Mycorrhizal Fungi 101
“It hardly states the case to say that mycorrhizas are important to ecosystem function. It is much more accurate to say that mycorrhizas are ecosystem function.” – Ted St. John, Ph. D.
Mycorrhizal fungi form symbiotic relationships with plants at the root level. These fungi enshroud and, in some case, penetrate the structure of plant roots to form an intimate connection that facilitates a 2-way nutrient exchange. The mycelium of mycorrhizal fungi essentially extend the roots system of their associated plants to help the plants easily draw in nutrients, minerals, and water from afar. In return, the mycorrhizal plant provides the fungus with photosynthesized sugars. The oldest plant fossils have been found with this association and it has been theorized that this relationship is what enabled plants to first come out of the oceans and on to land nearly 500 million years ago.
Today, nearly all plants still form mycorrhizal associatations. The few plants that do not are considered divergent weeds that have developed alternative strategies of survival. Most all cultivated plants perform much better when associated with mycorrhizal fungi and some plants require such associations to grow at all. Thus, it is highly recommended to learn to grow mycorrhizal fungi to improve soil fertility and increase plant health and productivity.
Types of Mycorrhizal Fungi
Most mycorrhizal fungi fall into two broad categories:
Ectomycorrhizal Fungi – These fungi are often specific in the plants they associate with and include many of the commonly wild-harvested mushrooms (e.g. Chanterelles, Boletes, Matsutake, and Russula species). They form complex multi-species relationships that are somewhat difficult to reproduce commerically. As such, these mycorrhizal fungi are not commonly cultivated.
Endomycorrhizal Fungi – Also known as Arbuscular Mycorrhizae (AM), these fungi include all the Glomeromycota species. These species are generalists, meaning that they can associate with many different plant species. One mycelial network of an endomycorrhizal fungus can be associated with numerous plants of various species and genera. Thus, these fungi literally connect the plants of the forest (or garden) together and channel resources among them. These fungi build soil structure and porosity through the creation of a sticky protein called glomalin, which is what distinguishes soil from dirt. These fungi are quite easy to grow and are very beneficial for the soil.
The mycorrhizal associations that form between plants and fungi are by and large the most studied plant symbiont interaction that has been scientifically explored. Study after study confirms the supreme benefits that plants derive from these ancient and incredible relationships. A list of some of the reasons to grow these fungi and the benefits they provide includes:
- Plant Fertilizer Impacts – Increases nutrient use efficiency by plants (especially phosphorus), decreasing application needs – Decreases run off and leaching – Improves Water Quality
- Soil Quality – Improves soil structure & stability via Glomalin – Decreases erosion & topsoil loss – Enhances nutrient retention
- Disease – Suppression of pathogens – Increases plant health – Decreases pesticide use
- Efficiency & Profitability – Improves root growth & survival – Decreases production time – Enhances marketability
- Drought and Salinity – Increases efficiency of water use – Decreases crop loss – Increases acreage of farm land
- Product Quality – Alters phytochemical attributes – Increases flowering – Enhances nutritional value
Cultivating Mycorrhizal Fungi
Cultivating Endomycorrhizal fungi (AM) is relatively easy. It essentially requires introducing commercial AM spore blends or native soil to a host plant crop to which the AM will come to associate with. Over a period of 3-4 months the AM grows and forms an association with the host plant(s). After that time, the plant is cut down and watering is stopped. This forces the AM to produce spore “packets” in the soil. Another 10-14 days later the roots of the host plant are harvested, chopped, and either stored or applied in the field as inoculum. These roots serve as inoculum because they are covered with the mycelium and the spore packets. In essence, you have enabled the AM to amplify itself via the introduction of the host plant.
A great intro to this method was developed over 6 years by the Rodale Institute. You can read their technique here. However, we must note that while this technique calls for the use of a tropical grass (with some justification), we at Radical Mycology would encourage working with grass species that are native to your environment, despite the potential for a lower overall AM yield.