Frenchy21 said:@Zuni your method for planting the tomatoes could work for me. 
I will try 4 tomatoes in 15 gallon pots and the rest in the ground. this year. I normally plant about 8 to 10 indeterminate plants each year but have been putting them in the same spot for at least 20 years.
I have nowhere else to put them so I think I need to switch to large pots for a while. How much soil do you need for a 15 gallon pot @Zuni? and what kind? Do you use potting soil mixed with compost? Also which food do you feed them? Thanks for your and all the others' contributions on this thread. Very helpful.
@Frenchy21 Uh oh, one of my favorite subjects...prepare for a way too long post LOL...
What fun! I really think you could plant tomatoes in the same space forever, as long as you feed them, and add some good stuff to the soil when you plant them. But, to your questions:
Good question on the 15 gallon pot and how much soil you need - not sure - but, as a point of reference, I just planted my Zuni crape myrtle tree (X-mas present to myself) in a pot that is just a little under 2 feet square. The Zuni was in a 5 gallon pot, and I put that plus 72 quarts of soil in that giant pot (four 16 quart bags of Black Gold and 2 cheapo 4 quart bags of potting soil from Dollar Tree because I needed some more and was too lazy to drive farther to get better soil LOL). I found a calculator online and that equals about 2.8 cubic feet of soil.
For a 15 gallon pot, I'd guess it would be 1/2 of that, roughly. So, around 36 quarts (2-16 quart bags, maybe?) Or about 1 cubic foot. Here's the calculator I found:
http://www.metric-conversions....
My favorite soil right now is expensive, and I am not buying a lot of it, so keep that in mind. I use Black Gold, which is organic and just simply amazing stuff from my results so far with my bougainvillea and freesia bulbs and some cuttings I have going. I have found it on Walmart and on Staples, believe it or not. I have Staples rewards, so last time I bought some Black Gold soil from Staples with my rewards. Walmart has the best price, though.
https://www.walmart.com/ip/Bla...
I've looked at reviews for other soils and haven't been impressed. I personally have had bad results using the Miracle Grow soils that you find at Home Depot, etc., even though I've had good results using their fertilizer. I'm not impressed with their soil. Otherwise, I just bought whatever veggie soil that I could afford for my containers and fertilized them with Miracle Grow in a liquid form. I'm trying to be more organic now, but admit I'm not a purist. I don't use non-organic pesticides, but I will use synthetic fertilizers. I think you can use a cheaper soil, if you are religious about feeding, but I have learned with the Black Soil, that if you get a great soil, you don't have to feed as much, at least not for a while.
My new favorite Youtube guy is nctomatoman and he uses a cheaper soil that he swears by for both seedlings and plants. Can't remember the name of it, but he mentions it in this video where he shows how he dense-plants tomato seedlings - I am going to try this method, as I think it's brilliant. He sprouts seedlings all jammed close together in a cell, then separates them and buries them deep in their pots, getting better roots really early. Very cool. I bookmarked it, so I could also re-visit what soil he uses, too.
https://www.youtube.com/watch?...
As far as fertilizer - I admit that I used the Miracle Grow that is for tomatoes/veggies when I grew mine indoors, and when I grew tomatoes in containers outside with great results. I understand Miracle Grow is owned by Monsanto, so you may or may not want to give them your business. It's a simple synthetic fertilizer - so not dangerous to the environment, and safe on edibles, but not certified organic.
What I've done in the past, though, when I could plant them in the ground - and would enable you to keep growing yours in the same space over and over - is to dig a great big hole for my tomatoes, then fill that hole with composted manure & some soil mixed in, but mostly composted manure. If you can afford any organic soil amendments, you could add that, too. I never added any other kind of fertilizer when I used to just grow mine in the ground, except for really well-composted manure. I happened to have some in a barn, but you should be able to buy it. And it would be way cheaper than buying organic soil.
Then, you put a bunch of the composted manure into the hole, then put your tomato plant in the hole, but don't fill the hole all the way back up yet (unless you have to worry about a big rain storm filling the hole up with water). Then, as it grows, you prune the bottom leaves, and add more soil. By the way, this also works great with potatoes, but with potatoes, you just keep piling straw around the plants as they grow. Then, you can just lift up the straw and grab a few potatoes for dinner! Works famously.
Here's a guy on Youtube that I really like, who I mentioned in the previous post. He explains how to plant the tomato down into a pot (or the soil) and trim the side shoots and then keep burying it as it grows, to give you more/better roots:
https://www.youtube.com/watch?...
He has great tomato tips on doing it the way I do it. He actually inspired me to try growing them indoors in my apartment and it worked great. I had never grown them inside before, and when I was searching for videos, I found him.
Since you have the space, it might be cheaper and easier for you to just get a bunch of composted manure and dig some holes and plant your tomatoes in the ground. Watering would be way easier, too. You could mulch them. I really don't think you need to worry about wearing out the soil - not if you dig holes and add a bunch of composted manure, so you're amending the soil. Plus, I bet the worms would find it and help you out, too.
You can manage how tall they get by pruning them when they get to a height you want them to stop at. That nctomatoman shows how he actually was growing some tomatoes in containers that were really small containers, and he was aggressively pruning them to get them to flower and produce fruit more quickly. And he explains how to prune them to keep them to the size you want them to be.
I always did a modified version of that. I didn't want to deal with all of the work it would take to manage them to that degree, so I just got bigger pots and only pruned in order to get maximum production out of my tomatoes.
As you can see, even though I don't have the space for a huge garden anymore, I'm still addicted to seeing what other gardeners do and I love learning new techniques, etc., and the youtube guys above not only do what I learned, but have taken it to another level, and they're really good at explaining it with visuals that make it easy to see and learn.
I'm jealous of all of your tomato space! I'm going to try growing some plants for sale in my bedroom in my apartment this year. So, I was psyched to learn nctomatoman's technique for getting nice, bushy seedlings, so I can ask top dollar. Since I can't grow them all to fruit, I can still grow a bunch of them to sell and enjoy that part of the process anyway.
