Crop Rotation is a technology in Age of Empires II that can be researched at the Mill once the Imperial Age is researched. Once researched, it gives Farms +175 food (for a total of 550) before they need to be reseeded. Farms that were built before Crop Rotation was researched do not gain the +175 food bonus. If the Crop Rotation research is completed while a Farm is being built, the food bonus applies to that Farm.