Articles | Volume 14, issue 8
Research article
02 May 2017
Research article |  | 02 May 2017

Nitrogen oxides and ozone fluxes from an oilseed-rape management cycle: the influence of cattle slurry application

Raffaella M. Vuolo, Benjamin Loubet, Nicolas Mascher, Jean-Christophe Gueudet, Brigitte Durand, Patricia Laville, Olivier Zurfluh, Raluca Ciuraru, Patrick Stella, and Ivonne Trebs

Abstract. This study reports NO, NO2 and O3 mixing ratios and flux measurements using the eddy covariance method during a 7-month period over an oilseed-rape field, spanning an organic and a mineral fertilisation event. Cumulated NO emissions during the whole period were in agreement with previous studies and showed quite low emissions of 0.26 kg N ha−1 with an emission factor of 0.27 %, estimated as the ratio between total N emitted in the form of NO and total N input. The NO emissions were higher following organic fertilisation in August due to conditions favouring nitrification (soil water content around 20 % and high temperatures), while mineral fertilisation in February did not result in high emissions. The ozone deposition velocity increased significantly after organic fertilisation. The analysis of the chemical and turbulent transport times showed that reactions between NO, NO2 and O3 below the measurement height occurred constantly throughout the 7-month period. Following organic fertilisation, the NO ground fluxes were 30 % larger than the NO fluxes at the measurement height (3.2 m), while the NO2 fluxes switched from deposition to emission during certain periods, being negative at the surface and positive at the measurement height. This phenomenon of apparent NO2 emissions appears to be significant during strong NO emissions and high O3 ambient mixing ratios, even on a bare soil during August.

Short summary
Atmospheric nitrogen oxides (NO and NO2) are a threat for the environment and human health. Agricultural soils are a large but uncertain source, partly due to a lack of direct fluxes measurements. We quantified NO, NO2 and ozone (O3) fluxes above an oilseed rape crop rotation. We found that 0.27 % of nitrogen applied was emitted as NO, whose emissions were favoured by fertilisation under dry and warm conditions. We found significant interactions between NO, NO2 and O3 even above bare soil.
Final-revised paper