mycorrhizae tolerance to fertilizer

don at don at
Fri Dec 20 09:06:38 EST 1996

To get into a comparison of growing techniques that involve direct
feeding with annual applications of NPK fertilizer ("conventional"
agriculture) versus biology-based methods which emphasize soil
development could be a lifetime debate.

Sooner or later, the debate always comes down to the question of whether
current cultural practices are sustainable or not.  Can farmers simply
keep using NPK fertilizer every year to sustain yields forever?  There
are certainly doubts about this, from the USDA on down.  

Some very respected soil scientists feel that current practices are like
"mining" the soil, and that at some point the non-replenishment of humic
matter and trace elements will make the soil unproductive, and that this
unproductivity will occur suddenly some year in the future. 

Your argument about the economics of growing with mycorrhizae missed the
point, perhaps intentionally, that introducing crop-specific types of
mycorrhizal fungi would only have to be done once.  The application of
urea goes on year after year after year.

Depleting the soil because mycorrhizae boost the uptake of nutrients? 
No, that won't happen.  Think about wild plants and the tiny amounts of
leaf letter that give them nourishment.  There would have to be
replenishment in the form of crop residue or other organic matter, but
at a very low level compared to what is considered normal today.

If you are indeed taking a serious look at how mycorrhizae can fit into
agriculture, wonderful!  What I perceived as a sarcastic tone to your
initial posting may be incorrect. 

The greatest argument against bio-organic methods at the moment is
simply that there are not enough supplies available.  (And you do have a
valid point about the economic problems of converting over to a
biologcal approach).  We cannot begin to provide enough inoculant for
even one percent of the corn farmers of Illinois, for example.

The current best use of inoculant is on high-value crops, like wine
grapes, or as a nursery inoculant for propagation of highly-dependent
plants, like citrus or avocado. 

You seem to regard only only pesticides as "chemicals".  OK, but I am of
the opinion that fully-nourished plants are far less bothered by
insects.  I think the first step to cutting down or eliminating tocic
pesticides is to grow plants that have better defenses.  The lack of
some obscure trace mineral may trigger attack, and no amount of NPK will

Interesting points you raise.

Don Chapman
Bio/Organics Supply Center
Camarillo CA

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