Subject: Re: [SANET-MG] Phosphorus availability (was Loss of Minerals)

From: Dale Wilson <[email-masked]>
Date: Thu, 16 Dec 2004 09:14:47 -0800

Edna,

> I'd like to pick up on a hint that someone mentioned in this
> thread. I'd like to learn more about how phosphorus changes
> from "available" to "unavailable."  I've long believed that
> microbs are involved but would like to know more about how to
> encourage the conversion to "availability."

At the Agronomy Society meetings last month in Seattle I heard an
interesting talk by Shabtai Bittman (Agassiz, British Columbia) "Do
arbuscular mycorrhizae improve P uptake and growth of corn on manured
soils?" He showed that you can get early season deficiency even when
there is plenty of P in the soil if the VA mycorrhizae are disrupted.
Corn, and many crops are dependent on these fungi to get P from the
soil.  Tillage chops up the network and it takes a few weeks to
reestablish it.  Dr. Bittman knows a lot about mycorrhizae, and might
be a good source of information.

> As for the Loss of Minerals thread, I'm disappointed at how
> quickly it degenerated into personal attacks and counter attacks.

Yeah, all this stuff is interesting technically, I am more intereted in
that than in personal attacks.

Dale

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From: "Lawrence F. London, Jr." <[email-masked]>
Date: Thu, 16 Dec 2004 22:44:19 -0800

> be a good source of information.

 From 1995 here's something really interesting about VAM and the role of red clover:
I wonder what the state of Brendan's research is in 2004.

http://www.ibiblio.org/ecolandtech/orgfarm/cover-crops/crop-rotation+increased-fertilizer-from-VAM

 From [email-masked] Fri Mar  3 21:38:31 EST 1995
Article: 5512 of bionet.plants
From: [email-masked]  (Brendan A. Niemira)
Newsgroups: bionet.plants
Subject: Re: Mycorhizzae vs. Fertilizer
Date: Thu, 02 Mar 1995  11:04 est
Organization: Michigan State University

In Article <[email-masked]> "[email-masked] (Eric Grunden)" says:
 >
 > If a person was to isolate a fungus that would form a
 > mycorhizzae relationship with an agronomic crop, would
 > innoculation of that fungus into the field (once it
 > became established) be an effective method for reducing
 > the need for commercial fertilization? Wouldn't the
 > "strength/abundance" of the fungi grow exponentially with
 > the passing of years?

For agronomic crops, you're talking about vesicular arbuscular mycorrhizae (VAM),
a symbiotic endomycorrhizal fungus.  These are ubiquitous anyway, and not very
host-specific, so there is very little need to inoculate the field in order
to introduce them.  The big trick is getting them to colonize your crop plant
to such an extent that fertilizer inputs can be reduced.  You can a) build up
the population in the soil such that even moderately active fungi result in
heavy coloniazation, b) put something in the soil to stimulate the activity
of smaller populations to get heavy colonization.

Crop rotations have been shown to have a definite impact on the population
dynamics of VAM, and work is currently being done (by me, among others) to
determine how the different crop plants differentially select for certain
species of VAM among all that are availible in the soil.

Other workers have shown that certain natural, plant-produced chemicals can
stimulate the existing VAM to higher levels of activity.  These chemicals were
originally derived from red clover, a popular sequence in crop rotations.  This
may shed some light on why rotations are effective w/regard to VAM.

Good luck.
...........

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Brendan A. Niemira           |   "You know your Shelley, Bertie."
Dept. Botany and Plant Path  |   "Oh, am I?"
Michigan State University    |       P.G. Wodehouse
[email-masked]     |       *The Code of the Woosters*
         All opinions expressed are entirely my own.

--
L.F.London
[email-masked]
http://market-farming.com
http://www.ibiblio.org/ecolandtech