What We Learned in Part 4
In Part 4 of this series, we pulled back the curtain on how nutrients actually move through an ecosystem. We distinguished organic nutrients from inorganic ones and showed how they constantly shift between the two. We explored immobilization (nutrients getting locked up inside living tissue) and mineralization (nutrients being released back into available forms), and why healthy soils need a steady balance of both. Finally, we challenged two widely held assumptions: that plants can only absorb inorganic, water-soluble nutrients, and that synthetic fertilizers directly feed plants. The evidence says otherwise. Plants readily absorb amino acids, intact proteins, and even whole microbes. In fact, 40-60% of fertilizer nutrients never reach the plant in the year they’re applied, because the natural nutrient cycle, not the fertilizer bag, does most of the heavy lifting. The golden rule: microbes eat first.
That brings us to the most important question in this whole series: who are the stars of this show? In Part 5, we introduce the biological players that make nutrient cycling actually work. From mycorrhizal fungi that extend a plant’s root system far beyond what it could reach alone, to the newly discovered rhizophagy cycle, where plants actively “farm” microbes for nutrients. The Soil Food Web is the engine behind everything we’ve covered so far. Understanding it is the key to unlocking the fertility that’s already sitting in your soil.
Missed part 4? Check it out here.
Meet the Underground Herd
Abiotic vs. Biotic Nutrient Cycling
Nutrients become available to plants through two broad pathways: abiotic (non-living) and biotic (living) processes.
Abiotic pathways include the weathering of rocks by carbonic acid (formed when carbon dioxide mixes with water), along with glaciers, lightning, volcanic activity, and pressure. Some of these processes move quickly, but most take decades or centuries to make a meaningful contribution to the pool of plant-available nutrients.
Biotic activity is a different story entirely. Living organisms cycle nutrients on a timescale of minutes, days, and weeks. That speed isn’t luck or chance! It’s one of the defining features of life itself. Every organism needs a constant supply of energy and raw material to build and maintain its cells right here and right now. In other words: every living thing eats and excretes. No exceptions.
The Six Kingdoms of Life
Life on Earth has been categorized into six large groups, called kingdoms. Each is defined by distinct cellular structures and modes of survival.
Archaebacteria
These are single-celled organisms lacking a nucleus that thrive in extreme environments like hot springs, deep-sea vents, and salt lakes, often using unusual metabolic pathways to survive. Even so, many are found in the soil and play a role in nutrient cycling!
Eubacteria
Closely related to Archaebacteria, but distinct enough are the Eubacteria, or true bacteria, which are also single-celled.
Protists
Next, we move to organisms with a nucleus and other membrane-bound organelles. These organisms are termed the “eukaryotes”, while archaebacteria and true bacteria are termed “prokaryotes.” The Protists form a highly diverse group of mostly single-celled organisms, such as amoebas and algae, that don’t fit neatly into the other kingdoms.
Fungi
The Fungi, which include single-celled yeasts, molds, mushrooming species, and non-mushrooming species like the oft-discussed mycorrhizal fungi we will discuss later at length.
Plants
These are multicellular organisms that produce their own food through photosynthesis, forming the foundation of most terrestrial ecosystems.
Animals
Finally, the Animals are multicellular eukaryotic organisms that obtain energy by consuming other organisms and are typically capable of movement at some stage of their lives.
The Soil Food Web
This all might seem complex, but it’s actually pretty simple when you zoom out. Every organism on Earth survives by taking in outside resources and converting them into usable energy and the building blocks for its own body. The authors of Principles and Applications of Soil Microbiology put it well: “The overall goal of all forms of metabolism (biological activities) is essentially the same – to obtain energy and carbon needed for the production of cellular constituents necessary for growth, survival, and reproduction… the metabolic diversity among microorganisms comes down to differences in strategies rather than the goals of these strategies.”
Sometimes an organism gets ahead by competing with its neighbors for resources. Other times, it’s more profitable to team up and share. The late soil scientist Dr. Elaine Ingham calls the sum total of these relationships the “Soil Food Web“. “Food web” is a far better phrase than “food chain,” because nutrient cycling isn’t linear. It’s circular. Organisms at the “top” are eventually broken down by decomposers at the “bottom,” closing the loop. The nutrients locked inside something eventually become food for something else, whether eaten directly or from something else consuming its nutrient-rich waste. This incessant consumption-waste-growth-waste cycle is one of the most important processes that move nutrients around a landscape and makes our planet habitable in the first place. And, it turns out, the smallest among us are the most important players in this great cycling of nutrients.
Why Microbes Are Built for This Job
To understand how something as small as a microbe can be so important to life on Earth, you have to think about life from a microscopic point of view, not from ours. It’s a microbial world and we’re just livin’ in it.
Microbes are everywhere. They are hardy, they are highly adaptable and they reproduce astonishingly fast. Some bacteria can double in population size roughly once every 20 minutes, viruses even faster21. Compare that to humans, who might reproduce once or twice by age 30. That reproductive speed doesn’t just grow microbial populations quickly. It also raises the odds of beneficial mutations appearing and spreading. On top of that, epigenetic and quorum sensing regulation lets individual microbes switch genes on and off to adapt to changing conditions, while horizontal gene transfer lets microbes share useful genetic information from organism to organism with no reproduction required. Genius! If something works, it can spread and it can spread very quickly.
It’s no surprise, then, that microbes have figured out how to make a living in nearly every environment on Earth with their various levels of available nutrients.
If microbes can conquer landscapes from chilly mountaintops to underwater steaming-hot thermal vents, imagine what they do in a temperate, moist environment loaded with resources, constant moisture, and an ideal temperature. In many ways, healthy soil is exactly that: an optimum environment chock-full of resources and moisture in a moderate temperature range. For this reason, among others, some estimates suggest nearly 60% of all life on Earth lives in the soil, and microbes make up the overwhelming majority of that diversity.22
This diversity is crucial to nutrient cycling because every species carves out its own niche by extracting energy from a specific resource. Diazotrophic microbes, for example, pull nitrogen gas out of the air and convert it into ammonia or ammonium, which are forms life can actually use. That newly available nitrogen then supports other microbes that have carved out a niche in pulling phosphorus out of rock, and still others that do the same for potassium23, sulfur24, calcium25, silicon26, on and on. As these microbes die or get eaten, the nutrients they built into their bodies re-enter circulation within the food web.
And here’s the encouraging part: most nutrients, including phosphorus and potassium, are already abundant in soil. They’re just locked in inaccessible forms. As researchers studying phosphorus availability note, phosphorus is “abundant in soils,”27 and potassium is described as “an abundant element present in the soil but in an inaccessible form.”28 The fertility is already there. The job is unlocking it and cycling it.
The Rhizosphere: Where Plants and Microbes Strike a Deal
Feeding the Underground Herd
If you want this system of nutrient cycling to run efficiently, you have to keep feeding it. Without a steady food supply, hungry microbes will burn through soil organic matter faster than it gets replenished. Kentucky farmer Jesse Frost of The No-Till Growers pithily puts it, “If the soil is not being fed, the soil will feed on itself.”
And how do we feed the underground herd? Amendments like compost and manure certainly help when applied thoughtfully, but the single most effective way to feed soil biology is by growing a plant. It sounds too simple, but it is true. More photosynthesis occurring on the landscape means more organic matter to feed the underground herd, as the fixation of CO2 into glucose is the origin of all organic matter/humus.
This is a very important reason why “keeping a living root in the soil for as long as possible throughout the year” is one of the six principles of soil health. Living plants are the bottleneck that transforms solar energy into a form that all other life forms can use. That energy, then, is what powers the furious pace of biological nutrient cycling, a process which benefits every organism in the system, plants most of all.
Teaming Up
Plants have developed close relationships with the microbial communities that surround them on their leaves, stems, roots, and even inside their tissue. The zone of interaction between plants and microbes above ground is called the “phyllosphere“; below ground, it’s the “rhizosphere.” Microbes that live inside plant tissue are called “endophytes.”
The vast majority of archaea, bacteria, protists, fungi, and small animals associated with plants are neutral or beneficial for nutrient acquisition, even in the phyllosphere, where some leaf-dwelling microbes fix nitrogen from the air, much like the bacteria that partner with legumes.29 Unfortunately, the phyllosphere remains the least-studied of these relationships, so there’s still a lot of room for research, especially as foliar feeding grows in popularity. For now, we’ll focus on what’s best understood: the rhizosphere and endophytic relationships.
How Plants Feed Microbes And Get Paid Back in Nutrients
The rhizosphere is technically just the 2-3 mm zone surrounding a root, but don’t let the small size fool you. It may be the most complex ecosystem on the planet.30 Life, death, consumption, competition, cooperation, and constant information-sharing all happen here, every day, right beneath a farmer’s boots. Many regenerative producers describe a genuine sense of awe the first time they understand what’s happening underground and that awe tends to translate into a real sense of responsibility to protect it, which is both an ecologically sound and economically smart long-term strategy.
We all know that roots have the ability to absorb, which can drain an area of its easily available nutrients and water. What many people don’t know is that roots can also exude compounds from inside out. Plants exude organic acids and other compounds to release additional nutrients from nearby minerals and organic matter that are physically and chemically more protected. While this increases access to what they need, roots still need outside help to acquire everything they need to nourish themselves. Enter, microbes.
Microbes, namely viruses (sort of! Viruses, by definition, are not living creatures), archaea, bacteria, fungi, and protists, are like any good employee. In order to bring nutrients and water to the plant, they expect to get paid for their labors, and plants do pay generously. Plants feed microbes both passively (sloughed-off root cells and the mucus-like substance that eases root growth through soil) and actively (targeted exudates that recruit specific microbial species depending on the plant’s needs at that point in its life cycle). As a result, the rhizosphere hosts 10-50 times more bacteria and 5-10 times more fungi than soil away from the roots.31
In exchange, plants receive nutrients they couldn’t easily mine themselves. As mentioned earlier, all kinds of microbes have carved out niches making different minerals plant-available. Nitrogen-fixing partnerships legumes and rhizobia, as well as free-living diazotrophs like Azotobacter, Clostridium, and Azospirillum, are another well-known example. Certain strains of Bacillus, Pseudomonas, Burkholderia, and Acinetobacter can increase zinc and iron availability for crops like mung bean, rice, and corn.32 The same is true for every nutrient.
So, suffice it to say, more life means more nutrients become available to plants in the immediate rhizosphere.
The Rhizophagy Cycle: How Plants Farm Their Own Microbes
In one of the more exciting discoveries in soil biology, research now shows plants actively consume microbes from the rhizosphere for nutrition. Dr. James White and his team at Rutgers University were the first to detail this process. They called it the “rhizophagy cycle” (“rhizo” = root, “phagy” = eat) in 2018, and it has reshaped how scientists think about soil biology and plant nutrition.33
How the Rhizophagy Cycle Works, Step by Step
- Growing root tips exude compounds that attract bacteria and yeast-like fungi and cause them to multiply.
- These microbes enter the root at the growing tip and begin producing a compound called ethylene.
- Ethylene triggers root cells to produce superoxide, a reactive oxygen species that strips the cell walls off the microbes.
- Root enzymes break those cell walls down into individual nutrients (ie. carbon, hydrogen, oxygen, nitrogen, iron, zinc, phosphorus, potassium, sulfur, and more), which the plant absorbs directly.
- The now wall-less microbes also produce nitric oxide, which converts to nitrate, another nitrogen source the plant can use.
- Some stripped microbes die inside the root. Others survive, keep producing ethylene, and, once enough ethylene accumulates, trigger the outermost root cells to expand into root hairs.
- As root hairs expand, surviving microbes get trapped inside and are eventually ejected out the tip of the root hair, along with superoxide and ethylene. A single root hair can eject microbes several times over its life cycle.
- Ejected microbes rebuild their cell walls using nutrients from the surrounding soil, and the cycle can begin again the next time they’re drawn back into a root.
Root hairs, then, aren’t just specialized cells for absorption. Water and nutrient absorption through root hairs may actually be a secondary benefit of this process, not its original purpose. Arguably the main purpose of them is to eject colonies of microbes back into the soil. The image below from Dr. James White shows the abundance of root hairs with and without bacteria present.
Not so long ago, almost no one would have guessed that plants “farm” their own microbes for nutrients, but the evidence is mounting that this is certainly the case.
Nutrient Acquisition by the Rhizophagy Cycle
The million dollar question that producers need answered is whether or not the rhizophagy cycle supplies a good amount of nutrients to plants. If it doesn’t supply a significant amount, then it’s a fun story that doesn’t help much (from a production standpoint). It’s still early days, but initial research by Dr. White and his lab suggest that grass plants acquire 30% of their nitrogen from the rhizophagy cycle.34 His research also suggests that absorption of metal elements like zinc, copper, iron, and magnesium from microbes is an important benefit of the rhizophagy cycle. Stay tuned, because future results might surpass our wildest expectations.
For further information on the rhizophagy cycle, check out this great talk by John Kempf at the National No-Till Conference. John explains how he regularly sees producers cut their nitrogen bill by 30-70%, and in some cases 100%, by maximizing biological nutrient cycling. Of course, this is anecdotal, but there’s no reason it couldn’t be true given everything we’ve learned so far. Teaming with Bacteria by Jeff Lowenfels is also an excellent book that dives deep into the details of rhizophagy.
All of this is very exciting, but the rhizosphere makes up a remarkably small area of the total soil profile. What about all of the nutrients in the so-called bulk soil? Can plants access the nutrients and water outside of their immediate reach or are they simply inaccessible? If only plant roots had an extension out into the rest of the soil that could mine and transfer those nutrients…
Enter fungi.
Fungi: The Long-Distance Nutrient Delivery System
Mycorrhizal Fungi: Extending the Root System Underground
Soil fungi make up only 10-30% of the rhizosphere by population, but in healthy, undisturbed soil, they dominate by mass.35 One of the strengths of this mighty kingdom of life is its diversity. Some fungi specialize in decomposing organic material, such as the bread in your pantry, the day-old roadkill on the side of the road or the fallen tree in the woods. These are called “saprophytic fungi” (“sapro”- rotten or decaying, “phytic”- plant material or organic matter). We will discuss this class of fungi later on.
First, we will look at those fungi that make their living from forming direct partnerships with living plants. These are the “mycorrhizal fungi” (“myco-” fungus, “rhiz-” root). An estimated 80-90% of all plants are mycorrhizal, and this partnership may date back over 450 million years, to when plants first colonized land.36 Some researchers believe mycorrhizal fungi supplied most of a plant’s nutrients in that early period, serving as the initial root system. Plant roots, then, served as anchors in the soil. It wasn’t until much later that they developed the ability to absorb nutrients on their own.
To make matters more complicated, there are four main types of mycorrhizal fungi: Endomycorrhizal, ectomycorrhizal, orchid, and ericoid. For the purposes of this article, the first two will be described:
1. Endomycorrhizal fungi, including the well-known arbuscular mycorrhizal fungi (AMF), that grow inside the root root tissue of nearly 75% of all vascular land plants.
2. Ectomycorrhizal fungi that form a sheath around the outside of the root of only about 2% of plant species, primarily woody plants such as those from the birch, pine, beech, willow, and rose families.
Another difference is that ectomycorrhizal fungi can produce organic compounds that chisel nutrients directly out of minerals and organic matter, while endomycorrhizal fungi can’t do this themselves. Rather, they feed smaller-yet mineral-solubilizing microbes to get the job done.
Finally, research suggests ectomycorrhizal fungi tend to excel at delivering nitrogen, phosphorus, and water in exchange for carbon and energy. Endomycorrhizal species specialize more in shuttling phosphorus, copper, and zinc to plants.37
The great thing for us is that these partnerships don’t just benefit the plant. This shuttling of nutrients to plants results in more nutrient-dense food for us. As an example, tomatoes grown with endomycorrhizal fungi were shown to have higher levels of lycopene, vitamin C, vitamin A, and antioxidant activity.38
So, to summarize, both groups of mycorrhizal fungi dramatically increase a plant’s access to soil nutrients, like an auxiliary, extended root system. Not only do they explore a bigger area, their hyphae (the thread-like fungal bodies) are roughly 1/60th the diameter of a plant root, letting them explore soil crevices where roots simply can’t reach. Hyphae are also hollow, allowing nutrients and water to flow through them much like water through a pipe. This enables them to send material from the bulk soil back to the plant root in exchange for photosynthetic sugar. As Kristin Ohlson writes humorously in The Soil Will Save Us, plants are the sugar daddies of the soil.
Saprophytic Fungi: Nature’s Recycling Crew
As discussed earlier, fungi (and bacteria) that break down dead organisms are called “saprophytes.” It’s an unglamorous job, but saprophytic fungi are arguably the single most important regulator of nutrient cycling in soil. We would be up to our eyeballs in garbage if it were not for these microscopic marvels.
Saprophytes return nitrogen, phosphorus, potassium, calcium, and every other nutrient into the circulation of the living within minutes or days of an organism’s death. White rot fungi are a standout example worth mentioning because they are among the only organisms that can break down lignin, the compound that makes wood “woody,” thus returning carbon to living circulation centuries faster than it would happen otherwise.
Soil Predators
Protozoa and Nematodes: Nature’s Nutrient Release Valve
So far, we have extolled the wonderfully useful ability of bacteria and fungi to cycle nutrients efficiently. While this is true, there is a small catch: too much of a good thing can be a bad thing.
Picture a cover crop pumping food into the soil, which feeds bacteria and fungi and stimulates them to multiply rapidly. That’s a good outcome up to a point. Left unchecked, booming bacterial and fungal populations can actually hurt plant productivity by locking up too many nutrients inside their own bodies. In the animal world, this is like deer populations without anything to keep them in check. Wolves, coyotes, wild cats, and other predators are essential for preventing herbivores from defoliating and destroying a landscape.
In soil, that job belongs to protozoa and nematodes, which keep bacteria and fungi populations from spiraling out of control. Protists, or protozoa (“Proto” meaning early (prototype), “zoa” meaning animal (zoology)), are amoeba-like creatures, while nematodes are worms, placing them in the animal kingdom alongside earthworms. Before writing nematodes off simply as pests, it’s worth knowing they’re the most abundant animal on the planet, making up roughly 80% of all animals, with an estimated 57 million nematodes for every human alive.39 If they were mostly harmful, we wouldn’t be here. Problems only arise when one species, like the soybean cyst nematode, takes advantage of an imbalanced system with too much of its preferred food source available and nothing to keep them in check.
Interestingly, many farmers have started to look at their soil under the microscope to see which type of nematode is most prevalent in their soil. They can tell by the mouthpart of the nematode: round, flat mouths indicate microbe eaters, while with a protruding sharp stylet indicate root eaters.
In reality, protozoa and nematodes are overwhelmingly beneficial, largely because of what they leave behind after eating bacteria and fungi. Every organism maintains a fairly constant carbon-to-nitrogen ratio (C:N) in its cells. Bacteria run a very low C:N ratio, so they’re often called “little bags of fertilizer”. Their bodies are nitrogen-rich relative to carbon. Fungi carry less nitrogen than bacteria, but still more than their predators. So when a protozoan or nematode eats a bacterium or fungal cell, it takes in more nitrogen than it needs and excretes the surplus as ammonium (NH4+), one of the most plant-available forms of nitrogen there is.
Nematode activity also directly shapes root architecture: research on tomato seedlings found that higher nematode populations triggered more branching and thinner roots.40 Thinner roots are a good thing, as they create more surface area for nutrient and water exchange, the same reason human capillaries are only one cell thick, allowing oxygen to pass efficiently into the bloodstream.
Both protozoa and nematodes need good soil structure to do their job. They’re aquatic organisms that move through thin films of water in soil pores, so they depend on well-aggregated soil with enough macropore space to swim through and hold water properly. Compacted soil slows them down, slowing down nutrient cycling right along with them. It’s one more item on the long list of reasons soil aggregation pays off!
For a deeper look at protozoa and nematodes, this fact sheet from The Ohio State University is a great resource.
Insects and arachnids: Shredders and Predators
As nematode and protozoa populations grow, they attract larger predators, springtails, and mites being two of the most common types. Beyond preying on smaller organisms, these microarthropods shred plant residue and organic matter into smaller pieces. That shredding increases surface area, which speeds up microbial decomposition, the same reason shredded leaves break down faster than whole ones on a lawn.
Springtails
Springtails (Collembola) are among the most abundant soil arthropods on the planet, often numbering in the tens of thousands per square meter of healthy soil. Named for the forked appendage (furcula) they use to spring away from predators, springtails feed primarily on fungi, but also graze on bacteria, algae, and decaying plant material. As they feed, they leave behind nutrient-rich micro-manure that are more accessible to bacteria than the original organic matter, effectively pre-processing food for the next trophic level downward. Their grazing also keeps fungal populations from running unchecked.
Mites and Spiders
Mites are arachnids like spiders, and their sheer diversity and abundance make them one of the most important groups in the soil food web, cycling nutrients and regulating microbial and fungal populations as they feed. Within this group, oribatid mites (often called “beetle mites” for their armored appearance) are especially significant decomposers, slowly breaking down tough organic material like leaf litter and woody debris over long periods. Other mite groups are predatory, feeding on nematodes, springtails, and even other mites, adding another layer of population control and manuring out nutrients to the soil food web.
Most spiders are found at or near the soil surface and add to the checks and balances of a soil by preying on insects and other arthropods, helping keep those populations in check so no single group dominates the decomposition process. Some organisms break organic matter down mechanically, others regulate microbial populations by grazing, and still others keep the decomposers themselves in check through predation. It’s this layered division of labor, more than any single organism, that keeps nutrient cycling running smoothly throughout the soil ecosystem. Not surprisingly, then, many producers note the tremendous quantity of spider webs they see on the farm or ranch as they implement regenerative systems changes.
Beetles
Beetles occupy nearly every role in the decomposition process. Ground beetles and rove beetles are voracious predators, feeding on slugs, fly larvae, aphids, and other soft-bodied invertebrates, which helps prevent any one group from overwhelming the system. Dung beetles take a more direct approach to nutrient cycling by burying manure underground.They not only reduce surface waste but also aerate the soil and deliver nutrients directly to the root zone, where they’re more available to plants. In addition, the drying and moving of manure by dung beetles helps reduce fly populations in pasture, no insecticides needed. Ironically, research shows insecticides added to cattle feed lower dung beetle numbers, which may lead to an increase in the number of flies.41
Beetle larvae, meanwhile, often live and feed within decaying wood or leaf litter, mechanically breaking it down in much the same way springtails and mites do, just on a larger scale.
Ants & Termites
Ants contribute to nutrient cycling less through direct feeding and more through the physical structure they create. Their tunneling aerates soil and improves water infiltration, similar to the effect of earthworm burrows, while their nests concentrate organic matter, fungi, and nutrients in ways that can locally enrich soil fertility. Some ant species also farm fungi or tend aphids for honeydew, creating small, self-contained nutrient loops within the larger soil ecosystem.
In many regions, especially warmer climates, termites are one of the most important decomposers of woody and cellulose-rich material. They rely on a gut full of symbiotic protozoa, bacteria, and fungi to break down lignin and cellulose that few other organisms can digest efficiently. This partnership allows termites to process enormous volumes of dead wood and plant debris, cycling carbon and nutrients back into the soil at a scale that few other insects can match.
Millipedes and Centipedes
Though technically myriapods rather than true insects, millipedes and centipedes are common soil arthropods worth mentioning alongside this group. Millipedes are detritivores, slowly consuming decaying leaves and wood and, like springtails, producing nutrient-enriched manure that fuels further microbial activity. Centipedes, by contrast, are predators, feeding on other arthropods and helping regulate the very decomposer populations millipedes belong to. Together they represent the same predator-prey balance seen elsewhere in the soil food web: decomposition and population control working in tandem.
Earthworms: The Original Soil Engineers
Earthworms round out the underground herd. These annelids eat plant litter, microbes, and soil, consuming 2 to 30 times their body weight in soil every day. As food passes through an earthworm’s digestive system, it gets squeezed, shredded, enzymatically broken down, and compressed, with help from the bacteria and fungi living in the worm’s gut.
The resulting earthworm castings are a hotspot of organic matter, plant-available nutrients, and biological activity. Some earthworms deposit castings on the soil surface; burrowing species line their tunnels with them, giving plant roots an easy path to grow through, straight into a nutrient-rich zone. Burrowing earthworms also reduce nutrient loss (particularly nitrogen) by pulling manure and plant residue down into the soil profile, away from erosion and volatilization.
Even the worms’ own bodies are a nutrient reserve once they die and decompose. Research shows plants growing in soil with large earthworm populations may take up an additional 45-80 lb/acre (50-90 kg/ha) of nitrogen through this process.42 If earthworms are already active on your land, that’s a resource worth protecting and building on.
The benefits of earthworms can’t be understated. In fact, Charles Darwin himself became so fascinated with earthworms and their importance as ecological engineers that in his later years he wrote and published The Formation of Vegetable Mould Through the Action of Worms in 1881, which became his best selling book while he was alive.
Key Takeaways: Putting the Soil Food Web to Work For You
Phew! That was a lot of information. Congratulations on making it to the end. I did my best to condense this article as much as I could, but the fact is that biology and ecology are messy, complex subjects. Understanding them takes time and repetition, so use this article as a reference that you can come back to again and again.
For those who just want a too long, didn’t read (TLDR) summary, here’s one for you. The soil is a living system where nutrients cycle at lightspeed compared to non-living systems. Bacteria and fungi unlock nutrients from soil minerals and organic matter. Mycorrhizal fungi extend a plant’s reach far beyond its own root system. And through the rhizophagy cycle, plants may be farming a meaningful share of their own nitrogen and micronutrients directly from microbes. Protozoa and nematodes keep microbes in check and release that fertility as plant-available nutrients. Bigger animals, including insects, eat these primary predators and release the nutrient inside of them once again. Finally, earthworms engineer soil structure and deposit nutrient-dense castings, among other benefits.
The next installment in this series will continue the story of nutrient cycling by taking a deeper look into the role that organic matter plays in the nutrient cycle, why conventional soil tests lead producers to purchase more fertilizer than they need, and how to accurately test soil for nutrients in your soil.
Understanding nutrient cycling is one thing. Applying it successfully on your farm or ranch is another. If you’d like help identifying opportunities to improve nutrient efficiency, reduce input costs, and strengthen the biological function of your soils, reach out to an Understanding Ag consultant. Our team can help you translate these principles into practical management strategies tailored to your operation.
References
21https://www.ncbi.nlm.nih.gov/books/NBK209710/
22 https://www.bbc.co.uk/newsround/66519247
23https://annalsmicrobiology.biomedcentral.com/articles/10.1186/s13213-022-01701-8
24https://www.sciencedirect.com/science/article/abs/pii/B9780128183229000101
25https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10667278/
26https://www.sciencedirect.com/science/article/abs/pii/S098194282100352
27https://www.sciencedirect.com/science/article/abs/pii/B9780128183229000101
28https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10667278/
29https://springerplus.springeropen.com/articles/10.1186/s40064-016-3286-y
30https://www.sciencedirect.com/science/article/pii/S2452219817300459
31https://pubmed.ncbi.nlm.nih.gov/33103781/
32https://www.nature.com/articles/s41598-021-82768-2
33https://pmc.ncbi.nlm.nih.gov/articles/PMC6164190/
34https://onlinelibrary.wiley.com/doi/10.1002/ps.5527
35https://ohioline.osu.edu/factsheet/anr-37
36https://pubmed.ncbi.nlm.nih.gov/34657204/
37https://www.intechopen.com/chapters/85101
38https://link.springer.com/article/10.1007/s13199-021-00756-6
40https://www.sciencedirect.com/science/article/abs/pii/S0038071706000253
41https://cals.cornell.edu/news/2025/06/dung-beetles-combat-flies-insecticide-overuse-harms-beetles
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