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Re: [compost_tea] Re: adding VAM ?



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


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