Swine manure management and storage have been implicated as major sources of increasing agricultural ammonia (NH 3 ) emissions resulting in increased ammonium deposition in North Carolina. This study was conducted to establish how improvements in manure and animal management have affected lagoon nutrient loading and subsequent NH 3 emissions determined from measured lagoon chemistry and climate data. Archived lagoon chemistry analyses from 182 farm lagoons (106,000 sample analyses) were used to evaluate trends in lagoon chemical properties. Process and empirical (statistical) NH 3 volatilization models were used with the data to calculate changes in NH 3 emissions from 2001 through 2018. Lagoon nutrient trends for finisher and sow farms showed that annual averages of nutrients had decreases ranging from 18 to 93%, except for a 41% increase in copper for finisher primary lagoons. Because of reduced nitrogen and pH in the lagoons, a process model of NH 3 emissions suggested decreases from primary lagoons of 49 and 25% from finisher and sow farm lagoons, respectively. Empirical (statistical) models predicted even larger relative NH 3 decreases (up to 54%).