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Home  > Question of the Week

Question of the Week

Permalink What information can you give me on mycorrhizae and soil health?

New Hampshire

Answer: I am pleased to provide you with information regarding basic information about mycorrhizae and soil health and plant nutrition.

Mycorrhizae are the symbiotic fungi that surround and penetrate plant roots. Studies have shown that these organisms can aid plants in conditioning the soil, as well as help in disease prevention. The amount of plant that form these beneficial relationships, is not yet completely known, but you can get a list at the Mycorrhizal Applications website, a commercial supplier (listed below under further resources). This letter outlines these benefits as well as lists suppliers below.

Soil Conditioning:

A recent study printed in Acres Magazine, showed that inoculation of grass seed with Mycorrhizae formulations, also called AM, doubled soil carbon percentages(1). This study was conducted with perennial grasses, but inoculating a perennial cover-crop seed with AM may increase soil carbon in the soils that you are particularly concerned about from the flooding. Below is a list of a few distributors of AM fungi.

The following article outlines the importance of soil carbon for your farm and how Micorrhizae associations can help with this.
Soil Carbon: A Diamond in the Rough
By, Mike Amaranthus

Disease Prevention
How do mycorrhizae fungi help control diseases? The ATTRA publication I recommend for a review of this topic is listed below along with a direct link.

Sustainable Management of Soil-Borne Plant Diseases

In particular, refer to the section in Sustainable Management of Soil-Borne Plant Diseases titled Mycorrhizal Fungi and Disease Suppression. The mechanisms for biological control, the means by which this symbiotic fungi helps control pathogens, are worth repeating here:

The mycorrhizal fungi protect plant roots from diseases in several ways:

• By providing a physical barrier to the invading pathogen. A few examples of physical exclusion have been reported. Physical protection is more likely to exclude soil insects and nematodes than bacteria or fungi. However, some studies have shown that nematodes can penetrate the fungal mat.
• By providing antagonistic chemicals. Mycorrhizal fungi can produce a variety of antibiotics and other toxins that act against pathogenic organisms.
• By competing with the pathogen.
• By increasing the nutrient-uptake ability of plant roots. For example, improved phosphorus uptake in the host plant has commonly been associated with mychorrhizal fungi. When plants are not stressed for nutrients they are better able to tolerate or resist disease-causing organisms.
• By changing the amount and type of plant root exudates. Pathogens dependent on certain exudates will be disadvantaged as the exudates change.

Two web links outline the above mentioned concepts:

Managing Soilborne Diseases by Managing Root Microbial Communities
Dr. Robert G. Linderman, SARE 2000 Conference Proceedings

The Importance of Mycorrhizal Fungi and Other Beneficial Microorganisms in Biodiversity Projects

Content: Ted St. John paper presented at Western Forest Nursery
Associations, 1992.

Suppliers of Mycorrhizae or AM

According to the Organic Materials Review Institute (OMRI), there are four companies whose microbial products are approved for organic production. The first company listed below, Mycorrhizal Applications, Inc., is a leading manufacture of AM fungi. It is not clear as to whether or not the other companies specifically manufacture AM fungi or other types of mycorrhizae.
Mycorrhorizal Applications Inc.
Dr. Michael Amaranthus
P.O. Box 1181
Grants Pass, OR 97528

Custom Biologicals, Inc.
Mr. Thomas Baugh
1239 East Newport Center Drive Suite #117
Deerfield Beach, FL 33442 (561)998-1699

Amaranthus, M., et al. 2009. Building Soil Organic Matter Biologically: The Benefits of Mycorrhizal Seed Inoculation. Acres USA.

Further Resources:
Types of Mycorrhizal Plants



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