Living on a farm owned by father son has been working the farm paying all the bills and making improvements

It is the son who has been living on his father's farm? Is there any agreement in writing regarding this? If not, yes he can be evicted.

I see that this appears to be related to another post, apparently another facet of the same issue. The two should be combined; it would help us give a better answer, for one thing. It might be possible to counter-sue for what the son has done and paid. See my other answer. But a mechanic's lien wouldn't normally be necessary for such a counter-suit.

Is there a lease agreement between father and son? If not, the son is considered a month-to-month tenant, and the father may evict him with proper written notice giving a date when the son should be gone (per laws of the state) followed by obtaining a court order.

Some laws are cut and dry; many aren't. If you would be willing to tell us the whole story, we can perhaps give extra advice for a father and son to help settle their differences.
The son has done improvements and maintenance, while the father has provided a place to live. Each is worth something. Rather than suing and evicting, maybe they can make a list of what each feels is the value in dollars of what they contribute.

As noted, more background is needed. Also please advise whether this is related to your post about a Mechanic's Lien. If so they will be combined.

Merely living there as a tenant, gives him no rights,

What will matter, is any written agreement between them,

What repairs where made ? Why? What was agreement about the repairs,

But normally, without a written agreement, or without him being part owner of property, yes he can be evicted