“Mycor” – “rhiza” literally means “fungus” – “root” and defines the mutually beneficial relationship between the plant and root fungus.
These specialized fungi colonize plant roots and extend far into the soil. Mycorrhizal fungal filaments in the soil are truly extensions of root systems and are more effective in nutrient and water absorption than the roots themselves. More than 90 percent of plant species in natural areas form a symbiotic relationship with the beneficial mycorrhizal fungi.
There are major classes of mycorrhizae and many types within the classes. One type grows into the root forming a root extension while another grows around the root system. Both provide benefit but the actual extension of roots provides the greatest benefit.
There are numerous mycorrhizae products available for both landscape construction and all manner of nursery production. A thorough read of the available literature suggests that this industry produces good, better, and best products with some possibly shipping mostly dead product. Much research aimed at inoculation of planting soils has produced limited positive results in some cases and none in others. Some nursery field growers move soil from adjacent wooded areas to their growing fields to inoculate the soil.
Composted manures can contain mycorrhizal populations. We amend our soils with 120 tons of compost per acre before each planting rotation but have never sought to prove the existence of viable mycorrhizae populations.
Researchers have long known that significant plant benefits exist when mycorrhizae are present in the soil. However, at least some researchers will state that the more they know the more research is required to truly understand this phenomenal development of nature.
My research indicates that we should be cautious primarily for two reasons; first the production and delivery of live mycorrhizae products is challenging, and second, research shows that consistent, repeatable soil inoculation is even more challenging. Further, efficacy may not be obvious.
Does this all sound a bit confusing and contradictory? The benefits and advantages cited by Davies would encourage me to jump right in. Yet the facts listed by Scagel and Lindeman cause me to proceed with extreme caution. Most of us are not in a position to prove that we have successfully inoculated the plants. Unlike soil amendments with fertilizer or compost which usually produce near-term visual proof of efficacy, it appears that we may have difficulty assuring success with mycorrhizal inoculation.
It is not my intention to discourage the use of mycorrhizae. For me, based on the facts, I would be very cautious before spending money for product and labor to achieve a potentially elusive, verifiable benefit. I would be pleased to hear from anyone who has proven successful inoculation.