US farmers are facing a bigger fuel bill as diesel prices hit record highs just as the corn and soybean harvest gets underway, pushing up the cost of running combines, tractors and trucks. The national average price of diesel reached $5.85 a gallon on September 4, the first time it had risen that high, and climbed further to $6.05 a gallon on Friday, according to AAA. That is 60% higher than the roughly $3.76 a gallon average recorded before the US and Israel launched their war against Iran in late February.The rise has added to a difficult year for farmers already paying more for fertiliser, seeds, equipment, chemicals and other inputs. The higher fuel costs are also affecting the movement of crops, from fields to farms and eventually to buyers.“Those prices hurt,” Paul Mitchell, a professor of agricultural and applied economics at the University of Wisconsin-Madison told AP. “And it’s not just the harvesting. It’s the hauling of everything, moving the grain or the silage from the field to the farm and then from the farm to wherever they’re selling it.”For farmers, diesel is difficult to avoid during harvest. Jason Kurtz, who grows corn and soybeans near Forest City, Missouri, said his fuel bill had doubled this year. His combine alone burns about 200 gallons (760 litres) of diesel each day, and he expects to operate it for 30 days. He also needs fuel for a tractor and trucks.“We have to harvest,” Kurtz said in an interview at his farm about 90 miles (145 kilometres) outside Kansas City on Tuesday. “We have to run the machines. We have to use the diesel, so it cuts into our bottom line.”Kurtz, 49, said his finances were “already tight” after having to spend more on fertiliser and chemicals this year.The surge in diesel prices has followed a jump in crude oil costs, with disruptions to tanker traffic through the Strait of Hormuz during the war affecting fuel supplies. Crude oil is the main ingredient in both diesel and petrol.The higher costs are putting particular pressure on farms that have less financial room to absorb another increase in expenses.“Farms that are cash strapped, they’re the ones that are most having to figure out what to cut to make this work,” Mitchell said. “There are a lot of farms facing that.”Kurtz, who voted for US President Donald Trump, said he planned to postpone some farm work in the hope that diesel prices would ease later.