I have always raised a very large garden and usually set out a hundred tomatoes if not way more! I always dealt with blossom end rot and would usually throw a wheel barrow load away while picking ....until I had an old truck farmer give me some advice! He told me to get a bag of "basic slag" and put a handful under my plants when i plant them! I cant speak for anyone else but it has absolutely worked for me! I have been doing this for probably ten years and I bet i have not thrown a bucket full away since then! I do the same thing under my pepper plants also.