Q.Eggshells for Tomato Rot
Can you put eggshells by the root of your tomato plants to prevent tomato rot? Will this add enough calcium? When I planted my tomatoes this year, I put eggshells in with the tomato plants to prevent tomato rot, but I still have it.

Certified GKH Gardening Expert
Eggshells can help prevent blossom end rot, but not immediately. Working eggshells into the soil or composting them will eventually raise the level of calcium in the soil but it will take several months, even a year before it has an effect.
Beyond that, most blossom end rot issues are caused by the inability of the plant to take up calcium in the soil and this is normally cause by not enough water or uneven watering. Increase water to the plants and this should help.
This article has more information:
https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossom-rot.htm