In a letter last week to President Trump, Zippy Duvall, president of the American Farm Bureau Federation (AFBF), wrote that diesel prices are squeezing farmers’ margins. As Duvall wrote: Higher diesel expenses are hitting farmers at one of the most fuel-intensive times of the year — harvest… We ask the Administration to temporarily suspend the federal highway diesel tax for agricultural transportation and quickly waive federal penalties for emergency use of dyed diesel on highways. Higher diesel costs hit everything from tractors, combines, and irrigation equipment to over-the-road transportation of crops, livestock, and inputs. Trump signed an executive order yesterday that would allow red-dyed diesel to be used for over...