While the proximity to the road makes me wonder a bit, I’ve seen plenty of naturally-occurring features like that before. It could have started as a natural deposit, or it could have started with people putting out salt licks a while back, that eventually seeped into the soil. Either way, over time it gets trampled and torn up, and can be hard to say for sure (unless you still see remnants of a salt block…). But natural salt/mineral deposits are not an uncommon thing, particularly in a lot of western soils.