Mycorrhizae#

What it is and why do you need it?#

The relationship between good fungi and plant roots is called mycorrhizal associations, or mycorrhizae.  The awesome effects of mycorrhizae can be seen in vibrant healthy plant growth, robust flowering, and healthy, living soil.

These two organisms (fungi and plant roots) live together in a mutually beneficial symbiosis where the fungi get either nutrients, metabolites, or a combination of both from the host.  Fungal symbiosis occurs all the time in nature, but we don’t always see it.  You can often find mushrooms living around tree bases in forests, but there is a lot more going on underground that we don’t see.  And in fact, the vast majority of symbiotic fungal relationships live their whole lives in the soil where we don’t see the important impacts of these relationships.

Mycorrhizae is everywhere#

The majority of all vascular plants (potentially up to 95%) on earth should have mycorrhizae living in connection with their root systems.  There is now have evidence that mycorrhizae are over 400 million years old. Some scientists believe that mycorrhizae actually facilitated life on land for vascular plants.  We cannot overemphasize the importance of the relationship between plants and mycorrhizae.  They need each other for optimum life.

Ectomycorrhizae vs Endomycorrhizae#

There are two basic types of mycorrhizae- ectomycorrhizae and endomycorrhizae.  Ectomycorrhizae have hyphae that surround the cells of the host plant.  This accounts for about 5% of mycorrhizal associations and is most often seen in forests and around tree root systems.  This is why you will often find mushrooms around the bottoms of trees and along the forest floor.  Endomycorrhizae, or Arbuscular mycorrhizae, occur when the hyphae of the fungi actually enter the cells of the root cortex; and, are by far the most common type of mycorrhizal associations. Although this type of mycorrhizae does not form the button mushrooms we commonly associate with fungus, they do often live closely together.

Collectively the network of fungal hyphae is often referred to as mycelium.  Hyphae are very small and this network often resembles white fuzz surrounding root systems or growing across the soil.  According to Ian Dickie from the University of Minnesota, forest mycorrhizae can increase the root mass anywhere from 300 to 8000 times.  By increasing the footprint of the soil plants can mine to attain life sustaining molecules, mycorrhizae ensure optimal water and nutrient absorption. And thus, mycorrhizae not only increase your overall yield but also improve the nutrient density and flavor profile of your edibles. This isn’t a one way street. In return for improved yield, flavor, and nutrient density, plants provide the fungi with life sustaining carbohydrates produced during photosynthesis.

And I mean it is everywhere#

Amazingly, mycorrhizae can grow in an extremely wide range of habitats.  Mycorrhizae can be found on every continent.  Until recently, it was thought that mycorrhizae couldn’t grow on Antarctica, except in greenhouse cultivation.  A new study says “NOT SO!” to that assumption after finding native mycorrhizae on Antarctica.

Like I said earlier, almost every type of plant on earth should have some sort of mycorrhizal association.  Mycorrhizae are actually the primary and more efficient means for plants to get their nutrients from the soil. Roots are in fact the backup system, just in case mycorrhizae are not around to absorb soil nutrients. 

 

How do mycorrhizae work?#

When arbuscular mycorrhizae penetrate the root cells of host plants, they create an organ called an arbuscule. This arbuscule looks kind of like the branches of a tree. It is the space where nutrients are exchanged between the plant and the fungi. Additionally, the hyphae of mycorrhizae are very small, which gives them access to much smaller soil spore spaces.  This allows the fungal hyphae to unlock nutrients that the roots themselves would not be able to access.

What’s good for the goose, is good for the gander#

As plants photosynthesize carbon dioxide, they release carbohydrates that the fungi need for fuel.  In exchange, the fungi provide the plant additional access to soil nutrients and water.  This makes growing, surviving, and fruiting a much more efficient process for the plant.  Instead of doing all of the work themselves, plants get mycorrhizae to do it for them!

Mycorrhizal relationships also increase the immune systems of host plants.  When the mycorrhizae connect to a plant, it triggers the plant to release “defense-related chemicals.”  It makes the host plants more disease-resistant for the future.  So in a way, mycorrhizae also immunize plants against future diseases.

On a much larger scale, mycorrhizal associations act as a sort of soil internet.  Plants are inter-connected via the mycelial network created through their connections to mycorrhizae.  Plants then get to share nutrients like nitrogen and phosphorus.  Some scientists believe that older, more established trees are actually able to share nutrients with smaller, younger ones through this network.  The mycorrhizal network ensures the survival of a young tree that might not have access to the amount of nutrients or sunlight it needs to thrive.

Helping to balance carbon dioxide#

Soil is one of nature’s best CO2 sinks. As the soil absorbs environmentally harmful CO2, mycorrhizae get to work converting it into beneficial, bioavailable plant nutrients. And the more CO2 present, the more mycorrhizae develop.  Mycorrhizae are taking lemons and making lemonade!  Imagine if every industrial farmer and hobby gardener was cultivating mycorrhizae in their soil!

The movie Carbon Nation, which focuses on climate change solutions, suggests this very thing as a viable solution to excess carbon dioxide.  It claims that creating land use policies that encourage mycorrhizal development could reduce current carbon emissions by as much as 39%.  That’s a lot!

How can mycorrhizae improve your yield? (benefits)#

There is ample evidence that mycorrhizae are beneficial for both the small garden and the larger ecosystems on earth.  How exactly does all of this evidence result in a higher yield in your personal garden?  When plants have access to adequate nitrogen, you will see stronger vegetative growth.  Phosphorus increases root growth, flowering, and fruiting.  Potassium helps with fruit ripening, disease resistance, and overall plant health.  And that is just what you get with primary macronutrients! 

Unlocking more nutrients#

Mycorrhizae give roots better access to these primary macronutrients, secondary macronutrients, and micronutrients by expanding their root systems and unlocking smaller areas of soil.  In addition, they increase water intake capabilities.  Mycorrhizae open the flood gates to an all you can eat buffet every time they form a relationship with a root system.  On top of that, they help make plants more resistant to drought and diseases. This buffet, coupled with the added disease/ drought resistance can increase your yields anywhere from 23% to 37%.  However, the amount of yield increase with mycorrhizae will depend on the total nutrients available in your soil.

Keep in mind that a controlled growing environment will require a solid source of nutrients for mycorrhizae to do their job.  It’s always a good idea to get your soil tested if you are unsure.  In an outdoor growing environment, nutrient needs may not be quite the same.  You have to be careful with Phosphorus, though.  Recent studies show that Arbuscular Mycorrhizae are extremely important in the uptake of Phosphorus. However, studies also show that too much phosphorus in your soil can inhibit mycorrhizal development.  Some evidence shows that an excess of phosphorus forces mycorrhizae to go dormant, while other evidence shows excess phosphorus actually killing fungi. Either way, excess phosphorus is not a good thing when it comes to the success of our lemonade stand.

Be mindful with Phosphorus#

Colorado State University Extension recommends optimal levels of phosphorus in your soil stay below 50 ppm.  Because of this, we have debated a bit about using mycorrhizae in highly amended soils.  It is hard to say for sure, but definitely worth experimenting with. Synthetic liquid fertilizers are not recommended for use with mycorrhizae. So keep that in mind when considering how to supply your plants with the necessary nutrients.

How to use mycorrhizae in your garden#

Proper use is important#

If you are excited to see what mycorrhizae can do for your garden, there are a few things to know when looking for a good source.  There are a lot of growing mediums that already have mycorrhizae in them.  Mycorrhizae will never give your plant nutrient burn, so the more the merrier!  But, since mycorrhizae need healthy, living roots to cultivate and survive, the closer you get them to the roots, the better.

We recommend Great White Premium Mycorrhizae a product that you can apply directly to your seeds, seedling roots, or transplant root balls.  There are a lot of good powdered and liquid products, but be sure to always check expiration dates.  If using seeds, you can soak your seeds in inoculated liquid.  Alternatively, you can spray them with water and roll them in powdered spores.  With seedlings or the root balls of transplants, you can dust the roots or dip them in a mycorrhizae product.  Some people prefer the simplicity of a soil drench, but others question its effectiveness. Since mycorrhizae can take as long as 90 days to cultivate, the earlier in your plant life cycle you inoculate, the better.

How do commercial products stack up?#

Knowing that mycorrhizae need living roots to thrive, I was skeptical of most products on the shelf.  So, I did some research.  I found out that most retail mycorrhizae products are actually the spores or propagules of cultivated mycorrhizae that are in a dormant state.  Once they are introduced to healthy soil and roots, the plant roots pump a certain exudate into the soil that “wakes up” the mycorrhizae.  If you do decide to go with a mycorrhizal product, there are some other important things to note.  You should treat this product like a living organism.  Heat, harmful conditions, and chemical exposure can destroy the viability of the spores.  So be sure to keep your mycorrhizae in a cool place.  Mycorrhizae can tolerate certain fungicides, but you have to be careful what you use on your plants.

If you are extra ambitious and don’t want to invest in a commercial mycorrhiza product, you can cultivate your own mycorrhizae. 

Long term mycorrhizae maintenance in your garden#

In outdoor applications, like fields or garden beds, you can keep your mycorrhizae alive throughout the year and avoid re-inoculating annually.  If you want to establish a strong mycorrhizal relationship for life, it’s a good idea to think about cover crops.  If fields are allowed to go fallow, then mycorrhizae will die off without viable roots present.  If you use cover crops in the off-season, mycorrhizae can stay alive as long as you take good care of your soil and keep roots alive.  Despite common belief, cover crops can be used in home gardens and are really easy to care for.  Inoculating your garden with mycorrhizae can be an expensive process, so if you want to do it once and maintain all of that awesomeness with cover crops. So, whether you are a container gardener or an industrial farmer, mycorrhizae can be a beneficial addition to your soil microbiota.

Do you have experience inoculating with mycorrhizae? Have you maintained healthy mycorrhizae populations in your raised beds with cover crops? Tell us about your experiences. Comment below!

Sources:

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/17462/fs304-e.pdf

http://www.dictionary.com/browse/mycorrhiza

https://www.certifiedcropadviser.org/files/certifications/certified/education/self-study/exam-pdfs/197.pdf

http://mycorrhizas.info/

https://www.certifiedcropadviser.org/files/certifications/certified/education/self-study/exam-pdfs/197.pdf

http://www.jstor.org/stable/3760760?seq=1#page_scan_tab_contents

http://mining.state.co.us/SiteCollectionDocuments/MycorrhizaAndSoilPhosphorusLevels.pdf

https://books.google.com/books?id=627Qopsj7bsC&pg=PA1111&lpg=PA1111&dq=how+much+do+mycorrhizae+increase+root+size&source=bl&ots=RWf2ELjrdN&sig=pRYCdoNVgr3iiX5VXOKgWOnYK3Q&hl=en&sa=X&ved=0ahUKEwiD1beq49LMAhUH5mMKHR28AhMQ6AEIPzAG#v=onepage&q=how%20much%20do%20mycorrhizae%20increase%20root%20size&f=false

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http://www.countrysideinfo.co.uk/fungi/habitats.htm

https://www.anbg.gov.au/fungi/mycorrhiza.html

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