly well, I don't have to keep feeding them throughout their lifecycle. And so that's what I did last year and having a banner crop of tomatoes and zucchini and all kinds of stuff. That is to say that if I was growing cannabis in those same flower beds using that composted soil, I would have had incredible yields and great looking great smelling plants.

What are challenges and advantages for indoor and outdoor cultivation in terms of soil?

Hildenbrand: Oh, that's a good question. Well, I'll just jump in there. Adam is far better versed to address this one. Ah, you know, indoor, you're talking controlled environment agriculture (CEA). And so theoretically, you can produce a better-quality plant because you can control the environmental variables, the humidity, the temperature, the wind, and you can keep pests out. So theoretically, you should be able to produce a better product indoors than outdoors. Higher cost to produce, I would say. And then also, I mean, we've seen indoor cultivation, like if something goes wrong, and let's say you get a bad batch of soil. Actually, we have a project where this happened to one of our colleagues. They bought what they thought was organic soil, and it was loaded with aphids and so boom, now you got an aphid problem. It's a systemic problem, and you got to nuke all the plants and it's just not a favorable position to be operating from.

So, yeah, I think the indoor cultivation has its pros and cons, in that you're in a confined space. And if you keep all the various environmental variables consistent, you can produce a great product. But if something gets out of whack there, you're also in that same confined space, that's going to be difficult to manage. Whereas with outdoors, you know, you have a little bit more latitude. If something goes wrong, you can play around with some of the variables. So yeah, that would be my two cents. Adam, what do you think?

Jacques: I mean, it's a big question. And when you're talking about outdoor, are we talking about container outdoor or inground outdoor?

Hildenbrand: Yeah, that's a good point, as well. Is it a greenhouse, hoop house, those sorts of things. So, let's just assume it's just, you know, straight up, outdoor.

Jacques: So, I mean, for indoor, let's say you're pulling your soil out every time indoors, right? You're not doing like a living soil, raised-bed kind of solution, and you're switching your soil out every time and re-composting it, and slipping it through. Easy, that's really good. It's gonna get you really good flower. Doing no-till inside, even better flower, more risk, and then we'll get to that later. Outdoors container planting and soil, it might as well be inside, you're just getting free lights, you're not really changing much by having that soil outside.

Nature does a really good job of pest management. So, your soil generally doesn't have a lot of pests in it when you're outside and containers. That changes when you put things into the earth, because then you're adding something into a cycle of nature that has preexisted you, so you're moving into somebody else's house at that point. There can be bug or rodent issues planting in the ground. When you're planting into the earth, you need to make sure, ‘are you digging out a hole and filling it with soil or using direct native soil’? If so, what do your soil tests look like? Most soil is not directly plantable for cannabis, if you're growing for quality.

What are some major concerns with soil, from seed to harvest?

Hildenbrand: I think my chief concern would be the aspect of bioremediation, where you're sucking up those heavy metals and just the accumulation. And so, you think that you've done a great job throughout the whole cycle, when your plant looks great, we harvest it, and it's frosty. And you know, it's going to test well, and boom, there you go, you test hot for arsenic, or lead, or cadmium, or something like that, that would be my chief concern.

Jacques: We're kind of at the point where, in our grows, there is no concern with that, but we're pre-testing all of the variables to know. So, I think that if you're an operator that knows your processes inside and out, and you have good standard operating procedures (SOPs), and you know exactly what you're doing the seed-to-sale, there's not a lot of worry in there. But, that's plants. It's not microchips.

So, there's all sorts of variables that can happen during a grow and I would guess, from clone-to-sale or seed-to-sale type things, there's a lot of data you have to collect. There's a lot of things you have to look at. Are you using an old genetic that you've run through 20 times then, you know, at that point, it's probably like walking. You know, it's really easy. Are you doing a phenohunt on a new genetic and trying to get something new end of the cycle and it's starting in a new space, or something like that. Then there's a lot of variables you need to look at, track, and understand, to make what you're doing of value, right? The most important things as a producer to look for though, is remediating and removing anything that might cause harm to others. So, you know, molds, very specifically molds, heavy metals are an issue, but things of that nature, as Zac said, I think those are the things you need to make sure that you're not doing damage to anybody with your product. And that your product's clean, and they're as healthy as possible.

What have been some of the major innovations in soil that you’ve seen since becoming a cannabis grower, and where do you hope to see more advancements?

Hildenbrand: Well, Adam could go into much greater detail, I think. From what I've seen is, just the integration of amendments and all the additives and the probiotics that really take a flower from exceptional to elite. That's what I've seen and there's a lot of folks that have spent a lot of time creating their master mix of these things. I don't even want to pretend to know a fraction of what all that goes into, like an "Adam Jacques" soil composition, but it's kind of like a good gumbo. There's like a million things in there. And you know, it tastes awesome, and you're just happy to be eating it.

Jacques: The innovation is retroactive. People are going back to setting up, you know, plants live in a place where there's a buffet of things available for them decomposing in the soil and so they eat as they need. When cannabis, I would say really kind of had a renaissance in the late 90s, early 2000s, you had a lot of growers coming online. It was all about salt-based nutrients. Forcing plants to uptake as much nutrient as possible, using plant growth regulators (PGRs), things of that nature; trying to get weight, as much weight as you could off of the plants. That was the name of the game. Weight equaled money and so, quality was seen as super dense buds, right? Like that was high quality. As we’ve move forward and started using different methods to grow cannabis and living soil methods and things of that nature, we've reintroduced a very elegant, very nice buffet to the plants. So, what we're saying to the plant is ‘we're not going to force you to eat anything, but anything you want is available and sitting here for you’. And so, the plants uptake as needed for optimal health. Instead of using chelated copper or something else to force uptake in a massive-like way, we are letting the plants dictate how they eat. That's nothing new.

Grandma back in the ‘70s was probably doing the same thing with her compost pile and chicken shells and coffee grounds in the backyard, making some of the best vegetables ever. So, it's nothing new. What is new is the technological advances, us being able to take a look at the actual composition of the soils; what we're putting into it, how much is it breaking down during the flower? With the amendments we use, we have a much stronger dataset that Grandma probably didn't have. Our recipe is much more refined. But it's kind of a return to the natural, organic way of doing things. There was definitely 20 years of hydroponic and salt-based needs, though that hasn't stopped yet.

What have been some of your personal experiments or successes with soil? Any surprises?

Hildenbrand: So, Adam and I try to avoid surprises, per se. We've done a lot of experiments in the genetic front and focus mainly on lighting as a key variable to modulate, as far as adjusting phytochemical content. But as far as surprises, you know, we're always documenting everything that goes into the soil: the amendments, the water quality, the flow-through, the conductivity of the flow-through, because at the end of the day, you don't want any surprises in the cultivation setting. I will say the one example where we did have that, there was very limited note taking by colleagues of ours and we came to find out that when you have a reverse osmosis filtration system that was supposed to be removing hardness elements, carbonates, bicarbonates, magnesium, calcium, and softening your water, they actually were putting the reject from that—not the actual flow-through, not the effluent—the reject into the soil. And then that accumulated that magnesium and calcium accumulated in the soil, which ultimately led to nutrient lockout, and the plants did very poorly.

Jacques: There was complete soil failure in the next grow.

Hildenbrand: Yeah, and that was just really just a function of not collecting proper notes. I mean, if you collect the proper notes, information, and data, and you're making data driven decisions, then you really don't have room for any kind of surprises, or emotions, or ‘I feel like it should be this way’. No, it's all just based on science.

Jacques: The unbelievable thing to me, and the difference I've seen between organic soil grows and then salt-based nutrient grows, is the cleanliness of the flower. And I think that's something that people don't really understand until they see it. A lot of flower that's grown now in traditional soil or salt-based nutrients and things like that are full of carbon. So, when you smoke it about halfway through your bowl, you're left with like a black chunk of waste in the bottom that that won't smoke properly. You're left with like this mess. Cannabis should burn to a clean, white ash, when you smoke it. There should be really nothing left in your bowl when you're done smoking except for a clean, white ash and you see that now to where we have our soil, that's all you get is a good, clean, white ash. The surprising thing was developing it to that point.

So, you’re really offering the plants a buffet that runs out of certain things. Be it nitrogen at very key times, so that you can pull all of that extra out of the plant via sugars, via chlorophyll, whatever you're trying to remediate or remove from that plant that causes a bad experience in use. How well the living soil does that without the addition of anything outside of the realm of like pure organic inputs is mind boggling to me. I love it, I love it. It's the difference between me actually smoking flower and me not smoking flower at this point.

Are certain types of soil more prone to mold/pest issues?

Jacques: Types of soil. Yes, additives in the soil can cause issues. A lot of people put bark chip on the soil, which I would not recommend. Then it matters what you're doing with your soils. No-till soil will build up heavy metals and a big one right now is Aspergillus people are getting in their living soils, no-till style. That is just bad input. Building up over time and then by remediating into the plants. So, I would say that’s not great. As far as issues go, if you get a bag of soil, a lot of what I see is bag soil companies are using municipal compost, which is fine as a thing. But generally, municipal compost comes with all the problems of that area.

Generally, that’s fungus gnats. So, when you use a bag soil, especially indoors, you're going to see an influx of fungus gnats into your space. For us, we just are constantly by remediating with predator insects, so it's not a huge deal for us. But a lot of people bring bag soil home, and all of a sudden, they have an insect infestation of some sort. It's coming out of the bag from the municipal compost, so that can be an issue. And then soil and ground, I think Zac could probably speak stronger to the issues with groundwater and ground soil at this point.

Hildenbrand: A healthy plant does better against pests and pathogens than an unhealthy plant. And so, if you have this kind of crappy soil, which has been amended with all this stuff, I just look at it as like, the human body. So, if you eat garbage food, and you don't exercise and live a sedentary lifestyle, you just take all these pills to kind of maintain your health, you're still susceptible to getting sick.

But if you eat properly, and you exercise, you do all the right things then you don't need to have all these additives. And so I think, even if you have propensity for some of these things based on the soil quality, if the plants are healthy, because they're eating right, and are getting the right light, and there's proper drainage, and all these other things. Then they're going to be able to fight those infestations off much more readily than, you know, a sickly plant.

Do you have any advice for cultivators?

Hildenbrand: My key take home here, and I'll set the stage for the master here, my key take home is notes. You have to take notes all the time. I mean, this right here, this is my notebook, I have about 20 volumes of this on my bookshelf. This is single-handedly the most important tool that I have in my arsenal, because if I take proper notes and something goes wrong, I can go back and see ‘okay, where might have the issue been’, but without proper note taking, you're just kind of wandering around in the dark without a flashlight. So notes, notes, notes, data driven decisions, that would be my advice to anyone in the space.

Jacques: My piece of advice used to be if you walk out and you look at your garden, and your brain doesn't instantly go to ‘here's what's wrong, or here's what's right’, and you got to like, you really have to be connected to the plants that you're growing. You really have to be able to know what they look like on a day in, day out basis and this connects directly with Zac's taking notes, right? You need to have a lived experience with your plants, understand how they grow, what's happening at what times are things happening, and that's very important., whether it's tomatoes or cannabis, you know, when does pollination happen? When does the fruiting set? When does the fruiting finish, at what times during that fruiting or flowering does the plant want x, y, and z? You know these are things that I think if you want to be a successful grower of anything, that you need to learn.

I could go on all day about things that you can do and whatnot but at the end of the day, the things that are going to affect you the most are the things you can't see. Generally, when you see a plant reacting to something, you're already too late, right? Hey, if you walk out and your tomato plants all curled up and the leaves are turning yellow and falling off, it's a little late, you know. You can get the plant to bounce back but it's immune system is already shot. For starting gardeners, I would take notes, a trial grow with your plants is really good. Don’t expect to be super successful. Actually, be expected for you to be super successful the first time you grow anything. Beginner's Luck is a very real thing. You're gonna think you're awesome and then, the next time everything's going to go to crap. As long as you keep your notes tight, you know exactly what the plant is requesting at what times. You can do a really good job of things, but you just have to be aware, present, and pay attention.

About the Author

Madeline Colli is the Editor for Cannabis Science and Technology magazine. Direct correspondence to: MColli@mjhlifesciences.com.

How to Cite this Article

Colli, M., Back to Basics: Soil’s Crucial Role in Cannabis Cultivation, Cannabis Science and Technology, 2024, 7(2), 36-41.