The Rhizosphere
The Metropolis
Human beings cannot fully comprehend the microbial interactions going on beneath our feet, in the soil, and at the rhizosphere, or root-zone of our plants. Generations of thousands of species of living microbial populations explode with complex economies of extraction, manufacture, construction, trade, and war, and many individuals go extinct within days or weeks. For some, their entire lives are mere minutes.
But It all starts at ground zero- the surface. Surface or subsurface dwelling detritivores such as worms, earwigs, crickets, wood lice, termites, and springtails chew up debris and excrete the remains as frass, a delectable food source for many other fungi and bacteria. These organisms churn some of this debris down into the root zones of plants, where it is further processed by soil microorganisms.
Soil microorganisms, or microbes, include hundreds of thousands of species of bacteria, archaia, fungi, protozoa, nematodes, and others all interacting in a community network of billions of different interactions- feeding, and feeding off of, each other and working in a dynamic group. Sometimes they are symbiotic, sometimes not.
These organisms are creating and processing an innumerable array of chemicals, many of which are only useful to a small handful of other organisms with whom they form relationships. Some microbe species are called saprophytes. These may or may not form direct associations with the plants and do not need to live in or on them for survival.
Many of these organisms are efficient nutrient extractors and foes of pathogenic fungi. They can be highly beneficial in their extraction abilities and in their abilities to parasitize plant pathogens, but many may also compete with, or consume other beneficial microbes. An example of this is Trichoderma viride. Several species of Trichoderma are often used as a readily available fast acting filler ingredient in microbial mixes, but will opportunistically feed on both pathogenic fungi, as well as many species of beneficial mycorrhizal fungi, making them particularly dangerous to a system where mycorrhizal fungi is wanted, and under certain conditions, may even parasitize the plant itself, or humans with compromised immunity.
Some organisms extract phosphorus and potassium ions from the mineral layers deep below the plant using chemicals such as carbonic, oxalic, citric, and acetic acids. Expansion and contraction of soils allow access to trapped potassium. Others are extracting phosphorus from minerals, abandoned roots, and the bodies of other organisms.
Still other bacterias and fungi are bounty hunters- seeking highly toxic chemicals to capture, and break down into new resources, and then trade those resources to others. Extremophiles are organisms that can live in extreme environments, such as highly toxified soil, or extremely high or low temperatures. Many scientific studies have been conducted in which plants have been grown with rich colonies of specific microbes in soil that was highly contaminated with various contaminants. When the plants were harvested they were analyzed for toxins, and no residual toxins were found in the harvested plant- all thanks to the healthy populations of microbes in the soil.
All these interactions are made possible by photosynthesis of sunlight and gases, and the resulting production of sugars. Every microbe has a different function and each consort will grow and thrive depending on what their environment has to offer.
What is Mycorrhizal Fungi?
Plants extract minerals from the soil using secretions of carbonic, oxalic, citric, and acetic acids and other enzymes in root exudates, but fungi are more efficient. Plants, on the other hand, are extremely efficient at turning sunlight into sugars through the process of photosynthesis. By forming a mutually beneficial relationship of exchange the plants can barter sugars for nutrients from the fungi, thereby each organism performing the tasks that they are particularly suited for and getting the rest of what they need from the other. Many species of fungi have specific mutually beneficial relationships with certain species of plants. These organisms may be completely dependent on the roots of plants, often attaching themselves, thereby shortening the distance and increasing efficiency of the exchange.
For example ericoid mycorrhiza have a relationship with blueberries and related plants. The plant’s relationships with these organisms will improve your blueberry crop and plant hardiness. Orchids form a relationship with another group of mycorrhizal fungi.
One of the most important groups of beneficial fungi is the ectomycorrhizal fungi group, which forms relationships with many hardwood and conifer tree species, more than 5% of all plants tested for these relationships. This group of fungi weave sheaths of mycelial lattice around the individual roots like an impenetrable hedge, or filter, thereby protecting the root from the entrance of pathogenic bacteria and other organisms, toxic metals, and other harmful chemicals. In an effect, this lattice of mycelium becomes the gatekeeper. In short, if the population of ectomycorrhizal fungi is healthy, the plant may be completely resistant to soil-borne disease.
By far the most useful clade of mycorrhizal fungi for gardeners and orchardists is one which forms a strong beneficial relationship with more than 85% of all plants that have been tested for mycorrhizal relationships. This is known as the endomycorrhizal fungi group. In this group, the allied populations of fungi embed mycelial hyphae, or fungal “roots,” into the roots of the plant and can then serve as a sort of root extension, extracting nutrients that are otherwise unavailable to the plant and making an exchange. This can greatly accelerate the growth of the plant’s roots, and thereby, its overall health.
These “root extensions” can embed themselves into the root systems of many plants and species simultaneously. Thus the root exudates of one plant may actually become the resources of another through the mycelial network, and visa versa. Because of how these organisms interact with the root system of the plant, they are mutually exclusive. If they have a relationship with ectomycorrhizal fungi they won’t have a relationship with endomycorrhizal fungi.
Allied populations of endomycorrhizal fungi embed themselves into the cellular structure of plants, sending mycelial hyphae into the soil to extract nutrients to trade with the plant for some of its offered sugars. Many are hungry for carbon and a few spend their energy sequestering carbon by manufacturing it into a sort of soil glue called glomulin. This very stable organic carbon glue makes up a huge amount of soil carbon by volume in healthy soils.
Fungi has a different type of respiration system than plants. Plants inhale carbon dioxide and exhale oxygen. The Animal and Fungi kingdoms breathe in oxygen and exhale carbon dioxide. It’s opposite of the actively growing specimens in the plant kingdom. Thus another way that a close relationship with fungi is beneficial to the plant is via the elevated CO2 levels in the rhizosphere where fungi is present. CO2 is inhaled through the root system as well as the leaves, and both the plant and the fungi benefit.
The Rhizophagy Cycle
The term Rhizophagy Cycle represents the process by which the plants attract several specific species of bacteria by secreting superoxides into the soil from their root tips. The attracted bacterias are then taken in by the plant, as if sucked up by a straw, and cycled throughout the entire system of stems, leaves, flowers, and fruits (and yes, become a nourishing part of our foods and digestive flora).
As the bacterial cells travel through the plant active enzymes in the plant’s fluid dissolve the bacterial cell wall. The cell wall is broken down into amino acid sugars (a very usable form of nitrogen) and assimilated by the plant as a nitrogen source needed for growth. As the bacteria near the end of their journey through the plant they are then excreted back out into the soil as protoplasts, or cells without a wall. The bacteria then regrows its cell wall, is attracted back to the plant by its superoxide secretions and the cycle begins again.
The Nutrients
Misunderstanding N-P-K
Many of the scientists and farmers who study the rhizophagy cycle have determined that nitrogen is rarely a limiting nutrient factor when the soil microbiome is healthy. Most of the time, plants are able, through their relationships with fungi, bacteria, archaia, and other organisms, to supply all the nitrogen needed for necessary growth, environmental factors contingent.
However, our misconceptions of nitrogen (N), phosphorous (P), potassium (K) and other nutrients have resulted in a dramatic change in soil dynamics. In human ignorance we think that if we give the plant some N-P-K it’s all going to be fine. As a society we have an expectation that we must feed our plants with chemicals, and that we can somehow substitute the interdependent relationships embedded in evolutionary plant DNA with human contrived solutions. In reality, these common misconceptions come from not understanding things that we cannot see.
In fact it has been proven time and again in university studies (some on plots in continuous plantings for more than a hundred years) that a continual dosage of nitrogen fertilizer over time will decrease carbon. Carbon = fertility, therefore, decreased carbon means decreased fertility. Fertility implies many things, including the soil’s ability to retain an adherent structure. Without this, the result is rapid desertification.
Microbes use approximately 24:1 to 35:1 Carbon to Nitrogen ratio optimally to break down material. Different sources of organic material supply different ratios, and regardless of the ratio, as long as moisture is consistent, you’ll eventually get compost,… eventually. If microbes have a lot of cellulose carbon available, they must have nitrogen to break it down, even if it means taking it from the plant or from available soil N.
Why would it be any different with nitrogen? It’s not. If microbes have nitrogen, they must have carbon, which means that they will consume all the necessary carbon from the soil carbon bank in order to process the available nitrogen, thereby resulting in decreased fertility.
So farmers and scientists have traditionally been applying way more nitrogen than the plants actually need and the soil microbes feel it their eternal duty to create a balance. Thus, poof! Your carbon just vaporized into carbon dioxide gas. Along with your optimum fertility. Better to be high on the stable carbon side, thereby culturing an environment that encourages a healthy population of bacteria that can supply that nitrogen in forms that nature’s complex system is used to doing. But burning up available carbon may not be the only down side of heavy applications of ionized nitrogen; it may cause other challenges as well.
Endophytes, which are any beneficial bacteria that live in or on plant material, such as on and inside seeds, are generally quite robust. They usually have little problem surviving treatments such as scalding water baths, high chlorine concentrations in municipal water supplies, and other factors, but are actually quite sensitive to ionized nitrogen. The epitome of this irony? Fertilizer coated seeds. Recent scientific evidence has shown that many attempts to improve germination and active growth of seedlings by applying a coating of fertilizer to crop seed, has resulted in comparatively poor initial growth compared to untreated seed. As healthy populations of endophytes are an important addition to the successful growth of new seedlings, this is likely the reason.
Unfortunately few available lab tests for available nitrogen will account for the nitrogen derived from the amino acid sugars provided by the breakdown of bacterial cell walls within the plant itself, or in the surrounding soil profile and generally only account for available ionized nitrogen.
No One Fertilizes the Forest
If you spend any amount of time in wilderness areas, you may find wild fruit trees and berry bushes in the forest for which nobody is broadcasting fertilizer, and yet they’re loaded with fruit. Why is that? You may see trees that are growing out of a crack of rock on the side of a cliff. There’s not even any soil there! Where are they getting NPK from? Certainly not from agricultural fertilizer or runoff.
They are getting it from bacteria on their roots. No human is going up there and pouring a watering can of Super-gro fertilizer down the crack of the rock on the side of the cliff. If they did they would probably kill that tree. This plant is actually farming bacteria on its roots- feeding off of the nutrients from the bacteria. Those bacteria are breaking down rock and extracting minerals the tree needs through root acid exudates and enzymes. Nutrients are supplied to the plant in exchange for the one thing that the plant has in relative abundance: sugars from sunlight.
At Eden Institute, we propose that if you have a healthy population of microbes you may not need to fertilize at all. A bold proposition to be sure, but nature does the job that it was designed to do. And once that population is established people don’t need to be there to do it. Many, many plants are very beautiful and productive with little to no human intervention.
If farmers, gardeners, and landscapers were to give up fertilizer and instead focus on introducing and sustaining the beneficial microbes, over time these microbes will adapt with interactive populations that have the ability to give the plant everything that it needs, including nitrogen, phosphorus, and potassium, the “essential” N-P-K.
Soil Nutrition = Food Nutrition
The United States Department of Agriculture (USDA) recently published a comparison of 13 different nutrients in 43 different garden crops from 1950 to 1999. The results were quite telling. The experiment first adjusted data to account for differences in moisture content before calculating ratios of nutrients in foods. While there was no statistically reliable decline for 7 of the 13 nutrients tested, there was a statistically significant reduction for 6 primary nutrients: protein, calcium, potassium, iron, riboflavin (vitamin B2) , and ascorbic acid (vitamin C). The nutrient density of our modern average grocery store produce pales in comparison from that produced in 1950.
In addition to the actual mineral and nutrient content of our modern produce, the “living” probiotic quality of our foods is empty by comparison because of modern agricultural practices. Beneficial bacteria are normally taken in at the roots and translocated throughout the plant; they’re not just found in the roots, but also in the leaves, tissues, flowers, fruits, and seeds. The fruits and vegetables grown in soil with a healthy microbiome will themselves have a healthy dose of those same probiotics resulting in sweeter flavor, more easily digestible, mineral rich, nutritionally dense, and medicinally capable. As an aside, studies have even been performed showing that foods that are grown in a healthy microbiome may also last longer on the grocery shelf and in the refrigerator.
Those same microbes will add to, and diversify, your gut flora making nutrients more readily available to your body. A healthy gut flora also leads to an internal production of B Vitamins, from the breakdown, and subsequent digestion of gut bacteria. You may be getting as much B Vitamins from these microbes as you do from the food that you eat. The bacteria is feeding your body in a similar way that it feeds the plants. Those microbes end up populating our digestive systems resulting in a diverse gut flora that displaces pathogenic gut bacteria and is essential for good health. Without this plant/bacteria relationship and cycle our food will be devoid of the very bacteria that our digestive system needs to thrive.
Living Soil Amendments
Compost
Compost can be fantastic… if done right. It can potentially be a microbially diverse, nutrient rich soil amendment that can change the productivity of your agricultural ventures. But it can also contain pathogens. It’s soil life consists mostly of saprophytes which are bacterias and fungi that can be powerful for breaking down nutrients, but they may, or may not, have a direct relationship with plants.
Manures
Manures may contain the primary bacteria organisms essential to the healthy production of healthy plants, but may also contain high concentrations of salts, undigested weed seeds, and if the livestock was raised in densely populated confined stockyards and feedlots, may contain hormones, chemicals, and pathogenic species that are highly detrimental to human health. They also do not include the mycorrhizal fungi essential for optimum plant growth.
Traditional Microbe Products
Traditional microbial soil amendment products can be a very useful option to populate species of beneficial microbes in your soil microbiome. But they also have some downsides.
Traditional microbial soil amendment products are usually liquid in form because they work faster as a liquid, but either need to be refrigerated or they have a short shelf-life. Dry concentrated microbe products contain microbes that are stunned through a freeze-drying process that detrimentally affects their productivity for an extended timeframe and usually take weeks to populate after reconstitution. They often contain cheap, easy to obtain filler organisms that work quickly to break down material into available nutrients, but are usually pathogenic to beneficial mycorrhizal fungi. And of course they are designed as a mixture of a limited number of microbes added together much like a recipe that you could compile yourself from online wholesale sources.
Soil Fertility Accelerator
Soil Fertility Accelerator (SFA) is a step above the rest. This product contains no fillers, is pathogen free, is not a blended recipe, but rather a naturally developed consortium of hundreds of millions of microorganisms that are in “suspended animation” and will activate within seconds upon reconstitution with water.
SFA also contains the most powerful biostimulants and microbial food sources available, necessary for the support of native beneficial microbial populations. It increases Brix levels, plant proteins, soil carbon, soil fertility, plant health, vigor, and nutritional content of fruits and vegetables.
Conclusion
Understanding, and taking advantage of the powerful interactions that are taking place below our feet is the first step to healing our soils. We now have what is necessary to make that happen.
Happy Gardening!