If the farms are passed down as an asset that will continue to be worked by the heirs, there should be no inheritance tax. If there is, it's most likely parts of the farm will need to be sold off to pay.
If the farm is passed down and subsequently sold, possibly with a stipulation of timeframes allowed, then inheritance tax should be paid.
That way, the loophole of buying farms simply to avoid paying inheritance tax is closed, and family farms can continue the great work they fo of feeding the nation.