Nitrogen Dynamics in Tropical Pastures: Relating Soil–Plant–Animal Interactions to Improve Productivity and Reduce Greenhouse Gas Emissions

Nitrogen fertilization plays a central role in the intensification and sustainability of tropical pasture systems by influencing forage production, animal performance, and greenhouse gas (GHG) emissions. Although the individual components of these systems have been extensively studied, studies that simultaneously integrate soil nitrogen processes, forage responses, animal performance, and environmental outcomes within a unified framework remain scarce in the literature. This structured narrative review aimed to synthesize current knowledge on the role of nitrogen in tropical pastures, addressing soil–plant–animal–environment interactions with a focus on nitrogen use efficiency, productivity, and GHG emissions. Studies were selected from Google Scholar using keywords related to nitrogen fertilization, tropical forages, GHG emissions, and animal performance, prioritizing research conducted with C4 forage species. The reviewed evidence demonstrates that nitrogen fertilization consistently increases forage accumulation, tillering, crude protein concentration, stocking rate, and animal productivity per unit area; however, nitrogen recovery efficiency decreases at high application rates. The timing of nitrogen application, dose splitting, and the choice of nitrogen source are key management strategies to reduce N losses through volatilization, leaching, and gaseous emissions, improving nitrogen use efficiency in tropical pasture systems. Future studies should focus on providing integrated answers that simultaneously consider soil, plant, animal, and environmental components, in order to support more efficient and sustainable nitrogen management in tropical livestock systems.