Oh Yes, How Soil Works

It's all just it's exactly what we hoped it would be. And we cannot wait for you to get your hands on it. Yes, we can't. Um, and you don't have to wait. Actually, well you do have to wait, but you don't have to wait to order. You can go preorder the book right now everywhere you get books, and you will eventually get a special gift for preordering, which we're working on right now. That's right, So check it out soon coming this fall. Welcome to Stuff you Should Know,

a production of My Heart Radios How Stuff Works. Hey, and welcome to the podcast. I'm Josh Clark and there's Charles W. Chuck Brian over there, and this is Stuff you Should know, the Dirty Dirt edition the best I could come up with. And I even had days to think of that, and that was it. Chuck, I'm sorry. Yeah, this is a cool one. You know, we're into gardening,

so it's always nice to talk earth biology. Yes, agreed, Agreed, And like I had a pretty I guess I thought a dcent idea about this, but wait, did this article open my eyes? Yeah? And this, you know, we covered sand, and we covered compost, permaculture, perma culture, like we sort of danced around soil. We danced in soil. Yea, our toes are all dirty. But yeah, this is good to finally check this one off the old list. Agreed. So people are probably like, I don't know about this one.

I would hope that it's been, you know, long enough. We've been at it long enough to just trust us that if it sounds boring, we're gonna find something interesting in it. And I dare say that that is going to be the case with this one too, Chuck, I hope. So to understand soil, we have to understand what soil is, where it comes from, and soil is basically just worn down rock, just like sand is. Right, I think we talked about and like, are are we running out of sand?

Episode that like, rocks get weathered and kind of taken down stream all the way to the sea and they get gently um broken down over time into this very nice little beach sand and washed up on shore, and that's where sand comes from. Well, basically that is also part of the same process for producing dirt as well. It's just weathered rock that's broken down into different um sizes that that are that that basically make up different types of so oil. That's one the main structure of

it is basically just weathered rock of various sizes. Yeah, so you can you know, wind can do that over time. Water and obviously the combination of all these is where you really get your money money's worth. You've got your win, you've got your your water um. When you get weather going on in your seasons, you get the freeze law cycle,

which is a really kind of speedier way. Once that water gets in those little tiny fractures in the rock and freezes and unfreezes and cracks, that will really speed things up. And then you get a little help from our our little tiny critters under under our feet. Yeah, tiny critters of all shapes and sizes from like microbes like bacteria and fun guy all the way up to like prairie dogs and gophers. They're basically taking all this

stuff and mixing it together. But the stuff that they're mixing together is so you've got the structure of the soil from broken down rocks. But that's just one big component. You have to have life living among it or else it's not gonna do anything. It's just it's just dead. There's nothing to it. So um part of the process of forming soil is taking those little gritty pieces of weathered rock and adding decomposing organic matter to them. And that's where we finally start to get to what we

understand is soil. Yeah, because once you have that, it can hold a little bit of moisture, and then that means little plants can grow. Those little plants grow, they eventually die. It's very sad for the plant and the

plant's family, but it happens to all of us. And then those little plants that die, they decompose and they're holding all that carbon dioxide and their little skinny stems and leaves and body, and that carbon dioxide stays behind and it's dissolved by water, and then that forms carbonic acid, which isn't you know, if you want to throw a body in a barrel, you don't want to use carbonic acid. Now you're gonna get caught. Still, you're gonna get caught.

So it's not super strong, but it is strong enough to help break down all those little rocks and everything even more, and before you know it, you've got soil. Baby, Yeah, you've got so So those decomposing all that decomposing organic matter is full of like nutrients that kept the thing

alive while it was living. And then all those little tiny animals and microbes that eat that stuff break it down even further, which unlocks all of the nutrients and within, and that means that plants can start to take them up in its roots and use those nutrients to grow. And so that's a big part of what soil is. It's like a nice little substrate of medium for holding nutrients, and then the whole thing is actually held together itself even further by the roots that the plants that grow

in the soil spread out in stabilized too. So I think one of the things we've just hit upon. One of the reasons I love soil so much. It's harmonious and um symbiotic, Like everything living in the soil almost is involved in keeping everything else going and alive. It's like part of a really beautiful, complete system. Yeah, and that's why, you know, we always make a big deal and science makes a big deal out of the disruption of this and not just this process, but all earth processes.

One little tiny thing will lead to another little tiny thing, and before you know it, you got you got issues on your hands. Yeah, you do, for sure. You can't let it get out of whack. Luckily, from what I found, I started to get into um into like long care and stuff like that happen at some point and it's fun to me years ago and I was like, you just wait, Yeah, it's true. It's true. And I've learned not to flood my lawn with a quarter inch of

um of water. But um, the best fertilizer and aeration that I found is just basically feeding microbes to your lawn. Like you don't need to like go dig holes and core plugs in your lawn, just if you add the right kind of microbes to your lawn and all of that will just kind of turn it into this healthy soil beneath it on its own, which I just love because it's just springing microbes onto the ground. What's more beautiful than that. Well, we've got the opposite. We have

zero grass now. Basically, oh, I know, I know, you just love to my face and that. But still no, it just kept going more and more and it got smaller and smaller, to the point where I was like, why am I holding onto this tiny little patch of grass? Why do I even have a weed whacker? At this point, I know I've used a weed whaker in two years. It's great, that's awesome. I got a big old honking gas powered lawnmower even too. So I'm basically going the

exact toposite direction, is you do you have a writer now? No? No, No, it's not that big. It's not that big. Yeah, it runs on like the tier of baby deer. That's what John Dear means. So, um, if you're talking soil, you need to talk soil horizons, and you know, we'll get to sort of the list of the different horizons here

in a few minutes. But soil horizons are these horizontal levels, these striations that you know, if you look at like if you go to any science center, they'll probably have some kind of cool um piece of glass with a frame, and you have soil in there, and they have little lines drawn to mark these different soil horizons, because soil is not all the same. From the the very top of the top soil down three feet, it gets very different.

And you want space in there, you want air in there. Uh, you want to have water to be able to travel through there. I think they say if you want, like really good soil should be about fifty just fifty percent soil and then fifty just space for air and water. Yeah, exactly, And then you want about half of those spaces to be filled with water. So you've got about soil air pockets, water filled pores. That's ideal for sure. And that's yeah.

And that the reason the way that you get those those pores in those pockets and everything is because there's different types of soil. There's different shapes of soil um, and there's different sizes of soil. Like we said, you know, there's sand, but there's also silt, and there's also and get ready for your socks to be not clean off your feet. There's also clay, which clay Whenever I think of clay, it's like a big hunk of something that I'm like having to dig through to plant a plant,

and it's enormous. But it turns out that clay is actually the finest, uh smallest type of soil, and it's so fine that it compacts together into these large aggregate pieces of clay that we think of when we think of clay, But that's actually huge, enormous chunks of extraordinarily tiny pieces of dirt of soil that are so small you can only see them with an electron microscope if you want to look at them individually. Yeah, and clay is important. It's all part of the mix that we'll

talk about here in a minute. But you know, if you start off with just a barren rock landscape. There's a very smart lady who who did this one? Was this? I think that Grabster helps us out with this. This

is the Grabster um. He must have been interviewed doctor Caitlin Hicks Priests, who's an assistant professor of biological sciences at Dartmouth, and she said, you know, if you start off We've seen it happen if you start off with just bedrock in about a hundred years, you could probably grow a tree there in the soil that you would

get seen it happen a million times hundred years. That's all you need, right, And well, reason why it can happen so fast is because some plants are early colonizers and they can grow and just a little bit of you know, soil, just a little bit of fine rock um, and as long as there's like nutrients and water coming to it, it's it's fine. It doesn't need a big thing of like top soil or potting soil. It can

make do like that. And then once those plants start to die, they start to decompose, and then it really kicks off. So yeah, you can have like soil, a couple of horizons of soil in a hundred years if you're really boogian. Al Right, should we boogie on down and take a break. Yeah, let's let's get her hands dirty and we'll come back and we'll talk about these

horizons right after this, okay, chuck. Horizons. And speaking of horizons, I think there was a Disney World ride or at Epcot Center ride called Horizons or something like that, and there was this group of people who infiltrated it they figured out how to get basically behind the scenes and would hang out there for like entire weekends and like high during the regular hours and then just hang out like they were part of the set um after hours. After no it was about future life, like what life

was going to be like in the future. It's really cool. But the upshot of all this is that they documented the whole thing with pictures and it's somewhere on the internet. I can't remember where, but I'm pretty sure it was called Horizons. But it's a closed down Epcot ride where a bunch of people documented it in the early nineties, just with cool pictures of it. So check it out, and that's probably why they closed it down. I don't remember why they closed it down and what it became,

but think it's not nearly as cool. I never got to write it, but seeing those pictures, maybe I wish I'd been able to go. So here are a bunch of the horizons. When if you're talking about pedology, which is a study of soil, it's a bit of an unfortunate name. Um, but we're gonna talk about horizons, not the event horizon, not the Gateway to Hell itself, No chaos and disorder of unparalleled horrible nous. Did you see that? I loved it? Yeah, Yeah, it's pretty good. Huh. Yeah,

when's the last time you saw it? But when it came out, I don't think I ever repeated that one. I saw in the last couple of years, and it holds up. I've been several times since it came out, and it's it's a really genuinely good horror movie. Yeah. I agree. I also saw Solaris too recently, and that's a really great movie too. The Russian version of these, I've still never seen the Russian version. I've seen the Soderberg version. Yeah, it was good. I would recommend the Tarkovsky.

It's a bit of a grind, but worth it. Sure, his movies are all worth it, but they're just you know, they're tough. You don't if you're sleepy, don't try it. Okay, Okay, it's like The Irishman, but Russian and in space and good okay. Um. So the o horizon, these are some of the different horizons. The horizon is that's like not even top soil yet. It's the leaves that blow off of trees and are sitting sort of on top that

counts as the horizon. They're basically the things that are in the initial state of decomposition right on top of the dirt. Yeah. Exactly underneath that then is the A horizon. So this makes zero sense already because we went from oh to A. None of this makes sense. The A horizon um is what we would consider like top soil um. It has most of the organic matter that's really begun to decompose and break down into smaller and smaller bits,

and it's usually kind of dark in color. This is where the highest concentration of minerals are and this is also where you're going to find them the roots of plants to because they really like those those minerals and nutrients. Yeah. And by the way, when I said this makes no sense, I'm sure and our scientists is gonna say, guys, it

makes perfect sense. And and here's why. Uh, you have the E horizon next, which stands for alluviated horizon, and that's where you've got this water draining down and those minerals that you were talking about in the A horizon, it's leaching those minerals and all that stuff out, and you've got sort of this light colored soil in its wake. Right, Um, that is not a common or I shouldn't say common, it's you're not going to find that in every UM

soil sample that you take. Right. It's usually a product of say, like um, a patch on like a hilltop where it's it's like the dirt's in place, but all the nutrients have been leached out over time. So anytime you just dig with the shovel into some dirt, you're not necessarily going to find an E horizon. Yeah, and we should say that for all this stuff, it's all going to vary according to where you are and what kind of rain and flooding and uh and drainage that

you have and stuff like that. What's next, You got the B horizon that's the subsoil, and this is where you finally get down to some of the finer uh particles, and you've got like a lot of silt, a lot of clay. Uh. It's it's you're starting to get down to the good stuff at this point. And all this makes sense too if you think about it, like, um, when the water, when rain water trickles down through the soil and percolates, it's far easier for it to bring

with it smaller and smaller particles. So the further it travels, the further or the smaller the particles you're gonna find going down with it. So you've got your bigger particles, your looser, coarse or bigger top soil. Then you've got the subsoil, which is a little tighter together, and then in that um in the b horizon, in the subsoil,

you've got compacted. That's where you're gonna hit like your lay layer, because again, clay's made up of those tiniest little particles that have been brought all the way down as far as it can go with the water that's percolated. That's right, And it's much more stable than top soil as well. For sure, sometimes it's too stable and like water and roots can't really penetrate it. Yes, or shovels it can be. It can be a problem child as

far as soiled soil horizons. You know my story when I was trying to dig my fence post holes for my privacy fence years ago, was I rented a two man auger, a two person auger, and it just spun, it just it compacted the clay even more. It did not break it up at all. It's spun it like a potter's wheel. Nice, did you go give me some clay? Oh wait, that was bad? Did you get it? That was a pottery joke, but it tied into your problem. That was maybe the smartest joke I've ever made in

my life. Well, no, wonder I didn't get it. Uh And and I think I mentioned this on the show before. If you if you do have that kind of problem, if you're going to plant and you have really tough clay that you're trying to get through, or rock for that matter, get a San Angelo tool, which is that big heavy spike um that you see at the hardware store that's, oh yeah, six ft long, has a pointy end on one side and a flathead on the other in ways like you know, twenty pounds or something. Yeah,

I never knew what they were called. They look like sharp pointing lightning rods basically, right. Yeah, I mean you just it's backbreaking. But if you voice that thing into the ground as hard as you can and just wiggle it back and forth a million times, and then you're gonna be able to well, you're gonna be able to break up anything. Basically, and then you hit it with the auger or post hole diggers. Uh no, I mean the augur was useless at that point. You just loosen

and use a shovel. Did you get your money back and say this augur is worth nothing? No, because they would say welcome to Georgia. Thing. That's the slogan, and not all over Georgia, but particularly where we are, like up in the mountains and stuff it can get it can. The soil is very rich and very uh a pliable. Yeah, yeah, for good stuff as long as you don't hit the

granite underneath, which can happen. Yeah, as a matter of fact, because those those pieces of granite that you hit as you get closer and closer to the Appalachians further north and Georgia, that's bedrock that's like the outermost rock of the Earth's crust, right, so you're actually touching the earth. It's almost like the soil that builds up on top of the bedrock is I don't know, dander maybe, And

the bedrock is really the Earth's outer skin. So you're touching the Earth's skin when you're touching bedrock, which can which can poke through the ground every once in a while is what we call rock outcroppings. Yeah, and so as far as the horizon levels go just above the bedrock, I don't think we mentioned the sea horizon that is also rock. But that's rock that um his weather down some but didn't quite make it to soil level, right, because remember, some plants can come in and colonize that

rock and pretty quickly start building up soil. And if that's that rock beneath isn't exposed to that weathering process from wind and freeze, thaw and all that stuff, it's never gonna get broken down, right, It's just gonna be hard on the old auger uh, and then the bedrock. And then you've got what's called hard pan and these are mineral deposits that I mean, this stuff, I don't know. I guess it's harder than bedrock. It just sounds like nothing will will grow and there's no chance for anything

to permeate it. Yeah, and hard pan the is not under bedrock bedrocks as low as it gets before you like that's the Earth's crust. Hard pan is just kind of I think he's just kind of tossed that on where it's like this is this is another. It's like an e horizon, like an alluviated horizon. You're not gonna

find it everywhere. When you do, you'll know it because it's very hard to dig through and there can be streaks of it within another you know, soil system um of different horizon layers, uh, and you just don't want anything to do with that. Neither do plants either. It's basically impermeable as far as water and roots and shovels go no good. Another term that I think is really just cute is parent material, And that doesn't mean whether or not you would be a good papa or a

good mama to a human child. Parent material is the type of rock that you started out with, the type of mineral that you started out with millions of years ago that was weathered down there to create what kind of soil you've got, And depending on where you live and what was there hundreds of thousands or millions of years before you, you're gonna have much different kind of

soil than uh, maybe another place in the world. Yeah, Like if it started out as igneous rock from a lava flow, that's going to be different kind of it's going to produce a different soil from you know, sedimentary that was weathered down from a granite outcropping by a river. It's just different soil. But it can also come about in different ways, like like that rock outcropping that was worn down by a river and just kind of sunk further and further into the ground and was built up

a top of it. Soil layers were that would be called residual, where it's developed in place. There's also transported where it could be moved by like ice, like a glacier pushing soil from one place to another. Um and then there's also cumulose, which is basically like peat, where organic materials basically suspended in in suspended animation by water. It's it's prevented from full decomposition. That's right. Those are the kinds of parents that soil can have. So let's

talk about the soil texture triangle. Okay, this is where it gets pretty cool because if you're talking soil and and I think people should start using the word soil more than dirt because I just think it's more evocative of what you're really talking about. I think it's kind of reductive. I saw a dude who is like a soil sciences professor explain that to him, at least dirt

is like dead soil. Soil is like living, breathing, you know, it's almost like a It's a symbiotic organism formed by the by all these different other bits of life working together, whereas dirts is like dead stuff that maybe will become soil one day if it behaves itself right, if it if it plays his cards right. So this texture triangle, if you're talking soil is a mixture, and this is all soil of uh, sand, silt and clay sand. Well,

it's a really good podcast episode on it. I think we did um that is the most course, which is funny to think about because sand seems super super fine, but when compared to silt, I think sand is two to point zero five millimeters in diameter compared to silt, which is point o five to point o two. And then, like you mentioned earlier, it's hard to wrap your head around, but clay is a really really fine kind of soil

point o o two millimeters in diameter. And you've got to get that microscope out if you want to take a look at it. Yeah, and because the different sizes when they're put up against one another. If you've got a bunch of sand, the pores in between the grains of sand are going to be really big, which is why beaches don't have a lot of plant life growing on because water just drains right through them and it's

very difficult to keep organic matter suspended within it. Right silt, it gets a little easier, a lot easier because the from what I saw, the pores in between silts are basically ideal. They're just big enough that they drain really well, but they also can hold some water. And then clay because the pieces are so close together, the pores between them are so small that they hold a lot of water and they they basically sealed off the waters escape. So clay can either prevent water from coming in or

it can hold it in and and drown things. Either way, it's not necessarily very good for roots. Super compacted clay. Yeah, you want a nice mix, and it doesn't all have to you know, it depends on what you want to do and what you're working with, But it doesn't have to be the exact same mix either. Um. I'm sure there are ideal versions, but uh, depending on where you are, you can only do so much with your soil, Like, you can't make an entire farm uh something that it's not.

You can augment it and help it out, but you're kind of working with what you got to a certain degree. Um. I think one of the cool things from this research was that you know, if you see a farmer in a movie bend down, and that the scene that's in every movie about a farmer when they grab that soil in their hand and they look at it and twist it between their fingers and then let it fall gently out of their hand onto the ground. Not only does that make for a nice movie moment, but that's real

deal stuff. If you're a pro farmer or a soil scientist, you can tell exactly what's going on with that soil by how it clumps in your hand, how it moves in your hand, how it holds together, what shape it is. Uh. So it's not just a sort of a BS thing you see in movies. No, you can also run a lab test to figure out what the ratios are. Right. Yeah, hey, college boy, you need to get yourself a farmer um

with hands either way? Right, But if you if you, um, you there is an ideal combination between it depending on what you're trying to do. For sure, Um, you don't want it to clay, you don't want it too sandy, you don't want it although I don't know, I think you do kind of want everything to be kind of silty. But um, where they interact is going to going to describe what kind of dirt you're dealing with. And there

are things you can do too. There's a reason for understanding that because you can say, oh, if I add this, if I if I bury a bunch of grass clippings, is going to turn this clay into more silt um and everything's going to just jump for joy from that point on. Yeah, And if you're a home gardener, uh, you can certainly manipulate your yard or any potted soil that you have. You can amend all that stuff until you get exactly what you need. Um. And then once

you have it in a good place, there's upkeep. But it's it's not like you just have to do it once, but you have to do it once really really well and then just sort of keep that good mix going. Yeah, and then you can just go get one of these things that you you hook onto the end of your hose and spray it once in a while with some microbes and sit back and watch everything that's exactly right made out of deer hide. O. God, it doesn't It doesn't burn very well and it's kind of noxious smelling,

but it really makes a point, you know. I know we mentioned regularly and I want to say terraforming and other episodes mm, but this Sometimes people say this as a word for soil, but it's really much more than that. It's kind of like anything on top of the bedrock basically can be called regular, and that's not And we mentioned terraforming because if you talk about the Moon or Mars, you talk about regular as well, and whether or not

we could grow stuff there, which apparently we could, right. Um, yeah, if we added the right nutrients and water, it would it would hold, which is essentially all it is. At that point, It's like what that that soil science? This guy was saying that it's um, it's a it's it's dirt, not soil. It's dirt because it doesn't have anything living. But you can add that stuff to it as needed, right, make Mars great again? Oh God? So you want to talk about the carbon cycle? Yeah, what is I mean?

Does carbon have anything to do with the Earth. No, has nothing at all to do with it. Um. But actually it has quite a bit to do with it, right, So so um carbon is essentially the building block for life, and there's a big cycle of carbon moving through the environment.

There's a lot of it in the atmosphere in the form of c O two, and the atmosphere itself forms what's known as a carbon sink, which, if you haven't been paying attention in the last few decades, one of the reasons that climate change is happening is because we've been um overwhelming that carbon sink in the atmosphere by burning fossil fuels and releasing a lot of carbon dioxide that have been sequestered in the ground, which leads us to this point that plants and soil help lock carbon in,

so that in addition to the atmosphere being a carbon sink, soil is also a really major carbon sink too. Yeah, and you're thinking about agreeing with that or not. No, no, no, I totally agree with it. But I mean it's kind of like when you know, Amazon rainforest caught on fire. Uh, that's it's almost like you're getting a double whammy there, Like even just cutting the Amazon down to to grow

crops there too. Like you're you're, you're creating quite a bit of harm even without burning it down, because all those trees are really good at sequestering carbon dioxide from the air and creating a carbon sink in the ground. But then also it will find out later when you till the ground, a lot of that carbon that's been trapped under there, and we'll stay that way for a thousand or so years, is suddenly released just by tilling it.

So there's basically the main point I would like everybody to take away from this entire episode, maybe our entire podcast, Chuck, is leave the rainforests alone. Just stop messing with the rainforest, because it's really screwing things up in ways that we are yet to fully realize. Yeah, agreed, that was my soapbox. That's you and Don Henley Man arm in arm Yes, he's a big rainforest guy. You know. Well we're always

chatting it up about the rainforest. I got a lot of my ideas from him, you know, thanks to stuff you should know. Listener Clayton Jaynes, who was a guitar Well, I'm not gonna say exactly what he does, but he he worked on this last tour for the Eagles and invited Emily and I down before the show. I got to like touch Don Henley's drum kit and Joe Walsh's guitars. I remember you saying that, and Joe amazing because he happened to be standing next to his guitars at the

same time. It's pretty cool man. And you're like, I'm sorry, I'm sorry. He's like, it's okay. Life's been good to me so far. Uh, something's wrong with me today, man, something's bad wrong, all right. So let's talk about carbon dioxide, um for a second here, because plants draw that in from the atmosphere and then eventually they're going to break that down because as uh think, you know, photosynthesis happens and they use that carbon to build up that plant.

We're talking about the roots, the leaves, the stems. Carbon plays a big part in that. But eventually, like I said earlier, that plant is gonna die or leaves just fall from a tree or whatever, and that carbon is locked inside that leaf or that dead plant on the

ground that you stepped on right exactly. So, Um, what's great about this is that plant used that carbon and when it died, it died with that carbon and it was locked in like you said, but it's able to be used by other plants that come along, which is part of that whole like beautiful system that just works so intricately well because to unlock that carbon you have, that's where all that life that lives in the soil comes along and uh becomes extra extremely important because they

break that stuff down and decompose it. Depending on whether you're talking about bugs that chew up leaf litter um into smaller, smaller pieces, which makes it easier for microbes to break down more quickly. Um, the microbes themselves get eaten, and that carbon that was locked in the plant is suddenly unlocked and available in the soil for other plants to take up through their roots and build their own

structures and use for photosynthesis too. It's it's the circle of life, right, or it doesn't use at all, and some of that carbon is then released back into the atmosphere. Uh, then we get to the humus. And I think we might have talked about this. Surely we did in composting, Yes, we definitely, maybe we did. One of earthworms, right, yea, they talked about in earthworms. We talked about um in permaculture. I believe we may have also talked about it in

desertification and droughts. Right, that was a good one. That was good. So humist is that? Um, it's basically, if you'd compost something years later, you're gonna finally get down to humus. It's what's left over after all that snacking is done. Uh. And it's you know, if you have a home composter, I don't think that you have humus after a couple of months of doing a really good

job composting, because it takes like many years to become humans. Yeah. Um, And like it's just a very small percentage of the stuff you compost will break down into humus because apparently the precursor of humans is proteins, and most compost is made up of carbohydrates, plant materials, or carbs, right, Um, yeah, that's right. Um. So when it breaks down, this humus is it's almost like a Some soil scienists apparently consider humus a third state of life where it's not just dead,

it's very dead. Decomposition is not really happening anymore. But there's a lot of minerals kind of locked in their inorganic materials. UM. But the thing is you want humus. The more humis you have, the more lively in life, affirming your soil is UM. It's like eat, prey and love down there, you know, because humis forms an ideal house for all that other life to live in. It's like, exactly what is needed for the other organisms that make

soil alive in this um symbiotic network. That's what they want, is humist and and it's it's extraordinarily important stuff. But we don't fully understand why it doesn't necessarily keep breaking down after a point. Yeah, it's it's very dark, it's like black. Basically, it's very spongy. UM. It has great water retention. It can hold nine of its weight and water. Uh. And it's sort of like the bond. It's like the

cement that helps. You know, when you clump that soil together in your hand and it stays together, you can thank humus for that. Yeah, as a matter of fact, you should thank humans out loud when you can. When you squeeze soil in your hand, you totally should thank you humus. So it's like you said, like humust holds the stuff together, but it also creates those air pockets or those gaps that are so important in um in healthy soil, right, it keeps things from getting sticking too

close together. Yet it also keeps it in aggregations or aggregates, right, So it's really weird if you really stop and think about it. It holds things together, but not too much together. It kind of holds them together at just the right distance so that you have that ideal mixture of soil um gaps. And then those gaps are you know, can hold water moisture. Yeah, and you've got to have that that right mix, because too much sand is not able to hold any water. Like you mentioned, if you go

to the beach, you can just see this in action. Um, you've got to have some of that clay though, because that's the smallest one and it's uh those little micropores. They're gonna as what's called capillary action. That's uh adhesion and surface tension mixed together in a bag basically, and that's super super strong. And if you have clay in your soil, it's gonna hold that water and it'll even draw water up from the water table and say here

you go go out and feed. Yeah, I saw yet another soil sciences professor talk about capillary action, and he surprised me because he showed that um sand has the least amount of capillary action. There's some you know how like when you're digging into the sand, right before you get to the to the water beneath it, it's wet. That's because the sand has still been wicking some water up through those gaps. Um And But rather than clay being the the strongest with capillary action or the best

for soil, I should say, um, it's actually silt. He had like three tubes silt, sand and clay, all next to each other, and the silt one just rocked the other two for how far it had wicked water up this tube. So apparently that's the ideal. Silt is just as good as it gets. Is from what I can tell, it's your own team silt. I am super team silt

from now and forever. All right, I think we should take another break perhaps, and we'll talk about what all's living down there in that soil and what this all has to do with climate change right after this, all right, So we talked about early on things living in the soil. UM. I know it's It's easy to think about um, little mike robes and bacteria and things in soil because we know it's just rife with that stuff. But you can't

ignore the big things too. There are little moles that live in the soil, their prairie dogs, their lizards, there are snakes, um, all this stuff. Every like kind of larger animal disrupts the soil. But that's a good word in this case. You want that soil disrupted because it's redistributing nutrients. It's you know, you want them peeing and pooping in that stuff and mixing all that stuff in. And you've got this sort of larger, small to larger

animal system acting as a little composters along the way. Yeah, and and they're actually also mechanically mixing the soil. Like, you don't want your soil just be big, medium small. You want it to be fairly mixed together, because big is just to the the the gaps between are too big and small the gaps between or two small, you want them mixed well. And so like an earthworm burrowing

actually is mixing the the earth together. Gophers apparent mixed together something like eighteen hundred cubic meters per square kilometer every year. That's a tremendous amount of soil mixing in there. It's they're doing it for free, basically. Yeah, and that's when they're getting along. Like you want to really mix up some soil, you get a gopher rumble, Sure happening. You can get ugly, but your soil is gonna be

super mixed afterwards. Oh man, it's gonna be fantastic. Plus you can roll cigars out of their hides, the hide of the loser. Oh boy, you've also got spiders. You've got a little scorpions. Um, you've got centipedes, you got millipedes, you got termites, you have uh roaches. Unfortunately, I think right here it says in a sample of one square foot of two inch soil in the forest, two hundred species of mites alone. Yeah, that pretty impressive. I've got

one even better than that. Right, let's go down in order a magnitude or so. Oh, I know where you're headed. So, the microbes in the soil are so abundant and so prevalent. Apparently a teaspoon of soil has more microobs in it. Microbes is another pronunciation, um than there are than there are people on Earth and one teaspoon of soil, right, and all these little microbes, their bacteria, there's viruses, there's um, there's fungi. All these my all this microbial life are

like the last the last layer of decomposition. But they do even a lot more than just decompose dying things. Um. There's there's a function of fungus that we're just now starting to wrap our heads around called um micro riz a, which is a symbiotic relationship. So so soil itself is a symbiotic relationship. This is a symbiotic relationship within the symbiotic relationship where fungus basically says, hey, roots, I like

what you're doing there above me. Um, I'm gonna hang out around you and maybe grow my own system of roots out of fungus me that connects to your roots but also goes through the ground and connects to other roots too. And I'm going to take up, you know, nutrients from the soil and help you accept them into your roots, maybe bring you some water here there, and I'm gonna let you communicate with other plants through your roots, through me to the roots of the other plant too.

So it's like if you look at um. A micro is a if you pull up like a plant, it has like this thin, almost long like film around it. That's the fungus. That's it's like a root system around the roots system made up of fungus. And we're just starting to understand this and it's just beautiful to know that it exists like that. It's the fungus amongus. It is, And there's actually humongous fungus amongus, isn't there. Yeah, so, um, what you were talking about is a mutualist. They're kind

of three kinds of fungus. And I love that they call it a mutualist. It's a great name for that. Uh, the symbiotic relationship. There's the name for like a neo folk. Sure, yeah, why not get it? Get a tweed vest and a jaw harp and have have a good time. I just got a jaw harp in the mail. By the way, is that the one that has the shoulder mountains? No, the jaw harp is the twangy thing you put in your mouth. It's like to have it here. If you want me to go get it, I would love you

to go get it. I think we'll wait. The fungus that eats decaying matter is called a sacrifice. Then you've got your mutualist, and then you've got an actual parasitic fungus. Those are the jerks of the of the forest world. But you were talking about humongus fungus. I know, I feel like we've talked about this at some point. Pando. Was it in Pando? Okay? I thought it might be

um in mal Here National Forest. Um there is something called Janet D and a big network of fung i is a genet and Janet D is the humongous fungus is considered the largest living individual on Earth two thousand acres worth. Apparently it's all connected. Yeah, and it was not. It's the biggest by area. I think in Panda is

the biggest by mass. Like if you wade Pando, it would weigh more like this one was still covers a lot bigger area, but it's just one big, single organism and it is it's underground and it sucks onto um onto roots. And actually they found it because there was a bunch of dead trees and they're like, what's going on here? And they discovered that it was this one a m A stoy a fungus that um was killing off trees because it can be one of those jerk kinds.

The parasitic fungus, what are they called, just parasitic fungus. There's not a great name for them. Uh, No, parasitic fungus. But the ones that so they live in the soil. No one likes them. They're they're they're considered jerks, like you said, um, the ones that everybody likes. So the mutualists are the sacrifices which eat decaying matter and then sometimes they eat one another and all this stuff just the I don't want to say the point of it,

because who knows if there even is a point. But if there is a point, it is that UM that nutrients that get used by living things and locked into the living things when they die get unlocked so that other things can use them. All right, So do you want to talk about the nitrogen cycle? Yeah, because I mean that's another thing they can get locked and unlocked thanks to these organisms in their symbiosis. UM nitrogen is extremely important to plants. They used to make chlorophyll, They

use it to make some of their UM proteins and structures. UM. But it's and there's it's super abundant in the atmosphere, in the air. But now plants are really good at unlocking it um actually, which is right, which is why you need some plants called nitrogen fixers to come along. And I think legums are a really good example of this in like alf alpha peanuts, you know those things um and they can take it out of the air and turn it into a usable form. And they actually

do that, I saw, not on their own accord. They have to become infected by a bacteria called rhizobium, And it's actually the infection from ryriezobium that alters the plant to make it so that it can take nitrogen out of the air and deposited in its roots for storage. Yeah, most plants can't do that. They have to draw it

from the soil around them. And you know, we we mentioned the balance and nature that we always are seeking that homeostasis, which you would like is a balance between these nitrogen fixers and dead plants adding nitrogen into the soil and then also those plants that are drawing that soil out, like you want that all to sort of balance out together, right exactly, And again it's because there's help from bacteria helping fix nitrogen and nodules on the

on the roots that other plants can come along and use, and to fix what's called a fixed form, so it's fixed nitrogen. Like you can have, UM, say a glass of sea water, and you're really thirsty, but you can't drink it because it's not in a usable form, even though it's still water. But if you run it through a reverse osmosis filter and desalinate it, now it's usable water. So you can think of nitrogen fixing is like the Earth's version of reverse osmosis for nitrogen converting into a

usable form for plants. The thing is that we kind of talked about it before UM and you just hit upon it. There's like a natural cycle and natural process to all this, which things like agriculture, especially UM has really kind of disrupted. And even after the research that's been produced over time, we're still we're either being like willfully ignorant or still figuring it out, or people are still trying to get the word out. I don't know what the issue is UM. If it's just too expensive

to do it right, I don't know. I'll have to go back and listen to our permaculture episode again. But one of the ways, like you said, that we we disrupt this natural cycle, or the nitrogen cycle in particular, is by not um planting things like cover plants that are nitrogen fixers to replenish the soil. Instead, we use factory made fertilizer, which is just fixed nitrogen itself UM to replenish the soil, which is much harsher and can have um all sorts of uh cascading negative effects on

the surrounding environment as well. Yeah, because if you're doing a major agriculture job and you're pulling that nitrogen out, you've got to artificially put it back in. And that's all fertilizer is, because you're feeding that manure or whatever fertilizer you're using. Manure has a lot of nitrogen, so that's why it's used as a fertilizer, but you're just

pumping it back into the soil. Uh. There's a great documentary that's called I Think Big Little Farm maybe not about this couple who you know, dropped out and started their own farm, but started a farm that they wanted to do right and to be and balance like naturally with itself. It's really good and daunting and inspiring all at once. It's it's cool. It sounds a bit like um, the movie All of Me, where Lily Tomlin takes over Steve Martin's body and they have to learn to coexist

together kind of harmoniously. And I think they do at the end if I remember correctly. It's not big little farm, Biggest The biggest little farm is what it is in Texas. Uh No, that's a Burt Reynolds movie, right, Okay, And you said this is a documentary Biggest Little Farm. It's really good. You should check it out. Okay, Um, well, people should check out All of Me too, if you

ask me. Um. The thing is, Chuck is when you're talking about nitrogen fixing and say like, okay, well, farmers should just grow alfalfa and then whatever, say, if you harvest corn or something like that, you till it into the grass. Whatever is left over after you've harvested the corn, you till it into the ground. I mean, and that buried stuff actually provides a lot of food for all of those microbial life and um, earthworms and all that stuff.

So they actually leave the roots of your plants alone. That's great, but even doing that requires more care than you would think, because if we go back to humus, remember, humus is a really great way to lock in carbon for hundreds or thousands of years. But we're finding that it can be fairly easily disturbed by agricultural practices like tilling, and that once you disturb it, all of a sudden,

it's like, oh, yeah, well I'm done, I'm out. If you're not gonna appreciate me, I'm not gonna hold onto your carbon anymore, and it starts to release it. So we're finding that agricultural practices like um tilling are actually having a contribution and impact to climate change as well. Yeah, and it's not uh and I think this came from the same interview with the professor assistant professor Um. She's saying, it's not like it's the same as the burning of

fossil fuels. UM. There was an estimate is that soils

have lost a hundred and twenty uh pg. What does that stand for pedigrams of carbon since we've been since the dawn of agriculture basically, and that since seventeen fifty one, uh fossil fuel burning has had a cumulative total over four hundred pedigram so it's not on par but it is, you know, something to think about, and especially when you're talking about perma frost, and you know that's why we talk about when UH climate change is sort of like

this vicious cycle where things are heating up and then UH ice caps are melting, and when that stuff melts, that's releasing this perma frost. Soil that has been stored you know, stored carbon for thousands and thousands of years, all of a sudden released back up into the atmosphere. Yeah. Yeah, because humus is most stable as a carbon sink when it's cold. So if it's so cold that it's been

frozen for years, um, it's very stable. But yeah, as climate change warms it up, that starts to get released, and that is a problem. I mean, yes, a hundred and twenty pedigrams over the last years. It doesn't seem like much, but we're getting to the point now where every little bit counts, and I think as part of the Paris Climate Agreement, you can um count your carbon sinks, like the kind of soil you have against your output to to show whatever reduction you're working on. So it

does count, it is taken into account. It's just nothing like fossil fuels, but it is an important component, it seems like. Yeah, So basically, you know, that's what they did in the biggest Little farm is get back to basics of the dawn of agriculture when they practice really sound soil management. Um for the most part, tilling you know,

only what needs to be tilled. Don't go super deeper, super wide if you don't need to that ground cover that you were talking about, shades that soil, and don't burn. And this is one of the big problems with Big agg is burning plant waste. Yeah, you don't want to do that. You want to bury that stuff and put it back into the earth. Put it back into the earth, everybody, because the life down there wants It's right. That's the

slogan for this one. Okay, agreed. So get out there and get your hands dirty and go feel the soil and remember to say thank you Humus as you let it move through your fingers. Okay, okay, everybody. And in the meantime, I think, chuck, it's a listener mail. Yeah, this is uh from a teacher. I think is this a teacher? Yes, biology teacher. Appropriately, Hey, guys, just listen to the episode of arcolepsy. Thought it would clear up a confusion about the difference between a disease and a disorder.

As a high school biology teacher, I had to explain the difference every year. The difference is subtle, but there is a simple way to remember. A disease is caused by a path pathogen like a virus or bacteria. A disorder is a malfuncttion malfunction due to genetics, trauma, chemical toxicity, or other non living factor. The lines can become blurred a bit because the disorder can be triggered by a disease. Some cancers are triggered by viruses. May be a clearer example,

as HIV AIDS. A person can be HIV positive and if the viral disease is discovered in time and treated, they may never succumb to the disorder that is AIDS, which sets in when the infected person's immune system has been effectively eliminated. Hope this helps the issue. Thanks again, keep up the good work. And that is from Rich Brusk from Manhattan, Kansas. That's a man of hat A, Kansas. That's right. That is a world class biolo g teacher.

Chuck totally what was his last name, Brusque with a B. Sure, Thanks Mr Brusk from Manahatta, Kansas, UM. We appreciate that, and we appreciate you being a biology teacher in a world class one at that. If you want to show off what a world class person you are, you can get in touch with this too, like Mr Bruss did. Uh, you can send us an email send it off to Stuff podcast at iHeart radio dot com. Stuff you Should Know is a production of iHeart Radios How Stuff Works.

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