Add lime or calcium carbonate to your tomato plants when you dig the whole at planting time mixing in about one cut per one gallon sized plant. If you are growing tomatoes in a container use half a cup per plant, mixing in with the potting soil before you plant. Not all soils need extra calcium and a soil test will help you decide. You may not need calcium at all if you use a complete plant food like Osmocote that contains all the major nutrients plus miconutrients including calcium in one application. Keep growing, Marianne Binetti