**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** COMPATIBLE RHIZOBIA STRAINS ARE ESSENTIAL FOR NODULATION AND BIOLOGICAL NITROGEN FIXATION OF THEIMPORTANT WINTER ANNUAL COVER CROP SPECIES HAIRY VETCH (VICIA VILLOSA ROTH), YET BOTH PROCESSES AREREDUCED AT LOW TEMPERATURES. UNDERSTANDING AND IMPROVING THE SYMBIOSIS BETWEEN NEWLYDEVELOPED COLD-HARDY HAIRY VETCH CULTIVARS AND RHIZOBIA SYMBIONTS COULD ADVANCE THE USE OF HAIRYVETCH AS A NUTRIENT SOURCE FOR FARMERS. THE GOAL OF THIS PROJECT IS TOUNDERSTAND THE EFFECTS OF TEMPERATURE, PLANT GENOTYPE, AND RHIZOBIA SYMBIONT ON HAIRY VETCHNODULATION AND BIOLOGICAL NITROGEN FIXATION AT LOW TEMPERATURES. IN THIS PROJECT, I WILL IDENTIFY HAIRYVETCH VARIETIES BEST ABLE TO SELECT FOR EFFICIENT RHIZOBIA STRAINS FROM TYPICAL UPPER MIDWEST SOILS, ANDI WILL DEVELOP A PIPELINE FOR INOCULANT DEVELOPMENT BASED ON RHIZOBIA TRAITS THAT LEAD TO IMPROVEDBNF AT LOW TEMPERATURES. OPTIMIZING HAIRY VETCH BNF AT LOW TEMPERATURES WILL IMPROVE HAIRYVETCH PRODUCTIVITY AND HELP FACILITATE EXPANDED HAIRY VETCH ADOPTION THROUGHOUT THE NORTHERN U.S.BY IMPROVING ECOSYSTEM SERVICESPROVIDED BY A CROP THAT FITS INTO THE GROWING SEASON OF NORTHERN CLIMATES, WE CAN REDUCE RELIANCE ONSYNTHETIC FERTILIZERS AND SUPPORT RESOURCE-LIMITED FARMERS.