Corn futures closed down almost 9 cents, giving back almost all of Monday's entire rally. Falling ethanol production and dropping margins weighed on the market, and noncommercials seemed to want to lighten their positions ahead of Monday's reports. General Comments Until now, corn and soy markets have seemed to mostly ignore the 50 percent-plus collapse in the value of crude oil as though they could somehow escape its impact. For the last few months, fat production margins kept ethanol plants humming even as gasoline prices worked steadily lower. However, it would be very naive to assume that biofuels would not be negatively affected by what has been going on in the energy markets, and that reality finally appears to be forcing itself int...