Articles | Volume 12, issue 5
Research article
12 Mar 2015
Research article |  | 12 Mar 2015

Spatial variability and hotspots of soil N2O fluxes from intensively grazed grassland

N. J. Cowan, P. Norman, D. Famulari, P. E. Levy, D. S. Reay, and U. M. Skiba

Abstract. One hundred N2O flux measurements were made from an area of intensively managed grazed grassland in central Scotland using a high-resolution dynamic chamber method. The field contained a variety of features from which N2O fluxes were measured including a manure heap, patches of decaying grass silage, and areas of increased sheep activity. Individual fluxes varied significantly across the field varying from 2 to 79 000 μg N2O-N m−2 h−1. Soil samples were collected at 55 locations to investigate relationships between soil properties and N2O flux. Fluxes of N2O correlated strongly with soil NO3- concentrations. Distribution of NO3 and the high spatial variability of N2O flux across the field are shown to be linked to the distribution of waste from grazing animals and the resultant reactive nitrogen compounds in the soil which are made available for microbiological processes. Features within the field such as shaded areas and manure heaps contained significantly higher available nitrogen than the rest of the field. Although these features only represented 1.1% of the area of the field, they contributed to over 55% of the total estimated daily N2O flux.

Short summary
The spatial variability of N2O fluxes measured at the field scale were investigated using a high-precision closed loop dynamic chamber. The results highlight the large and often unpredictable variation in N2O flux magnitude measured from agricultural soils at a relatively small scale. Available nitrogen content of the soils accounts for some of the variability in N2O emissions. The study suggests animal waste is an important source of N2O emissions released from livestock farms.
Final-revised paper