Two former officers at a northwest Iowa agriculture cooperative have pleaded not guilty to federal fraud charges. The Sioux City Journal reports that Kenneth Ehrp and Calvin Diehl entered the pleas Thursday in U.S. District Court in Sioux City. Prosecutors say the two directed Farmers Cooperative Society workers in Sioux Center to layer higher-value soybeans over oats in grain bins and in trucks and then concealed the scheme from customers and federal inspectors. Prosecutors say the scheme led to the overvaluing of the co-ops grain inventory in order to influence a lender’s action on a loan.