When overtaking a tractor with a loaded trailer you must assume that the operator driving the tractor has very poor rear visibility.
You must also be aware of the fact that tractors can turn off the road – both to the right and left – almost anywhere. The tractor operator might be heading out onto a field or into a forest.
Just as with heavy trucks, there is also a risk that tractors increase their speed going downhill and that the tractor operator may not be able to keep to the right – or in the worst case, is forced to veer left – due to an obstacle further down the road, which you cannot see.