The Important Role of nosZII Clade N2O Reducers in Reducing N2O Emissions After Soil Rewetting in a Neutral Vegetable Soil

Future climate models indicate an enhanced severity of regional drought and more frequent rewetting events, which may cause cascading impacts on the nitrogen cycle and nitrous oxide (N2O) emissions, and the underlying microbial mechanism remains largely unknown. Here we conducted an incubation study on the impact of different soil moisture statuses on N2O producers and N2O reducers following the application of different fertilizer types (urea and manure) on a neutral vegetable soil. The different soil moisture treatments included 100% field capacity, drought, and rewetting (50% to 100% field capacity). Results showed that the N2O emissions significantly decreased under drought conditions. Only ammonia-oxidizing archaea (AOA) and fungal nirK were well adapted to drought stress in the control soil. Different fertilizers modulated the resilience of the functional guilds. Ammonia-oxidizing bacteria (AOB), nirK-type denitrifying bacteria and nosZ clade (both I and II) showed significant resilience in both fertilized and non-fertilized soils in response to soil rewetting. Soil rewetting also changed the underlying microbial mechanisms of N2O emissions. The results show a more significant negative relationship between N2O emissions and nosZI clade at 100% field capacity, as well as nosZII clade after soil rewetting. We highlight the significant role of the nosZII clade following soil rewetting events, which might be one factor that led to relatively lower N2O emissions compared to those at 100% field capacity. Our results provide new insights into developing mitigation strategies by fostering nosZII, which should be studied further in other cropland ecosystems or vegetable systems with frequent irrigation.