Understanding Compost – Garden Magic


Compost is amazing stuff. In all the years I worked with the Master Gardener program and taught classes, whenever I was asked what’s the best thing a gardener can do for their garden I always answered: “add compost.” But there’s a lot more to compost than just “Use it in your garden.” And that’s why I’m here today to help you understand compost. Hi, I’m Gardener Scott and compost is simply decomposed organic material that we use as a soil amendment or as a mulch. It can be very simple to make and very simple to use, but I think a lot of beginning gardeners are intimidated by making compost. They’re worried they’re not going to get it right. And many experienced gardeners use compost but maybe they’re not doing it in the best way possible or they don’t fully understand all of the benefits. So today I’ll be discussing the science behind composting, a little on how to compost, then more importantly, the benefits that compost can add to your garden. Organic material is constantly decomposing all around us and we don’t think much about it usually, but when we supervise that decomposition process, we call it composting and the finished product of composting, well, that’s compost. To make compost all you do is mix greens with browns. But it is more complicated than that because the greens represent nitrogen and the browns represent carbon and with the proper ratio of carbon to nitrogen all the bacteria and the fungus and the insects that get involved in the composting process have food. They eat it and the result is a decomposed organic material… compost. And this is where some of the intimidation factor settles in because choosing the right greens and the right browns seems like it might be a bit difficult. And why do we call them green and brown when we’re really talking nitrogen and carbon? Well the greens typically are plants that have been recently growing. So they’re still green. They’re high in nitrogen, typically. The browns… well, they’re also typically plant-based, but they’re much older, they’ve dried out, which typically makes them turn brown. That nitrogen has mostly dissipated and what’s left behind is a much higher ratio of carbon. But you should look beyond the color in determining what to compost because any organic material that’s high in nitrogen is considered a green. Manures for example are considered a high nitrogen source but there’s a lot of manures out there that are brown. As far as the carbon sources… yeah, a lot of them are brown, but there are many leaves that stay green after they’re dried. They’re still carbon. Newspaper is a carbon material, but it’s white. I’ll be going much more in depth as to what materials are greens – nitrogens – and what are browns – carbons – in another video. For now, I want to begin discussing the actual science behind these two materials and how they turn into compost. I’m in front of the composting bins that I recently built and you may have seen that video on how I did it. It’s here where the magic takes place, where we mix the greens and the browns together and provide a smorgasbord for the workhorses of the composting process. And those workhorses are bacteria. There’s three primary bacteria that turn our organic materials into compost. And that’s the Psycrophiles, the Mesophiles and the Thermophiles. Now you don’t need to remember the names of the bacteria, but it helps to understand how they work together. First the Psychrophiles. Well, they can handle pretty cool even cold conditions. They work best at about 55 degrees. And that’s when they’re chomping away at all this organic material. In the process they generate heat and that heat slowly raises the temperature of the pile that’s in this compost bin. As the pile rises then the Mesophiles kick in at about 70 degrees. 70 to 90 is their ideal range. They’re also generating heat as part of the decomposition process and when it hits a hundred degrees, that’s when the thoroughbreds kick in, those thermophiles. And they’re munchin’ fast and they’re generating a lot of heat. They can generate heat well above a hundred and forty degrees, all the way up to a hundred and sixty degrees. Above that point, well, they’ve pretty much eaten everything and they start to die off. It’s important to understand the concept of heat and bacteria because if the conditions are right, well, not only are they generating heat but they’re also generating a lot more bacteria in the process. So the decomposition, the composting, can happen very quickly if you’re aware of the bacteria, what they need to grow, and how to get the different bacteria to work together. There are basically four things that bacteria need to survive and to thrive. The first is food, and we’ve provided that with those greens and browns. The second is heat because at different heat levels those different bacterias will either live or die off. The third component is very important. That’s oxygen. These are all aerobic bacteria. They need oxygen. So typically how we do that, when we’re making compost… is to flip the pile. We get in with a shovel or a garden fork and we physically mix up the material and introduce oxygen in the process. That’s why I’ve got two bins here because I can take one pile and flip it into the other pile introducing oxygen during that process. And the fourth component… well, that’s water. Like most living things, it’s important for survival. So a typical compost pile should have a moisture level of about 40 to 60%. Don’t let your pile dry out. You’ll typically need to be adding water on a regular basis especially if you live in a hot dry environment like mine. If you get all of those factors together you’ll get compost. There are many other characters at play during the decomposition process. Fungi gets involved to decompose some of the particles. Anaerobic bacteria is involved in some of those sections that doesn’t have a lot of oxygen. And there are many insects that will burrow in and eat the organic material and all together what they do is break down all of that organic matter into its basic elements. And it’s those basic elements that we put into the soil for the plants to use. How long it takes to compost is variable depending on those many factors. I’ve had piles that take a year to turn into compost because I don’t work very hard at it. But when I work hard I can turn a pile into compost in just a month. It’s a little bit of art mixed in with science. It’s experience. It’s learning. And it’s experimenting and just doing it. To get the compost going you’re basically looking for a ratio of four browns to one green. That’s the easiest way to think about it. So as you start putting the materials together is four to one. However, if you get the science involved you’re actually looking at a carbon to nitrogen ratio of 25 to 1. And that’s because some materials are very high in carbon and some materials are low in carbon and some materials are high in nitrogen or some are low in nitrogen. And I’ll be covering that in that later video. Just think in terms of 4 bunches of dried material with 1 bunch of good green material and that’s a good way to get your pile started. Your compost pile will actually talk to you while it’s decomposing. So listen to it. If it’s not decomposing very quickly, well, it’s probably one of two reasons. It’s because it’s too high in carbon and doesn’t have enough nitrogen or it doesn’t have enough moisture and/or oxygen. So it takes a long time. I’ll get in there. I’ll make sure the pile is moist. I’ll turn it and I may need to consider adding more nitrogen. It shouldn’t smell. If your pile smells, well, then you’ve got the opposite problem. It’s one of two things. It’s either too much nitrogen or too much water. The solution is pretty much the same. Get in there, turn the pile, dry it out a little bit during that turning process, if it is too wet. If the moisture level seems okay, well, then add more brown material. Add more carbon. So we’ve covered the basics behind the science of composting and how to get a pile started. But now let’s talk about those amazing benefits of compost. Well, chief among them is the nutrient value of compost… all those bacteria have broken down the leaves and the grass and all that other organic material. And they’ve broken down usable nutrients for plants. It’s the nitrogen, the phosphorus, the potassium, all those other micronutrients. Well, they exist in compost. So when you add all of those materials in your pile you get a smorgasbord for plant roots and they’ll definitely grow better. Another important benefit to compost is that it improves soil structure. You can take pretty bad soil and turn it into pretty good soil. If you have a soil that’s high in clay, for example, by using compost as a soil amendment and mixing it in you’ll be separating those very fine clay particles with little bits of compost. Now they will allow oxygen and water to get down to the roots of your plants. If you have soil that’s very high in sand, where water normally just drains right on through, by adding compost you’re essentially adding little sponges that will absorb and retain the water in your soil. In fact soil with compost can retain four times the amount of water as soil without compost. That can be very important if you have an erosion problem. Another awesome benefit to compost is that it’s free if you make it yourself. If you buy it from a store in bags, you really don’t know where it came from and what’s in it, but when you make it yourself, you know exactly the source of all of that organic material. And all that organic material is yard waste that maybe you would have had to bag and pay somebody to cart away. Now you can take your yard waste and kitchen waste and turn it into this black gold that has all of these soil benefits and nutrient benefits and it doesn’t cost you anything. There are many reasons why you should compost and why you should use compost and I’ll be covering much more in those future videos. The last important advantage in my mind is that compost creates bio diversity. Both within the pile and within the garden, it creates a world that makes it all happen. That compost in the ground that wasn’t fully decomposed by the bacteria… well now it becomes food for earthworms and beetles and many other animals and insects. And those animals and insects become food for other animals, which become food for other animals. And you have an entire cycle that benefits your garden and the world. And it begins with compost. And it’s so easy to do. And so there you have some science, and some how-to, and some why to compost. There are a lot of questions that still are unanswered. So let me know in the comments if you have any other questions. Now if you want to see those videos or any other Gardener Scott videos, well, then subscribe to the Gardener Scott channel, if you haven’t already done so. And be sure to click on the bell and to make it easy you can click on my face that’ll show up in a couple seconds. If you like this video, you can give me a thumbs up and share it. I’m Gardener Scott. Enjoy gardening.

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