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  • From: "Lawrence F. London, Jr." <lflj@bellsouth.net>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: [permaculture] Fwd: Mycorrizal "fertilizers"?
  • Date: Fri, 22 Mar 2013 13:09:06 -0400


Date: May 24, 2011 8:37:00 PM PDT To: cnpssd-L@ucsd.edu Subject:
[Cnpssd-L] Re: Mycorrizal "fertilizers"?

Hi All,

Speaking as someone who did his PhD on mycorrhizae...

For native plants, the best inoculum for native plants is to go out
into nature with a bucket and shovel, find a healthy specimen of the
plant, get a bucketful of soil (and leaf litter), bring it back, and
put it in the planting hole. You actually don't need more than a
couple of handsful.

I don't recommend buying commercial mycorrhizal preparations for use
on native plants. The reason is that the fungi they use are ones
that produce huge numbers of spores in the greenhouse. I should
know, because I cultured the same species for the same reason. They
don't necessarily work well in your garden, in part because fungi
that invest all their resources in producing spores don't always
produce a big body to gather lots of nutrients for the plant.
Conversely, species that produce big fungal bodies (mycelia) can be
really hard to grow from spores. That's why I recommend the bucket
of soil approach. Additionally, you get all the other good bacteria,
mites, etc. that aren't mycorrhizal fungi. There's a whole complex
ecosystem in the soil, and the mycorrhizal fungi are only one part.

How mycorrhizal fungi work (massively simplified): basically, the
fungi are better than the plants at getting phosphorus (and other
nutrients) out of the soil than most plants are, while the plants are
better at producing sugar than the fungi are. The plants contract
out phosphorus acquisition to the fungus, for up to 20% of the sugar
the plants get from photosynthesis. As with any contracting
relationship, there are complexities. If the plant isn't short of
phosphorus, having mycorrhizae can actually hurt it--this is why you
don't want to inoculate plants in a well-fertilized garden. In fact,
well-fertilized plants will boot the fungi out of the roots, which is
why mixing mycorrhizal spores in with phosphate fertilizer is a waste
of time.

In general, native plants are very efficient with their nutrients,
meaning they don't need much fertilizer. I think having native
mycorrhizal fungi on the roots is a great way to go, in that you
probably won't need to fertilize them much if at all. However, if
you're planting natives in an area that's already been heavily
fertilized, the mycorrhizal fungi are unlikely to help. In any case,
I don't recommend buying the commercial preparations, simply because
I don't think they're worth the cost.

My 0.002 cents,

Frank





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