Why would the loss of farms make it especially difficult for the southern economy to recover?

They would have to repair their farms and that will take a while

Assuming you are speaking about the United States the looks of farms in the south would be devastating. Farming is raising animals and crops. Much of the beef, corn, and many varieties of beans comes from the Southern states. If all of the farms went away the stock of those foods would dramatically drop and the prices would sky rocket. We would then have to import meats and crops from other countries because the north east and western parts of the states are not big on cattle and crops. This would dent the economy of the U. S and the lives of all the people living there.