[NAFEX] Microflora and soil pH

Lon J. Rombough lonrom at hevanet.com
Tue Oct 25 23:20:12 EDT 2005


	I did some inquiring about the possibility of mycorrhizal fungi being 
able to affect the pH of soils.  Dr. Robert Linderman, who has been 
working with soil microflora for 40 years or so had a very interesting 
reply:
	" Interesting that you ask the question you did just now as I am 
writing another paper for a presentation in Denmark on the 
mycorrhizosphere.  As it turns out, the real story about weathering 
mineral rock to release nutrients is that bacteria live in association 
with the mycorrhizal fungal hyphae, and they are the source of acid 
that can etch the rock, solubilizing it for uptake by the mycorrhizal 
fungus and on to the plant.  Pretty neat, huh?  C. Y. Li, now retired 
from the Forest Service here in Corvallis, was the scientist who 
documented that fact.  He was able to isolate the bacteria from the 
hyphae and show that they could dissolve even marble with the acids 
they produced.  It is the bacterial association with the mycorrhizal 
fungal hyphae that perform many functions previously attributed to the 
mycorrhizae.  I call this phenomenon the “mycorrhizosphere effect”.  We 
have shown that the fungi selectively increase populations of bacteria 
that can do many things as part of a team, even help suppress diseases 
(the subject of my own research).  So I have described a new paradigm 
for the mycorrhizosphere wherein the host plant associates with the 
mycorrhizal fungi and the soil bacteria (certain ones) associate with 
the mycorrhizal fungus, making a marvelous microbial team that has been 
a winner for some 460 million years!!  By the way, we have shown that 
some of the bacteria can produce acids, some ammonia; both can change 
the pH around them.  I really do think it can account for the way 
ericoid mycorrhizal fungi function on blueberries; that is by changing 
the pH in order to allow their proteinases to break down organic 
substrates.  Those enzymes require very low pH to function at a 
maximum."

	-Lon J. Rombough
Grapes, writing, consulting, my book, The Grape Grower, at 
http://www.bunchgrapes.com  Winner of the Garden Writers Association 
"Best Talent in Writing" award for 2003.
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