permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

Subject: Re: Regulation of compost teas
Date: Fri, 25 Oct 2002 01:22:32 EDT
From: Elaine Ingham <Soilfoodweb@AOL.COM>
To: SANET-MG@LISTS.IFAS.UFL.EDU

For those of you interested in learning about the microbiology of
compost teas, you might want to read the Compost Tea Brewing Manual,
from Soil Foodweb Inc. in Corvallis, OR.

With respect to organisms in tea, white sugar is rarely used, as it
selects for ess-than-wonderful species of bacteria.  Blackstrap molasses
with no sulfur, is more common, since it contains a much wider diversity
of sugars, along with a bit of fungal food.

Fish emulsion is a good food to grow some very diverse bacteria, and
improves several groups of quite beneficial bacteria.  But more
important than these additives are the soluble materials that come out
of the compost.  They enhance the growth of quite a few beneficial
species of bacteria.

We need to be careful that we are discussing AEROBIC compost, not
putrefying organic matter.  Species diversity is quite limited in
putrefying materials.  And unfortunately, that is the material often
mistaken for compost by academics who don't know what real compost is.

By definition, composting is an aerobic process, producing microbial
biomass, some metabolic wastes and carbon dioxide.  Anaerobic digestion
leaves a good 25 to 50% of the carbon present as organic matter -
stinky, smelly organic matter in many cases..

So, aerobic, ok?  If you have aerobic conditions, then you have MANY
species of microorganisms, up to as many as 25,000 unique DNA sequences
from a gram of compost.
We use morphological methods as well, and have come up with as many as
20,000 unique morphological types of bacteria and fungi in a gram of
compost as well.

Plate counts don't even get you close to that, because, as Joel Gruver
points out, most of the organisms in soil, or compost or compost tea
can't grow on lab media.  We don't know the mix of foods, temperatures
and moistures/humidities they need to grow.  Thus using plate count
approaches is nonsensical for assessing numbers or species diversity in
environmental samples.  To grow an organism for whom you know their
growth conditions, then that's a different story.  But we only know this
for a few species of bacteria and fungi.

Aeration in tea is needed to set up conditions that select against human
pathogens (which require reduced or low oxygen conditions), against
plant pathogens such a Pythium and Phytopthora, Rhizoctonia and
Fusarium, which do better in oxygen reduced conditions.  Reduced oxygen
allows these diseases to be competitive, while in fully aerobic
conditions, they cannot out-compete or inhibit anyone else growing.
That's why compacted soils have so many disease problems.  The diseases
are being helped out by the soil conditions.

The added foods help to grow some very beneficial species, at least
species that researchers tout as beneficial.  We see many fluorescent
pseudomonads which produce the desired growth hormones, bacillus species
that result in repulsion of many insect pests, nitrogen fixing bacterial
species, and the species of bacteria that are especially good at
decomposing recalcitrant carbon compounds, and pesticides enhanced as a
result of the added foods.

Diversity of the kinds of carbon is important.

But simple occupation of space is critical too.  If there is no space
for the disease spore to reach the leaf surface, there is much less
likelihood of disease.  If the leaf surface is covered, then all the
infection sites are occupied.  If the leaf surface is covered, then all
the foods the plant produces are used by the protective layer, and there
is no food to grow the pathogen.  So, multiple mechanisms of control.
Let us not rely on just one.

All the species possible, completely covering the leaf, blossom, bark,
etc.  We have some astounding results in protecting plants against
disease, both on the leaf surface and the root surface.

So, yes, teas work better with aeration (suppress and get rid of the
disease organisms), with the right foods (grow just the good guys), and
with nutrients.  But often the added nutrients are really for the
plant.  As the organisms grow on the leaf surface, they respire, and
that elevated carbon dioxide causes the stomates to open, and the
nutrients move into the plant more rapidly, for a longer time.  Some
impressive greening up as a result.  Temperature is of course important,
as is water, and other nutrients not limiting, but given those being ok,
plants can show marked improvements.

I hope this helps explain what is going on with 24 hour compost tea.
These are not slimy, smelly 3-week brews but they are 24 hour, aerobic
tea brews.  Cleaning the machine is extremely critical.  Control of the
quality of the tea maker is important.   Testing is necessary.  No human
pathogens in the compost!  Quality products in, quality out.

Elaine Ingham
President, Soil Foodweb Inc, Corvallis OR
President, Soil Foodweb Institute, Lismore, Australia
Affiliate Faculty, Southern Cross University
Director of Research, Soil Foodweb New York
Director of Quality Assurance, Soil Foodweb Europe
(I was assistant and then associate professor at Oregon State University
for nearly 15 years, but last December decided to go full time with SFI.)