DES MOINES, Iowa (AP) — Cover crops top the list of tasks U.S. farmers are told will build healthy soil, help the environment and fight climate change. Yet after years of incentives and encouragement, Midwest farmers planted cover crops on only about 7% of their land in 2021. Many worry the practice will hurt their bottom line. A study last year indicates they could be right. Researchers who used satellite data to examine over 90,000 fields in six Corn Belt states found cover crops can reduce yields of cash crops. The smaller the yield, the less money farmers make. Cover crops are plants grown on farmland that otherwise would be bare. They stabilize soil, reduce fertilizer runoff, store carbon in plant roots and potentially add nutrients to the dirt.