Does adding calcium or eggshells around the tomatoes help prevent splitting?
Certified GKH Gardening Expert
The splitting of your tomatoes is is called cracking and is common with tomatoes that have uneven watering. This article will help: https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-cracking.htm
Splitting is caused by irregular watering. If you allow too long a gap between watering so the soil gets fairly dry then give the tomatoes a good soaking, the plants take up too much water and the skins can't keep up with the growth of the tomato so they split. The answer is to water regularly and not let the soil dry out between waterings.