feeding a large army

ok for very large armies it requires daily work
first, buuils farms, lots of farms, researc agriculture as high as you can, and capture high level valleys that give you food bonus, look for the best you can manage

this will helpp for mid size armies, but for big armies, the invasion kind of 50k plus troops you need to farm
farming npc's gives you lots of food, your over all production will be red, but if are farming properly and often,
you will have a stockpile of millions, this feed army