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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

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