permaculture

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

-------- Original Message --------
Subject: Re: [SANET-MG] maintaining plant available P --> buckwheat
Date: Tue, 29 Mar 2011 23:47:34 -0500
From: Steve Diver <steved@IPA.NET>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Sanet -

Here's a few research items that address buckwheat's
unique ability to solubilize and/or "etch out" phosphorus in
rock phosphate, etc.

1.

This first item was posted on Sanet in 1998.

The following abstract is from the Cover Crops Manual, a publication
that resulted from a University of California-Sustainable Agriculture
Research and Education Program database project.

Annan, C. and A. Amberger. 1989. Phosphorus efficiency of
buckwheat (Fagopyrum esculentum). Zeitschift for
Pflanzenernhrung und Bodenkunde. Vol. 152. p. 181-189.

"The ability of buckwheat to acquire phosphorus was characterized
by investigating P uptake, morphological features, and
chemical changes in the rhizosphere. Root weight and length, and
frequency of root hairs were higher when plants were grown under
P-deficiency. P uptake rates were only moderate, concentrations of
P in the shoot were high (1.8% of dry weight). Release of Mn from
MnO2- and P from FeP04- and glucose-6-phosphate were not due to a
buildup of organic acids in the rhizosphere, but P release was due
to high activities of acid phosphatase for plants grown with low P.
The following parameters in which buckwheat is outstanding were
regarded as important for its P efficiency: (1) a finely divided root
system of considerable length, with a high ratio of root surface to
root or shoot length; (2) a high storage capacity for inorganic P;
(3) an increased release of protons and FeP04- or Mn02- solubilizing
substances by P-deficient plants; (4) a favorable ratio of P uptake
to root mass increase, especially at low P supply; and (5) a high
activity of acid phosphatase in the rhizosphere and the capability
to use P from organic sources."


2.

Cationic Activities and the Exchange Phenomena of Plant Roots
Relationship to Practical Problems of Nutrient Uptake
E.O. McLean, D. Adams, and F.E. Baker
Arkansas Academy of Science, 1952
http://libinfo.uark.edu/aas/issues/1955v8/v8a6.pdf

Table 3 notes buckwheat has a high ability to utilize rock phosphate.
McLean explored the ability of plant roots to bond calcium, a kind
of weathering process that releases P from tricalcium/rock phosphate.


3.

Truog, E.  1916.  The utilization of phosphates by agricultural crops,
including a new theory regarding the feeding power of plants.
Wisc. Agr. Exp. Sta. Res. Bull. 41.

In:

Research Bulletin / Wisconsin Agricultural Experiment Station,
Issues 34-44
Google Full-Text eBook, 1915
http://books.google.com/books?id=b0U3AQAAIAAJ&pg=

See Bulletin 41, pages PDF-338 to PDF-389

Truog found that buckwheat has a unique ability to feed
on rock phosphate and equated this with a high level of
calcium oxide in the plant, release of carbonic acid,
and other factors.

We have alkaline soils in Texas which ties up phosphorus
so anything that helps make rock phosphate more effective
 -- such as a buckwheat cover crop -- is worth adding to
the farmer's toolbox.

Steve Diver