The use of nitrogen fertiliser and nitrogen-fixing crops has led to a significant increase of nitrous oxide (N2O) in the atmosphere, according to a study published in the journal of Nature Climate Change.
A group of international researchers looked at the global atmospheric N2O concentration data and found that between 2000-2005 and 2010-2015 N2O emissions increased globally by 1.6 teragrams per year.
The researchers said that the use of nitrogen fertilizers and the widespread cultivation of nitrogen-fixing crops has led to this increase.
When comparing pre-industrial N2O levels and current emissions (2007-2016), the researchers found that cropland soil emissions have increased more than ten times.
Cropland soils are now responsible for about a third of all global soil emissions.
This is about twice the amount reported in the United Nations Framework Convention on Climate Change.
The authors suggest that this discrepancy is due to an increase in the emission factors associated with a growing nitrogen surplus, which the Intergovernmental Panel on Climate Change (IPCC) may have underestimated.
Dr. Chris Wilson from the School of Earth and Environment and National Center for Earth Observation at the University of Leeds said: ‘We already knew that atmospheric N20 levels were increasing, but our study was able to assign this increase to specific regions and emissions sources, which is important for informing strategies to limit the growth of this greenhouse gas.’
Study lead author Dr. Rona Thompson from the Norwegian Institute for Air Research said: ‘Our results suggest that reducing nitrogen fertilizer use in regions where there is already a large nitrogen surplus, will result in large than the proportional reduction in N2O emissions.’
‘This is particularly relevant in regions such as East Asia, where nitrogen fertilizer could be used more efficiently, without reducing crop yields.’
Co-author Professor Martyn Chipperfield from the University of Leeds said: ‘The study highlights the need for more detailed algorithms and region-specific emissions factors to estimate N20.’
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