Hi tennegreen - As you say, you have done your homework, so I'm sure the last thing you want is more reading to do. ;) But there are so many discussions and FAQ's here on BER that covering them all in detail is impossible. So, a search on "blossom end rot" and more reading is in order.

It is a complex problem and has many contributing factors in addition to water and soil ph. These include the variety of tomato, air temps, weather (ie. excessive rain), over-watering, calcium soil levels, stress factors, over-fertilization, etc. Bottom line - something??? interferes with the plant's ability to uptake and move internally the needed calcium. And the opinions on how to deal with it are as varied as the factors that cause it.

I think most will agree that adding lime without first getting a soil test should be avoided. There is also the question as to how effecting adding lime after planting can be. In my personal experience, the BER is only a problem on the first fruit sets and with time the plant adjusts on its own. Most aggressive attempts to "fix" the problem only make it worse. Once the weather stabilizes and once any overwatering problem is eliminated all but a couple of the Roma varieties will eliminate the BER on their own.

As to how to measure? It isn't so much measuring as checking the moisture in the soil. Some weeks they may need more than 1" and some weeks less. A hose set on a medium flow and few minutes at the base of each plant each week should easily give them enough but first, you need to stick you finger in deep to check the soil moisture. When the soil 2-3" deep is dry they need water. If it isn't, they don't. Or when the plants begin to droop, they will tolerate that ok, water them. Keep in mind that over-watering is far worse for the plant than under-watering so when in doubt - wait. ;)

Hope this helps. Good luck with your garden.

Dave

Here is a link that might be useful: Blossom End Rot