Re: [compost_tea] Typical brew

From: <soilfoodweb_at_aol.com>
Date: Sun, 20 Apr 2003 17:47:13 -0400

Since it was asked on the list serve, I'll answer, even though the question was not directed to me.

A typical brew has a "lag time", which is a period of time that the organisms are not growing, because they have to adjust to the new conditions they find themselves in, and get geared up to reproduce. Think of them being just like tiny people. If you get parachuted into a new country, survival is usually first on your mind, finding a place to live, food, and so forth are first on your mind, not reproduction. Same with bacteria and fungi.

Reproduction rates will depend on:

1. water temperature (if you were dumped into 10 degree water, would you be thinking about reproduction? Me neither),

2. how many people got put in the room. opps, that should be bacteria or fungi, right? The more the merrier..... more offspring will be produced after that lag period if there were more individuals to start out with

3. how much food is there? No food, no babies. Lots of food, many more babies.

4. habitat has to be right. If the individuals require oxygen, calcium, iron, etc to reproduce, then these nutrients need to be available. Has to be enough space, surfaces to attach to (if you are a fungus you don't reproduce well hanging out free in the water), and if you need some friends to help you. The more friends about, the faster this all goes, up to the point that the friends are occupying in the space your babies would have taken. No more babies if there isn't enough space.

So, if conditions are right, then typically, bacteria start growing rapidly in 3 to 5 hours. Fungi take off a bit slower, maybe about hour 8 to 10.

Max growth rates usually take awhile to achieve, and is most dependent on food. Maximum reproduction (sum of both bacteria and fungi) usually occurs between hours 14 and 20. On average, the peak occurs at hour 20. Given that the brew does not go anaerobic, of course. If the brew goes anaerobic, that means that the rate of oxygen use (demand) by the bacteria and fungi was greater than the rate of supply of oxygen by your aerators. Control of oxygen demand is generally through the amount of food put in, given that all else is equal.

So you have to have ALL things right. Then the typical brew can occur.

Which is why when V. Bess measured oxygen concentration at hours 0, 8, and 24 it was so ridiculous for her to then say she had the data proving that the "tea brews" had stayed aerobic through the whole brew cycle. The max oxygen demand occurred during the 16 hours she didn't bother to measure oxygen.

Anyway, fungi are attacked and consumed by anaerobic bacteria when oxygen content drops below 6 ppm, or there abouts. We have some great pictures of fungal hyphae happily growing until the oxygen content drops too low, and then, the ravening hordes of anaerobic bacteria attack and take the fungal strands out! You don't even know that those are fungal hyphae, they are so buried in bacteria. Only in oxygen below 6 ppm

So, low fungi are OFTEN the result of too low oxygen. The fungi could have been in the compost, but they are no longer in a tea that dropped low in oxygen. They were consumed.

So, low fungi could be the result of several possible conditions:

1. not in the compost to begin
2. not extracted from the compost (fabric bag is a usual culprit; poor movement of water through the compost, compaction of the compost in the basket)
3. no foods to feed the fungi (no soluble fungal foods in the compost, none added in the tea brew)
4. fungi killed by lack of aeration (anaerobic bacteria had a feast)
5. fungi sliced and diced by pumps (there are centripetal pumps that don't slice and dice much; don't ask me which they are, that was not my research that figured that out)

What else did I forget?

Hope this helps -

Elaine Ingham
President, Soil Foodweb Inc.
SFI Corvallis, OR
SFI Port Jefferson, NY
SFI Lismore, NSW, Australia
SFI Hilversum, The Netherlands
SFI Cambridge, New Zealand
www.soilfoodweb.com

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Received on Sun Apr 20 2003 - 20:39:03 EDT

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