permaculture

["Lawrence F. London, Jr." <lflj@bellsouth.net>]

> 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