The archaeologist Payson Sheets, in his excavations at the archaeological site Joya de Ceren in El Salvador, found that in addition to growing corn the residents were growing manioc (also known as yuca and cassava). In fact he found that corn alone was not sufficient to support the population that existed there, but that manioc was capable and would have provided enough nutrients to sustain the population. He feels that in many cases the estimated population of ancient sites has been under estimated based on a diet of corn alone, but that if manioc were included that the populations would have been much greater.
In comparisons manioc has twice as many calories and twice as much carbohydrate as corn so a grower can basically grow twice as much in the same space with manioc than with corn. However corn seems to have more of the vitamins and minerals than manioc so there would be trade offs in the use of each one.
Manioc is easier to grow than corn. It is draught resistant and can be grown in poor soil. It is more resistant to pests and disease. It is propagated by cutting the old stems into 6"-10" lengths which are then planted by inserting into the earth 4-5" and waiting for it to grow. The new growth sprouts out of the nodes that are above earth. Manioc takes longer to form the tubers than corn does to form ears, but many chose to grow manioc instead of strictly corn. Manioc can be grated up and dried and then ground or pounded into flour.
These are some videos that illustrate the growing of manioc:
https://www.youtube.com/watch?v=cG0jpI8UvRU
https://www.youtube.com/watch?v=TkvJ7P9U1Ws
https://www.youtube.com/watch?v=jyKPhaZw_0w
