The price of diesel is hitting record highs just as many U.S. farmers are harvesting two of the nation’s largest commodities, soybeans and corn. That means they'll need countless gallons of the fuel for combines, tractors and trucks. Diesel hit a record price in the U.S. last week, soaring to an average of $5.85 a gallon for the first time as the six-month war with Iran disrupted the world’s flow of fuel. On Friday, it was at $6.05. The diesel spike adds to an already tough year for many farmers, who also faced higher costs for fertilizer, seeds and equipment.