Here is a part of Richard Manning's essay, The Oil We Eat.
$this->bbcode_second_pass_quote('', 'C')orn, rice, and wheat are especially adapted to catastrophe. It is their niche. In the natural scheme of things, a catastrophe would create a blank slate, bare soil, that was good for them. Then, under normal circumstances, succession would quickly dose that niche The animals would colonize. Their roots would stabilize the soil, accumulate organic matter, provide cover. Eventually the catastrophic niche would close. Farming is the process of ripping that niche open again and again. It is an annual artificial catastrophe, and it requires the equivalent of three or four tons of TNT per acre for a modern American farm. Iowa's fields require the energy of 4,000 Nagasaki bombs every year.
Iowa is almost all fields now. Little prairie remains and if you can find what Iowans call a "postage stamp" remnant of some, it most likely will abut a cornfield. This allows an observation. Walk from the prairie to the field, and you probably will step down about six feet, as if the land had been stolen from beneath you. Settlers' accounts of the prairie conquest mention a sound, a series of pops, like pistol shots, the sound of stout grass roots breaking before a moldboard plow. A robbery was in progress.



