Refresh the soil in the planters, adding a bit of new material, and be sure to fertilize. If you didn't have any diseases last year, it should be fine.

Josh

You can do that to guard against wilt diseases. You might load your clean tank sprayer (no herbicides) with a 10% solution of household bleach or H202 and spray it down. Bleach prolly needs rinsing but the H2O2 doesn't. Toss the old soil on the compost pile. If you're up for it, you can make your own soil at (usually) less than half the price of commercially prepared mixes.

Al

Here is a link that might be useful: More about soils if you click me!

If you did not have any disease problem, last year , I don't see a reason to toss the old soil or do anything other than refreshing it , adding nutrients, manure etc.

There is an old schooh called "ROTATING CROPS". It is supposed to be a preventive measure, BUT it is not practical for a backyard gardener with limited land/container resources. The guy who advised you, probably did not know what he is talking about. With a small container (several gallons soil) It would be probably wise to change the soil completely but with a big planter (16 cu-ft = over 1/2 cu-yd), which is very similar to a raised bed, replacing the whole thing does not make any sense, at least to me. some of My raised beds are 2.5 ft by 5ft by 1ft ( 12. cu-ft, much smaller than your planter)

This is just my opinion.

I think that any diseases in one planting box would easily be transferred to the other boxes. I have planted tomatoes in my garden without worrying about where I planted them last year with no problems yet.

It is also suggested that you do not have potatoes where you had tomatoes last year because they get many of the same diseases. This is a rule I have also had no problem ignoring.

Like everyone else, I would ignore that advice for a home garden. Just be cognizant of the issue if soil diseases become a problem.

Another thing is that MOST tomato diseases are AIR BORN.