The Organic System – Mycorrhizae

The Organic System – Mycorrhizae

The Organic System – Mycorrhizae

And everyone says, “What?”  Please don’t just pass this article because you think it is going to be one of those dull, technical pieces that you read to go to sleep at night.  I admit that there is going to be a bit of technical information, but, on the whole, I think once you begin to read, you will be as fascinated by the subject as I am.  If you are at all interested in the health of your soil, you need to have some understanding of how fungi fit into the picture.

Fungi, you say?  Don’t we try to avoid fungus on our squash plants and in our turf?  Well, yes.  But you have to understand that in the world of micro-organisms, there are thousands of different fungi.  Some are problems, while others perform vital roles in the health of our soil and the support of strong plants.  Mycorrhizae is one of these.

What are Mycorrhizae

Mycorrhizae fungi are an interesting part of the soil ecology.  First described in the scientific literature in 1881 by a Polish mycologist, Franciszek Kamienski, who was commissioned by the King of Prussia to investigate the association of fungus and plant roots.  His work was carried further by a German, A. B. Frank, who sought to increase truffle production.  His research focused on the relationship of the fungus that produces truffles and the roots of oak trees.  Frank was the first to hypothesize that the two formed a symbiotic partnership in which the fungus extracts nutrients from the soil, making it available to the plant, and the host plant feeds the fungus.  After 130 years, most of Frank’s theory has been proven and is now accepted science.

How it works

The Organic System – Mycorrhizae

Plant roots are covered in tiny root hairs, almost microscopic themselves.  These root hairs are what absorb nutrients and moisture from the soil.  However, many of the nutrients that plants need, particularly phosphorus and zinc, have limited mobility in the soil, making then generally unavailable to the root hairs.   Also, plant root structures are relatively small, limiting the soil area that the plant root hairs contact.  Increasing this soil contact area is where mycorrhizal fungi come into play.

Bigger is Better

Mycorrhizae fungi build a “body” called hyphae that resembles filaments that can extend for long distances around and away from a plant root structure.  The hyphae grow huge masses among the root structure of plants and extend the hyphae to great distances.  The effect is that the mycorrhizae hyphae greatly increase the effective surface area of the plant’s root structure.  The fungi hyphae find nutrients and moisture and return these to the plant root system in return for food in the form of carbohydrates that the plants exude from their roots.

The Benefits to the Plants

The host plant gains several benefits from this symbiotic relationship:

  • Nutrients normally unavailable to the plant are more easily absorbed and obtained even from long distances away.
  • Moisture is more readily available to the plants, making them more drought-tolerant and less likely to suffer stress.
  • Studies have shown that plant roots closely associated with mycorrhiza fungi live longer.
  • Mycorrhizae fungi can help plant resistance to some pests and diseases as well as mediate the presence of some heavy metals in the soil.
  • Mycorrhizal fungi exude a compound known as glomalin.  This byproduct of the fungi is a gooey, sticky substance and is the primary product that binds soil particles together to form aggregates.  Aggregated soil is healthy soil and is a primary goal of anyone interested in soil health.

Underground Communications

The Organic System – Mycorrhizae

There is research indicating that plants “communicate’ with one another via the mycorrhizal fungi network.  One study focusing on broad bean plants found that when one plant was stressed, it produced a volatile compound called methyl salicylate.  This compound serves several functions for the plant, including acting as a repellant to pests and an attractant to beneficial insects that prey on the pest insects.  The study found that not only did the stressed plant create this compound, but neighboring plants showed an increase in the production of this compound as well.    Plants situated the same distance from the stressed plant but not connected to the mycorrhizal network did not show this increased level of compound production.  The conclusion is that the fungi network acts as an intermediary between the plants.

Keep the Fungi Happy

Fostering a healthy sub-soil biome should be the core concept of any organic landscape system.  There are several things that you can do and a few that you should avoid at all costs.

  • Feed the Soil, not the plant. 
    • A healthy sub-soil biome will provide everything the plant needs in a balanced and easily obtained manner.  There are problem associations with using synthetic salt-based fertilizers in your landscape and garden.  Adding salt-based synthetic fertilizers makes a high concentration of nutrients readily available for a short period.  Because of the availability of these nutrients, especially as young plants are developing, the bulk of the nutrients are spent on foliage production and not root production.  The plants also do not exude the required carbohydrates to foster the connection with the fungi and other organisms in the soil, and the soil network fails to develop properly.  When the last of the synthetic nutrients are gone, either through use by the plant or migration down through the soil, the plant begins to stress.  Without the soil network in place, the plant doesn’t have the symbiotic relationships it needs.  The lack of connection with the soil network causes the plant to divert energy to root development at a late stage in growth and turn that energy away from leaf and fruit production until it can re-establish that symbiotic relationship. 
  • Don’t Disturb the Soil. 
    • We advocate a no-till approach to gardening.  Every time you disturb the top few inches of the soil, you are effectively disrupting the soil network.  This network is fragile and is easily destroyed by tilling, hoeing, or digging.  Avoid that at all costs by using an organic system approach that controls weeds, moisture, and soil temperature.
  • MULCH!
    • Mulching your garden is essential for good soil biome health.  Fungi and bacteria are susceptible to damage from the UV in sunlight.  UV is a natural sterilant and can severely damage the top few inches of exposed soil by killing the bacteria and the fungi.  A layer of mulch protects this top few inches as well as continually feeding nutrients into the soil and helping to maintain soil moisture by restricting evaporation.
  • Don’t use synthetic fertilizers, herbicides, or pesticides. 
    • The soil network is a complex ecological system.  As we have discussed, the introduction of synthetic fertilizers can create an imbalance in the soil that can affect the way the soil network develops.  The application of herbicides and pesticides are even more disruptive.   Herbicides can kill many of the fungi that are beneficial to your plants as well as some of the microscopic organisms that exist in healthy soil.  Pesticides, especially the broad-spectrum variety, are indiscriminate killers.  The many bugs, insects, and earthworms that are essential to the biological processes happening in your soil are killed just as quickly by the synthetic pesticide as the harmful insects you are trying to control.  Remember that healthy plants connected to a thriving soil network are much more resistant to pests and diseases.
  • Feed Naturally. 
    • Even when utilizing a good organic system in your garden or landscape, you may still need to feed your soil.  A routine of mulching with fresh local wood chips is the first step.  As these materials break down, they begin to release nutrients, properly balanced and in a form easily available, into the soil.  At times of peak growth or fruit production, it may be necessary to introduce extra nutrients.  The best method for this is the use of compost tea.  Compost tea can be sprayed as a foliar fertilizer or applied as a drench to the soil in your growbeds and landscapes.  One of the major benefits of using natural organic fertilizers is that there is virtually no way to burn or harm your plants by overfeeding as you can with synthetic salt-based fertilizers.  The addition of high-quality compost occasionally is another method of adding nutrients to your soil safely and economically. 
  •  Stay in touch with your soil. 
    • Get your hands in your soil.  Feeling your soil in your hands is one of the best ways to understand how healthy soil feels.  You will soon be able to “feel” the soil and distinguish any problems that need to be addressed.  Smell your soil.  Your nose can be a reliable indicator of good soil health.  It should have a pleasing earthy odor, much like a forest.  If there is any foul or unpleasant odor, there are problems in the soil that need to be addressed.

Growing your underground garden is as important as your above ground garden.

Who knew that you were growing two gardens at once.  The part above ground that we all enjoy so much is dependent on the garden you are growing below ground in the form of all the micro and macro organisms, especially that mycorrhizal network.  You should be as concerned about that underground part of your garden as you are the above-ground part.

Links and Resources

For more information about organic gardening, lifestyles, and living, visit our website at West Texas Organic Gardening.

If you found the information here helpful, you might also find these articles on our website of interest.

Organic Growing Myths

Toss Your Tiller


If you have more specific questions or problems, you can contact us using the contact form on our website. You can also post your question to our community forum at this page; West Texas Organic Gardening Community Forum.

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