Is the a separate drivers license for a low speed vehicle like a tractor?
A driving licence is needed only for driving a vehicle on a public road.
A code B licence (light motor vehicle) allows one to drive a tractor too. A B5 licence authorises the driving of a tractor only, not other light motor vehicles.
The B licence covers all industrial and farming equipment.
The 5 and 7 are endorsements to a Code B licence:
A list of the basic driving licence codes is shown on this Web page:
Learner’s Licence & K53
Driving Licence Test Info