For the last 4 years I have lived right next to two crop fields that are worked, but not owned, by a local family that has been farming here for many generations. They have never rotated crops in the time I've been here. One field is always corn, and the other is always squash. Every year they plow in fertilizer, flood irrigate, and spray who-knows-what on everything. What's more, they rarely harvest any of it. At the end of harvest, they always tell us we are welcome to pick whatever we want. Did that once and never did it again; everything was completely flavorless. Then they plow it all under and do it again the next year!
I can think of only two possible reasons for this behavior. One is that they would lose subsidies and the land owner would lose tax discounts if they don't grow anything on the land. The other is the big increase in deportations since Obama got in office and tougher state level regulations have made getting farm labor to pick stuff more difficult.
With millions of pounds of food uneaten and wasted every day around the world, I don't think crop yield is a problem. Economics and logistics are the problems in getting food from the field to the people that need it, when they need it. The business model of companies like Monsanto, getting rid of small local farmers in favor of big industrial farms and prosecuting seed savers, makes those problems worse, not better.