Re: [compost_tea] Re: adding VAM ?

From: <soilfoodweb_at_aol.com>
Date: Thu, 12 Jun 2003 12:03:38 EDT

I disagree with the statement most organic farmers have VAM already. Data
are what is important here, and from the data we see, it is surprising the
number of organic folks that don't have mycorrhizal fungi in one or more of their
fields. How do I know? We look at their roots for mycorrhizal colonization.

If you fertilize, you lose mycorrhizal fungi? I think that's too broad a
generalization. You have to look at what concentration of fertilizer is being
added, and organic people rarely if ever add enough fertilizer of the type that
would negatively impact mycorrhizal fungi. Most of the problem is left-over
from previous intensive management practices. But VAM don't just walk back
onto hammered soil. They don['t seem to return that easily or that well after
they were depleted.

So, amend statements about mycorrhizal fungi to include consideration of type
and concentration of nutrients added. If you are adding organic fertilizers
at reasonable rates, it should not affect the mycorrhizal fungi at all. If
you get carried away and over-apply, then yes, you take out your mycorrhizal
fungi. But if you have good mycorrhizal colonization, you don't need the
intensive fertilizers.

The mycorrhizal fungi need to adapt to the nutrient conditions of your
farming practices, so when you start your management, the fungi have to adjust. It
can take some time to have that happen. Expect a shift in species. You may
need to inoculate a set of fungi that are better adapted to nutrient-rich
conditions.

If you inherit a soil that had high chemical use management previously, you
will have to replace the VAM. You can take samples and document where on the
land you need to replace the mycorrhizal fungi, if you want. Or just add
spores, and then check whether the VAM is at decent colonization levels, or not,
come harvest. If the colonization is too low, then you know where you have some
work cut out in getting rid of something that is preventing adequate
colonization.

Hope this helps -

Elaine Ingham
President, Soil Foodweb Inc.
www.soilfoodweb.com
SFI Oregon, USA
SFI Australia
SFI New York
SFI Europe
SFI New Zealand

"Hope is not a feeling. It is not the belief that things will turn out well,
but the conviction that what we are doing makes sense, no matter how things
turn out." -- Vaclav Havel, former President of the Czech Republic





Received on Thu Jun 12 2003 - 12:50:22 EDT

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