A bushel is 8 gallons of dry goods, or roughly 32 liters. A bushel of wheat, for example, weighs 27 kilos, or 60 pounds.
We can't expect a single soldier to carry more than a bushel, really, and even that is probably a stretch. Even then, that means a medium sized army could remove 500 bushels from a single region, which is certainly enough to cause problems in most cities.
27kg? That's heavy. I do not think a soldier can carry even a bushel if you think about the weight of equipment a single soldier carry around. If they are well armed, they will probably carry at least 15-30 kg.
But if we want to make things simple, I guess we can make them carry 1 bushel. Don't forget. BM is a high tech game.
