Key production processes and influencing factors of nitrous oxide emissions from agricultural soils

Nitrous oxide (N₂O), as an important greenhouse gas, has been greatly concerned due to its high potential to climate warming. N₂O emissions from agricultural soils become research focus with the increasing of nitrogen fertilizer application. Nitrification and denitrification are thought as the two dominant pathways for N₂O emissions, and are significantly influenced by agricultural managements (e.g. fertilization, irrigation) and environmental factors (e.g. soil pH, temperature). This study summarized the main pathways and regulatory factors of N₂O emissions from agricultural soils. The purpose of this study is to explore the mechanisms of N₂O production and the responses of N₂O emissions to the main regulatory factors (e.g. available N, available carbon, soil moisture, oxygen concentration, soil pH and temperature, etc.), which would provide scientific basis to the future research. The N losses as N₂O from nitrification are little in agricultural soils. The processes of biological denitrification (including nitrifier denitrification and nitrification-coupled denitrification) are often regarded as the principal source of N₂O emissions. The fungal denitrification and chemodenitrification play an important role in emission of N₂O in acidic soils. Meanwhile, the N₂O emissions caused by the dissimilatory nitrate reduction to ammonium (DNRA) cannot be ingored with high content of soil organic matter and anaeribic conditions. Future researches should focus on the mechnisms of N₂O production and consumption, combining with decreasing the ratio of N₂O to N₂ and the processes of N₂O reduction and related influencing factors. Moreover, the new techniques (e.g. planar optodes, robot incubation system etc.) should be used to investigate the effects of soil physicochemical and biological factors on nitrogen transformation, to evaluate the response of related microbial diversity from the hotspots of N₂O emissions, and to establish the nitrogen balance and related N₂O emission models. These works may further deepen our understanding of the mechansim of N₂O emission and its related influencing factors.