Any farm worth less $3.5 million wouldn’t get taxed at all. And farms worth more than that are already getting taxed for inheritance at 40% for the amount of value over $5.45 million (over $10.9 million for a couple).
And any farm worth millions of dollars is a really big farm. Not the close family-owned mom-and-pop operation you imply. A farm that big can have parcels of land sold to others or people can buy interest in the farm in order to pay taxes. Or, as this would be a one-time tax bill, a payment plan can be worked out with the IRS. There are any number of ways that an heir to a farm that size can keep it or keep most of it.
But I realize this ruins the narrative of the right, to do away with the estate tax altogether, because — “the farms! the farms!”