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?