DES MOINES, Iowa (AP) – A nonprofit network of investors, companies and public interest groups says in a new report that manufacturers depending on U.S. corn and other commodities must send strong signals to farmers to help preserve water and soil. The Boston-based group called Ceres is working with several companies, including food giants General Mills and Unilever. Both of those have adopted sustainability programs suggested by Ceres that set specific goals for suppliers and farmers.

The report calls for the establishment of corporate policies setting specific goals for suppliers that reduce environmental impacts, procurement contracts requiring that crops be sustainably grown, and efforts to identify areas of high water stress, groundwater pollution and overuse of fertilizer.

Ceres also recommends companies substitute other grains for corn where environmental benefits are well-demonstrated.