Agricultural subsidies- more digression.
Corn is the primary U. S. dollar crop because of the demand for meat products, cattle, hogs and poultry, and its use in many human foods as processed grain as well as sweetener. It is important in the fattening stage and is often mixed with soy; grass cannot support the cattle and hog populations. Grass-fed cattle take much longer to reach saleable size and thus are more expensive to raise. The cost of fossil fertilizers is a factor in raising corn, but also every other agricultural product on the mass market, human or animal.

Corn was, and is an important food for humans- first in America, and currently in Africa.

U. S. Subsidies-
Corn- $4 billion
Cotton- $2.3 billion
Wheat- $2.2 billion
Soy- $2 billion
Rice- $0.5 billion (as high as $1.5 billion in 2003)
etc.