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.