Who will do the work? Not excusing illegal immigration, but to be honest there are few people period working right now.
The corn used for ethanol is not going into human food, and the places that grow that corn do not grow human food.
With input costs the way they are, CRP land may be the only way to make positive cash flow. Even with that, most farmers are going to plant.
The question is will they harvest?
People adapt to a change in environment. When the welfare state was introduced over half a century ago, people didn't change overnight. In time our culture has changed to where there are lots of people who expect money for nothing and chicks for free.
If we get rid of the welfare state people will adapt again to working for their food like before. It's amazing what people will do to keep from starving.