Re: Mycorhizzae vs. Fertilizer

In Article <3j30kl$s12@vixen.cso.uiuc.edu> "egrunden@prairienet.org (Eric Grunden)" says:
> If a person was to isolate a fungus that would form a 
> mycorhizzae relationship with an agronomic crop, would
> innoculation of that fungus into the field (once it
> became established) be an effective method for reducing
> the need for commercial fertilization? Wouldn't the
> "strength/abundance" of the fungi grow exponentially with 
> the passing of years?
For agronomic crops, you're talking about vesicular arbuscular mycorrhizae (VAM),
a symbiotic endomycorrhizal fungus.  These are ubiquitous anyway, and not very
host-specific, so there is very little need to inoculate the field in order
to introduce them.  The big trick is getting them to colonize your crop plant
to such an extent that fertilizer inputs can be reduced.  You can a) build up
the population in the soil such that even moderately active fungi result in
heavy coloniazation, b) put something in the soil to stimulate the activity
of smaller populations to get heavy colonization.  
Crop rotations have been shown to have a definite impact on the population 
dynamics of VAM, and work is currently being done (by me, among others) to 
determine how the different crop plants differentially select for certain 
species of VAM among all that are availible in the soil.
Other workers have shown that certain natural, plant-produced chemicals can
stimulate the existing VAM to higher levels of activity.  These chemicals were
originally derived from red clover, a popular sequence in crop rotations.  This
may shed some light on why rotations are effective w/regard to VAM.
Good luck.

Brendan A. Niemira           |   "You know your Shelley, Bertie."             
Dept. Botany and Plant Path  |   "Oh, am I?"
Michigan State University    |       P.G. Wodehouse
niemirab@student.msu.edu     |       *The Code of the Woosters*
        All opinions expressed are entirely my own.