What causes tomatoes to have soft, black bottom?

[Fineas_Ranch]

My last experience with tomatoes was back in 2008. We purchased several small tomato plants from a local greenhouse to grow. When the tomatoes started to turn red, most of the tomatoes had soft, black bottoms. What would cause this? We had several different plants and it happened to everyone.

[Kisal]

That was probably blossom end rot. If you use those words to search the forum, you'll find a lot of information about the problem and what to do about it. It's been discussed here quite a bit.

[Fineas_Ranch]

Thanks. I'll definitely look it up

[Kyt]

The cause of end rot, blossom rot, is due to a calcium defficency. You have a lack of calcium in your soil, it's an easy fix just add calcium to your soil. I would suggest Calmax, it's a concentrated liquid or Neptunes Hravest Crab Shell.

[TZ -OH6]

You can induce BER by growing in soil that is calcium deficient, but in most cases there is no problem with the soil. Even with normal calcium levels in the soil physiological stresses cause problems with calium transport within the developing fruit. Fluctuating soil moisture and rapid growth caused by high nitrogen are factors, as are weather conditions. Deeply dug, well amended soil usually takes care of the problem in multiple ways. If the soil is lacking in calcium you would expect the pH to be too low (acidic) for optimal growth.

[rainbowgardener]

As noted, please use the search the forum to read some of what has already been written here about Blossom End Rot.

Here's just one sample:

https://www.helpfulgardener.com/forum/viewtopic.php?p=86031&highlight=blossom+end+rot#86031

Agree with TZ that the problem is rarely a lack of calcium in the soil. It is a stress reaction in the plant that causes it to have difficulty uptaking the calcium. You need to figure out what is causing the stress.