Hainan is the only province in China entirely situated within the tropical region, characterized by abundant light, heat, and water resources, making it the most typical tropical agricultural production base in China. However, restrictive factors such as "poor, acidic, and leaky" soils, coupled with high nitrogen (N) fertilizer inputs in crop cultivation, led to significant risks for N loss in farmlands and severe environmental pollution. The agricultural non-point source pollution situation in Hainan is severe, N and phosphorus discharged from agriculture enter nearshore waters via short transport pathways, leading to serious degradation of coral reefs and seagrass beds. However, the generally weak foundation of research on N cycling in Hainan"s tropical farmland soils hindered the development of scientific and targeted N regulation measures. In response to the characteristics of tropical agricultural resources, we propose that future research should focus on four key areas: the characteristics of N transformation, the fate and loss pathways of N, the mechanisms of efficient N utilization in crops, and the principles and regulation measures for reducing N fertilizer application while enhancing efficiency. More attention should be paid to the effects of organic matter-mediated soil fertility and acidity improvement on soil N transformation in Latosols, the mechanisms underlying high ammonia emissions in acidic soils and nitrate accumulation in deep soil profiles, as well as the impact of organic material inputs on nitrous oxide emissions. We emphasize the need to clarify the relationship between the transformation and migration characteristics of N in farmland soils and crop N use efficiency, and to elucidate the mechanisms by which soil carbon (C) pool expansion affects N transformation, migration, retention, and loss prevention. Thus, to propose a principle for reducing N fertilizer application while enhancing efficiency, centered on "increasing C to retain N, coupling C and N, controlling losses, and coordinating N supply". This approach will form an innovative theory and solution. The finding would provide scientific and technological support for the development of efficient and green tropical agriculture and offer a scientific basis for understanding regional differences in N cycling across global climate-soil zones.