One way is to get a 4-wheel drive tractor...but that is not a sure cure either. If the tractor is not climbing a dry dirt path, that must be pretty steep!
Another way might be to put chains on the rear tires.
I don't have any luck at all going up my back hill, even with chains on and in 4-wheel drive, if I have to climb over a root that is maybe 4 inches above the ground surface, and the ground is damp...the tires will not grip it, the chains will not grip it...the tires just spin and I have to take a different route...and again, I have 4 wheel drive.
So I doubt that if the tractor will not climb on dirt, that it would climb any better on wood, expecially if it has to climb up onto the wood, even if only a couple centimeters...
It is amazing how strong a tractor can be on the flat ground and how it can be stopped cold on a slope by something like a a root or your board (maybe).
My guess is that the board would not help much, if at all, but I have been wrong enough in the past to try anyway. Sometimes what one thinks should not work, ends up working...
How steep are those slopes? Maybe you could measure them and report back. Might help someone to give better, specific advice... /forums/images/graemlins/smile.gif