Note, it is far different for these crops that were once farmed: -cotton -Tobacco And that is about 30 percent of USA farmland....the main pollutant bei

Note, it is far different for these crops that were once farmed: -cotton -Tobacco And that is about 30 percent of USA farmland....the main pollutant being arsenic Even in land producing corn...the soil loses enough that several tones need to be added per acre. They use to rotate between beans and corn to keep that expenditure down....as beans replaces nitrogen taken from soil by corn... my bias, worked Uncles farms during childhood each summer.