MYCORRHIZAL FUNGI (VESICULAR ARBUSCULAR MYCORRHIZAL)
Even though this idea could seem counter-intuitive, the truth is that the radicular system of a healthy plant does not end with its roots. Not with its own roots, at least. Beyond the roots of the plant itself, a network of fungi expands and brings from the deepest parts of the soil all of the necessary nutrients for the plant’s tasks of producing food and sustaining itself. This type of fungi is called mycorrhizal fungi, from the Greek words ‘mýkes’ and ‘rhiza’; ‘fungus’ and ‘root’ respectively, and these mycorrhizal fungi and plants maintain a mutualistic relationship that goes back millions of years. A simple mycorrhizal fungi definition is that these are root-funguses that form associations with the roots of their host plants that result in a direct benefit for both parts involved, by serving as extensions of their roots and providing the plant with nutrients to which it would otherwise not have access. The fungus, in turn, receives excess sugars from the plant, which serve to feed it and allow it to expand even further into the ground, in search of new nutrients to keep its host plant growing.
Some mycorrhizal fungi examples are ectomycorrhiza (the fungi responsible for a lot of the mushrooms that can be found in a forest), orchid mycorrhiza (that help orchids and similar plants obtain nutrients from the air) and arbuscular mycorrhiza. Arbuscular mycorrhizae are the most widespread type, occurring in over 85% of all plant families and throughout most crop species.
What are the benefits of mycorrhizal associations?
Extending the reach of the plant’s roots (often doubling and triplicating them, under favorable conditions) thus increasing not only the depth they can reach but also the amount of surface covered by root mass.
Stimulating the absorption of all important nutrients (nitrogen, potassium, iron, manganese, magnesium, copper, zinc, boron, sulphur and molybdenum) by enhancing their availability.
Particularly improving the rate of uptake and mobilization of phosphate across all crops, thus reducing phosphorus fertilization requirements.
Outcompeting harmful pathogens by rapidly colonizing the roots of the plants, creating a protective barrier against root diseases. Mycorrhizal soil is much harder for pests to colonize, simply because there’s no space for them.
Generating an immune response in the plant that, while not killing mycorrhizal fungi, increases the resistance of the plant to future fungal diseases, thus serving as something akin to a ‘plant vaccine’.
Producing chemical compounds that attract pest predators when a plant is under attack by pests, mirroring the processes that the plant uses to produce such compounds and boosting predator attraction.
Dramatically increasing plant resistance to changing climate and soil conditions such as drought, heat, and even salinity increase. Water absorption, in particular, is enhanced by the mycelia of mycorrhizal fungi serving as root hairs for this purpose.
Increasing the overall yield of your plants, by the combined functions of improved nutrient and water absorption and increased resistance to disease and climate conditions.
Reducing soil erosion through the production of glomalin by the mycorrhizal fungi, which serves as a binding agent that improves soil structure and increases carbon content. When applied to soil mycorrhizal fungi will produce this protein to coat their hyphae, beneficially releasing it into the ground when they die.
A case in practice: mycorrhizal inoculation in corn crops
For a simple answer to the question of what are mycorrhizal fungi (and, above all, why do they matter), in the image at left it is possible to see a graphic depiction of how well corn responds to a mycorrhizal fungi inoculation. Arbuscular mycorrhizal fungi grow from within the cells of the roots themselves, serving as ‘branches’ for the expansion of the root system. The fungi associate themselves with the cellular structure of the roots, and begin expanding their hyphae through the soil, bringing nutrients and water to the plant and increasing their reach as their plant host grows stronger and larger. This increases the efficiency with which the plant absorbs the nutrients present in the soil, reducing nutrient runoff and fertilization requirements, as well as improving resistance to drought and disease; ultimately increasing yields and overall plant health.
Methods of application of mycorrhizal fungi:
The following table provides a basis for how to use mycorrhizal fungi in different scenarios, detailing in particular the doses required according to each method and to the type of plant being grown (annuals vs. perennials):
1. Application by seed dressing:
In an appropriate container for the volume of product required, mix the mycorrhizal inoculant with crude sugar at a proportion of two parts of sugar for one part of mycorrhizal inoculant (for 20-100 kilograms of seed, 100 grams of sugar per 50 grams of mycorrhizal inoculant) in sufficient water to make a slurry. Use this liquid preparation to coat the seeds, and allow them to dry in the shade before sowing, casting or dibbling them in the field. Do not store the coated seeds for more than 24 hours before planting.
2. Application directly into soil:
Mycorrhizal fungi can be directly applied into the soil through several different strategies, detailed next.
Mix the mycorrhizal inoculant with compost at the required dosages, and apply this mixture directly into the soil at the early life stages of the plants, along with any other biofertilizers that may be used.
Mix the mycorrhizal inoculant with water at the required dosages, and apply this mixture directly into the soil at the early life stages of the plants, along with any other biofertilizers that may be used.
Apply the mycorrhizal inoculant mixed with water under a drip irrigation scheme, filtering out the solution before adding it to the drip tank if any insoluble particles are noticed during its preparation.
Use mycorrhizal fungi to boost the continued growth of perennial plants by dissolving the mycorrhizal inoculant in water at the adequate dosage, and drenching the soil where the roots are (for trees, use the drip line as a reference) twice a year. It is recommended to make a first application of this mixture before the onset of the spring, rainfall season or first monsoon, and the second application after the end of the main monsoon, rainfall season or spring season.
3. Application of mycorrhizal fungi as spray.
It is recommended that mycorrhizal fungi are applied as close as possible to the roots they will colonize, to ensure maximum effectivity and inoculation rate. If applying as spray, mix the mycorrhizal inoculant at a proportion of 5 milliliters per liter of water, and spray at the drip line of the canopy of the plant. The total volume of mycorrhizal mixture required may vary depending on the canopy size (and its corresponding drip line).
Shelf life and packaging:
Shelf life: The product is best before 24 months. Store at room temperature, away from sunlight, heat and humidity.
Packaging: The product arrives in a one-kilogram pouch.