Crushed rock, probably 4" plus is the classic inexpensive solution.
If you are not in a hurry and don't mind a little hand work, and assuming you have rocks available (looks like there is a little in the photos):
Throw stone into wheel tracks when the ground is soft. Drive over it, and repeat. Rock gets driven into the ground and becomes firmly bound and actually rut-proof.
Your wheel tracks will be solid like cement, and the rest of the road can be seeded to grass. Done correctly no rock will stick up and the road can be mowed.