Agricultural activities degrade the environment, and efficiency and demands on the food supply will continue to grow with increasing population and urbanization. Gas phase ammonia (NH3) is emitted both from livestock operations and fertilizer application, with agricultural sources dominating about 80% of its global budget. Ammonia, however, has large negative consequences on human health, ecosystem health, regional haze and climate through fine particle formation (PM2.5). Existing measurements of ammonia are scarce due sampling challenges associated with its low concentration, high dynamic range, and partitioning between the gas and aerosol particle phases. In the past decade, new observations of NH3 from satellite-based instruments and on the ground in the Ammonia Monitoring Network (AMoN) have provided new opportunities to study the emissions of this pollutant beyond targeted field studies, which often have questionable representativeness. By using a high-resolution sampling algorithm for the IASI and CrIS satellite data, my group has investigated the spatial and temporal trends of ammonia over the United States, India, and China. Different seasonalities of NH3 over the major agricultural regions are linked to different farming practices and land use. Emission inventories (e.g. NEI, EDGAR) neither reflect the seasonality nor the magnitude of the observations in most source regions, with most emissions underestimated by factors of several in many hotspot regions. In addition, the AMoN network stations in the U.S. are located are far away from source regions with only a handful of 100+ sites located in the areas of the largest emissions. Satellite NH3 measurements provide a link to bridge scales beyond the ground-based network and improve emission inventories, providing improved bases for mitigation efforts for PM2.5 and nitrogen deposition.