pH Measurement
 

I garden on "Cheltenham Sand" which according to
http://www.gloucestershire.gov.uk/me...ded%20appendix
%20%20D.pdf is "composed of medium grained quartz sand with limestone
fragments and gravel lenses"

I've measured my soil pH several times with the 1 pound soil testing
kits and it always comes out at slightly alkaline which is what you'd
expect.

Recently I bought a probe type pH meter and found:

- Nowhere in my garden is alkaline according to the probe - even places
that I limed in the Winter!
- A lot of places have a pH of around 6. This includes a tub of
erricaceous compost where a blueberry is living happily.
- I've even found spots with a pH of 3.5 but a few inches away, it's a
more reasonable 6.
- Unused multipurpose compost has a pH of 6
- I tested the probe with plain water and got 7. A splash of orange into
the water moved the reading down to 6

Anyone think anything is going wrong here?

Steve Harris - Cheltenham - Real address steve AT netservs DOT com
A useful bit of gardening software at http://www.netservs.com/garden/

"Steve Harris" wrote in message
...
I garden on "Cheltenham Sand" which according to
http://www.gloucestershire.gov.uk/me...ded%20appendix
%20%20D.pdf is "composed of medium grained quartz sand with limestone
fragments and gravel lenses"

I've measured my soil pH several times with the 1 pound soil testing
kits and it always comes out at slightly alkaline which is what you'd
expect.

Recently I bought a probe type pH meter and found:

- Nowhere in my garden is alkaline according to the probe - even places
that I limed in the Winter!
- A lot of places have a pH of around 6. This includes a tub of
erricaceous compost where a blueberry is living happily.
- I've even found spots with a pH of 3.5 but a few inches away, it's a
more reasonable 6.
- Unused multipurpose compost has a pH of 6
- I tested the probe with plain water and got 7. A splash of orange into
the water moved the reading down to 6

Anyone think anything is going wrong here?

Steve Harris - Cheltenham - Real address steve AT netservs DOT com
A useful bit of gardening software at http://www.netservs.com/garden/

I would tend to believe the pH meter.
Take a lump of soil and mix with water -allow to settle and test the
clearish liquid with the probe and then with a few drops of indicator from
the test kit.
Hopefully you should get the same answer from both.
You should really use distilled or deionised water for the test--it is very
unlikely the tap water is totally neutral (usually slightly on the alkaline
side) which would be sufficient to give a false result

On Tue, 10 May 2005 21:52 +0100 (BST), (Steve
Harris) wrote:

I garden on "Cheltenham Sand" which according to
http://www.gloucestershire.gov.uk/me...ded%20appendix
%20%20D.pdf is "composed of medium grained quartz sand with limestone
fragments and gravel lenses"

I've measured my soil pH several times with the 1 pound soil testing
kits and it always comes out at slightly alkaline which is what you'd
expect.

Recently I bought a probe type pH meter and found:

- Nowhere in my garden is alkaline according to the probe - even places
that I limed in the Winter!
- A lot of places have a pH of around 6. This includes a tub of
erricaceous compost where a blueberry is living happily.
- I've even found spots with a pH of 3.5 but a few inches away, it's a
more reasonable 6.
- Unused multipurpose compost has a pH of 6
- I tested the probe with plain water and got 7. A splash of orange into
the water moved the reading down to 6

Anyone think anything is going wrong here?

Steve Harris - Cheltenham - Real address steve AT netservs DOT com
A useful bit of gardening software at http://www.netservs.com/garden/

Scientific pH meters use a very delicate 'glass electrode'. I wouldn't
trust a meter that used any other sort of electrode.


--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net