Glucosinolates and isothiocyanates are breakdown products from
sulfur-containing brassicas, thus producing a fumitoxic effect in the
soil which controls soil-borne diseases and nematodes.
See the ATTRA publication below for further details on brassica
fumigation and other biological farming methods that help provide
non-chemical nematode control:
Alternative Nematode Control
However, I've never heard of a parallel chemical suppression system
obtained from buckwheat. What buckwheat is known for is its fast
growing habit and ability to crowd out and shade the soil, thus
functioning as a "smother crop" in controlling weeds and protecting
the soil in hurry.
Buckwheat is also known for its ability to solubilize phosphorus in
soils. In practice, it would make sense, for example, to apply
rock phosphate prior to a buckwheat cover crop. The
buckwheat increases the bioavailability of slow-release P in rock
phosphate. The roots of buckwheat exude substances which help
solubilize P. It is important to recognize that as green manures
are turned into the soil and decomposed by microbes, organic acids
are released which help solubilize and mineralize insoluble mineral
precipitates especially phosphorus. Thus, green manures in general
do this too, but buckwheat is unique because it actively solublizes
during its growing period through root exudates.... as well as
become an organic acid source when it is turned down as a green
Another way to increase the bioavailability of rock phosphate
is to run it through a compost pile. Research reports in Am. J.
Alt. Agric. showed that bioavailable phosphorus in rock
phosphate-amended compost was equivalent to single super phosphate
Singh, C.P., and A. Amberger. 1995. The effect of rock
phosphate-enriched compost on the yield and phosphorus
nutrition of rye grass. American Journal of Alternative
Agriculture. Vol. 10, No. 2. p. 82-87.
The same can be said for minerals contained in rock dusts.
Mineralized compost is a term used in biodynamics to describe
rock mineral amended compost. When she farmed in New Jersey,
Helen Atthowe put soil amendements (greensand, sul-po-mag, rock
phosphate) into the compost windrow to create a complete mineralized
compost fertlizer for organic vegetable crops. In the Controlled
Microbial Compost system developed in Austria, rock dusts are used
in compost windrows, as described in the following article by George
Leidig, George. 1993. Rock dust and microbial action in soil:
The symbiotic relationship between composting and mineral
additives. Remineralize the Earth. Spring. p. 12-14.
This 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. Phosphorous 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."
Anybody else heard of biofumigation with buckwheat?
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