Corn
From Tolkien Gateway
Corn is a general name for various cereal crops, barley, rye, wheat and oats.
In the Middle-earth, corn (of unspecified type) was brought out of the west by the Númenóreans during the Second Age.
Portrayal in adaptations
In Peter Jackson's The Fellowship of the Ring, due to the dialectical homonym of the New World crop (Zea mays), the Hobbits walk through a field of maize.