If the plants are 4' tall and look healthy, you probably don't need to do anything this year.

And the only soil you want to use in pots or containers - anything with a bottom - is potting soil....NOT compost, not manure, not spent mushroom soil or garden soil or clay or sand. Just a soil-less mix labeled for use in pots and containers. Even Miracle Gro, which is a pretty inferior brand, is better than your mix.

And it doesn't hurt to add more potting mix now but probably not necessary.

gardengal, may I ask you to elaborate why manure and compost will not work in pots?

They serve no particular purpose and being solely organic matter, will continue to degrade and decompose, resulting in increasingly small particle sizes that adversely affect drainage and aeration. The soil mix collapses and compresses and becomes excessively water logged.

This should be required reading for anyone growing in containers :-) Container Soils - Water Movement and Retention

It's a long read but oh, so worth it for the amount of info it contains!!

gardengal, Thank you very much for the link. I started reading it and it is very informative but it is huge! In addition could you recommend a concise guide for a noob tomato grower, specifically a container one!

LOL!! I don't have any published reference but to condense what was stated in the link.........

• Use a good quality potting/container soil. Nothing else added.
• Use a large enough container to accommodate root development and with adequate drainage.
• Water as necessary to keep the container soil consistently moist - never too wet nor too dry. When you do water, flush the pot thoroughly so that water runs freely from the drainage holes.
• Fertilize weekly with a quarter strength solution of any liquid or water soluble fertilizer.
• Follow other tomato growing practices: plant deeply, use a cage or trellis to support; provide plenty of sun, etc.

Thanks for the summary. I read it all - at first I got an impression that is would be very long read like 800 pages but it was just few pages long. It was very informative.

My problem is that I already have my plants planted and they are in a wrong soil. I am trying to find a solution on how can I improve situation now. Obviously. I need regular fertilization. But since several plants have a lot of extra space on the top of the pots available to add additional soil I am would like to learn what will happen if I add about 4-5 gallons of good soil on the top of the pots? Will tomatoes make new additional roots in the new soil or it will just make the stem to rot and some other side effects or problems?

I would add a couple of inches of a good POTTING MIX and carefully (maybe just using your hands) gently mix it with the first couple of inches of what is already there then add maybe a couple more inches of just the mix.

I bought several bags of Miracle Glo potting mix and the reason I did not use it much was that it did not look like soil which I remember from my childhood. I understand that is was intentionally made this way to control watering of roots. At the same time it looks like it has not nutrients! Is it a wrong impression? It says it is good for 9 months - can I trust its label? Would I need to fertilize it often?

If the leaves are green and healthy looking, don't worry. Unless the stuff in your pot has a time-release fertilizer in it, fertilize regularly with a diluted liquid fertilizer.