Soil Composition

by Jason Amores Sumpter
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forget everything you see on this page. Guys, soils, just dirt. It's just dirt. So I was just dirt Doesn't matter. That's actually not true. Soil is a highly dynamic composition of inorganic minerals, organic matter, trapped gas, IDs, liquids, mostly water and many living organisms. Soil begins when weathered rock breaks up into gravel, sand, silt and clay. This composes the base of soil soils, then enriched with organic matter. The good stuff is what we call humus. This is decaying. Organic matter usually comes from like dead cells and feces that organisms add to the soil, and this adds tons of nutrients. Now the texture of soil that is, the proportion of components like gravel, sand, silt and clay has a huge effect on plants. It affects the ability of plant roots to penetrate and absorb nutrients. It also affect the ability of soil to hold water and oxygen. And you might not realize what that oxygen is important for. Well, guess what? That oxygen is gonna be the final electron, except er in the electron transport chain of roots so super important, right? Obviously, it's key to cellular respiration, very fundamental process. Now loam is a special type of soil. This is like this is the good stuff. This is This is like the Dom Perignon of soil, right? This has equal proportions of sand, silt and clay with lots of humus. This is like, This is la creme de la creme. This is that good, good soil. Now, when we talk about soil, what we're usually thinking of is topsoil. Because, you know, generally speaking, I don't know how much you dig around in the dirt, but I'm not going that deep. Topsoil is that outermost layer and has the highest concentration of humus and microorganisms. It's usually why it's a lot darker than the layers below it. Uh, it's composed of tons of different organisms, including bacteria, archaea, fungi, algae, nematodes, protests, insects and worms. And those worms. Those guys air super important to soil. They move the soils around, they cycle nutrients, and they break it up to make it better at retaining gasses and water. Now those other organisms also do a ton to help maintain and enrich soil. In fact, we're going to really focus in on what bacteria, archaea and fungi do in later lesson. When we talk about nitrogen fixation so anyways, we talked about topsoil. There's other layers to soil. We call these soil layers, soil horizons, Uh, kind of a funny name. But when you actually see a picture of it, it makes sense, Right? Have you ever seen a like a sunset off in the horizon, Scott? Layers of color, right? Well, here we've got layers of color in the dirt. And this is, uh, you know, this right here is an actual image. You can see that it's about 3 ft down from the surface. That's, you know, in actual picture, Uh, here we have a diagram of some soil horizons that's going to go deeper than what we see here. This is really ending in the subsoil. Um, but as you can see, the soil horizons go deeper and eventually hit what's known as bedrock. That's like rock bottom. Over here, you can see different types of soil compositions of soil textures. This nifty little chart put out by the off federal government, actually, um, kind of cool little chart. Don't worry about, you know, memorizing any of the information they're even really, you know, trying to read too much into it. It's just to illustrate that there's a wide variety of soil textures and this stuff matters right. Our Department of Agriculture, that's who made this try. You know, they care about this stuff because, well, if they don't get it right, you know we don't eat so soil. PH actually varies greatly, depending on where you are, and this can have an impact on nutrient absorption. Acidic soils like you'll find in Conifer forests like forest with lots of pine trees, usually come from lots of decaying organic matter because this decaying organic matter produces organic acids. Now, alkaline soil, on the other hand, tends to be from limestone or calcium carbonate. This limestone, when it breaks down into the soil, will form bicarbonate, which is a week base and but just to be clear, acidic soil. We're talking about low pH alkaline soil. Hi Ph. Just to be crystal clear. Now, soil erosion is when wind and water carry soil away from a place. Uh, roots actually help prevent soil erosion. They help lock the soil in there by sort of creating matrix toe. Hold it in place. Roots also tend to excrete acids, which in general is going to lower soil pH. And you'll see soon why this could be really important. So with that, let's flip the page