As long as you won't be driving it on the road, buy a tire tube (used way back before radials). Depending on how big the cut is, you could put some rubber, a tire patch, or other material inside to cover the cut so the tube does not squeeze out. Tubes can be found at places like Tractor Supply or farm stores as they are used in older front tractor wheels and implement wheels.

Once again, DON'T DRIVE IT THIS WAY.