After Geoffrey had obtained wheat seeds, he convinced Zion to produce wheat on the surface. They found a location where working power lines still stood, far away from the cities that the Machines had taken over, and began to set up ultraviolet (UV) lights. These UV lights, which drew energy from the power lines, allowed the wheat to grow and were protected from the rain by tents that they had put up. Geoffrey's plan had been a success, growing the wheat on the fields and transfering it back to Zion where it was made into bread for the other members of the Resistance to eat.
The operation slowly expanded and the skill of both farmers and bakers improved. While the trips to the surface still proved dangerous and problems did occur, they remained undetected by the Machines for years, mostly due to the fact that they were using a relatively small amount of power compared to what the Machines used. Eventually, however, the Machines found out about the wheat fields and moved into attack.
The Battle Edit
The events of what was later called the Battle of the Wheat Fields were unknown, but Resistance members eventually found out what had happened to them by hacking disabled Machines and looking through their recordings of the event. They found out that the farmers stood and fought the Machines as well as they could, but were ultimately no match against them.
The Resistance also found out that the Machines did not carry their bodies back to the liquefaction facilities, deeming it too costly, and left them in the wheat fields. Zion did not attempt to start another farming operation on the surface. Instead, they kept what stock of wheat seeds they had left in order to make bread for the citizens once every six months in honor of the sacrifice that Geoffrey and the farmers had made.