Re: [compost_tea] What do the nasties breathe?
Bob asked "what do the nasties breathe?"
Most of them ones we can't have in tea are autotrophs, which in non-science
words, means they "breathe" carbon dioxide (CO2), or nitrate (NO3), nitrite
(NO2), sulfate (SO4), and other materials containing oxygen tied up in
chemical forms. If you notice, all those chemical formulas contain oxygen,
but not in gaseous form. They use "solid oxygen", if you will. (All my
scientific colleagues just cringed when they read that, but I think it makes
the situation more understandable to people who haven't spent years studying
the subject, OK?)
The problem isn't so much what the nasties breathe, as what they produce.
So, to consider this, we need to go back to understanding plants. Plant
growth is the whole reason we are fussing about all this, right? What does
the plant need?
And, oh, yeah, we can't have any human pathogens in the tea either.
So, how do we set the stage so that the plant gets a soil condition that it
needs, and we exit any human pathogens?
Back to plants. Roots of plants do not tolerate anaerobic conditions. But
why don't they tolerate anaerobic conditions?
Plants roots can do just fine in conditions that just lack of oxygen. Roots
don't need oxygen, per se. Remember, plants take up CO2 and release oxygen.
So, lack of oxygen is not the problem. Number one consideration is what the
anaerobic bacteria produce. Number two consideration is the fact that the
good guys that outcompete the bad guys require aerobic conditions. If you
don't have the organisms that compete with the disease organisms, then the
diseases "win". Almost all (please read that, ALMOST all) disease organisms
do much better when oxygen is reduced, because the good guys aren't there to
prevent the bad guys from doing well. Simple competition. Aerobic enzymes
are better at grabbing foods than enzymes produced by facultative or true
anaerobes.
Generalization however. A few anaerobic organisms are better than aerobes,
but they are at the bottom of the ocean, or in thermal pools. Other
environmental factors keep them out of your soil. Unless you have a pH 3
soil, or you have high reduced iron, or high sulfate, for example.
How reduced does the oxygen have to be to "go over the edge" into anaerobic?
What is the cut off level of oxygen for the bad guys to take over because the
organisms that normally grab food away from the bad guys are no longer able
to grab? It depends on which bad guys you have in your soil or compost.
So, the more pathogens and bad guys you were able to kill during the
composting operation, either by proper heating regime in thermal composting,
or by enough passes through earthworm guts, the less you have to worry about
anything during the tea brewing cycle.
But what is the cut-off? It depends is not a really useful answer. What we
have seen, based on plant responses to tea, is that 5.5 to 6 mg oxygen per
liter is a safe cut-off level. Below 5.5 to 6 we often see production of
substances that can cause leaf-curl, root-death, and burning of the plants.
It doesn't always happen, however. I think that if you have fermentative
bacteria instead of putrefying bacterial species, there is less problem.
Really bad substances aren't produced, BUT you are still setting the stage on
plant surfaces and in the soil that are less than beneficial for the plants.
The beneficial fungi are all strict aerobes. If you have fermentative
bacteria, you may not have alcohol production, but you have low pH organic
acids produced, which harm the fungi, kill the protozoa and benefical
nematodes. The effect is not so much a direct burn or kill of plant tissue
as a slow decline in soil health, as you lose the organisms that combat
Pythium (wilts), Phytopthora (blights, mildews), Rhizoctonia (root rots),
etc.
So, if you have fermentative bacteria in the tea brew, lack of oxygen may not
result in directly toxic materials, but the organisms you add are not the
beneficials from a plant's point of view. You did alot of work making and
spraying tea, got a little benefit from competition for foods on leaf
surfaces, but went backwards in the soil.
And that's where we're trying to head - to soil health, so you don't have to
keep putting out the teas even. As time goes by, with GOOD TEAS, you should
be able to stop spraying weekly, or even monthly, because you will have
gotten the soil back into a condition of health.
Can't happen with anaerobic teas. That's why you have to have aerobic tea.
Hope this helps -
Elaine
President, Soil Foodweb Inc.
www.soilfoodweb.com
.
Received on Wed Jan 15 2003 - 12:06:34 EST
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