A bushel of corn weighs 56 pounds (shelled) or 70 pounds (still on the ear). Using the shelled bushel in this case, 1 pound of corn = 1,656 calories so each bushel is roughly 92,000 calories. With the record yield of 500 bushels/acre that can feed 60+ people for a year!
I can't think of anything else that can come close to that kind of yield. No wonder corn syrup is in everything...
500 bushels/acre is probably not scalable. For corn, if you get 150 bushels/acre, you are doing well.
I think the grand champion of caloric yield per unit area is actually the sweet potato. But potato is second place, has more protein, and a better sale price. Also, sweet potato contains raffinose, meaning that it will give you gas.
Browse fao.org for a bit for more information on the nutritional yields of various crops. Though last time I checked, there was no comparison with perennial tree crops like oil palm, neem, and jackfruit.
I think you're making an error there somewhere, possibly mixing calorie yields per year with human requirements per day.
Divide that by 365 for a more realistic estimate. About 60 people per acre if you can maintain the world record yield, or about 15 with the mean US yield.
I can't think of anything else that can come close to that kind of yield. No wonder corn syrup is in everything...