When Yvonne Lawley wrote her research proposal for a study of cover crops, she was specific about the wording of the title: Testing the cover crop hypothesis across Prairie Canada. It’s the word “hypothesis” that grabs you. What could be theoretical about cover crops? Some farmers have been using them for decades to help build soil, reduce erosion, graze animals and more. The practice is common in Ontario and Quebec, as well as in the Northern Great Plains region of the U.S. What’s not to know?