If they are using the futures market to sell forward, no cash exchanges hands until settlement. And why would higher production be a problem. Lower production would be a problem, i.e. promised to deliver 100K bushels and a flood wiped out 50k so trouble. The farmer would have to go into the market and buy 50K to deliver. In real life they would go flat on those 50K before expiration and pay the cash difference.
I said if actual production is higher, the price will go down. But yes, that’s a problem for the buyer, not the seller.