Your resource tiles, like your farms, ONLY produce new food if you have extra room to store it. This can become a problem if you are trying to store an unlimited amount of resources.
In my earlier example where my farms have room to store 1.5 million food, my farms will stop producing new food when I get to 1.6 million food because my farms can only store 1.5 million food. Even if I’m supposed to be producing 100,000 food an hour my farms won’t produce food because there is no where to store it. Again going back to my point earlier. Why bother having farms? I only need 1 level 9 farm for my research. I can buy food or loot food from other players. Somehow the game has a bug where I can loot or buy more food than I can store in my city. I can also transfer resources between my cities and go over my storage limit. It seems as if the storage limit only effects whether or not my farms, mills, quarries, and mines produce new resources.
Ok I sort of lied. Your farms will produce food if you are negative. This will help offset the amount of food you are negative. Maybe that was a bad example. Let’s use another example. When you have say 15 million lumber your lumber mills aren’t producing any more lumber. You may need to either sell off some lumber at the market or build more lumber mills to store the extra!
I really just hate food that is why I used that example! 😉