----- Original Message -----
From: Matt Leamy
To: compost_tea_at_yahoogroups.com
Sent: Tuesday, June 29, 2004 8:38 AM
Subject: [compost_tea] Brix response
Hi Lloyd
Your post was a wee while back, I'm often 1 or 200 posts behind with this=
.
I have a refractometer and have been making general observations with it.=
Can you detail for us your methodology for measuring brix response to a s=
pecific input?
Cheers Matt Leamy
Matt I have cut and pasted several of my brix replies below (all copyrigh=
t of course)
hope that may answer some questions tho just reading your next post you h=
ave most of this figured out pretty good.
cheers
Lloyd Charles
Sampling for brix
1. keep it simple
2. be consistent
3. be very aware of weather conditions - sunlight - temperature - wind -
barometric pressure -
4. keep good records - write all of the above down for each sampling alo=
ng
with time of day
5. - dehydrated plants - any sort of stress can cause
accumulation of sugars - Hugh Lovel had an excellent posting on bdnow (ba=
ck
a while)
explaining the daily cycling of brix - Elaine explains this really well t=
oo,
her "cake and cookies" story is great!
6. What part to test - this is gut feeling only, I have no scientific ba=
sis
for what follows -in a new wheat crop - to three leaf stage - we would ta=
ke
whole plants from about 1 inch above ground. From five leaf on we mostly
sample the third leaf. As the crop progresses we would do some tests from
younger leaves and also stem sap. As we go into grain filling, just befor=
e
the leaves shut down, I want to see good brix in the stem sap - figuring
that is the last feed the grain will get.
7. In all of this what I am most interested in is checking response to
foliar applications - we do this before we spray -using small pump spray
bottles on meter square test plots we come back and measure brix from
45minutes to two hours after spraying our test brew - we look for at leas=
t
two brix or better increase and would not apply any material that will no=
t
give it -
8 If you have a neighbour that grows conventionally see if you can take
some brix measurements there for comparison .
Allan you're right -High brix can be the result of any number of things=
-
moisture stress for one -
But what I am interested in is an INCREASE (or decrease) in plant sap bri=
x
in response to a foliar application of nutrition (compost tea or whatever
else) on growing plants and I AM certain of the meaning in the numbers in
that scenario.
I am also certain that there would be some stages of crop growth when
application of good quality compost tea could easily be detrimental to th=
e
short term progress of that crop - (I'm thinking of critical stages of fr=
uit
initiation and set) - use of the refractometer will indicate this - wheth=
er
or not.
My testing proceedure as follows
1. spray several different test bottle brews (usually four) on a square
meter of crop about 5 meters apart so no crossover effect - always spray =
in
line with the seeder travel so no distortion due to seeding rate, depth, =
or
fertiliser quantity (still using a little non acid starter down the tube)
2. 30 to 45 minutes later come back to test results with refractometer
3. I do one untreated test at one end then test each plot then another
untreated at the other end of the plots, if the untreated readings are no=
t
reasonably consistent with one another I would probably abandon that set =
and
start again. Hey I'm trying to do this properly you know!
4 . Usually there would be one or sometimes two brews with nicely elevate=
d
brix on the first test
in an actively growing crop - with
changeable weather conditions, sunlight, temperature etc, there should be=
a
wide range in the "normal" brix throughout the day, (Hugh Lovel refers to
'the ebb and flow of sap' and thats whats happening). I think its extreme=
ly
important to do the measurements of treated vs untreated at the same time=
of
day, under the same conditions, otherwise we can get misleading results =
-
30 minutes can easily turn into an hour - and an hour of increasing sunli=
ght
and warmth can easily raise the reading a couple of brix points. With any
testing method we must always strive to eliminate the un necessary variab=
les
that cloud the results.
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Received on Tue Jun 29 2004 - 04:57:53 EDT