On 12/11/12 5:26 PM, Peter Jason wrote:
On Tue, 11 Dec 2012 17:55:17 +1100, "David
Hare-Scott" wrote:

Peter Jason wrote:
On Tue, 11 Dec 2012 13:54:39 +1100, "David
Hare-Scott" wrote:

Peter Jason wrote:
I have a plant that likes a pH of 5.5.

Can I just use a potassium phosphate buffer
adjusted to this value to water the plant with?

Peter

My TOTH answer is probably not as buffer solutions are designed to
hold pH steady not to alter it but it might do some good depending
on the situation. I am guessing that you want to lower the pH in
which case the traditional method is to add elemental sulphur and
wait.

What exactly is the content of this buffer solution? What is the pH
of the soil now? How much soil do you want to amend? What is the
soil like, as in how much clay and organic material is there
compared to sand and grit?


David

I have one of these
http://en.wikipedia.org/wiki/File:Wo...bilis_fg03.JPG
that is doing rather well in a large pot, but it
will need transplanting out next season.
I mix my soil 50:50 from two types; an industrial
heavy clay from a dirt road that has been sloughed
up by large turning trucks (easy to dig), and the
usual sandy stuff collected from the roof
guttering and yard sweepings.

I fertilize with cow & chicken manure.

I could make & adjust the buffer from KOH & Phos
Acid with a pH meter, and I have some flowers of
sulfur. How does one test the pH of soil?

My assumption that you want to lower pH is clearly wrong as at this point
you don't know that, so hold on to the sulphur.

The most reliable cheap way to test soil pH is with a dye indicator. You
can get a kit with the dye, colour reference card etc for about $20 and that
will do hundreds of tests. I am puzzled that you know what a buffer is and
how to make it but you are charging off to alter your soil chemistry without
first finding out if it is required.

I am so happy that my roof gutters don't collect enough sand to be useful to
make soil. :-)

I live in town and I don't trust that synthetic
soil in plastic bags. It dries out too quickly.

I tested the soil in the Wollemi Pine pot by
slurrying some in water, and it gave a pH of 6.
Maybe this is why it's doing so well.


I have a few other plants in pots and so perhaps I
need to take greater note of pH requirements.

Is there some database of plants and the soil-pH
requirements? The botanical name is usually
given on a tag when a plant is purchased.

Peter




If you are west of the Rocky Mountains in the U.S. or Canada, the major
portion of Sunset's "Western Garden Book" is a plant encyclopedia that
indicates climate, water, and soil requirements for each listed garden
plant. No, the soil requirements do not indicate pH; but they do
indicate whether a plant tolerates alkaline, acidic, or saline soil.

There is also a Sunset garden book that covers the whole U.S., but I
don't know if it is as comprehensive. I would suspect there are
excellent garden books specific to other nations and climates. Also, a
good plant nursery -- not a hardware store or lumber yard -- should be
able to advise you on whether a particular plant requires an alkaline or
acidic soil. Finally, there are various national and international
societies devoted to specific plant families: roses, bromeliads,
daylilies, orchids, etc.

--
David E. Ross
Climate: California Mediterranean, see
http://www.rossde.com/garden/climate.html
Gardening diary at http://www.rossde.com/garden/diary