Thursday the Chicago Board of Trade increased margin requirements in corn by about 50% and soybeans 30%.  NYMEX raised the nat gas margin shortly after and it is rumored that all commodities will be hit by the increased margin. 

The result is funds deleveraging all commodities, which in turn is pressuring prices downward.  Almost all commodities are still getting hit, but will re-equilibrate and start back up on their fundamentals.

So just another correction, this time likely engineered by the government.