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. In the Midwest, on-highway diesel averaged $5.26 per gallon during the week of Aug. 3, up nearly 39% from $3.79 per gallon during the same period a year earlier, according to the U.S. Energy Information Administration.
Diesel prices have remained elevated beyond the spring planting season, with farmers now approaching the fuel-intensive fall harvest. In the Midwest, on-highway diesel averaged $5.26 per gallon during the week of Aug. 3, up nearly 39% from $3.79 per gallon during the same period a year earlier, according to the U.S. Energy Information Administration.
American farmers spent an estimated $1.4 billion more on diesel during the 2026 planting season than they did a year earlier, according to a July analysis released by the congressional Joint Economic Committee Minority.
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). Florida led the country in percentage increase at 90.6%, followed by Alabama (86.2%) and Oklahoma (85.9%).
The calculations only took into account the diesel used to plant corn, soybeans, wheat, cotton, and rice.
It did not take into account “other war-related increases such as the increased costs of running diesel generators that power some greenhouses or the increases at the pump that farmers and truckers face when they drive products to market,” the committee stated.
The committee also estimated how much more farmers paid to refill common pieces of equipment at peak diesel prices during the 2026 planting season.
Nationally, compared with the same period in 2025, it estimated farmers paid an average of:
- $1,538 more to refill a typical 750-gallon on-farm fuel tank.
- $205 more to fill a typical grain truck.
- $250 more to fill a typical tractor.
Iran conflict ripple effect
The analysis comes at a time when the Iran-U.S. conflict has created uncertainty in the oil markets and threatens the world's most important oil-shipping route. Investigate Midwest previously reported that about a quarter of the world's seaborne oil trade passes through the Strait of Hormuz, a key shipping route whose disruption can affect global fuel prices.
The effects of the conflict could also extend beyond this year's fuel bills. Farm Progress reported this month that fertilizer prices could remain elevated even if shipping through the Strait of Hormuz stabilizes.
Ed Thomas, vice president of government affairs with The Fertilizer Institute, told Farm Progress that even if normal shipping through the strait resumes, it could take 18 months to two years for fertilizer markets to stabilize.
Data Harvest (formerly Graphic of the Week) is Investigate Midwest’s way of making complex agricultural data easy to understand. Through engaging graphics, charts, and maps, we break down key trends to help readers quickly grasp the forces shaping farming, food systems, and rural communities. Want us to explore other data trends? Let us know here.
