[tomato] Mycorrhiza

Orchid (Tomato@GlobalGarden.com)
Thu, 15 Jul 1999 20:10:36 -0400

I've decided to go all organic when I plant my fall crop of tomatoes this
year. (except perhaps for the SuperThrive)  I'm going to give Mycorrhiza
fungi a try.  I was a little hesitant because I was afraid that once I
innoculated my plants and trees (mango, citrus, cherry hedges) that I was
committed forever to very low levels of fertilizer. If my landscaper, my
wife, or someone should apply the usual chemical mixture, then everything in
sight would be burned.  I was also thinking about using it on my lawn, but
then which fertilizer do I use on that?  I went to a few websites, and this
is what one advocate said.  I present it here for list member comments and

Pete, South Florida, Zone 10

**Your comments indicated a concern about the effect of fertilizers on
There are situations where fertilizers have produced a burn when applied to
plants.  This can occur if the fertilizers are applied at rather high
levels.  The burn effect has nothing to do with the mycorrhiza.  It has
everything to do with the chemistry of the fertilizer.  The presence of
mycorrhiza does not make a plant more susceptible to burn.  (If anything, it
may make the plant less susceptible to burn.)

Most plants, including tomato, citrus, mango, and cherry are mycorrhizal in
their natural state.  In fact, unless they are grown indoors under very
controlled conditions, it is very difficult prevent them from becoming
mycorrhizal via the intervention of Nature, at least to some degree.  So
your worry that inoculating these plants will forever change their response
to fertilizer is quite misconstrued.  In fact, by incorporating more strains
of mycorrhizal fungi into the life of these plants, you will reduce their
dependency on externally-applied fertilizer.  (Of course, potted plants
involve a closed system.  While the fungi will be better able to extract
nutrients from the existing soil, they will still be limited by the absolute
amount of minerals present in the pot.  That is, after a while, they will
not be able to gain more nutrients for the host plant by perfusing more
As a rule of thumb, when utilizing a biological approach to plant growth and
nutrition (mycorrhizal fungi and beneficial bacteria), you should avoid the
unnatural applications of high levels of fertilizer, which can inhibit or
reduce the degree of symbiotic cooperation which is the mainstay of the
biological approach.  Use slow release fertilizers, or relatively low NPK.

You should not attempt to use the traditional chemical approach to plant
nutrition (involving repeated application of high NPK to promote rapid
growth)simultaneously with the biological approach (involving mycorrhizal
fungi and beneficial rhizosphere bacteria, together with slow-release NPK at
lower levels).  This is true, not because the combination will cause a burn.
Rather, the high levels of fertilizer tend to interfere with the
establishment of the smooth biological cooperation between the associated
soil organisms and the plant.
I hope that this explanation proves useful to you.