Considering that the farmer had to cut down mature trees to clear enough land to plant a first crop, the answer might be 5 to 10 acres, at first. Over a number of years, this would be enlarged.
The main reason why the Allies agreeh to fight until the Axis Powers surrendered unconditionally, which possibly prolonged the war, is because anything short of an unconditional surrender would leave room for the Axis to re-mobilize.