Soil Health


Our guest speaker in January, Mr. John Evans of Palmer, got me thinking about soil.  He created Alaska Bounty, a “soil stimulant system” that replaces natural bacteria and fungi lost in chemical fertilizing, harvesting, and even tilling the soil.  His unitque system breeds microorganisms by aerating a special compost tea, versus the organisms found in such things as “soil soup” or even regular compost tea, and he claims this is better for the soil.  And better soil means better plants.


Now, first of all, what do these microorganisms do exactly for us gardeners?  Well, first of all, they break down the insoluable nutrients in the soil, as well as in the orgainic fertalizers we might use.  In this process, they release the nutrients into the soil in soluable form for our plants to use.  And their little bodies hold on to a continuous supply, like a slow release fertilizer, as long as we keep them – ie. our soil – healthy.


You cannot use too much according to John, because it is not a fertilizer and will not burn plants.  Used along with organic fertilizers, it will reduce fertilizer use by up to 70% because the organisms utilize the nutrients and improve the overall soil structure.


According to John, this allows the plants to grow not only larger, as his many giant vegetables attest to, but also sweeter.  He regularly uses a refractometer to measure the sugar levels in his produce as well as the produce in the grocery stores for comparison.  And the plants are better able to shrug off diseases and pests, and even neglect or drought.



After John’s visit, I decided to do a little bit of research on mycorrhizae in particular.  Remember, fungi do not create food on their own, like plants do.  Mycorrhizae is a type of sybiotic fungus that interacts with plant roots, exchanging absorbed mineral nutrient ions for the sugars the plant produces.


Mycorrhizae also increases a plant’s effective root system by up to 700% by breaking down and absorbing nutrients  farther away – up to 30 feet away.  Mycorrhizae not only distribute nutrients, but also depress many root diseases caused by pathogenic fungi and nematodes.  When you disturb natural soils, by digging or rototilling, you break up mycorrhizal systems and force them to start over, interrupting the absorptive area they share with the native plants.  More than 99% of the earth’s plants utilize this fungus to their benefit. There are six types of mycorrhizae, but only two are more considered major types, so that is what I will cover here: ectomycorrhizae and endomycorrhizae.



Ecto is the suffix for outside, so ectomycorrhizae tend to grow on the outside of the root tips.  They penetrate the spaces between to cells of the root’s outer layer, covering the root like a glove, and then fungal hyphae (hair-like filaments) grow outward from the roots into the surrounding soil.  These gather water and nutrients and share them with the plant. They have been shown to be particularly good at absorbing phosphate, potasium, and alkaloid metals.


Ectomycorrhizae also seem to be able to protect a plant from soil born diseases and pathogens.  They do this by producing a sort of antibiotic that keeps bad bacteria at bay, rather like penicillin.  The “glove” they form around the roots may also act as a physical barrier against invasion.


Ectomycorrhizae also produce growth hormones and regulators which can alter the metabolism and growth of the roots themselves, encouraging healthy growth.  This type of fungus tends to colonize coniferous trees and hardwoods.



As you may guess, endo is the suffix for inside, therefore endomycorrhizae grow mainly inside the cells of the plant root’s outer surface, rather than between the cells.  These do not form the glove around the plant root like the ectomycorrhizae, and therefore are impossible to see without a microscope.  But they do send out a net of hyphae to gather water and nutrients.


John talked about using “BioVAM” in his compost aeration mixture, and now I know what VAM stands for.  It is short for vesicular-arbuscular mycorrhizae – two structures formed by endomycorrhizae within the cells of the root.  90% of the world’s higher plant types have a relationship with this kind of mycorrhizae.  Arbuscules are bodies made up of hyphae that take carbohydrates from the cells and increase until they fill the cell completely, then they break down and release their stored nutrients to the host plant.  The mycorrhizae then moves on to another plant cell.  Little is known about vesicles, but scientists suspect that they play a role in propagation.


VAM in particular are good at absorbing phosphorus, copper, iron, zinc and calcium, plus some potassium, though this is highly affected by the balance of calcium, nitrogen, and potassium levels in the soil.  This type of fungus tends to favor turf grasses, ornamentals, hardwoods, and fruit and nut trees.


Other Facts

Another interesting theory about mycorrhizae is that it allows plants to communicate with each other.  There are cases where a plant is stripped clean of foliage by insects faster than it can regrow the leaves.  As soon as one plant becomes infected, the other plants in the area change chemistry and begin to secrete toxins to keep the insects from preying on them.  Scientists believe mycorrhizae may play a role in this communication.


Though most mycorrhizae are invisible to the naked eye, there are a few that produce fruiting bodies.  Small fungi that appear near birch, hornbeam, larch, and spruce may be a type of ectomycorrhizal fungi.  Believe it or not, truffles are also a type of ectomycorrhizal fungus.




Ectomycorrhizal trees Endomycorrhizal trees
Arborvitae Ash
Aspen Buckeye
Basswood Crabapple
Beech Dogwood
Chestnut Ginko
Birch Huckleberry
Cottonwood Hawthorn
Fir Holly
Hemlock Horsechestnut
Hickory Locust
Larch London Planetree
Oak Magnolia
Spruce Maple
Willow Redbud