Heavy Plow is a technology in Age of Empires II that can be researched at the Mill once the Castle Age is reached. Once researched, it gives Farms +125 food (for a total of 375) and allows Villagers to carry +1 food. Crop Rotation is the further upgrade of this technology. Farms that were built before Heavy Plow was researched do not gain the +125 food bonus. If the Heavy Plow research is completed while a Farm is being built, the food bonus applies to that Farm.