How large is the tree, and what kind is it? It is certainly possible to successfully move a tree this way. In fact, a lot of nursery specimens are field grown, then dug up for sale (ie, ball&burlap). OF course, cutting off some of the roots is damage, but the tree will most likely recover.

Alex

Here is a rough guide to how big a rootball should be. Soil type, tree species, and other factors are not taken into account, but it will give you an idea:

For trunk diameter below 1/2", multiply the diameter by 20 to get approximate rootball diameter.
For trunk diameter between 1/2" and 1", multiply the diameter by 18 to get approximate rootball diameter.
For trunk diameter between 1" and 1-1/2", multiply the diameter by 16 to get approximate rootball diameter.
For trunk diameter between 1-1/2" and 2-1/2", multiply the diameter by 14 to get approximate rootball diameter.
For trunk diameter between 2-1/2" and 4", multiply the diameter by 12 to get approximate rootball diameter.

Here are guidelines for rootball depth:

For a rootball with a diameter of 1', depth should be approximately 8".
For a rootball with a diameter of 2', depth should be approximately 1'.
For a rootball with a diameter of 3', depth should be approximately 15".
For a rootball with a diameter of 4', depth should be approximately 18".

A similar chart (measurements are in metric) can be found on Wikipedia, and I will supply a link below.

Here is a link that might be useful: Wikipedia Article on Transplanting Trees