The plants were mostly grown in petroluem based fertiliser, factory farming of crops puts 10 calories in to get 1 out. Pre WW2 it was 1 in 2 out. The separatio

The plants were mostly grown in petroluem based fertiliser, factory farming of crops puts 10 calories in to get 1 out. Pre WW2 it was 1 in 2 out. The separation of livestock fed on subsidised corn from farms growing plants means lakes of "waste" manure that used to be used as fertiliser become an environmental problem instead of a solution. And for business minded farmers thinking about mixed agriculture they discover that corn feed is cheaper to buy than to grow.