Mycorrhizae are the filamentous body that fungi form underground as they grow from spores. These white, rope-like strands are commonly seen holding together clumps of particularly healthy soil. In addition to increasing soil stability, these fungi are known to associate with the root systems of 95% of all plant families.
This ancient connection between fungi and plants can be exploited to the benefit of soil-based and most hydroponic gardens, whether indoors or in a greenhouse, through a variety of means. In order to understand the benefits of using mycorrhizal additions, it’s important to understand the basic nature of the relationship these fungi form with different substrates and plants.
The most familiar effect of mycorrhizal additions in home gardening is their ability to increase the availability of nutrients in the substrate. Mycorrhizae achieve this by exuding enzymes into the area surrounding their root-like hyphae, which serve to break down these compounds so they may be absorbed.
Essentially, they externalize their stomach and collect the pieces of “food” after the enzymes break them down. This serves to increase local nutrient availability because the fungus does an imperfect job of absorbing the nutrients this process generates. However, these “leftovers” constitute a small amount of nutrients generated and mostly serve to benefit bacteria in proximity to the reactions taking place. Plants benefit most from this process because of the relationship formed between the mycelia and the plant’s root system.
Upon encountering your plant’s root system, mycelia begin to cover the roots in fungal cells, either surrounding them on the outside or also penetrating through the cell wall into the cytoplasm of the root cells. This gives the fungus either indirect or direct access to the roots of your plant, allowing for the exchange of nutrients.
While this might seem like a bad thing, with the fungus now sapping away the fruits of the plant’s labor, in reality this association creates a two-way exchange of nutrients between the fungus and your plant that the fungus can then use to their mutual benefit.
Once the mycelia colonize the plant’s root system, the connections then link the plant’s roots to the rest of the mycelial network underground. Compared to roots without them, these connections serve to increase the surface area for nutrient absorption enormously.
Mycelial filaments are many times smaller and more prolific than any plant’s roots and as such are much better at finding and extracting the water and other nutrients present in their surroundings. In return the fungus gains access to a steady supply of carbon leftover from the plant’s conversion of atmospheric CO2, which can then be used to expand the mycelial network into new areas.
The benefits of this relationship are not limited solely to the increased acquisition of nutrients. Mycorrhizae have been demonstrated to protect plants against drought, changes in pH and soil pests. In other words, they serve as a barrier for the plant against environmental stressors.
The benefits of using mycorrhizal additions depend on the method of gardening. Soil-based gardeners derive the most benefits from these mycorrhizal associations because this technique most closely mimics the natural environment in which these associations originally developed. Increased soil stability, nutrient absorption and stress protection are all achieved through the use of mycorrhizal additions in soil-based gardening.
Similar benefits can be derived through the use of a coco-based hydroponic system. With mycorrhizal additions to coco, the plants not only absorb more nutrients from the solution through the mycelia, but the fungus is also capable of decomposing the coco itself and directing the nutrients it derives towards plants. The only gardening method where mycorrhizal additions provide no benefit is a flood and drain system using expanded clay pellets where the fungus has no time to establish itself before being washed off of the roots and out of the substrate.
One other factor for consideration is that fungi also respirate in the same way humans do—breathing oxygen and exhaling CO2. As such, a well-established mycelial mat serves as an oxygen sink for your garden and should alleviate some of the need for supplemental CO2 over time. Additionally, portions of well-colonized coco and soil can be reused to inoculate future crops with mycelia as they possess the ability to form a completely new colony from a single cell and form an aggregate as they encounter other mycelia of the same species as they colonize your substrate.
Mycorrhizal additions can do much to improve the quality and yield of your plants. By increasing surface area for nutrient absorption, generating more nutrients to be absorbed, creating a protective layer against drought and pests, emitting CO2, all with enough material to inoculate your future plants, mycorrhizal additions provide a great deal of support for most all gardening techniques.