Water was spilling out of creeks, ditches and prairie potholes last week in corn and soybean fields across northern Iowa, which has been deluged by one of the wettest springs in decades.

“We’ve got water in places I haven’t seen since I was a kid,” says 38-year-old Pocahontas County farmer Brian Dreith, who said conditions are reminiscent of floods that occurred in 1991 and 1993.

Meanwhile, last week’s storms brought relief to farmers in far southern Iowa who had been...