Those smart farmers will eventually come to a realization that the only real form of money is the food they put in their mouth.
Because of that reason, the value of their farm cryptocurrency will only go up. Other paper currencies will always be manipulated and beaten down by central banks' frauds.
Here's an example:
A lobster farm will release their own cryptocurrency called Lobster coin
A clam farm will release their own cryptocurrency call Clam coins
A crab farm will release their own cryptocurrency call Crab coins
A tuna farm will release their own cryptocurrency call Tuna coins
These farm coins will be back by real money value also known as food value.
(put money where their mouth is)
I think it make no sense to build coins for every farm/food. Because cryptocurrencies are backed by blockchain technology, which supports decentralized services.
First thing food is composting material so it has limitation in distribution globally. Also if such coins listed in crypto market who will decide price of such coins.
And most important thing is we can use blockchain technology as service to give better administration, governance and system. We cannot use it for trading of physical things bcz price matters. In such cases fiat currency always play important role.