What would cause vine tomatoes to burn on bottom?

Question

1st year growing garden in raised pine boxes. Tomatoes at 3-4″ diameter, show large discoloration. See photo.

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Answer 1

This is blossom end rot. This is caused by a lack of calcium, and often magnesium. The solution to correct this is absolutely simple, but can be caused by environmental factors as well.
Dolomitic lime works well. It will provide calcium, magnesium, as well as keep the soil pH balanced. This, alone, will stop the rot completely most of the time.

This article will help: https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-blossom-rot.htm