The majority of the readings are very acid, which suprises me greatly as we have a very heavy clay soil naturally.
I suppose the vegetable garden actually in the main has beuatiful crumbly relatively light soil and has had loads of garden compost and fertiliser added over the years (thanks to the previous owners who were very keen gardeners) and is almost always watered by the rain or from a water barrel.

Are these electrical pH meters accurate?
I was expecting before i tested the soil to add a touch of line before planting the asparagus, and to have to keep the blueberrries either in pots, or devise some sort of raised bed with ericacious compost in - but maybe i don't. I will be very upset though if I do plant out the blueberries and they die from being in the wrong soil as they were jolly expensive. Wouls I get lots of warning they weren't happy with the soil, ie laves changing colour, or would they just not crop or suddenly die?

Thanks for any help you can offer
Sorry it was so long!

You can confirm or see how far out your meter readings are by using the little colour change pH testers, they aren't terribly sensitive either but do generally provide a reasonably accurate test, accurate enough for gardening anyway. Again ensure you use distilled water, they don't always not that on the instructions.

Plants and their tolerance of pH as you know varies, however, they won't die suddenly if they are in the wrong pH, they will suffer because they won't have access to their required amount nutrients and trace elements so it's noticable through the plants reaction such as leaf discolouration or overall health.

You obviously know you need specific pH requirements for your Blueberries and that your asparagus has a more restricted range than most and that you need to know the soil pH before deciding how best to keep them so I suggest the little colour test tubes and distilled water I mentioned above.

The general rule is that a clay soil is acidic. I used to garden Wield clay in West Sussex, which was criminally acidic (let alone badly drained and heavy to work). But then it does depend a bit on the parent material — a chalky clay may be alkaline, usually only slightly so. However, poor drainage, usually associated with a clay soil, can increase acidity.

The part of the garden which has been regularly worked has probably had lime added to it over the years, which is why your preliminary results are reading as alkaline. Liming helps to create a good soil structure in a clay soil, and needs to be continued to be added if you regularly manure your soil in future to counter any increase in acidity which almost always ensues. Be sure to test your soil pH before liming, however, as it is possible to overcompensate. I have known old boys who have limed their allotments routinely annually and have ended up with a soil which was excessively caustic.

Most likely a natural soil pH of 4-5, but with isolated pockets of high pH due to builders' rubble (= alkaline mortar) dumped in patches when the house was built. Very common, and a far more likely explanation than the pH meter being wrong.

Resin

There are plenty of alkaline clay soils. My subsoil is a blue calcareous clay. There are also many calcareous clays along the upper parts of the Thames.

One advantage of the chemical test kits is that you will get an average reading for your soil while the probe only reads the bit of soil it is stuck in. You might wish to collect a dozen or so samples from around the bed, mix them together thoroughly, wet appropriately, and then stick the probe in that. A chemical test would still be a useful confirmation, and worth the fiver it will cost when you are going to spend a bunch of money on correcting your soil to the necessary pH.