The Foundation Of Everything: The Soil Food Web

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In a natural setting plants acquire their nutrients through the following process: (reference)

      1. The plant releases “exudates” ( a mixture of sugars and proteins) into the soil around its roots

      2. These exudates feed a specific type of bacteria or fungi living in the soil.

      3. The bacteria or fungi extract specific nutrients from the inorganic matter (rocks, sand, clay, etc) or from the organic matter (decomposed organisms) in the soil

      4. These nutrients are incorporated into the bodies of the fungi and bacteria as they grow. They are not plant-available

      5. The bacteria and fungi are then eaten by nematodes, and other microscopic organisms, which releases the nutrients in a plant-available form directly at the plant root.

      6. The roots absorb these nutrients, and the process repeats. The plant can acquire any nutrient it needs by simply sending out the correct exudates to feed the specific organism which mines those specific nutrients.

The soil food web is simply the collection of soil organisms which support plant growth. Some of these organisms acquire nutrients for plants (as described above), some of them build a well structured soil so that plant roots can access the oxygen they need, some of them protect plants from disease, etc.

The soil food web determines agricultural productivity, sustainability, human health, water quality, global climate and more. Without a functioning soil food web plants can not grow. Without plants all animals, including ourselves, cannot live. Even our fossil fuels and synthetic chemicals originally came from plants who were also dependent on the soil food web.

Can’t Plants Just Absorb Nutrients Directly Through Their Roots? Why Do They Need Microorganisms?

This is the paradigm of plant growth that has been sold to us by chemical companies. It is a seriously damaging paradigm.

  • Nutrients must be water soluble in order to be directly absorbed by plant roots, water soluble forms of nutrients quickly leach out of the topsoil if they are not immediately absorbed by plant roots.
  • Nature has solved this problem by keeping the vast majority of nutrients in insoluble forms (like rock) the vast majority of the time. These insoluble nutrients stay in the soil indefinitely until they are needed by a plant, and only then are they converted into a soluble form, and only in the amounts required by the plant at that time. No nutrients are lost with this system, that is what makes it sustainable.
  • If we apply soluble fertilizers to the soil directly we severely disrupt the soil food web (either through directly killing microorganisms or by simply depriving them of the exudates they need to survive). When the soil food web is disrupted in this way it can no longer supply all of the nutrients the plants need, so the plants suffer, unless more fertilizer is applied. Thus we begin to believe that plants require fertilizers to grow, not realizing that they would be able to provide for their own needs completely if the soil food web was in a healthy state.
  • Tillage/cultivation is probably even more damaging to the soil food web than fertilizer. So when the “green revolution” (invention of chemical fertilizers) happened the soil food web in most farm soils was already damaged, so plants were not getting the nutrition they needed. Applying fertilizers suddenly gave these plants the nutrients that the soil food web was no longer providing them, so they grew much more vigorously than before. This created the belief that “plants grow better with fertilizers”. In truth plants only grow better with fertilizers when the soil food web has been degraded.

So we have two options to produce plant growth, to sustain life, and human civilization:
Direct Fertilization and The Soil Food Web.

Pasture on the left has had a one-time compost application to restore the soil food web, no fertilizers. Pasture on the left has been grazed several times, pasture on the right has only been grazed once.
Pasture on the left has had a one-time compost application to restore the soil food web, no fertilizers. Pasture on the left has been grazed several times, pasture on the right has only been grazed once.

 

Direct Fertilization:

Usually chemical fertilizers are used, although there are also many organic fertilizers available. Chemical fertilizers (and, to a lesser extent, organic fertilizers as well) kill beneficial microorganisms in the soil, which means that plants become more and more dependent on Direct Fertilization to grow.

Fertilizers are one of the world’s biggest sources of water pollution.

Chemical fertilizers are made from non-renewable fossil fuels.

Organic fertilizers are either mined (non renewable, resource intensive), taken from plants (who grew either via fertilization or the soil food web), taken from sea life (which is closely tied to terrestrial ecosystem health and therefor the soil food web), or taken from animals (who ate plants for their nutrients) (reference).

*Compost and other “bio-fertilizers” do not apply significant amounts of nutrients directly to plants. Therefore they are not fertilizers. They are used to directly boost the health of the soil food web.

So, if you look closely you will realize there are only three sources for plant nutrition: non-renewable mined resources (including fossil fuels), ocean plants/animals (the harvest of which damages ocean ecosystems) or the soil food web.

Clearly any sustainable agriculture must rely on the soil food web. In fact, the soil food web is responsible for all terrestrial life as we know it.

To replace fertilizers we must feed the soil food web.
To replace fertilizers we must feed the soil food web.

Understanding The Soil Food Web

The health of any soil food web is determined by the diversity and size of the beneficial microorganism populations which are a part of it (bacteria, fungi, nematodes, etc.). (reference)

The diversity and size of the microorganism populations are determined by these five factors:

      1. The biodiversity of organisms. If a soil is severely disturbed (tilling, heat, chemicals, etc) biodiversity will have to be reintroduced from outside sources. Each plant will support a different set of organisms (although they are not mutually exclusive) so having a diversity of plant species will also increase the diversity of soil organisms.

      2. Beneficial microorganisms require oxygen. Oxygen enters soil when the soil is loose. A healthy soil food web creates soil that is naturally loose (no mechanical tilling required)

      3. Soil organisms also require water. Water is held in soil either by tiny particles of organic matter or by particles of clay. The more organic matter in a soil the more water it can hold (the clay content of a soil cannot be easily changed).

      4. Soil organisms require energy. They get their energy from living plant roots. Plants will put up to 40% of the energy they produce back into the soil as exudates (reference). In the absence of living plant roots some microorganisms can live off of the organic matter in the soil and on the soil surface, but many cannot. Even a short period of time without living plant roots will quickly degenerate the soil food web. This is why perennial plants provide more benefit to the soil than annual plants.

      5. Microorganisms require nutrients. These are provided by bacteria and fungi. The bacteria and fungi get their nutrients either from inorganic rock particles, or from organic matter. It is far easier and faster for them to obtain the nutrients they need from organic matter than from rock particles. Therefore the more organic matter in the soil the less energy plants need to use in order to acquire their nutrients.

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In conclusion; the soil food web becomes healthier:

  • the longer it operates undisturbed (increased aeration and oxygen)
  • the more organic matter there is in the soil (for water and nutrients)
  • the more exudates released by living plant roots (energy)
  • and the more diversity in the plants providing those sugars (biodiversity).

It is by controlling those four factors that a Regenerative Farmer is able to do what they do.

The Importance Of The Soil Food Web:

The soil food web is the foundation of any sustainable civilization. There is no other way for plants to acquire their nutrients in the absence of non-sustainable fertilizers.

If a plant has adequate sunlight and adequate genetics than the soil food web is the primary factor determining the health of that plant.

The soil food web effects:

  • Rate of plant growth (productivity)

  • Soil water-holding capacity (drought resistance)

  • The nutritional content of our food

  • Water infiltration rate into the soil (influencing surface runoff, erosion and floods)

  • Plant resistance to disease and insects

  • The diversity of plants (healthier soil food web supports a greater number of species)

What does this mean for human food production?

  1. It means that the total amount of land needed to produce our food is dependent on the health of the soil food web. A healthy soil food web will produce more productive and vigorous plant growth which equates to higher total food production per acre. Fewer acres are needed to produce the same number of calories with a healthy soil food web. An unhealthy soil food web has the opposite effect.

  2. It means that the total amount of water needed for agriculture is dependent on the health of the soil food web. A healthy soil food web will make even small amounts of rain more effective, dramatically reducing irrigation needs. It does this by increasing the percentage of rain that is actually absorbed into the soil (since a healthy soil is loose and not compacted). A healthy soil food web also means that there is more organic matter in the soil to hold water. And it is almost inconceivable to have a healthy soil food web without a layer of “litter” on the surface of the soil which dramatically reduces the rate of evaporation from the soil. A healthy soil food web almost always includes extensive networks of “myccorhizal fungi” (you can imagine them as cosmetic hair extensions, but for plant roots). These myccorhizal fungi draw water from deep in the soil and from distant areas and give it to the plant in exchange for energy. The less healthy the soil food web the more dependent agriculture will be on unsustainable irrigation practices.

  3. It means that the amount of pesticides applied to crops is dependent on the health of the soil food web. A healthy soil food web directly protects plant roots from harmful organisms. Plant roots are one of the main vectors for plant diseases. The plant is also better able to defend itself with its natural forms of defense because it has all the energy and nutrients it needs to produce protective chemicals and to recover after being attacked. If the soil food web is not healthy than farmers are forced to put pesticides on crops to keep them alive.

  4. It means that the prices of food are heavily dependent on the health of the soil food web. A healthy soil food web increases agricultural productivity while keeping costs low. This increase in the profit margin for farmers means that prices for consumers will go down. The reverse happens with an unhealthy soil food web.

  5. It means that the health of our food (and therefore our health) is dependent on the health of the soil food web. A plant growing with a healthy soil food web will receive all of the nutrients it needs, including micro-nutrients, and incorporate these into its cells. So when we eat a plant grown in a healthy soil food web we are getting the maximum amount of nutrients that that plant can provide us based on its genetics. A plant growing without a healthy soil food web will usually have trouble finding all of the nutrients it needs, especially micro nutrients, so when we eat it we will also not be getting those nutrients.

The total amount of land, water and pesticides needed for agriculture; the price of food; and human health are all dependent on the health of the soil food web. Wow!

Learn More About The Soil Food Web:

Elaine Ingham @ Putting Grasslands To Work conference

Life In The Soil

Soil Food Web Inc.

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