Yes....but it is calcium and regular watering that helps to prevent blossom end rot in tomatoes. Just don't let the tomatoes dry out then soak them water. Keep the soil evenly moist and use a fertilizer with calcium and other micronutrients to prevent the cracking of the skin. The most important ingredient for happy tomatoes is sunshine and warm nights. Keeping the foliage dry also helps to prevent cracking and leaf blight disease. Keep growing, Marianne Binetti