Rotating crops is beneficial because:

1. It helps discourages buildup of pests and diseases in any one area of the garden.
2. It helps prevent depletion of the particular nutrients that any given crop uses the most.

There are other more esoteric reasons, such as using heavily cultivated or mulched crops to break up a weed cycle, and 'scheduling' rotation to take advantage of beneficial relationships between different types of veggies.

That said, there's no reason you CAN'T plant things in the exact same spot every year.

Even Eliot Coleman, the well-known organic guru who has made rotation as much an art as a science, deliberately keeps a tomato plot, which he even uses composted tomato vines on, to prove that good organic methods can overcome
less-than-optimal conditions.

So if you're adding back organic matter and mineral supplements at least every other year, you should be fine.

Alan I am an organic grower and I use a lot of compost in my garden. I have grown tomatoes in the same place for 16 straight years now with no ill effects.

My mother has grown tomatoes in the same spot for over 30 years now and has had good success as well.

I look at it this way. If weeds can grow in the same spot year after year after year, tomatoes can too...:)

I grow tomatoes in the same beds year to year, but I do improve the soil before planting. I dig in grass clippings and fallen leaves. It seems to be a good thing.

You just need to do a bit of research. Figure out which nutrients tomato plants leech from the soil as they grow (the major ones anyways). I think they use lots of nitrogen but I'm not sure . . . anyways, look into that. Then, when you ammend the beds for the next year's planting, use lots of organic material and compost, and pay extra special attention to those nutrient to make sure you replenish them.

If you replenish the soil properly and completely each year, there is no reason why you can't grow them over and over in the same spot.

Hi Alan and the group, one thing I like to do is not plant next years crop in the exact same spots as last years. Try to picture what the root zone of each tomato plant would look like under ground (a large 18 in or so pot would be close).

At the end of the season the root zone can be dug up and fresh compost and amendments added. Then next years tomatoes can be planted off to the side by 3 feet or so to allow the soil to recover. I use this trick to help keep root knot nematodes (RKN) at bay. Don't think you will have a problem with RKN but this trick may help keep your garden going forever.

Later, DC

Alan,
You're testing heirlooms, so I guess you plan on saving seeds for replant? I would be more concerned about cross-pollination with 25 varieties than whether or not to replant in the same place. Just a thought.
Tom

I grow in the same dedicated beds now every season. If you don't own a farm you can't be that picky about "rotation". Basically, you put the tomatoes where the good sun and soil are. I replenish my soil with plenty of organic matter and I never have a problem.

Tomatoes are self-pollinating.