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.