permaculture

[Soil Doctor <soildoctor.org@gmail.com>]

Hi Dieter

Your response demonstrates my point.  

You're not just putting down organic material.  The organic material is 
coated and infiltrated with microbes (viruses, bacteria, archeae, fungi, 
ciliates, flagellates, amoebae, rotifers, nematodes) and the recent 
environment that the organic material came from determines what kinds and 
numbers of microbes and what mixture ratios of these microbes are on that 
material.  Manures come from an anaerobic environment and contain a 
completely different mixture of microbes than a finished thermophilic aerobic 
compost pile. Both are "organic material" but the presence of pathogens and 
their numbers relative to non-pathogenic or predatory microbes is completely 
different. Raw manures (that have NOT been aerobically hot composted or given 
enough time in a static compost pile or gone through the crushing crop of a 
worm) are going to have higher numbers of pathogenic microbes. 

Plus, as you say, adding a wide range of organic material to soil is good 
but, frankly it's a buckshot approach way of feeding different sets of 
microbes and ultimately your plants. There are different microbial mixtures 
that support different plant groups.  I wrote about this a couple of years 
ago on another permaculture site discussing a workshop that Elaine Ingham 
gave.  When I talk about the bacteria and fungi below I'm talking about 
aerobic bacteria and fungi.  I'm just going to copy it in here.

*****
Hi Greg, it might be helpful in understanding Dr. Ingham’s work to know that 
there is an underlying ecological pattern of the relationship of soil 
microbiological population mixes to the above ground plant population mixes. 
For me a fundamental part of permaculture is identifying ecological patterns. 
Once you get the patterns, you can analyze and understand many ‘different’ 
locations, plant populations, etc.

If you’ve ever been to an old growth conifer forest and looked at the forest 
floor you’ll see lots of fruiting fungi in the form of mushrooms. Dig into 
that old growth forest soil and you’ll see kilometers of mycelium strands (no 
wonder Paul Stamet who lives in the Pacific Northwest USA old growth forest 
country sees fungi as key to ecological restoration). In contrast, if you go 
to a drylands environment you’ll tend to not see fungi fruit (mushrooms) or 
visible mycelium strands in the soil. Or similarly, I think most of us would 
be surprised to see mushrooms growing in tilled agricultural farm fields. Why 
is this?

Its because there is an underlying ecological microbiological pattern to all 
soils which is at its base the ratio of fungi to bacterial biomass in the 
soil. Over the past several decades soil microbiologists have been able to 
pin down a pattern of soil microbe and plant changes through time and space 
that they call “succession.” I think understanding microbial/plant succession 
is vital for any permaculturalist. Microbe/plant succession is a continuum. 
If you start on the extreme left of the continuum you get very “early” 
successional soils and plant communities where weeds (in the biological sense 
of weeds: annual, fast growing, tons of seeds, nitrate loving plants) thrive. 
A key to understanding why the weeds thrive is that the soil microbe 
population is bacterial DOMINATED. The fungi to bacteria biomass ratio is 
8-10 more bacteria than fungi. The bacteria produce a sugar substance loosely 
called bacterial slime that is alkaline (slime is for protection, transport 
corridors, etc.) The slime drives the soil alkalinity here. So these 
bacterial dominated soils have a high ph. Without going into the details of 
microbial nutrient cycling, let me cut to the chase and say that the alkaline 
soil conditions results in a bunch of specific bacteria converting microbial 
cycled soluble Nitrogen into Nitrate. This process is called nitrification. 
And the bacteria that do it require high (alkaline) ph for the enzymes they 
use to convert Nitrogen into Nitrate to work. Weeds love high Nitrate levels. 
They’ll out compete “higher successional” plants any day if there’s tons of 
Nitrate in the soil.

If you move to the right on the succession continuum you get a tighter fungi 
to bacteria ratio. In a soil where the fungi to bacteria biomass ratio is 
more balanced, lets say 1 to 1, you’ll find that “higher” level plants thrive 
and out compete the weeds. Higher level plants means in the context of the 
successional pattern and include annuals like tomato, cucumber, pepper,corn, 
etc. All these plants like to have their Nitrogen in two flavours: Nitrate 
and Ammonium. In soils that have a more balanced mix of bacteria to fungi the 
soil alkalinity is more neutral. This because fungi, as part of their 
‘eating’ secrete acids as well as enzymes. The extra fungal biomass means 
extra acids being generated in the soil resulting in a soil ph change. As the 
ph moves closer to 7 (neutral) the nitrifying bacteria I mentioned above 
can’t as easily convert Nitrogen into Nitrate. Just a note, the soluble 
Nitrogen I originally mentioned above is actually Ammonium. So, if less 
Ammonium is being converted to Nitrate, the Ammonium to Nitrate balance is 
changing. Weeds like high pulse levels of Nitrate. When they don’t get it, 
they are on a diet and can’t thrive. In contrast the tomatoes and peppers do 
well with a bit of both Nitrate and Ammonium. Its important to understand, 
that the soil microbes are responsible for this. If we leave an area alone, 
the plants that grow will tell us the story of the fungi to bacteria ratio in 
the soil.

If we move more to the right on the successional continuum we get ever 
increasing fungal biomass and ratio dominance. In a healthy vineyard soil you 
might see 3-5 times the fungal biomass compared to bacteria. A fruit orchard, 
5-10 times fungi. A healthy old growth conifer forest 100-1000 times as much 
fungi to bacteria. Think about the plant systems we just moved into, they’re 
perennials. As we jumped from annuals to perennials we jumped into a fungal 
dominated soil. As the soil gets increasingly fungal dominated we get more 
and more fungi secreted acids entering the soil, resulting in an increasingly 
lower soil ph (acidity). When the soil ph drops below a nuetral 7 and becomes 
acidic, those nitrifying bacteria I mentioned above can’t convert Ammonium 
into Nitrate. The enzymes they use to do this just don’t function in acidic 
soils. So, the form of soluble Nitrogen in the soil becomes ever increasingly 
Ammonium. As we move into more advanced (in terms of succession) Perennials 
we get a greater love of Ammonium as the desired plant Nitrogen food. If you 
give any organism its preferred food it will out compete other organisms that 
have different preferred foods. Broccoli, for example, likes a more Nitrate 
rich soil with a fungi to bacteria ratio of .3-.7 approx (bacterial 
dominated). Chances are slim that you’ll find a ‘natural’ growing broccoli 
plant in an Ammonium rich old growth forest in California. Likewise, chances 
are slim that you’ll find a confer thriving in a tilled broccoli field. The 
soil fungi to bacteria ratios are different and give a competitive advantage 
to different above ground plants groups.

When thinking about your field ask yourself some questions about the type of 
grasses you WANT to grow and the types of plants that seem to thrive there. 
Do you want to grow perennial grasses but lots of high seed yielding annual 
weeds thrive there? If so, you’ve got a bacterial dominated soil. Most of the 
time, we do need to move our soils along the successional continuum pattern 
and get more fungi in there, especially if the soils have been farmed 
(chemically or often organically). Farming practices of tilling, chemical 
ferts, pesticides and evening dumping manure on fields either kill fungi or 
overfeed bacteria. Both result in bacterial dominance.

But here’s the rub. If I live in an old growth conifer forest in say Oregon, 
USA, and I want to grow a veggie garden I’ll most likely need to make my soil 
more bacterial. I mention this to point out that understanding the 
successional continuum pattern and what your specific soil microbe population 
is in relation to the plants you what to grow is always the first step. 
Getting fungi into many soils is often the first answer, but not always. Then 
once we’ve got the right fungi:bacteria ratio for the plants we want to grow, 
we need to look at the other members of the soil food web (ciliates, 
flagellates, amoebae, nematodes, micro/macro arthropods) and ensure their 
numbers and diversity are OK. But, first step, is the fungi-bacteria ratio.
*****

Deiter, as you say in your reply, there's nothing very new about this stuff 
and you are correct.  Microbes have been doing this for 4.9 billion years.  
Its our understanding that's new. It's the work of soil microbiologists over 
the past 20 years that's helping us understand it now and how to use it.

Lastly, Dieter, you ask what does this mean in practical terms.  Well, for 
starters what's the "organic material?"  Putting out aerobic composts and 
compost extracts not anaerobic raw manures or manure teas is a big start. And 
figuring out whether our soil is bacterial or fungal dominated and whether 
the current ratio benefits the plants you want to grow is another.

Doug
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Doug Weatherbee, M.A.
Certified Soil Foodweb Advisor
http://soildoctor.org

San Miguel de Allende, GTO
Mexico
415.152.3410 (San Miguel #)
310.359.8549 (U.S.A #)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


> 
> ------------------------------
> 
> Message: 4
> Date: Fri, 3 Dec 2010 09:58:37 -0800 (PST)
> From: Dieter Brand <diebrand@yahoo.com>
> To: permaculture <permaculture@lists.ibiblio.org>
> Subject: Re: [permaculture] "Weird" Science - Microbes and Soil
> Message-ID: <414528.44347.qm@web63405.mail.re1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
> 
>> Sensing points to a fundamentally new way of thinking about
>> this in our farms.  We need to increase the r
>> atio of good-guy microbes in the soil and on the plant
>> surfaces in relation to the "bad-guy" pathogen
>> microbes.  Research on plant pathogen suppression with
>> composts backs this up.  It's the amount of a plant
>> pathogen species #s in a compost relative to the total pile
>> of microbes that determines whether the plants will develop
>> the disease.
> 
> And what does this mean in practical terms?
> 
> If I feed my soil with a wide variety of organic matter, this is likely to 
> produce a wide variety microbes.  And the resulting fertile soil is likely 
> to produce healthy plants that are capapble of withstand disease.  There is 
> nothing very new about that.
> 
> Dieter
> 
> 
>