** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** AGRICULTURAL SOIL DEGRADATION AND CLIMATE-CHANGE IMPOSED STRESSES HAVE INCITEDINCREASED ADOPTION OF SUSTAINABLE MANAGEMENT PRACTICES SUCH AS ORGANIC AMENDMENT. SUSTAINABLE AGROECOSYSTEM MANAGEMENT IS PREDICATED ON OUR KNOWLEDGE OF DESIRED PHYSICAL, CHEMICAL, ANDBIOLOGICAL OUTCOMES, HOWEVER UNDERLYING MECHANISMS AND POTENTIAL TRADEOFFS FOR THESE OUTCOMES ARE OFTEN UNCLEAR. FOR ORGANIC AMENDMENTS, WHICH ARE COMPOSED OF CARBON (C) BASED COMPOUNDS, FARMERS OFTEN DESIRE INCREASES IN SOIL ORGANIC MATTER (SOM) CONTENT BECAUSE SOM SERVES CRITICAL FUNCTIONS IN NUTRIENT STORAGE, MOISTURE RETENTION, SOIL STRUCTURE, AND EROSION REDUCTION. SOIL MICROORGANISMS HAVE BEEN IDENTIFIED AS KEY REGULATORS OF SOM BECAUSE THEY ARE RESPONSIBLE FOR BOTH FORMING AND DEGRADING SOM THROUGH GROWTH (E.G., BUILDING BIOMASS) AND RESPIRATION (E.G., C LOSS AS CO2). UNDERSTANDING THIS BALANCE BETWEEN C USED FOR GROWTH VERSUS RESPIRED IS KNOWN AS MICROBIAL C USE EFFICIENCY (CUE) AND IS ESSENTIAL FOR CONNECTING ORGANIC AMENDMENTS TO THEIR DESIRED AGRICULTURAL OUTCOME.FOR WOODY PERENNIAL CROPS (I.E., ALMONDS, PISTACHIOS, WALNUTS, STONE FRUITS, ETC.) IN CALIFORNIA'S CENTRAL VALLEY, ONE OF THE MOST PRODUCTIVE REGIONS IN THE UNITED STATES, FARMERS FACE LIMITATIONS ON BURNING-RELATED DISPOSAL METHODS FOR ORCHARD WASTE BIOMASS. FOLLOWING THE CALIFORNIA AIR RESOURCES BOARD (CARB) BAN ON AGRICULTURAL BURNING IN 2025, WHOLE ORCHARD RECYCLING (WOR) IS EXPECTED TO BECOME A MAJORTREE DISPOSAL METHOD THAT ALSO SERVES AS AN ORGANIC AMENDMENT. IN WOR, TREES AT THE END OF THEIR PRODUCTIVE LIFE CYCLE ARE GROUND INTO WOOD CHIPS AND TILLED INTO THE SURFACE SOIL BEFORE PLANTING THE NEXT ORCHARD.THIS RESEARCH WILL EXAMINE HOW WOR ALTERS THE COMPOSITION AND CUE OF THE SOIL MICROBIAL COMMUNITY DURING AN ORCHARD GROWING SEASON (MARCH - SEPTEMBER 2023). THIS WILL BE EVALUATED AT TWO NITROGEN (N) FERTILIZER RATES BECAUSE N IS AN ESSENTIAL NUTRIENT FOR ALL LIVING THINGS THAT IS COMMONLY APPLIED TO AGRICULTURAL LAND. SOIL SAMPLES WILL BE COLLECTED MONTHLY FROM AN ALMOND ORCHARD IN THE CENTRAL VALLEY, DNA WILL BE EXTRACTED TO IDENTIFY THE MICROORGANISMS PRESENT, AND MICROBIAL CUE MEASUREMENTS BE MADE FROM LABORATORY INCUBATIONS. IMPROVING OUR UNDERSTANDING OF HOW CUE IS REGULATED BY MICROBES WILL GUIDE ADVANCEMENT OF MANAGEMENT STRATEGIES THAT PROMOTE SOM STABILIZATION, AGGREGATE FORMATION, AND AGRICULTURAL SUSTAINABILITY. THIS PROJECT ALIGNS WITH THE US FARM BILL PRIORITY AREAS BIOENERGY, NATURAL RESOURCES, AND ENVIRONMENT AND AGRICULTURAL SYSTEMS AND TECHNOLOGY, DUE TO ITS IMPLICATIONS IN UTILIZING AGRICULTURAL BYPRODUCTS AS MANAGEMENT TECHNIQUES TO LEVERAGE MICROBIOME FUNCTIONS.