I save all my egg shells and when I have a bunch I grind them up in my Vita-Mix till they turn to powder. I put a mixture of 1/4 c. egg shell powder, 1/4 c. powdered milk, 1/4 c. epsom salts and a shovel full of compost in the holes before I
plant my tomatoes. Then I sprinkle 2 tablespoons of powdered milk on the surface around the
plants. (Do this last bit every 2 weeks throughout the season) This is called The Mighty Milk Tomato Blight Cure, (I added the eggshells to the recipe) but I haven't had any blossom-end rot either since I've been using it.