Root pruning while planting from one container to another

Here is a finished #3 container maple with nearly a 1/4" diameter root clearly visible on the outside edge of the rootball. This should be removed before planting the tree into a larger container or into the ground.

Here is the same tree with all roots on the outside edge of the root ball being removed with a shovel. This so called edge root pruning removes a large percentage of root defects including circling and diving roots.

The edge of the root ball has been completely removed and is laying on the ground.

The edge-pruned root ball (right) is smaller in diameter than a root ball that has not been pruned (left).