I've got one spot that is very sandy and has not had much organic matter added to the soil. Each year I plant my overflow tomato plants and interplant with melons. Even with daily irrigation the results are fairly marginal. The tomatoes always get BER and the melons are stunted with meager production. Last year I enriched each planting hole with commercial potting mix plus added a good handfull of pelletized lime and slow release fertilizer. The results were the same, very poor. This year I've set plants in 3 gallon nursery pots into the ground after adding lime and fertilizer to the planting hole. Catch basins were formed around each plant. So far results are much better. BER is spotty with some plants avoiding it all together and fruit on other plants being perhaps as much as 30% affected.
My guess is that this particular spot gives elevated BER for several reasons. The sand is very poor with almost no organic content. The sand is so porous that available moisture swings through wild extremes between waterings. The problem is likely made worse because the full sun area causes the sandy soil temperature to get very hot in the top several inches. Also, oak tree roots are competing with the tomato plants for available moisture and nutrients. Finally, the sand is a perfect home for nematodes which damage the roots and disrupt absorption. The roots of any discarded plants are always riddled with the tell-tell knots of root knot nematode.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.