"Premium lease with cash up front offer" - This sounds like cash rent/lease

"Heirs now claiming New tenant owes fertilizer bill to prior tenant." - This sounds like crop share.

Please clarify - which is it?

If it is cash rent/lease, and the old tenant bought and paid for fertilizer, and now is buying the farm..... why are the heirs worried about the fertilizer bill?

In the big scheme of things.... fertilizer bill is small potatoes compared to sale of property.  Sounds to me like heirs are focused on the wrong thing.  If they were worried about getting repaid for a fertilizer bill, they should have factored that into the price/settlement of the real estate sale.  My 2 cents.

Life is short. Time to move on.