There's an interesting article in the July Smithsonian Magazine which discusses the incredible success of corn yields since the introduction of synthetically produced ammonium nitrate fertilizer. Apparantly, it's all about "usable" nitrogen. There's lots of it, but it must be combined with hydrogen in order for living things to grow and prosper. Mother Nature can only do so much of this, so fertilizer takes over from there. The writer cites an author who estimates that 2 out of every 5 humans on earth today, would not be alive if not for synthetic fertilizer. Not a bad thought, only we don't get to choose who stays and who goes. But this success comes with costs (pollution from factories that produce the fertilizer, high energy use to produce, runoff into rivers and oceans, etc), which he also discusses.