** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** CORN AND SOYBEAN AGRICULTURAL SYSTEMS IN THE MIDWESTERN US CORN BELT EMIT LARGE AMOUNTS OF NITROUS OXIDE (N2O). THIS POTENT GREENHOUSE GAS IS THE SINGLE LARGEST CONTRIBUTOR OF CORN BELT AGRICULTURE TO CLIMATE CHANGE, BUT THE SOURCES OF N2O REMAIN POORLY UNDERSTOOD. IMPORTANTLY, N2O RELATED TO AGRICULTURE MAY BE EMITTED BEYOND THE FIELD EDGE, TERMED INDIRECT EMISSIONS. OUR PROPOSAL WILL RIGOROUSLY MEASURE INDIRECT N2O EMISSIONS FROM AGRICULTURAL DRAINAGE WATER, STREAMS, AND WETLANDS IN SEVERAL IOWA WATERSHEDS. THE STUDY WATERSHEDS DIFFER IN THEIR AGRICULTURAL MANAGEMENT AND PHYSICAL CHARACTERISTICS, ALLOWING US TO TEST FACTORS THAT INFLUENCE INDIRECT N2O EMISSIONS AND THEIR RELATIONSHIP WITH WATER QUALITY. WE WILL USE OUR MEASUREMENTS TO DEVELOP AND VALIDATE A NEW MODULE IN THE DYNAMIC LAND ECOSYSTEM MODEL (DLEM), WHICH WILL ENABLE US TO TEST THE POTENTIAL FOR REDUCING GREENHOUSE GAS EMISSIONS WHILE IMPROVING WATER QUALITY UNDER DIFFERING MANAGEMENT AND CLIMATE SCENARIOS. WE EXPECT THAT OUR FINDINGS WILL HELP INFORM PUBLIC POLICY AND MARKET-BASED EFFORTS TO MITIGATE CLIMATE CHANGE AND IMPROVE WATER QUALITY IN THE US CORN BELT.