[compost_tea] Re: Sustainable Farming News & Biological Agriculture Information. >

From: Tollefson Stacy <stacytollefson_at_yahoo.com>
Date: Mon, 19 Dec 2011 22:35:20 -0800 (PST)

Regarding David Eyre's comment about adjusting the pH of compost, microbes =
seem to do what they do and maintain a high pH in the process.  This summ=
er, I made very high strength compost tea and used it as a "complete" hydro=
ponic nutrient solution to grow tomato plants.  My starting water has a p=
H around 7.8.  When brewing it went to 8.5 and even up to 9.0 at one poin=
t.  After brewing it went down to about 8 and stayed there.  With one b=
atch of tea, I reduced the pH with citric acid, to 4.5.  Four hours later=
, the pH was back up to 8.  I couldn't keep the pH down!

In the other batch, I used the tea with a pH of 8.  I was still able to=
 grow tomatoes pretty successfully despite the fact that the pH was so high=
.   I suspect that either the microbes in the rhizosphere bring the pH do=
wn right at contact with the roots, and/or the microbes are producing chela=
tes/siderophores that are assisting with transport of the nutrients into th=
e roots, even when the pH is high (this was the case with iron in a 1960's =
study I saw)...Perhaps this happens with other nutrients as well?  Any bo=
dy have thoughts on this?

Stacy

 Stacy Tollefson
PhD Candidate Agricultural and Biosystems Engineering
University of Arizona
Controlled Environment Agriculture Center (CEAC)

Received on Tue Dec 20 2011 - 01:47:34 EST

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