Soil microbial sources of nitrous oxide: recent advances in knowledge, emerging challenges and future direction

The greenhouse gas nitrous oxide can be produced in soil during several microbial processes. Understanding of the regulation of these processes and the conditions under which they are likely to prevail have advanced in the last couple of decades. This is important for the development of targeted mitigation strategies. Here the focus is placed on the most recent advances in understanding associated with nitrous oxide production during ammonia oxidation, and the nitrate reducing processes of nitrate ammonification (or dissimilatory nitrate reduction to ammonium) and denitrification, including nitrifier denitrification in temperate soils. Some of the possibilities these offer for management to lower net emissions are outlined, and consideration is given to the current challenges and future directions required for these possibilities to be realised. These highlight the need for a multidisciplinary approach to understand the regulation of N2O production and reduction, synthesising relationships across a range systems, and increasing our predictive capability of interactions within the atmosphere–plant–microbe–soil continuum.

► A review of the recent advances in knowledge on microbial sources of N2O, including better characterisation of nitrate ammonification, possibility of co-denitrification and involvement of different functional groups in denitrification.
► Consideration of the possibilities this microbial nitrous oxide attribution offers for more targeted mitigation, and suggestions of the future direction to realise these.
► Recommendation for a multidisciplinary approach to enable greater understanding of interactions between processes, cycles and atmosphere, plant, soil and microbes.