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Beneficial Fungus in Garden Soil

Mycorrhizal Fungus Overview
Endomycorrhizal Fungus for Annuals
Ectomycorrhizal Fungus for Perennials
Complex Relationships
Plants Relationships
Fungal Bio-controls

Mycorrhizal Fungus Overview:

Beneficial mycorrhizal fungi are naturally present and have a mutualistic relationship with many plants. In this mutualistic relationship, carbohydrates are transported down the plant root, where the fungus steals some for their own growth. In return, the fungus frees up nutrients (especially phosphorus) and helps pull them up into the plant. The fungus and the plant need each other to thrive. Beneficial fungus also produce natural antibiotics which help to suppress harmful bacteria.

JSTOR - prairie mycorrhizae
Dr. Koide - mycorrhizal fungus overview - Mycorrhizal relationships
Gwinnett Master Gardeners - succinct study
University of Washington - detailed photographic study

Endomycorrhizal Fungus for Annuals:

The most common form of endomycorrhizal fungus is Arbuscular Mycorrhizal. [ Vesicular-arbuscular (VAM) and Arbuscular (AM) ] This fungus is appropriate for most vegetables and is present in undisturbed soil as long as it has roots and organic matter to feed on. It blooms underground and produces spores which are not easily spread by the wind, but are spread by insects, birds, animals, etc. If necessary, re-inoculate totally cleared areas with soil from healthy undisturbed areas. You do not need to buy mycorrhizal fungus. Leek, sorghum, legumes, and barley are excellent host plants that will increase the abundance of this fungus.

Homemade Arbuscular inoculant

Most Arbuscular fungus are obligate biotrophic symbionts. This means they can't grow or reproduce without the presence of a suitable and living plant root. With adequate organic matter they may survive as saprophytic hyphae or else they can only survive as spores.

Arbuscular fungus are obligate biotrophic symbionts
Saprophytic phase of Arbuscular fungus
Endomycorrhizal species by tree
Endo and ecto species

Ectomycorrhizal Fungus for Perennials:

Ectomycorrhizal fungus have fruiting bodies (mushrooms) that spread by wind blown spores. They mostly form relationships with woody or some perennial plants. For ectomycorrhizal fungus you can gather safe mushrooms within a reasonable distance of your orchard planting site to inoculate with. Inoculant fermented slurries may be useful for ectomycorrhizal fungi, but not Arbuscular fungi.

Homemade Ectomycorrhizal Spore Slurry
Ectomycorrhizal species by tree
Thunderstorm encourage fungal fruiting
Lavendar - nursery guild
Ectomycorrhizal slurry
Paul Stamets - Mycelium Running
Ectomycorrhizal Submerged Fermentation
FAO - Making Money by Growing Mushrooms
UN - Mushroom Cultivation
New Zealand Journal of Forestry - mycorrhizal relationships, dual

Complex Relationships:

We used to have a very simplistic view of fungus. We now know that fungal relationships are very complex. In the past, we believed that all Brassica, spinach, beets, buckwheat, amaranth, and quinoa never formed a relationship with mycorrhizal fungi. But some Brassica, such as Hercules cabbage and Chinese cabbage can form a relationship with Arbuscular fungi. And some Brassica have also been found to greatly increase the growth of ectomycorrhizae. Trichoderma spp. is a family of naturally occurring extremely common soil saprophytic fungi which are now widely used to stimulate Brassica growth. It does appear that some Brassica tend to be anti-arbuscular.

AGRIBUSINESS - Trichoderma
Brassica and ectomycorrhizae
Brassica inhibition of Arbuscular fungi
Brassica can be mycorrhizal if planted next to a host plant

Other surprising findings are that mature perennial grasses can form a relationship with ectomycorrhizal fungi, which we used to believe only worked with woody plants. Young grape vines start out with arbuscular relationships, but switch to ectomycorrhizal relationships as they age and become more woody.

Improving pasture with Ectomycorrhizae
Dual nature of ectomycorrhizal fungus as saprophyte
Grapes switch to ectomycorrhizal fungus

All plants can form relationships with mycorrhizal fungus under the right circumstances according to "Mycorrhizal Symbiosis by Sally E. Smith and David J. Read". Given our imperfect knowledge, the best choice seems to be a balanced approach. Disturb the soil as little as possible and never leave the soil without roots for long. Also use a wide crop rotation. Plant and fungal diversity is the key to a healthy environment.

PLOS ONE - mycorrhizal network shared across many plants
Nature - Complex Plant Fungus Networks
Willow, Cottonwood, Aspen, Hickory, and Walnut have both ectomycorrhizal and endomycorrhizal fungus


The major disadvantage of commercial fungal inoculant is that these introduced non-native fungus are almost always overwhelmed and replaced by native fungus. These commercial inoculants may not even survive the soil, PH, climate, etc. long enough to be replaced by native fungi. Commercial inoculant is seldom necessary unless soil has been greatly disturbed and undisturbed soil cannot be found. Make your own inoculant instead.

SunSeed - practical ideas for self made inoculant

Introduced Mycorrhizal persistance

Indigenous mycorrhizae

Cultivation of Fungus

Be sure to avoid parasitic mushrooms and fungal diseases: - parasitic mushrooms
Sudden Oak Death - fungus attacking oaks and other trees

If you are planning on using local soils to inoculate new plantings with, it might be a good idea to use one of these labs to test the source of your inoculant. And then of course, test your new plantings the next year to make sure everything has transferred over.

Soil Food  Web

Microbes In My Soil


Plant Relationships:

Classification of plants by types of fungal relations:

NIFG - fungal relations
Crops which encourage the widest variety of Arbuscular fungi: Sorghum - Sorghum bicolor (L.) Moench (C4) Leek - Allium porrum (L.) Crops which encourage the highest numbers: pea, Lentil, barley, bean

The more organic matter is worked into the soil, the more important it is plant a mycorrhizal cover crop soon after the organic matter has been incorporated into the soil. Without a new source of carbohydrates, fungal levels begin to drop.

Ideally, work manure and crop residue in during the fall and plant a cover crop such as flax, oats, etc.

Try to work the soil as little as possible and as shallow as possible unless large amounts of organic matter are being introduced. This will help keep the mycorrhizal population intact.

Agricultural Research Centre of Finland - impact of mycorrhiza
University of Manitoba - mycorrhiza in agriculture
Garden Design - All About Roots

Fungal Bio-Controls:

Trichoderma sp.:A beneficial fungus that can be applied as a bio-control agent. Scientific American - beneficial Aspergillus flavus used to suppress aflatoxin ATTRA - Trichoderma

Suppress harmful fungus by growing Brassica nigra or B. juncea in rotation.

GCIRC - Fumigation effect of Brassica roots
Kentucky State - Brassica juncea - Pacific Gold
Cornell - incorporation of Brassica
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