** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** WITH THE CONTINUED NEED TO SATISFY THE GROWING DEMAND FOR AGRICULTURAL PRODUCTS, ENSURING THE SUSTAINABILITY OF FOOD PRODUCTION SYSTEMS WHILE MINIMIZING NEGATIVE IMPACTS ON THE ENVIRONMENT HAS BECOME A MAJOR CHALLENGE IN THE U.S. CORN BELT. AGRICULTURAL PRODUCERS AND CONSERVATION AND WATERSHED PLANNERS NEED TO KNOW WHAT BENEFITS WE CAN ACHIEVE FROM IMPLEMENTING CONSERVATION PRACTICES SO THE USDA CREATED THE CONSERVATION EFFECTS ASSESSMENT PROJECT (CEAP) TO MEASURE THE EFFECTS OF AGRICULTURAL CONSERVATION PRACTICES. HOWEVER, CURRENT WATERSHED-SCALE EFFORTS MAINLY FOCUS ON ASSESSING THE EFFECTS OF CONSERVATION PRACTICES ON WATER QUALITY, WHILE GHG EMISSIONS ARE NOT WELL CONSIDERED. FURTHERMORE, AS THE MAIN WATERSHED-SCALE WATER QUALITY ASSESSMENT TOOL UTILIZED BY THE CEAP, THE SWAT MODEL LACKS THE CAPABILITY OF SIMULATING SOIL C/N COUPLED DYNAMICS AS WELL AS GHG PRODUCTION AND EMISSION PROCESSES. THEREFORE, THE OVERALL GOAL OF THIS STUDY IS TO DEVELOP A MODELING FRAMEWORK (SWAT-DNDC) BYINCORPORATING ALGORITHMS FROM DNDC TO ENHANCE SWAT'S CAPABILITY OF SIMULATING C/N CYCLING PROCESSES, AND GHG FLUXES, TO SYSTEMATICALLY EVALUATE THE IMPACTS OF CONSERVATION PRACTICES ON CROP YIELD, WATER QUALITY, AND GHG EMISSIONS IN THE CORN BELT. WE WILL LEVERAGE EXISTING IN SITU OBSERVATIONS, NEW FIELD EXPERIMENTS, COMPILED REGIONAL-SCALE GEOSPATIAL DATASETS, AND IN-STREAM HYDROLOGIC AND WATER QUALITY DATA FROM MULTIPLE SOURCES TO TEST SWAT-DNDC FROM SITE SCALE TO CEAP WATERSHED SCALE. WE WILL PERFORM SCENARIO SIMULATIONS OF ALTERNATIVE CONSERVATION PRACTICES AND CLIMATE CHANGE IMPACTS IN THE UPPER MISSISSIPPI RIVER BASIN (UMRB) TO INFORM BEST MANAGEMENT PRACTICES FOR CROP PRODUCTION, WATER QUALITY, AND GHG EMISSIONS IN THE CORN BELT.