Pt 4 — 21st Century Grower’s Guide to Sustainable Farming
For plants to farm the microbes and create useful partnerships in the rhizosphere, they need a diverse microbial community, that includes the right microorganisms, to be present in the soil.
Healthy soil usually contains 20,000 to 30,000 species of life. It can take a farmer moving from conventional, agrichemical-based methods a decade, using organic methods alone, to bring biodiversity in the soil microbe biome back into their land. The alternative is Robust Compost is any product with broad biodiversity across 7 types of life and in excess of 1,000 species.
These products are in the marketplace under a variety of names, including Living Soil, Soil Food Web compost or Bicomplete compost. Because of their value, they are often in short-supply and often appear expensive to those who do not understand their contribution to grower’s profitability.
Robust Compost is a generic term for compost that contains the full spectrum soil ecosystem includes bacteria, fungi, archaea, beneficial nematodes, amoeba, flagellates and micro-arthropods. Often it has other types of life, including animals (earthworms) and it may contain diatoms and other algae, phages and other types of protozoa.
When the microbiological component of soils is considered, direct and indirect benefits for agricultural production can follow. These include economic and environmental benefits. More efficient nutrient cycling processes and water storage translates into reduced input costs. Yield and crop quality may improve, especially through controlling pests and diseases and enhancing plant growth.
This is where SymSoil’s product line comes in. SymSoil is a leader in creating products for growers, based on a depth of knowledge about all the major components of heathy soil. The company farms soil microbes and creates solutions for a host of farming challenges. The flagship product, SymSoil RC, has more than 2,000 species and can be used to reseed the soil microbe biome. SymSoil Grow Cubes have the same biodiversity, but additional biology has been added to reduce powdery mildew and fusarium, root aphids, fungus gnats and thrips.
The Soil Food Web is a complex microbial community, with tens of thousands of species that cross 7 types of life. Described as a food web rather than a food chain, they pass nutrients, including elements like nitrogen (N), phosphorus (P) and potassium (K), back and forth between the plant and all the lifeforms in the soil microbe biome.
A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. They are often thought as linear: Seeds are eaten by a mouse, who is eaten by a bobcat, who is eaten by a coyote. The mouse it the first trophic level, the bobcat is the second and the coyote is the third trophic level.
“Dirt” is a dirty 4-letter word, you want “Soil”
Dr. Elaine Ingham
The Soil Food Web is more of a complex network than a food chain, and was first described in the academic literature Dr. Elaine Ingham. Her papers are still among the most cited in the field of soil science. The web has many layers, including omnivores who eat opportunistically, as well as many that live off debris. The population of the debris eaters grow during the decomposition process. In nature, there are diversity of species involved, unlike in commercial composting in which one or two bacterial species dominate and remain at the end of the process.
The Soil Food Web starts with plants farming the microbes near their roots. After capturing carbon dioxide in the atmosphere through photosynthesis, at least 10% or more of that carbon goes to the roots and some is shared with the soil microbes. The roots extrude sugars, proteins and carbohydrates which attract and feed bacteria, archaea and fungi.
Soil bacteria (and archaea which are similar in size but genetically distinct) represent some of the smallest single-celled organisms on Earth. Scientists have classified well over ten million unique bacterial species, and it is estimated the cumulative soil bacterial biomass is greater than the biomass of all the plant and animal the world combined! Bacteria can live in a wide range of environmental conditions.
Katharine Hinson, SymSoil’s President for Science is convinced that somewhere there exists a bacterium that can eat anything with a carbon chain. There are bacteria that can filter and breakdown most toxins. They have even found bacteria that consume iron. For plants, the most useful bacteria fix nitrogen — some in or near roots, some inside the plant, and some in the soil, separate from the rhizosphere.
In hydroponic cultivation, beneficial bacteria can be used as growth promoting inoculates, whose enzymes are helpful in soilless media. Soil bacteria can still produce many different functional groups of enzymes to cycle nutrients for plant uptake, even in soilless growth media.
In addition to bacteria, the extrudates stimulate fungal growth. There are an estimated 70,000 unique fungal species. Soil fungi have hair-like structures called hyphae or mycelium that grow throughout the soil. Some species of fungi can grow hyphae great distances, and these can bring water from the periphery to the plant roots. Fungi genetics are closer to animals than plants, but are neither. Molds, yeasts and mushrooms are the most common fungi. In nature, bacteria and fungi play key roles in decomposing organic matter.
Some bacteria and fungi, known as endophytes, enter the plant and spend much of their life inside the plant — enhancing the plant’s ability to fight pathogens or fixing nitrogen.
The plant root extrudates signal for specific bacteria and fungi which then tend to dominate, which harms the biodiversity of the community. Crop rotation increases biodiversity, improving resilience and strengthening the community. Farmers that only grow one crop on the land need to actively reseed the soil microbe biome to increase the biodiversity of their land.
At different stages of the plant’s life, the extrudates change, changing the species of bacteria and fungi come to dominate the area around the roots. Each of these life forms create their own set of chemicals, which include the macro and micro elements the plant needs. Some of these chemicals protect plants from stresses that would otherwise inhibit their growth. Stress can be caused by drought, heat or cold, pathogens or accumulation of salts. Studies have shown how some of these soil microbes can even alter the gene expression of plants to help them navigate sudden environmental changes.
With all of this chemical activity, it is easy to see why the early, primitive understanding of plants and their nutrient needs focused on chemistry.
Still, at the first trophic level (the bacteria and fungi), most of the important elements (N-P-K and the minor ones) are bound in the enzymes and unavailable to plants.
Complexity abounds! The prior paragraphs describe the first trophic level, out of four described by Dr. Ingham as the Soil Food Web. A trophic level, describes where an organism sits in a food chain. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it is from the start of the chain.
In the second trophic level, protozoa (amoebae, flagellates and ciliates) and beneficial nematodes consume the bacteria and fungi. In their digestion process, the “waste” releases the nutrients that have been “bound” in the first trophic level, in ionic forms that are plant available.
While amoebae, flagellates or beneficial nematodes all consume the bacteria and fungi, the most fun to observe are the group of amoebae known as pseudopods (fake foot). These amoebae grow out and around the food source, and then consume it.
Diagram of amoeba engulfing a particle of food by phagocytosis, by Kate Taylor from Wikipedia
For two centuries, humanity has understood this in terms of chemistry. At the molecular level, ionic chemicals are the result of biological process is known as phagocytosis, which is Ancient Greek for “to eat”. At the biological level, or the second trophic level, protozoa eat the bacteria and fungi and release waste in the form of amino acids and enzymes in an ionic form. That is, each molecule carries a mild electrical charge, with either an extra electron or missing an electron. The electron exchange is a critical component in nutrient cycling — making the key elements available to the plant roots.
Salts are a combination of two ions, which have the ability to separate in water — with both carrying a slight charge. This is why chemical fertilizers are salt-based. With the soil microbe biome, this is part of their biological process. Biologic farmers learn that plants in soil with poor chemistry and good biology can out produce the same crop in soil with great chemistry and poor biology. Salts are also the reason so much of the fertilizers used on farmland runoff into waterways.
Nematodes sometimes get a bad rap because a small percentage (10%+) feed on plant roots. But in healthy soil, the majority of nematodes don’t eat plants. Instead, they are active participants in this nutrient cycling from bacteria and fungi. What’s more, some feed on other pathogens, like the larvae of insects like fungus gnats and thrips, which would otherwise mature to attack the crop. The result of having biodiversity in nematodes is an overall lower level of crop pests, bypassing the need for chemical pesticides.
The second trophic level, like the first, has some pathogens, but in a healthy ecosystem the beneficial microbes outcompete the bad microbes.
Soil with significant biodiversity of the amoebae, flagellates and beneficial nematodes will generate complex foods for the plants — improving flavor, plant health and crop yields. In cannabis plants, it will increase THC or CBD and terpene levels.
Biochar, while not biology and chemically inert, acts like a Velcro for the electron exchanges, making it easier for the soil microbes to add or subtract electrons in their digestion/enzymatic processes. This facilitates the chemical reactions that create the nutrient cycling that benefits plants. In addition, biochar is a soil conditioner whose porous nature creates homes for soil microbes of different sizes.
The third and fourth trophic level are the wee critters that consume the protozoa, as well as fungi and bacteria. Some arthropods are too small to be seen with the naked eye (springtails and mites). Worms, insect larvae, larger arthropods (spiders, sow bugs, millipedes and other insects) consume the smaller lifeforms, as well as each other, adding yet more complexity to the chemistry to the soil. They also transport bacteria and fungal spores and create pockets for air and water, which allows all of the aerobic microbes to live.
In all, a healthy soil usually has over 20,000 species and at least 7 types of life: bacteria and archaea, the smallest building blocks, fungi, protozoa of various types (amoebae, flagellates), nematodes (most of which are beneficial), and micro-arthropods. There are other life forms, but these are the keystone, or most critical ones for soil health.
This is the fourth article in the series, which begins with 21st Century Farmer’s Guide to Sustainable Farming, An Overview which can be found here. We encourage you to follow us for all the updates.
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For more information, please visit our website SymSoil.com or https://symsoil.com/soil-food-web-soil-cities/
SymSoil Inc. is an evidence-based, soil health company with products and services for regenerative agriculture. Our flagship products are Robust Compost, Fungal Infused Biochar and Grow Cubes for the cannabis and hemp cultivators. Our science team has 35 years of experience developing solutions to growers’ problems based upon a deep understanding of the complete soil microbe biome. A core belief is regional soil microbes can be restored to regenerate the soil, which will significantly increase plant health, crop yields, flavor profile and nutrient density, as the plants access nutrients the way nature intended.