If you only worry about pH, here is a simple test. If both your beets (or chard) and your potatoes are nice, the pH is spot on. Beets really complain below 6.x, I don't know what x is, but somewhere between 0 and 5. Potatoes will complain above 7.0.

Just do a search for your local (county) Cooperative Extension. They'll tell you how to do it. I did mine up here in NY last year. It cost about $15.

glib, I understand that about beets, but in what way will potatoes complain?...extreme scab?

I assume scab. Perhaps I should have picked another veggie that prefers acid soil? None comes to mind readily, although I am sure there is a number, specially those originally from the tropics. The beet-chard thing is solid though. For a few years I was unable to grow them, until I started giving them massive doses of wood ash.

Well the beet/chard/potato thing is nifty! All did/are doing well!
My county doesn't do soil samples anymore (crazy! We're in a totally ag area!) they have to be sent out and cost about $35 last I checked.
That's too expensive for my frugal bones! I have several raised beds, all filled from different sources, different years.
I add as much compost as I can produce on my own each year and occasionally bring in a truck load to top everything off and mix into what I've got. Seems to work! Nancy

It's only $7.00 here for a soil test. That's the best and really only way to know what is going on in your garden. Worth every penny. It will tell you what your soil has too much and too little of and what to add to make it better.

I find scab starts above 6. But plenty of K and B probably mollifies that effect.

I think at least one soil test is a good idea.