Three Nebraska farmers will plead guilty to knowingly marketing non-organic corn and soybeans as certified organic as part of a lengthy, multi-million-dollar fraud scheme.Tom Brennan, his son James Brennan and family friend Michael Potter have each agreed to plead guilty to one count of wire fraud. Their plea hearings are scheduled for Friday in federal court in Cedar Rapids, Iowa.Prosecutors allege that the three conspired with the owner of a large Iowa-based company to dupe customers nationwide who thought they were buying grains that had been grown using environmentally sustainable practices.All three operated an organic farm in Overton, Nebraska, that was certified through the U.S. Department of Agriculture's National Organic Program, which requires crops to be grown without the use of fertilizers, sewage sludge and other substances. They also farmed other fields that weren't certified.