**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** EVERY GRAM OF SOIL HARBORS BILLIONS OF VIRUSES AND THOUSANDS OF VIRAL SPECIES THAT INFECT DIVERSE MICROBIOTA, INCLUDING PLANT-BENEFICIAL AND PLANT-PATHOGENIC MICROORGANISMS. WE KNOW VERY LITTLE ABOUT THESE SOIL VIRAL COMMUNITIES OR THEIR CONTRIBUTIONS TO AGRICULTURAL MICROBIOMES, BUT EVIDENCE FROM MARINE SYSTEMS SHOWS THAT VIRUSES HAVE GLOBAL-SCALE IMPACTS ON CARBON AND NUTRIENT CYCLING, MICROBIAL MORTALITY, AND AGGREGATE FORMATION. THIS PROJECT CONSIDERS DIVERSE SOIL BIOTA ACROSS TROPHIC SCALES (VIRUSES, BACTERIA, FUNGI, PROTISTS, NEMATODES, AND PLANTS) TO BUILD A SYSTEMS-LEVEL UNDERSTANDING OF AGRICULTURAL SOIL VIRAL DIVERSITY, VIRUS-HOST DYNAMICS, AND VIRAL CONTRIBUTIONS TO SOIL CHEMISTRY AND TOMATO DISEASE. USING MULTIPLE OMICS AND AMPLICON APPROACHES, VIRUSES WILL BE PLACED IN PRACTICAL CONTEXT BY MEASURING CHANGES IN VIRAL COMMUNITY COMPOSITION AND VIRUS-HOST DYNAMICS IN RESPONSE TO COMMON MANAGEMENT PRACTICES AND INPUTS THROUGHOUT THE TOMATO GROWING SEASON. THE PRIMARY OBJECTIVES ARE TO: 1) ASSESS RESPONSES OF SOIL DNA AND RNA VIRAL COMMUNITIES TO MANAGEMENT AND INPUTS, 2) LINK SOIL VIRUSES TO THEIR DIVERSE HOSTS AND EXPLORE HOW VIRUS-HOST DYNAMICS CHANGE OVER THE TOMATO GROWING SEASON AND DIFFER BETWEEN ORGANICALLY AND CONVENTIONALLY MANAGED SOILS, AND 3) EXPLORE SOIL VIRAL IMPACTS ON CARBON, NUTRIENTS, AND TOMATO DISEASE. THOUSANDS OF NEW VIRUSES WILL BE DISCOVERED, AND THEIR CONTRIBUTIONS TO SOIL MICROBIAL ECOLOGY, NUTRIENT CYCLING, AND PLANT DISEASE SUPPRESSION WILL BE INVESTIGATED. IN LINE WITH AFRI'S GOALS, RESULTS WILL IMPROVE OUR UNDERSTANDING OF AGRICULTURAL SOIL MICROBIOMES, LEADING TO OUR LONG-TERM GOAL TO LEVERAGE SOIL MICROBES TO IMPROVE CARBON STORAGE AND NUTRIENT CYCLING AND MITIGATE PLANT DISEASE IN SUSTAINABLE AGRICULTURAL SYSTEMS.