I have noticed that the yield of the fields was increased a short time ago (http://trac.wildfire...changeset/13405). How about instead the yield of the fields are lowered and when the fields are depleted, there is a regeneration period, probably represented by a grey progress bar, during which the fields cannot be harvested for food. Workers can still work on the fields, not collecting food, but making the fields regenerate faster. This would eliminate the need for new fields to be built when the old ones are depleted.