Subject: Re: Regulation of compost teas

From: Elaine Ingham <[email-masked]>
Date: Fri, 25 Oct 2002 01:22:32 EDT

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.)

---

From: Dale Wilson <[email-masked]>
Date: Sun, 27 Oct 2002 15:15:51 -0800

Elaine,

> 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.

But don't you think that after you leach into water, add molassas, and
aerate for a while you end up with a much simpler community?  Adding a
soluble carbon source in a liquid culture is akin to a lab medium.  I
don't mean to criticize the method, I just think it is simpler than
compost per se, and that plate counts might be a useful GC tool.

> 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...
> 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...
> I hope this helps explain what is going on with 24 hour compost tea

Sounds good!  If you had to guess, which species do you think are most
important in a good compost tea for disease control?  It might be
possible to add small amounts of something, like adjust the pH, SO2,
iron, or a bit of benzakonium chloride, to tip the tea ecology one way
or another.

Dale

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