Second year in containers - new soil?

[OrganicTexasMama]

Do I need to replace the (soilless) mixture in my containers for a new year? I have some tomato starts I need to get transferred, but have been putting it off as I haven't had a chance to get new soil. Wondering if I can just go get my hands dirty, now, or if I need to replace what's in my pots?

FWIW, I'm planning to put the tomatoes in a pot that had watermelon last year. Also looking to start new cucumbers (which were attacked by whiteflies or something of the sort last year and finally succumbed), but in the same pot as they were in before.

Thoughts?

[Marlingardener]

Can you add some compost, or composted manure to the old soil? I think that would be beneficial. If that isn't possible, you can always fertilize a little more heavily than usual to replace any nutrients the watermelons used up last year. And planting the tomatoes in pots where they were not last year is a very good idea!
If your cucumbers had problems in that pot last year, I'd replant it with something not in the curcubit family. The whiteflies can act as a carrier of viruses which attack curcubits, and might be in the soil. Maybe?

[OrganicTexasMama]

Thanks! That sounds like a good way to go!

[PunkRotten]

For some of my potted plants going on a new year, I added compost with rock dust and organic fertilizer mixed in.

[Green Lab]

How much part compost to part old soil. We have a 55 gal drum full of old dirt from pots used before. We want to use it to plant in containers. But we don't know how much compost or manure to mix per part of old soil. We have a compost pile we started last fall and we have a staff member that can get us manure (pig or horse).

Thanks