[compost_tea] Re: numbers
--- In compost_tea_at_yahoogroups.com, soilfoodweb@a... wrote:
> Hi Anthony -
>
> I'm out of time! But here's a first pass at the explanation for
you! Back in two weeks!
>
> Numbers of individuals in soil. OK, here goes.
>
> That's not possible to say, really, for fungi. A fungal individual
is difficult to know for certain. Plate counts mess up on that
measurement - in general, plate counts give you "how many spores of
fungi and pieces of hyphal strands were the fungi broken into when
you shook your sample", which isn't really a useful piece of
information.
>
> Colony forming units - CFU - do not tell you if the fungal
propagule was a spore, a tiny piece of hypha, or a mat of hyphae.
You need to do biomass, that's all there is to it, when you are
dealing with fungi.
>
> Especially when you want to compare fungi and bacteria, comparing
numbers is just plain nonsense. We could tell you how many
individual strands of fungi are present in soil, but that is
dependent on whether the soil was just plowed, or not. Doesn't
relate to anything useful.
>
> But what about bacteria? Bacteria clump together, they like to
form colonies. Just like people. People clump together in villages,
towns, cities, etc.. The group helps each individual better. Think
of a bacterial colony as being like a neighborhood of similar ethnic
people.
>
> Plate count approaches cannot separate all the colonies into the
individuals, so plate counts always underestimate the actual number
of individuals - but you don't know by how much. How many colonies
were broken up when you shook your soil sample in buffer? How many
were not, or were partially broken up? don't know. So, what are you
getting when you run a plate count?
>
> In direct microscopy, we count the individual bacteria that we can
see, including the bacteria in colonies, measure length and width,
and then using the typical density of bacteria in soil, determined
over the years by lots of testing and which varies from soil to soil,
season to season, we can determine biomass of bacteria in soil.
>
<><<><><><><><First you need biomass of one bacterium, right, or a
million and extrapolate. In direct microscopy count the required
number of fields, average and multiply by the scopes microscopic
factor. Then converson from bacteria per ml or gram of sample is
based on the densiity of items counted and you have biomass.Dennis
Kemnitz
> We are working on differences in bacterial and fungial densities in
the rhizosphere of different agricultural plants right now, so that
will be put into the data that will be used to fine-tune the SFI
report based on each plant that you tell us has been growing in the
area you want to know about.
>
> A good test for a lab that says they are doing direct measurements,
but are perhaps not actually giving good data because they don't work
with the person who developed the direct microscopic techniques they
purport to use, is to ask them how they figured out density of
bacteria and fungi in soil. What values do they use in their spread
sheets, and how those values change with season.
>
> SFI labs direct that question to me, because I developed the
knowledge. Sharing that knowledge, having someone able to understand
that level of seasonal change, and understand how to do the
assessment, generally takes a minimum of Ph.D. in microbiology. So,
yes, other academics can tell you the reason you need to pay
attention to this, but only by working with SFI labs will you get the
knowledge that has already worked that one out.
>
> People who stopped by SFI and spent a week, or even a couple
years, "training" with SF were not given this information. They
can't explain where each value in our spread sheets comes from, and
of course, that's critical in order to change the seasonal
parameters, the plant parameters, that need to be changed.
>
> Anyway, on to the numbers. We explain numbers versus biomass in
SFI courses, so, if this discussion is a bit too much, please come to
one of those classes.
>
Elaine which one of those classes do you suggest? Do you cover it in
any of the cd's? Dennis Kemnitz
> Bacteria generally run about 1 million per gram (about a teaspoon)
of dry weight of soil in conventional agricultural soil.
<>><><><><><>Isn't the mass (bio)of 1 bacterium all that's needed for
the conversion? ie Number of bacteria per ml. times biomass of one
bacterium is equal to xxx biomass per ml. SEE no PhD
required!!! Relax I'm just simply trying to save travel ,
tuition and time, time,time!!! Dennis Kemnitz
Typically a plate count will overestimate the actual numbers of
bacterial individuals, because the plate count will include dormant
stages of bacteria, not just the active bacterial cells. That's a
problem. If the information you need is - how many functioning cells
in my soil - then you cannot get that knowledge from a plate count.
>
> Bacterial numbers in HEALTHY agricultural soil, healthy defined by
the plant can grow without pesticides or inorganic fertilizer to help
it survive (not on drugs, if you will) are typically about 600
million per gram dry weight of soil.
>
> Numbers of bacteria per gram in a conventional lawn, maintained by
a chemical service? You may have only disease - causers, and you may
have only a few thousand per gram. Pesticides kill things. Oh,
surprise.
>
> In a healthy lawn, which is disease-free, so not requiring any
pesticides, we can find up to 2,000 million bacteria per gram of
soil. But that better be balanced by a fungal biomass to balance
nitrogen in a proper ratio to grow your perennial grasses.
>
> The proper biology does that for you. You must get the ratio of
fungi to bacteria correct, for the plant you want to grow, or you may
be setting the stage to grow weeds better than the plant you want to
grow.
>
> If that statement confused you, it may be time to come to an SFI
class.
>
> In a field of soil (about 2 million lbs of soil in the top ten
inches in an acre of soil), that's well into the billions of
individuals of bacteria, and possibly fungi.
>
> You need to be very careful when someone is talking about numbers
of individuals of bacteria or fungi that you get the units correct.
Did they say billions of individuals per gram of ag soil? Then they
are not correct.
>
> Did they say billions of individuals per gram soil in an old growth
forest? They are correct. How productive a system are you talking
about?
>
> If they say billions of individuals in an ag FIELD, then they MAY
be correct. In an old growth forest stand of trees? They are being
too conservative.
>
> And that's just bacteria and fungi. what about protozoa? Add them
in.
>
> Nematodes? Microarthropods? You CANNOT have a healthy old growth
forest without several hundred thousand microarthropods doing their
thing, during the right times of the year.
>
> Seasonal processes going on there, and we need to make sure they
are there, in order to have a healthy forest.
>
> Much to understand. But not impossible, nor even all that complex,
if you get an understanding of how it all works together. There's a
great deal of "well, of course that's how it works", once you have
someone explain the functions of the different critters for you.
>
> 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
> SFI Culiacan, Mexico
> SFI Jerome, Idaho
> http://www.soilfoodweb.com
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Received on Mon Apr 12 2004 - 19:55:25 EDT
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: Tue Feb 07 2012 - 14:15:11 EST