Impacts of waterlogging on soil nitrification and ammonia-oxidizing communities in farming system

Background and aims Waterlogging may affect soil nitrification rates, resulting in changes in plant-available nitrogen (N), and hence potentially influencing crop productivity. Because nitrification is a microbially-driven process and ammonia-oxidizing communities regulate soil nitrification rates, the aim of this study was to investigate the mechanistic response of ammonia-oxidizing communities and nitrification rates to waterlogging. Methods A field study was conducted by experimentally imposing two short-term waterlogging events when cotton plants were at the early- and late-flowering stages. Soil physicochemical properties, nitrification rates, and ammonia-oxidizing community abundance and structure in response to waterlogging were examined. Results Soil nitrate (NO3-) content, potential nitrification rates (PNR) and the abundance of ammonia-oxidizing communities significantly decreased upon waterlogging. Shifts in ammonia-oxidizing community structure were also observed. Both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) responded to waterlogging. PNR was significantly correlated with the abundance and structure of both AOB and AOA. Conclusions Waterlogging had strong negative effects on soil nitrification rates by altering the ammonia-oxidizing community abundance and structure, resulting in reduced soil N availability. Decreased plant-available N is likely to negatively affect primary productivity.