COVER CROPS, OR NON-HARVESTED CROPS, ARE ESSENTIAL COMPONENTS OF SUSTAINABLE FARMING SYSTEMS. FARMERS PLANT COVER CROPS TO SUPPORT CRITICAL ECOSYSTEM SERVICES, SUCH AS NUTRIENT CYCLING, EROSION CONTROL, AND WEED SUPPRESSION. DIFFERENT COVER CROP SPECIES SUPPORT DIFFERENT SERVICES DEPENDING ON THEIR TRAITS. FOR EXAMPLE, COVER CROPS IN THE LEGUME FAMILY SUPPLY NITROGEN TO FIELDS, WHILE COVER CROPS IN THE GRASS FAMILY HAVE EXTENSIVE ROOT SYSTEMS THAT HELP PREVENT NUTRIENT LOSSES FROM FARM FIELDS. COMBINING SPECIES WITH DIFFERENT TRAITS IN COVER CROP MIXTURES CAN THUS ALLOW FARMERS TO INCREASE MULTIPLE ECOSYSTEM SERVICES AT ONCE. HOWEVER, ACHIEVING THESE BENEFITS ON FARMS DEPENDS ON THE SUCCESSFUL GROWTH OF COVER CROPS, WHICH CAN BE A MAJOR CHALLENGE FOR FARMERS GIVEN WIDE VARIATION IN FACTORS LIKE SOIL TYPE AND MANAGEMENT PRACTICES THAT IMPACT COVER CROP GROWTH AND OUTCOMES. THIS IS ESPECIALLY CHALLENGING FOR COVER CROP MIXTURES, BECAUSE EACH SPECIES MAY RESPOND DIFFERENTLY TO THE CONDITIONS OF A GIVEN FARM. THERE IS A CRITICAL NEED TO DETERMINE KEY DRIVERS OF VARIATION IN COVER CROP PERFORMANCE IN ORDER TO PROVIDE FARMERS WITH IMPROVED RECOMMENDATIONS FOR OPTIMAL COVER CROP MANAGEMENT. TO ADDRESS THIS NEED, I WILL PARTNER WITH FARMERS ACROSS THE GREAT LAKES REGION TO CONDUCT HIGHLY RELEVANT, ACTIONABLE COVER CROP RESEARCH ON WORKING FARMS. SPECIFICALLY, I WILL DETERMINE: I) THE EXTENT OF VARIATION IN COVER CROP GROWTH AT THE REGIONAL SCALE, AND KEY DRIVERS OF THIS VARIATION, USING A CITIZEN SCIENCE APPROACH WITH 150 FARMERS, AND II) RELATIONSHIPS BETWEEN COVER CROP TRAITS, SOIL FERTILITY, AND INTERACTIONS BETWEEN SPECIES IN MIXTURES AT FARM AND FIELD SCALES THROUGH A PARTICIPATORY EXPERIMENT ON SEVEN FARMS IN TUSCOLA COUNTY, MICHIGAN. RESULTS WILL BE SHARED DIRECTLY WITH PARTICIPATING FARMERS, AND MORE BROADLY THROUGH COLLABORATION WITH REGIONAL SUSTAINABLE AGRICULTURE ORGANIZATIONS AND PRESENTATIONS AT FARMER CONFERENCES, TO HELP MAXIMIZE ENVIRONMENTAL AND ECONOMIC BENEFITS FROM COVER CROPS.