yes its possible. the only bad thing is if you planting or replanting substrates you can mix it up and could cause a mess. also if you have any fish that will kick up the substrate. make sure you get organic soil with no chemicals added.
ok well my plan would be to have a layer of soil then on top of that a layer of gravel to keep the soil undercontrol.
______________gravel___________________
--------------------soil--------------------------
Yes you can use "organic" potting soil as the under layer of a planted tanks substrate. People have been getting some amazing results using it for some time now. I have seen most people use a 2" soil layer capped by a 1-2" layer of sand or gravel.
They only things to watch out for is the initial decomposition of the soil once it is submerged. They say it last for a couple of months. And in that time you are not supposed to have any fish in the tank because the release of ammonia and gases is to extreme for your filter to keep balanced. But it needs to be fully planted during this time.
After that the only fear is mixing the layers and causeing a cloudy mess. You can pretty much bet that it will ahppen sooner or later when using soil. But just be aware of it.
My 29 gallon is planted with cheep potting soil and gravel on top. I don't have any bottom dwellers in this tank and I try not to move stuff. You can if your very careful and then do a water change carefully vacuuming the dirt off the bottom.
With this tank you rarely do water changes. Recommended to only do one every six months unless there is a problem.
This is not my first tank to set up like this but it is my largest.