Where do diesel prices stand now? Diesel prices have remained elevated beyond the spring planting season, with farmers now approaching the fuel-intensive fall harvest. The report estimates diesel costs for planting corn, soybeans, wheat, cotton and rice increased 63.2% nationwide between the 2025 and 2026 planting seasons, driven by higher fuel prices. The congressional committee, whose Democratic minority staff produced the analysis, said higher diesel prices followed the Trump administration’s military strikes on Iran. Illinois recorded the nation’s largest overall increase in planting diesel costs, at an estimated $163.2 million, followed by Iowa ($151.1 million) and Minnesota ($101.7 million).