Nitrous Oxide and Agriculture in the UK: Meeting the Challenges of Reducing Emissions Without Reducing Productivity

Keywords: nitrous oxide, greenhouse gas emissions, nitrogenous fertilisers, manure, inhibitors.

In the UK, agriculture accounts for approximately 10% of all greenhouse gas (GHG) emissions (CO2eq), of which the powerful GHG nitrous oxide (N2O) accounts for approximately 31%. While significant steps are being taken to reduce emissions of the GHGs carbon dioxide and methane across all sectors within the UK to meet Net-Zero targets by 2050, there is relatively little planned to directly tackle the issue of N2O emissions from agricultural sources, which are largely influenced by the widespread application of nitrogen fertilisers (mineral and manure) to fields in the UK. Emissions of N2O are released as a by-product of complex microbial processes in soils and aquatic bodies, which can behave unpredictably depending upon a variety of environmental conditions and agricultural practices.

Due to this complexity, it is difficult to predict where mitigation efforts will have cost-effective impacts or negative environmental consequences across the wide variety of farmland in the UK. As a result of this large degree of uncertainty, mitigation of N2O has been largely overlooked at the farm scale (farmers) and national scale (policy makers) in favour of other more established actions such as the use of renewable energy and planting forests to offset emissions.

This review highlights these complexities, and discusses some the pros and cons of several key N2O mitigation strategies that have been discussed in the GHG flux community. This review concludes that although large inefficiencies persist in farming practices in the UK, widespread generic actions may have negative consequences, such as pollution swapping (increasing ammonia emissions and nitrate leaching) or increasing the cost of farming. Future technology such as precision farming will help inform farmers of best practice in decades to come, but adherence to recommended fertiliser application rates and the avoidance of over-application will also be required. While diet change (away from meat and dairy) will play a role in the decades to come, efforts to cut food waste in the UK should be a priority, as large efficiencies can be targeted with relatively few negative impacts on farmer or societal wellbeing.

N. Cowan, J. Drewer, J. Maire, E. Carnell, P. Levy, U. Skiba.

UK Centre for Ecology and Hydrology, Bush Estate, Penicuik, UK

26 pages, 3 figures, 2 table, 46 references