Anney, I can't speak to growing potatoes where tomatoes had previously grown but I grow tomatoes in the same bed year after year with no problems. For instance, last year I had Tomato Spotted Wilt Virus affect two plants in two rows that were located side by side. This year, I've had no TSWV on any plants including the spot where the two plants that were grown last year. I know some large commercial growers that do rotate their crops but they are very large scale operations. At the end of each season, I amend each bed with compost and composted cow manure and thats it.

Jay

Same as Jay here - same beds year after year after year. A good load of leaf mold and goat manure in the fall and lots of fresh compost in the spring and lots and lots of straw or hay mulch after planted. Had a couple of early blight plants 2 years ago but no problems last year or this one...so far. ;)

I haven't grown potatoes, except in 55 gallon plastic drums. I have raised beds and containers and have been growing tomatoes in the same spots for about 8 years. This year (last fall) I "sacrificed" 1 tomato bed to plant 10 varieties of garlic... YES, it really hurt me to do it!

The only real rotation I do is on the 4-gallon containers; I try to dump 1/2 to 2/3rds of the mix where I grow pumpkins, reuse the rest of the mix and the tomato containers for peppers, and v.versa, use the pepper containers for the tomatoes. Most of the pumpkin "patch" is compost, at least the top foot or so, and the tomato & pepper mix was about 2/3rd ProMix BX or Fafard's and the rest compost, so it helps bind the compost together. That's about the extent of my crop rotation.

I think the biggest concerns with tomatoes/potatoes is Blights. That's why they recommend not following one with the other. Early blight is pretty common. Late blight isn't much, at least not in my area. Tilling the soil doesn't help the problem--it's been recommended to actually try to "flip" the soil to "bury" any traces of EB that was on the surface that can splash back up, since it's mainly a foliar disease. I don't have any real personal experience with late blight, though one year I grew All Blue potatoes in the drum and the symptoms may have appeared, in the drum, as the plants died "almost overnight," turning dark green to almost black with the consistency & texture of slimy, overcooked broccoli. I was using soil & soilless mix in the bottom, covered by shredded straw. The tomatoes 10 feet away were perfectly healthy. I haven't tried growing potatoes since.

Also, systemic diseases can build up over time and get worse, but sometimes they are harder to cure, short of replacing the soil.

Hope this helps.

I grow in the same beds too, but I do dig in compost, grass clippings or rotted leaves every year to improve the soil. This morning I was digging in grass clippings. Building the soil does make for better beds, so certainly do that for a continually good harvest.

Maybe all the microorganisms and micronutrients in continually replenished composted material guard against diseases/viruses or make them ineffectual by strengthening the plants.

Maybe you just have to do what you want and see what happens.

The reason I asked is because I want to grow some potatoes next year, and there will be only one section that hasn't had tomatoes in it over the past couple of years. And I thought I'd use that virgin spot for tomatoes next year.