Hi, I'm new on this forum.

We recently bought a house in east London. The garden has enviable soil -- sandy loam, well enriched over the years, that drains fast.

In one patch, I'm making a bog garden and have been testing the soil pH. Overall, the garden reads 7 in places and nearly 8 in others. The patch I'm interested has been slowly dipping below 7 as I add sulphur and saturate the ground.

But if you push the probe below the surface, you can hit 'hotspots' where the meter spikes out and goes above 10. It's not calibrated above ten, but it looks like a 12.

For those who don't already know, this is incredibly alkaline. pH 10 is 1,000 times more alkaline than neutral soil and pH 12 is 100,000 times more alkaline.

I know that the previous owners limed their compost, but these readings are bonkers. Could the fact that I recently used cement in this area have anything to do with this?

Any other explanations?

"Homer Sparrow" wrote in message
...

Hi, I'm new on this forum.

We recently bought a house in east London. The garden has enviable
soil -- sandy loam, well enriched over the years, that drains fast.

In one patch, I'm making a bog garden and have been testing the soil
pH. Overall, the garden reads 7 in places and nearly 8 in others. The
patch I'm interested has been slowly dipping below 7 as I add sulphur
and saturate the ground.

But if you push the probe below the surface, you can hit 'hotspots'
where the meter spikes out and goes above 10. It's not calibrated above
ten, but it looks like a 12.

For those who don't already know, this is incredibly alkaline. pH 10
is 1,000 times more alkaline than neutral soil and pH 12 is 100,000
times more alkaline.

I know that the previous owners limed their compost, but these readings
are bonkers. Could the fact that I recently used cement in this area
have anything to do with this?

Any other explanations?

Even over-liming would only give you a pH of 12 if there was a bag of the
stuff buried. I wonder what has been going on in the past as overall pH 7
to 8 is high unless you are in a salt pan, on bedrock of limestone or
something similar. Most natural soils, especially with a high organic
content, tend to be slightly acid.

Have you tried digging down at these spots to see what is there?

Are you sure your meter is accurate? The cheaper metal probe type can be
confused by variations in moisture and dissolved salts. Perhaps you can
callibrate it against a dye indicator system.

David

On 3 Wrz, 09:00, "David Hare-Scott" wrote:

Are you sure yourmeteris accurate? The cheaper metal probe type can be
confused by variations in moisture and dissolved salts. Perhaps you can
callibrate it against a dye indicator system.

IMHO that's most likely cause of problems. Correct procedure of soil
pH measurements calls for glass (or MOSFET) pH electrode (see
procedure outlined he http://www.ph-meter.info/pH-measurem...er-procedures).
Calibration of metal type probe against indicator won't help, as the
probe result will change with the soil humidity level, while
idndicator results will not.

Mr.pH
--
http://www.ph-meter.info
http://www.chembuddy.com

Those metal probe pH meters are pretty much of a joke.

The only way to measure pH reliably is to remove a sample and mix it
with water and measure it that way with a real meter or pH testing kit.

You can try the metal probe in the wet sample but your mileage may still
vary a lot.

js

--
PHOTO OF THE WEEK: http://schmidling.com/pow.htm
Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com