Research progress toward and emission reduction measures of ammonia volatilization from farmlands in China

Ammonia volatilization is the main mechanism of nitrogen loss in farmlands. It not only reduces nitrogen use efficiency but also causes ecological and environmental problems such as haze, atmospheric dry and wet deposition, and greenhouse effects. In this study, we briefly analyzed the research status of ammonia volatilization in farmlands within the past 10 years (2011−2020) and the corresponding temporal and spatial variation characteristics in China; further investigated the influence mechanism of ammonia volatilization; reviewed the development process, principles, advantages, and disadvantages of the determination methods for ammonia volatilization in farmland; and summarized the existing problems of the main measures for reducing ammonia emissions. Research on farmland ammonia volatilization has shown rapid development and significant international trends in China, but the international influence of this researches needs further improvement. Due to its vast territory, ammonia volatilization in farmland presents the characteristics of large temporal and spatial variations, which are closely related to crop types, fertilization, climate, soil, and crop growth period. To regulate and mitigate ammonia volatilization, nitrogen fertilizer application should be managed scientifically according to local conditions. After more than 200 years of development, methods for determining ammonia volatilization in farmland have gradually developed from initial indirect estimation to chemical measurement and spectral analysis, and the accuracy and scope of measurement have been greatly improved. Additionally, we summarized the main measures and existing problems in reducing ammonia volatilization from farmlands in China. In the future, researches on the microbiological mechanism and temporal-spatial variability of ammonia volatilization in farmland should be increased, air-space-land integrated monitoring technology for ammonia volatilization should be applied in farmland, and the mechanization and intelligence of farming should be strengthened; moreover, a more accurate evaluation system for reducing ammonia emissions should be gradually established. The suggested improvements will provide a reference for future research on ammonia volatilization and the formulation of reasonable emission reduction policies in China.