Continuous N supply at a low temperature produces less N₂O emission in a semi-arid grassland soil

Greenhouse gas nitrous oxide (N₂O) emissions in soils are mainly driven by nitrification and denitrification, which are sensitive to environmental change. However, the response of soil N₂O emission to N addition rates and elevated temperature in semi-arid grassland remains poorly understood, where nitrification dominates N₂O emissions. We examined N₂O emissions of a clay-loam loess to three N supply levels: no N supply (Control), 10 μg NH₄ ⁺-N g¹ soil per 3 days (continuous N supply, CN) and 100 μg NH₄ ⁺-N g¹ soil at one time (high N supply, HN) under two temperatures (15 °C and 25 °C). Our results showed that high N supply promoted the growth of ammonia-oxidizing bacteria (AOB) and N₂O emissions at both incubation temperatures. Continuous N supply led to lower N₂O emissions with no impact on the abundances of either AOA or AOB at both incubation temperatures. Elevated temperature significantly increased N₂O emissions without changing the abundances of either AOA or AOB. These results indicated that continuous N fertilization at a lower temperature may be an effective fertilization strategy for reducing soil N₂O emissions in this semi-arid Loess grassland.