How roots and fungi associate in the soil.
From the moment a root starts growing in healthy soils, it is quickly penetrated and colonized by myriads of naturally occurring soil-borne fungi. An extensive fungus-root association, called mycorrhizae, develops in which both partners in this beneficial relationship (called a symbiotic relationship) gain from each other’s presence. The fungi benefit by consuming sugars exuded from root cells for energy to growth. The plants benefit by fungi ‘pumping’ water and nutrients, extracted from areas far beyond the plants actual root system, directly into root cells. Plants colonized by beneficial fungi thus have an improved supply of water and nutrients for superior fruit and flower production. They also grow faster and bigger with consequential ability to withstand environmental stresses such as periods of drought and invasions by disease-bearing organisms.
The science behind beneficial soil fungi.
Visible proof of plant benefits from soil inoculation with beneficial fungal spores has been well documented by researchers. Biologists have long recognized that fungi naturally form extensive and complex beneficial associations with root cells. As far back as 1885, a German forester named A.B. Frank wrote about the close association of tree roots with fungi. But it has only been within the last three or four decades that research has shown the almost universality of root and fungal partnerships.
Researchers have been able to capture details of fungal spores producing extraordinary masses of microscopic-sized fungal threads (called hyphae) extending far away from a plant’s root zone. They have photographed the hyphae forming an intricate network surrounding roots and root hairs as well as penetrating between root cells and even right into the interior of cells. This fungal invasiveness is actually ideal for the plant as shown by further studies. Using radioactively-labeled water and nutrient molecules, researchers have followed the fungi conducting water and nutrients, from distances far beyond root cells, directly into the spaces between root cells and in some cases directly into root cells.
Are there beneficial fungi in your soil?
While fungus-plant partnerships are almost universally found in undisturbed, humus-rich native soils, it is rare to find gardens constructed on such ideal soils. Some gardens have to be constructed using truckloads of soil that have been stockpiled, neglected or abused for a number of years. In many residential developments, extensive compaction from heavy machinery traffic has squeezed the life out of what soil is left for the homeowner. Many imported soils, scraped from agricultural lands, have been previously laced with pesticides for crop production with resultant losses of beneficial fungi and other microorganisms. When a garden is constructed using these soils, there is no reservoir of naturally occurring fungi to team up with fresh-planted ornamental plants. Young transplants are reduced to relying strictly on their roots’ ability to extract nutrients and water from the existing poor quality soil.
While some fungi will, over time, re-establish in garden soils of any quality, the purchased fungal spore mixtures in those colorful MYKE tubs quickly inoculate the soil with appropriate beneficial fungi. Just about any plant soon develops a beneficial partnership with the fungi: roots grow more vigorously and extensively, plants have larger reservoirs of food and water to draw upon for active growth, plants become more drought-proof due to the larger area of fungus/root/soil inter-relationships, and yields of flowers, fruits and vegetables are increased.
Do Fungal Inoculants Benefit all Plants?
There are only a few plants that do not form beneficial partnerships with fungi. In the vegetable line, these include cabbage, broccoli, beets, spinach and radishes. Blueberries and cranberries are fruits that don’t develop fungal partnerships. Rhododendrons, azaleas, orchids, lupins, carnations, alyssums, and kochias are also not improved with fungal inoculants. But it should be noted, the plants just listed are not harmed in any way by the fungal inoculants.
Ready to Try Fungal Inoculants?
If you are now feeling more comfortable about gardening with fungal supplements, there is a series of consumer products, called MYKE, available in many Ontario garden centers. It is currently the only such product available to home gardeners, so naming it doesn’t give them any marketing edge.
Considerations for Growing with MYKE
It is important to choose the appropriate formulations for the target plants. There are formulations for vegetables, tomatoes, annuals and perennials, trees and shrubs, bulbs, indoor plants, roses, evergreens and lawns.
Fungal inoculants such as MYKE do not result in immediate noticeable plant improvements. It takes from four to six weeks for the fungi to colonize the target plants and for the plants to reap benefits from their symbiotic relationship with the fungi. Keep the soils moist during this period to allow the fungi and plants to establish their symbiotic mycorrhizal relationship. By the way, have you noticed the derivation of the trade name MYKE? It comes from the term mycorrhizae?
The fungal inoculants should be placed in each transplanting hole (or added to seed-starting soil mixes) at planting time. Root hairs need to be in direct contact with the fungal spores in the early stage of plant establishment. It is also possible to retroactively add fungal inoculants to gardens. For this, create a series of 2 inch-deep small holes around the base of plants and share the label-recommended amount of inoculant over the multiple holes. Water the area around each treated plant well to carry the fungal spores into immediate contact with the root system.
Fungi do not grow well with high doses of water-soluble, salt-based fertilizers – especially those high in phosphorus. The high-phosphorus transplanting fertilizers (with a formulation of 10:52:10) should not be utilized with fungal inoculants – the phosphorus (middle number) is much too high for fungi to survive.
In general, you can continue using most water-soluble fertilizers with fungal inoculation programs. Fertilizers with phosphorus percentages less than 10% of the formulation are recommended. For fertilizers with phosphorus percentages higher than 10, diluted the solution by at least 50% to bring the phosphorus level down to that supporting fugal development. Better still, change over to organic-based fertilizers (such as fish emulsions and vegetative composts) and mulches which decompose into nutrients better utilize by the fungi
The next challenge is to convince commercial plant producers to join the fungal inoculation practice. The soil-less mixes that are almost universally used in the horticulture trade are naturally devoid of beneficial fungi. It would be ideal to have all plants delivered to nurseries with the fungi already hard at work, in their nursery pots, as they await purchase.
Looking for more information on fungal inoculants?
There is an excellent article “Underground Partnerships”, by Jon Ardle, printed in the November, 2003 edition of The Garden published by the Royal Horticultural Society. This can be found in libraries or on the internet at:
http://www.rhs.org.uk/thegarden/pubs/garden1103/mycorrhiza.asp
Internet users can also tap into a bonanza of other sources including:
1. Information on MYKE products available at http://www.usemyke.com/mycorise/index.htm
2. A scientific report (from the Eastern Cereal and Oilseed Research Center, Agriculture Canada) “Biodiversity of Mycorrhizal Fungi” available at http://res2.agr.gc.ca/ecorc/mycor/bio_sols_e.htm
