RE: [compost_tea] Re: newpaper article - Update

From: Judi Stewart <js_at_olympus.net>
Date: Tue, 18 Jan 2005 16:49:28 -0800

 
Just thought you'd like to know that Chris Smith has an open
mind. When he sees the evidence of his compost tea tests, he'll be
happy to report the tests accurately. Chris is going to trial
compost tea this year on his tomatoes, thanks to one of our
list members. One cultivar will be grown without compost tea
in one area and the same cultivar will be grown with compost tea.
 
Judi
 
 
Thursday, August 26, 2004
Good Enough To Eat: Controls are key to testing compost tea
By CHRIS SMITH
SPECIAL TO THE POST-INTELLIGENCER
In last week's column on compost tea, I promised information on how
to conduct scientifically respectable research in a home garden.
Aspiring researchers without enough space of their own may be able to
take part through groups like the Master Gardeners, rose societies
and fruit growers' clubs, which have access to grounds spacious
enough to run a test or two.
Before you get started, you should be aware of a few requirements for
your work to be considered scientific. You'll need a control group
for each material or technique under investigation, you'll need to
eliminate as many variables from the experiments as possible, you'll
have to report what actually happens, not what you want or expect the
results to be, and you'll have to repeat the experiment. Let's
examine each of these requirements in more detail.
Having a control group -- that is, a comparison group of plants on
which a material or technique you're testing is not being used -- is
critically important. For example, if we're looking into the efficacy
of compost tea as a suppressor of the fungus disease late blight on
tomatoes, there should be plants we'll spray with tea and other
plants that don't get the tea.
If you're growing susceptible plants, the disease organisms are
present and the conditions for infection are favorable, then the
control group should get the disease. If it doesn't, and the tea-
sprayed group is also blight-free, you can't draw any conclusions
about tea as a suppressor of that disease.
Perhaps conditions for infection were unfavorable when you conducted
your test, or maybe the variety of tomato you were testing has
resistance to the disease.
If the control group gets the disease and the tea-sprayed plants
don't, the case for compost tea as a suppressor of the disease is
strengthened.
In the unlikely though not impossible event that tea-sprayed plants
catch the disease and the control group doesn't, you'll need to
entertain the possibility that tea somehow may abet the disease.
Planning for a control group is not difficult; eliminating variables
is another matter.
Let's start with the tea itself. Its constituents and the brewing
process should be the same for the duration of the testing period
(ideally, several years). Keep in mind that there are numerous
composts -- woody wastes, animal manures and household garbage, to
name a few -- from which teas could be brewed. Each could be expected
to contain a different mix of microorganisms, some of which might
control a specific disease or diseases.
 
 
 
 
Choose one variety of tomato known to be susceptible to late blight
for both the test and control groups of plants. Mixing tomato
varieties adds rather than reduces variables. If there are varying
degrees of disease resistance among three varieties you're using in
an experiment, how would you be able to sort out what's happening?
Finally, eliminate variables in the raising of the plants.
For starters, plants in the experiment should be the same age. Set
them in similar soil and fertilize, water, weed and otherwise care
for them the same way. Remember, when you drench the test group with
tea, drench the control group with the same amount of water;
otherwise one group will be getting more water than the other.
Your goal is to eliminate every variable except whether or not tea is
used on the plants. .
Part of being a scientist is observing carefully and reporting
accurately. Don't allow your gardening philosophy to color the
outcome of a test. You may hope tea turns out to be an effective non-
chemical control for late blight or conversely, that it fails
miserably. What you hope or expect doesn't matter. It's what actually
happens that matters.
Finally, do the follow-up tests. If you've discovered a truth, for
example about compost tea as a disease suppressant, it should repeat
itself in further tests. The same results in repeated tests
strengthen whatever claims you eventually make and lessen the
likelihood you've observed aberrant behavior.
It's what scientists do and it's what scientifically oriented
gardeners should do to advance knowledge in the field.
Chris Smith, who lives in Port Orchard, is a Master Gardener and is
retired from the WSU Cooperative Extension. His columns appear in the
P-I garden pages on Thursday. Send questions to P.O. Box 4426, South
Colby, WA 98384-0426.
 
 
 
 
 
 
 
 
 
 
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Received on Tue Jan 18 2005 - 20:27:10 EST

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