Ethanol is a value added product of feed production and as such we will grow the same amount of corn with or without ethanol.

In fact, we had more acres of corn in the the 1920s, 1930s, and 1940s than we do today with 1932 the greatest at >113 million acres.  Compare that to 2015, the year corn ethanol mandate maxed out, at 88 million acres of corn.https://quickstats.nass.usda.gov/results/08C6BF8A-850C-3EDB-A929-C39BD2395217

Also, believe it or not we used more fertilizer in 1980 before ethanol than after.

http://www.earth-policy.org/images/uploads/graphs_tables/highlights43_top_3.PNG

Eliminating ethanol will not cure the problems found in industrial agriculture one iota.

There is much hope though with a fast growing movement in ag towards soil health.  See this pioneering farmer named Gabe Brown from North Dakota and the amazing things he is doing.

https://www.youtube.com/watch?v=GxIyKfWf9kU&t=2682s