I'm not in aggrement on the mining of  nutrients, according to Einstein there is nothing lost or nothing gained, but it may be redistributed what is removed from the soil will be returned to the soil.  if you raise 200 bu. corn you are only removing approxiimately 30lbs/acer of P & K from the farm per year.  Even less is removed if you feed livestock and return manure to the soil.  As far as Nitrogen fixing bacteria yes it can do that, in good live ariable soil the oxygen is replaced every hour this is where bacteria can fix nitrogen from the air into the soil. This is why soil porrosity is so important.