U.S. farmers are poised to reap their biggest-ever corn crop, expanding global stockpiles to the most in 13 years and spurring hedge funds and other speculators to make record bets that prices will keep slumping.

The harvest in the largest grower will jump 30 percent to 14.036 billion bushels (356.5 million metric tons), the average of 27 analyst estimates compiled by Bloomberg shows. Thatâ??s 53 million bushels more than they expected a month ago and 86 million above the governmentâ??s July forecast. Record crops from the U.S. to Brazil to Ukraine will expand world inventories by 23 percent to 152.36 million tons in a year, according to the average of 12 predictions.