permaculture

["georg parlow" <georg@websuxxess.com>]

let me try to run that one by once again - admittedly i had to look through
my notes to get it all clear. but i am working on this so i will eventually
reach the point where it is all simple and easy to explain for me. ok, here
we go:

since this is a glance into the quite complex interactive web of life,
linear language fails me a bit. so please patiently follow my fragmented
narrations, and put them together within your systemic mind.

since us gardeners main interest is the health and production of the
plants, i will look at it from the point of the plant. how the degradation
of pesticides and other things tie in can then easily be concluded when
looking onto the various aspects of the action.

plants generate energy in their leaves. apparently they deposit up to 25% of
this energy in the soil through their roots - part as extrudates, part as
shedding of dead matter. this apparent loss of energy in the form of carbon
is actually a well spent investment. microorganisms living in the
rhizosphere gobble it all up, and due to the energy boost they multiply so
fast, that they use up all the available oxygen. this way anaerob
microniches are created. in order to understand why this is important we
will have to appraoch from a different angle as well.

soil is full of iron - 2 to 12% of it's weight are made up by it. in well
aerated soils this iron exists in the trivalent form of tiny ironoxide
crystalls. now if the microclimate turns anaerobic this fairly inert
trivalent iron crystalls fall apart and change to the mobile bivalent form,
also called reduced form. and this is important for 2 reasons: one is, that
this reduced form of iron is needed in order to produce ethylene - when
ethylene is generated in the soil, it stops the life processes of the
microorganisms that fed on the energy bonus given to them by the plants. but
fortunately ethylene doesn't kill them, but makes them inert. when the
microorganisms in the rhizospehere become inactive, they stop using oxygen,
thus oxygen can diffude back into these temporary anaerob microniches,
making them aerobic again. the inert microorganisms wake up and become
active, starting the cycle all over again.

the second good thing that happens when the iron oxyde crystalls
desintegrate, is this: these crystalls have a big surface and a strong
electric charge. thus they bind phosphate, sulphate and various trace
minerals closly to them, making those unavailable for the plant. when the
iron oxyde crystalls fall apart, they free those nutrients into the soil
solution, where they can be used by the roots of the plant. other nutrients
(namely calcium, potash, magnesium und ammonia) are tied to the surface of
clay particles and organic matter. these high concentrations of reduced,
mobile iron help break those nutrients free, thus making them available for
the plant as well.

just to round the picture off (and to expose some of the folly of till
agriculture) it might be good to take a look onto ethylene again. we need to
understand, that the bivalent form of iron can only make ethylene, if a
precursing substance of ethylene is already present in the soil. this
precursing substance is also supplied by the plant - but incidentially we
find it only in mature leaves. so without decaying mature plant matter the
ethylene cycle doesn't happen - the multiplying microbes are not stopped in
time, thus they keep going until they get killed by the lack of oxygen, when
they decompose in the anaerob situation substances are formed that are
burdening the health of the plant. i guess we could say, that ethylene is
needed in order to form a safe anaerob surrounding in the rhizoshere -
without it anaerob situations can still happen, but then they are a sign
that something went wrong.

it is also interesting, that in natural soils close to a hundred percent of
nitrogen in the soil is there in the form of ammonia, only traces of
nitrates can be found. plowing furthers a kind of bacteria that transforms
ammonia to nitrates. plants and microbes don't mind a whole lot, they can
use both forms. but nitrates interfere with the development of completely
anaerob microniches - thus the nutrients stay in their unavailable form,
because the iron oxyde crystalls never break up. also the ethylene cycle is
never triggered, even if everything is available, but the reduced form of
iron never becomes available.

while all this may sound quite complicated, it isn't, it is only complex.
the very beautiful thing about this cycle is imho that the nutrients become
available where they are needed - in the close vicinity of the plant root.
also it is a safe method, to make the nutrients available in their solutible
form in the anaerob situation  - because if they are not used up or washed
away from the root, as soon as they leave the anaerob situation, the
bivalent iron reverts back to ironoxyde crystalls, which again tie up the
nutrients in their immobile form.

georg

----- Original Message -----
From: "Mark Ludwig" <mpludwig@facstaff.wisc.edu>

> >between aerobic and anaerobic constantly happens - this ia what makes a
reed
> >bed working so effectively, and the everpresent ethylene-cycle works the
> >same way.
> >
> >georg
> interesting!
> Would this take place better in a saturated soil like a reed bed has or is
> a fairly dry soil similar.