Soil Fungi Critical to Organic Success
sgilman at netheaven.com
Sat May 26 22:58:41 EDT 2001
RE: Soil Fungi Critical to Organic Success
also at: www.ars.usda.gov/is/AR/archive/may01/fungi0501.htm
Mycorrhizal fungi have been known to be extremely valuable soil colonizers for a long time now. They work symbiotically with plant root systems and in exchange for carbohydrates provided by plants through root exudates their hyphae pipelines extend far and wide through the soil to capture and transport soil nutrients (especially locked-up phosphorus) as well as pumping deeper down water reserves back to the plants. They are effective disease suppressors, competing well with plant pathogens. They also bind soil particles together and help create porous aggregates needed by soil organisms and roots alike and promote soil oxygenation, drainage and moisture holding capacity. Further, numerous crops and fruits actually require mycorrhizal associations to function fully.
The ARS researchers seem to have things backwards, however. Selling mycorrhizae-rich plug transplants to inoculate soils only is effective if there is a suitable soil habitat to support fungal growth already in place and if there is, most likely mycorrhizae will be there too. It¹s a bit like buying ladybugs and having them all fly away because there is no supportive habitat in place to provide the room and board they need to function. While fungal associations are prolific in humusy forest soils and many trees and shrubs depend on it, most crop land has become dominated by bacterial systems as row cropping and tillage further chops up and destroys the hyphal strands. Chemical fungicides used by conventional farmers are especially destructive to mycorrhizae and so are the herbicides, fertilizers and other commonly applied biocides they use.
It has long been known that rotating portions of the field or garden periodically back into sod replenishes the habitat for beneficial fungi and helps balance soil fertility. Composts made with well decomposed shredded bark, leaves or wood chips are very rich in beneficial fungi. Wild plants, dandelions especially, provide an important over-wintering habitat for dormant fungi, so they can recolonize the new crops the following season. Biostrip intercropping and other farmscaping methods can help maintain permanent healthy and vigorous mycorrhizae populations. As in ³Field of Dreams², Build It and They Will Come.....
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