MODERN AGRICULTURAL SYSTEMS ARE FACING IMMENSE PRESSURE TO FEED A GROWING POPULATION, BUT DO SO WITHOUT ENVIRONMENTAL IMPACTS. MODERN DAIRY FARMS ARE INCREASINGLY CHALLENGED TO PRODUCE MORE AND MINIMIZE OFF-SITE IMPACTS OF REACTIVE NITROGEN (N) ON AIR AND WATER QUALITY. A SYSTEMATIC ANALYSIS OF THE SPECTRUM OF EXISTING AND POSSIBLE PRODUCTION SYSTEMS ACROSS MAJOR U.S. DAIRY FARM SYSTEMS IS NEEDED TO DESIGN HIGH PRODUCTIVITY, LOW IMPACT FARMS. THIS PROJECT WILL USE THE INTEGRATED FARM SYSTEMS MODEL (IFSM) TO ANALYZE AND QUANTIFY THE FARM-SCALE AIR AND WATER QUALITY IMPACT AND ECONOMIC VIABILITY OF DAIRY SYSTEMS IN FOUR GEOGRAPHICALLY DISTINCT, INTEGRATED, DAIRY PRODUCTION SYSTEMS (PA, WI, MN, AND ID). SURVEYS AND SITE VISITS WILL BE CONDUCTED TO COMPILE INFORMATION FOR A SPECTRUM OF FARM TYPES THAT WILL BE SIMULATED. MODEL SENSITIVITY WILL BE CONDUCTED TO IDENTIFY THE FARM-SCALE PRACTICES AND PROCESSES THAT HAVE THE GREATEST IMPACT ON REACTIVE N CYCLING, USE, AND LOSS. SUBSEQUENT ACTIVITIES WILL THEN IDENTIFY ALTERNATIVE PRACTICES THAT CAN SUBSTANTIALLY IMPROVE N USE EFFICIENCY ON DIFFERENT FARM TYPES. QUALITATIVE RESEARCH WILL ALSO BE CONDUCTED TO EXPLORE THE ROLE THAT BIOPHYSICAL SIMULATIONS MODELS CAN PLAY IN IMPROVING RESEARCHER/FARMER COMMUNICATION AND EDUCATION, WITH A VIEW TO DEVELOPING DECISION SUPPORT TOOLS THAT CAN BE USED ON FARMS TO AFFECT CHANGE. THE PROJECT WILL IDENTIFY THE MAJOR POINTS OF N USE INEFFICIENCY AND LOSS ON DAIRY FARMS, DEVELOP ALTERNATIVE SYSTEMS TO SUBSTANTIALLY IMPROVE N USE, AND PROVIDE INFORMATION ON HOW MODELS CAN BE BETTER USED TO PROVIDE REALISTIC ENOUGH EXPERIENCES FOR FARMERS TO IMPLEMENT NEW MANAGEMENT PRACTICES.