The question of holding or obtaining a licence is not the issue. Even if you did, by some surreptitious means, manage to obtain a licence, you are still not allowed to drive.
When you are disqualified from driving you will be told by the Magistrate (or District judge if the court is presided over by one on that day) that “...you must not drive any mechanically propelled vehicle on any road or other public place for the duration of your disqualification.”
This is quite a straightforward instruction and an agricultural tractor falls within the definition of a mechanically propelled vehicle.