** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THIS PROJECT AIMS TO ENHANCE AGRICULTURAL PRODUCTIVITY, SUSTAINABILITY, AND RESILIENCE BY INCREASING OUR UNDERSTANDING OF NITROGEN FIXATION BY SOIL MICROBES. DESPITE ITS POTENTIAL BENEFITS, WE STILL KNOW RELATIVELY LITTLE ABOUT THE DIVERSITY AND ABUNDANCE OF NITROGEN-FIXING BACTERIA COMMUNITIES IN THE PLANT AND SOIL MICROBIOME AND AGRICULTURAL SYSTEMS. TO ADDRESS THIS KNOWLEDGE GAP, WE WILL CONDUCT THREE CLOSELY RELATED OBJECTIVES. FIRST, WE WILL ANALYZE SOIL SAMPLES COLLECTED BY THE NATIONAL SOIL HEALTH INSTITUTE AND THE REGIONAL WASHINGTON SOIL HEALTH INITIATIVE TO SURVEY THE DIVERSITY AND ABUNDANCE OF NITROGENOUS ENZYMES IN THE SAMPLES. WE WILL ALSO EXAMINE EXISTING METADATA ON SOIL PROPERTIES, CROPPING SYSTEMS, AND ECONOMIC MANAGEMENT TO SEE HOW THEY RELATE TO NITROGEN FIXATION. SECOND, WE WILL EXPAND THE DEVELOPMENT OF NFIXDB, A DATABASE BEING DEVELOPED BY OUR PROJECT TEAM, TO INCLUDE AGRICULTURALLY RELEVANT SEQUENCES. WE WILL USE THIS DATABASE TO DESIGN NEW PRIMERS TO SURVEY ALTERNATIVE NITROGENASES THAT RELY ON DIFFERENT METAL COFACTORS SUCH AS MOLYBDENUM, VANADIUM, AND IRON. WE WILL THEN ANALYZE THE PHYLOGENETIC AND BIOGEOGRAPHIC DIVERSITY OF NITROGENASE ENZYMES IN RELATION TO AGRICULTURAL SYSTEMS, PARTICULARLY NOTING WHETHER THERE ARE NITROGEN-FIXING BACTERIA THAT ARE UNIQUE TO SPECIFIC REGIONS.FINALLY, WE WILL CONDUCT WHEAT EXPERIMENTS UNDER CONTROLLED CONDITIONS TO TEST WHETHER METAL COFACTORS LIMIT THE ABUNDANCE AND DIVERSITY OF NITROGEN-FIXING BACTERIA COMMUNITIES. BY DOING THIS WORK, WE HOPE TO EXPAND OUR KNOWLEDGE OF BIOLOGICAL NITROGEN FIXATION AND FIND WAYS TO MANAGE AGRICULTURAL SYSTEMS MORE EFFECTIVELY.