Dirt & Soil part 2
Dirt & Soil part 2
What makes the stuff that feeds our plants?
Now, there’s a big part of the soil not brought up yet-- and it’s the inorganic matter called dirt. Folks, including myself, often use these terms interchangeably, but that’s not really a good habit, because soil is the web of life within the ground, while dirt is the conditions the soil lives within—the sand, silt, and clay— the mineral piece of the soil composition. This is important, and something we hear too often, especially on Youtube. Some white suburbanite creates a channel and will say, “We did the ruth stout method and turned our clay backyard into beautiful, healthy soil”! Well, yes, you may have created some great soil, but you didn’t turn the clay into anything. It’s still there. There’s just that there’s an increased amount of organic matter wrapped up in it. The quality and texture may be similarly like a loam, but it’s the biological element which creates the ability of dirt to harbor life and be a successful medium for plants to grow successfully.
Generally speaking, the dirt in your soil is composed of one of, or a mix of, gravel, sand, silt, and clay— and those are in order from biggest to smallest—gravel, sand, silt, and clay. The bigger two, gravel and sand, are significantly larger— 100x larger— than silt and clay. And if you think about that for a second, the larger the soil material is, the better it drains because there’s more space between each individual particle. If you want to figure out what you have, get 3 tablespoons of moist soil, and form a ball— if it falls apart, you’ve got sandy soil. If it forms more of a ribbon, like it maintains some of its structure—it’s silty sand.
The takeaway is that water absorption is significantly impacted by dirt content, but soil compaction is significantly impacted—smaller material can compact more tightly, impacting soil aeration, which is a major factor in the biology of the soil. This is not to say there is any benefit to clay soil, which is the smallest material of the for— clay is actually superior at holding nutrients, and can be a very good material for soil. We won’t have time in this piece to discuss the impact of cations, but this is an area worth exploring to understand in more detail the impacts of clay on nutrient density.
Soil Horizons
Now, everyone going back to like third grade can remember when we all learned about the layers of different —let’s call it, stuff— in the ground. Well, we’re gonna do a very quick refresher, because while I’m sure you all remember everything from every grade of schooling, I don’t. So, these different layers are often called horizons. For most of us, the first two layers are where we’re farming, unless we’re working in raised beds, but even still, as we move soil it’s important to know what we’re moving and what we should be moving. Those 2 layers can be 3 inches or feet deep.
The first layer is organic matter, the recently decomposed and decomposing stuff. The second is the nutrient rich layer, which is that dark, lovely soil we all hope to find when we start digging into the garden. The third is called the fluvial layer, which is a leached layer, the fourth is a mineral-rich layer, the fifth is the transition layer, and the sixth is the parent material-- whatever base material is in the soil, where that mineral layer- the sand, rock, etc came from. The last 4 layers, for simple purposes, are essentially gradations of the parent material blending with the organic material.
So the big thing we have been referring back to in the value of dirt is how it impacts water, so let’s swing over in that direction. About 25% of the content in your soil should be water— and again, we’re talking about the type of soil we wanted in a garden. There are two ways water is held in soil—cohesion— which is water sticking to itself, and adhesion— which is water sticking to the matter in the soil. With wet soil, water will hold on to itself and soil particles. As the soil dries out, the soil particles grab to each other instead of going into the soil. I know, it seems ridiculous, but think about your houseplants. If you’re like me, you love the idea of houseplants, but are terrible about watering them because you always feel like you just watered them. Then you see they’re dying, and you rush to water them, and the water sits on the top of the pot after you pour way too much in, then it drains out the bottom all over your sideboard, and an hour later, the soil looks dry. While some of that is probably the perlite in the potting mix, a large piece of it is what we just described as well as surface crust, which is exactly what it sounds like.
Soil in this sense soil can exist in three different states—saturated, which is when the water can no longer be retained and runoff begins, which has lots of problems, namely nutrient loss, topsoil loss, and usually damage to the plants growing in that soil. Saturated soils mean there’s a limited, if any amount of oxygen in the soil, and you’re likely facing a massive case of root rot and other various diseases in your near future. The opposite state is the permanent wilting point, which is much like our poor houseplants dying in the corner. The soil is nearly incapable of breaking the strong bonds within itself to have any adhesion with the water, reinforcing its sad state. Field capacity is the middle ground— the soil is moist and capable of taking more water, while still being full of oxygen and providing the plants and beneficial bugs with everything they need to survive.
Oftentimes, folks will think they have clay beneath their soil or think that their soil is saturated because they will have massive water buildup in weird places—think like, a giant puddle on the top of a hill. However, sometimes this can be from plow pans, which is when plowing has compacted the soil below the plow, giving aerated soil above the plow pan, but once that plowed soil has been saturated, you’re experiencing runoff— which means your soil is actually holding less water than you think it is, since your mineral layer is often much deeper than where you’d find a plow pan—but not always. This difference matters because you can improve this situation with good soil health, whereas there’s not much you can do other than build more soil when your mineral layer is close to the surface.
The first step in figuring out what’s going on with your soil is to look at your drainage classification, which ranges from— you guessed it—well drained to poorly drained. Very technical, I know. Sandy soil is probably going to be well drained, while your clay and silty clays are poorly drained. If you’re digging into your soil and see sand, you probably know what it looks like. Remember, you want to get below the humus layer which may be from an inches to a foot or so deep before you get more of the sediment from the mineral layer. You probably know what sand looks like; grainy, brownish, maybe a light brown. Your silt— if you have lots of it, will be more grey, tan, creamy, and maybe even blackish material, and it’s very fine material. Again, you can try to roll it into a ball to confirm the content. Clay soils, by contrast, are usually a yellow or red color. If you come across blue clay, it’s not actually clay but silt that has had water trapped in the soil where oxygen has gotten into it and the soil has gone anaerobic. With this knowledge, you can get a better sense of why your soil may not be draining, and if your soil seems to be good, you may want to consider that you have a plow pan causing poor drainage.
So let’s talk about air in the soil— which should constitute about 25% of the soil content. We discussed the insects and bacteria— the aggregates— that can help aerate the soil from their relationship with plants. Additionally, there are a few other ways air builds up in soil—one is from older root pathways that have died and broken down, another is from shifts in the soil creating new spaces between soil particles, and the last is simply from the absence of water— like what we were talking about just a few minutes ago. These points where air can exist within the soil are crucial for soil development and are often indicators of healthy soil in themselves.
While air may seem like an obvious need for plants and the various bacteria and fungi that live within the soils— they too need oxygen— the other challenge comes from their ability to release harmful secretions that then release back into the air. This is why it’s important for the soil to be able to absorb moisture, retain it, but also work like a sponge— keeping the soil both aerated and moist. Contrary to what many might believe, the problem with clay soil isn’t just that it’s like a rock and roots struggle to break through it, but that it actually absorbs water & holds it, leaving no pockets of air for roots and the beneficial creatures in the soil.
Anyways, okay, so now you kind of have an idea of what’s in soil and sort of how it functions. Now, there’s a lot of middle ground between great soil and dirt, and, as you might expect, there’s an evolutionary process for the soil as it goes from bad to good.
The succession of the soil foodweb from being inhabitable to creating dynamic, healthy soil has certain evidence, and it’s something you can use as a framework as you assess your soil, and, for bonus points, it ties right back into the complex systems we had talked about when we were talking global warming.
Fungi & Bacteria Ratios
So let’s start kind of at a bare bones beginning; if you see soil where nothing can grow, there’s little to no fungi to create and move soluble nutrients through the soil— there’s only bacteria. When weeds take over, they rely on bacteria, but the new organic material added as they begin to die provides nutrients which fungi in the soil are now able to absorb, but the soil is still primarily bacterial, and generally in these situations they have lots of nitrates.1 We’ll discuss the nitrate component in another article, because it’s important but something we don’t have time to jump into quite at this moment. There is also new evidence that fungi travel within seeds along with the plants, meaning that each plant works with at least 1 fungi and helps to transfer specific fungi to new sites.2 Because of the limited amounts of fungi, weeds do exceptionally well in compacted soils, where nothing else will grow, so if you’ve ever had an above-ground pool and tried to plant grass seed there, you probably noticed perennial grasses really struggle afterwards and the weeds absolutely take over.
The weeds will, however, eventually drop enough organic material onto the soil to feed the fungi to break up the compact soil, and some grasses will begin to cohabitate the space with the weeds. What happens is that with each species— the early grasses like Bermuda grass, to the more traditional grasses— each of these adds more and different fungi to the environment, which helps break up the soil, add new dead materials to soil, create complex fungi networks, and brings the ratios of bacteria and fungi to a place where there is equal or more fungi to bacteria, while also absorbing much of the nitrates in the soil. When fungi to bacteria levels are equal, we are in a great place for growing most of our traditional crops—grains, tomatoes, etc. As the fungi outpaces the bacteria, we move from shrubs at 2:1 - 5:1 to trees at 5:1 to 100:1 and to ultimately old-growth forests, where fungi can outnumber bacteria 1000 to 1.3 Now, to put that number in prospective; within a gram of soil in an old-growth forest, almost 70% of that bit of soil you just picked up is fungi.4 It’s not that bacteria is leaving the soil that makes the soil healthy, because they’re not leaving. It’s the fungi increasing in number.
So, you want as much fungi as possible in the soil, right? Well, no. It depends on what you’re trying to grow, actually. Look at a blueberry bush— it’s a bush, so your first response might be, well, maybe in that 2:1 -5:1 ratio of fungi to bacteria. Well, that makes sense, but it’s not accurate, because blueberries tend to live in pine-dense deciduous forests that are prone to burning, so they are often secondary forests with low-Ph soil, so their ideal fungi to bacteria ratio is probably really in that 5:1 to 100:1 range, maybe at the high end of that range. And this points to an obvious issue with these being hard rules; plants don’t live in isolation; they’re surrounded by other species that have vastly different needs, so it’s not necessarily that these are strict rules regarding plant requirements.
But by understanding this relationship, you’re able to plan, plant, and contextualize what’s going on with your plants in your soil.
Let’s circle back to those ratios— what’s important to understand is while the ratio is important, the actual volume of bacteria and fungi matters as well. If we go from, say a 300 microgram 1:1 ratio of bacteria and fungi content in a soil to 400 microgram, crop sizes increase 30%.5 If we continue going up, we can double or production or more, because of faster nutrient cycling, and everything is healthier. And here’s the thing-- if you maintain the biology of the soil, you can continue to get those results. Let me say that again, you can maintain those results without the use of added fertilizer. What we have to do is provide the biology to feed our plants to be able to succeed in stimulating growth.
Now, in this shift from low-fungi to high-fungi soils impacts the rest of the soil matter, including its pH. pH of high-fungi soils are naturally acidic— if you’re not familiar with the term, it means the soil has a PH below 5.5. This can often be harder soil for grasses and other annuals to grow in; it’s the reason you might struggle to get grass to grow underneath trees in your backyard even if you have good lighting. High pH soils are primarily bacteria-driven, which is why grasses do better in these types of environments. When fungi grows, they release organic acids between 4 and 7 PH. So fungi are the key indicator of your soil being balanced. Further, the NH4—the ammonium— of the fungi and bacteria that is eaten by nematodes & micro-anthropods is released back as NH4. Without the fungi, however, the hydrogen is released from the NH4 and replaced with oxygen, which helps promote weeds instead of more complex, demanding plants.6
On this subject of pH, it’s important to understand that many essential nutrients are not soluble in large amounts in soils with excessively high or low pH— the most benefit comes from soil in that 6.2-7.2 pH range. If you’ve heard folks say that adding lime to your soil is like adding fertilizer, this is what they mean— the nutrients are essentially becoming unlocked to your plants.
What I’m saying here is that we don’t need fertilizers— not the traditional ones anyway.
What works is to understand the big picture of what’s happening in order to figure out how to fix the situation, using natural resources. And I really hesitate to use the term ‘natural’, which is always so slippery to pin exactly what it means. But, solutions that come from materials that you can get your hands on, is what I’m talking about here. We’ll dive into this concept further with the applications of Korean Natural Farming, JADAM, Vrikshayerveda, and biostimulants, and we’ll be diving into the other chemical impacts of fungi versus bacteria in our soil composition in future sections.
If you’ve enjoyed this piece, which is equal to a 12 page chapter, of (so far) a 56 page book with 46 sources, you can support our work a number of ways. The first is by sharing this article with folks you think would find it interesting. The second is by listening and sharing the audio version of this content, the Poor Proles Almanac podcast, available wherever you get your podcasts. If you’d like to financially support the project, and get exclusive access to our limited paywalled content, you can subscribe on Substack or Patreon, which will both give you access to the paywalled content, and in the case of Patreon, early access to the audio episodes as well.
Frąc, M., Hannula, S. E., Bełka, M., & Jędryczka, M. (2018, March 27). Fungal biodiversity and their role in Soil Health. Frontiers. Retrieved February 3, 2023, from https://www.frontiersin.org/articles/10.3389/fmicb.2018.00707/full
Lowenfels, J. (2022). Teaming with bacteria: The Organic Gardener's Guide to endophytic bacteria and the rhizophagy cycle. Timber Press.
Xiaoli Wang a d 1, a, d, 1, b, c, e, & AbstractBacteria and fungi are the primary consumers and. (2018, December 13). Fungi to bacteria ratio: Historical misinterpretations and potential implications. Acta Oecologica. Retrieved February 3, 2023, from https://www.sciencedirect.com/science/article/abs/pii/S1146609X18300389
Ingham, E. (2016, May 11). Building Soil Health for healthy plants by soil scientist dr. Elaine Ingham. YouTube. Retrieved February 3, 2023.
https://www.epa.wa.gov.au/sites/default/files/Referral_Documentation/All%20Research%20Paper%20-%20Appendix.pdf
Harding, D. P., & Raizada, M. N. (2015, August 10). Controlling weeds with fungi, bacteria and viruses: A Review. Frontiers. Retrieved February 3, 2023, from https://www.frontiersin.org/articles/10.3389/fpls.2015.00659/full