** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** TARGETED NUTRIENT MANAGEMENT IS A PROMISING CROPLAND MANAGEMENT PRACTICE TO ACHIEVE ACCUMULATION OF SOIL ORGANIC CARBON (SOC), A DOMINANT DRIVER OF SOIL HEALTH. WE HAVE A REASONABLE UNDERSTANDING OF THE REGULATION OF C CYCLING BY MACRONUTRIENTS (IN PARTICULAR, N) IN CROPLAND SOILS. HOWEVER, THE ROLE OF MICRONUTRIENTS - INDEPENDENTLY AND INTERACTIVELY WITH MACRONUTRIENTS - IN C CYCLING IS LARGELY UNKNOWN. EMERGING LITERATURE, MOSTLY DERIVED FROM FORESTED ECOSYSTEMS, HIGHLIGHTS THE KEY ROLE MANGANESE (MN) PLAYS IN REGULATING C AND N CYCLING. NO STUDIES HAVE EXAMINED MN'S ROLE ON C DYNAMICS IN AGRICULTURAL SOILS DESPITE AGROECOSYSTEMS EXPERIENCE MN ADDITION FROM FERTILIZERS AND MN REMOVAL THROUGH HARVESTED PRODUCE. IN ADDITION, CONTINUED N FERTILIZATION IN CROPLAND SOILS REDUCES SOIL PH, WHICH MAGNIFIES MN BIOAVAILABILITY. WE PROPOSE TO EXAMINE IF MN IS A MAJOR DRIVER OF C AND N TRANSFORMATIONS AND SOIL HEALTH IN AGRICULTURAL SOILS. WE WILL CREATE A GRADIENT OF MN AND SOIL PH CONDITIONS AND TEST ITS EFFECT ON PLANT MN UPTAKE, RESIDUE DECOMPOSITION, SOC MINERALIZATION AND STABILIZATION, SOIL PHYSICAL CONDITIONS, AND MICROBIAL COMMUNITY CHANGES. WE WILL ALSO CONDUCT A LABORATORY STUDY TO TEST IF CO-ENRICHMENT OF MN AND N AFFECTS C AND N TRANSFORMATIONS DIFFERENTLY THAN MN ENRICHMENT ALONE. THE PROPOSED PROJECT IS MULTI-DISCIPLINARY AND CONTRIBUTESTO THE FOUNDATIONALUNDERSTANDING OF SOIL BIOGEOCHEMICAL PROCESSES AND INTERACTIONS LEADING TO ENHANCED SOIL HEALTH. WE EXPECT TO DETERMINE IF MN BIOAVAILABILITY IS A CRITICAL DRIVER TO BE CONSIDERED FOR DEVELOPING SOIL HEALTH-BUILDING STRATEGIES.