Sulfur deposition suppressed nitrogen-induced soil N₂O emission from a subtropical forestland in southeastern China

Subtropical forestland soils are important sources of nitrous oxide (N₂O); however few studies have evaluated the effects of sulfate (S) deposition and its interaction with nitrogen (N) on soil N₂O emissions from subtropical forestland. A field experiment was conducted in subtropical forestland in Yingtan, Jiangxi Province, China, between June 2011 and May 2013, to measure soil N₂O fluxes under three N (NO₃⁻) application levels (0, 40, and 80 kg N ha⁻¹ yr⁻¹), two S (SO₄²⁻) levels (0 and 45 kg S ha⁻¹ yr⁻¹), and their combinations. The soil N₂O flux was significantly (P < 0.05) correlated with only soil temperature in all treatments over the study period; however, soil moisture, and NH₄⁺ and NO₃⁻ contents were also included in the stepwise multiple linear regression equations during the N and/or S application period (March to September). N₂O emissions under natural conditions in the subtropical forestland were estimated at 0.42 kg N₂O-N ha⁻¹ yr⁻¹, and were significantly (P < 0.05) increased by 97–330% under the N application. In contrast, soil N₂O emissions decreased to 0.36 kg N₂O-N ha⁻¹ yr⁻¹ in the S-applied soil and were significantly (P < 0.05) reduced by 27–36% in the S plus N-amended soils. Our results indicated that atmospheric N deposition potentially increases soil N₂O emissions in subtropical forestland, whereas S addition has the potential to mitigate N₂O emissions. Given that increased N deposition is expected in the future, S deposition in subtropical forestland soils could suppress N₂O emissions to some extent.