A teaspoon of Sodium Nitrate weekly(The Snack at Earthbox) goes a long way to preventing or greatly reducing BER, which tends to be more of a problem in containers, although its not organic. As I said before organics can be a real challenge growing in sterile medium. Possible but not easy, or cheap. Those microherds (which are needed to digest organics to make them available to your plants) have a tendency to die off in hot climate containers. Then your plants starve to death. Kind of a boom bust thing. I recall quite a few discussions about this here and we do have some committed organic growers who use containers. I'm just not one of them.
