Farmers will have to wait until Congress returns to work later this month to get a new federal farm bill. One Iowa State University expert says there’s a lot riding on that bill when it comes to land values. I-S-U economist Michael Duffy directs the annual I-S-U survey of farmland value.Duffy believes the farm bill is the largest driver of land value in Iowa and other farm states. He says that’s because the value of Iowa’s two main crops is linked directly to the farm bill.About 25 to 30 percent of the gross revenue from corn or beans is linked to government payments. Land values rose in Iowa for the second straight year in the latest survey. Duffy says the economy will also play a role into whether the increase continues.The average value of an acre of land increased to 19-hundred-and-26 dollars in the latest survey.