Articles | Volume 13, issue 16
Research article
29 Aug 2016
Research article |  | 29 Aug 2016

The influence of tillage on N2O fluxes from an intensively managed grazed grassland in Scotland

Nicholas J. Cowan, Peter E. Levy, Daniela Famulari, Margaret Anderson, Julia Drewer, Marco Carozzi, David S. Reay, and Ute M. Skiba

Abstract. Intensively managed grass production in high-rainfall temperate climate zones is a globally important source of N2O. Many of these grasslands are occasionally tilled to rejuvenate the sward, and this can lead to increased N2O emissions. This was investigated by comparing N2O fluxes from two adjacent intensively managed grazed grasslands in Scotland, one of which was tilled. A combination of eddy covariance, high-resolution dynamic chamber and static chamber methods was used.

N2O emissions from the tilled field increased significantly for several days immediately after ploughing and remained elevated for approximately 2 months after the tillage event contributing to an estimated increase in N2O fluxes of 0.85 ± 0.11 kg N2O-N ha−1. However, any influence on N2O emissions after this period appears to be minimal. The cumulative N2O emissions associated with the tillage event and a fertiliser application of 70 kg N ammonia nitrate from one field were not significantly different from the adjacent untilled field, in which two fertiliser applications of 70 kg N ammonia nitrate occurred during the same period. Total cumulative fluxes calculated for the tilled and untilled fields over the entire 175-day measurement period were 2.14 ± 0.18 and 1.65 ± 1.02 kg N2O-N ha−1, respectively.

Short summary
Using a quantum cascade laser we measured N2O fluxes before and after a tillage event on a long-term grazed grassland field using the flux chamber and eddy covariance methods. The measurements were gap-filled using a generalised additive model which used meteorological data at the site. Results suggest that tillage of soils containing plant material (crop residues) releases a relatively large amount of N2O-N, similar in magnitude to approximately 0.9 % of the nitrogen in the plant materials.
Final-revised paper