Originally Posted by treebeard55

Actually, Ganja, that looks to me like nothing more than a ring of mineral deposits that precipitated out of the water. Such deposits don't hurt anything unless they build up on the roots to the point where they interfere with the roots' function.

How's the tree's health? If it's showing no signs of distress, I would just keep an eye on it and proceed. With good drainage such deposits will eventually wash away.

Anyone else have a different opinion?