Farming is a rather simple requirement for all settlements. Farming is based on a settlement's geopolitical position. For example, a small village may have a lot of farmland to substain its self and make money by selling surplus food. A metropolis or city may import a lot of their food from the village (although the metropolis/city still must have farmland). All settlements with farmland must have acess fresh water or a river. All harvest from plants and animals count as agricultural resources, and can be exported to other settlements or other nations if said settlement has an abundance of that resource. River valleys tend to make way more agricultural resources then a mountainous or semiarid region. Arid & subartic regions cannot make mass farming regions and must use greenhouses to produce food. Fertile regions include but not limited to: European plains, the Fertile Crescent, south eastern China, India, Middle Eastern Coastal Plains, Nile River Valley, the Great Plains, and the Pampas. List of tradeable agricultural goods found here.